Use explicit width for finite width parameters #687
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Signed-off-by: Elazar Gershuni <[email protected]>
WalkthroughThe changes across multiple files focus on enhancing type handling, particularly through the introduction of template methods for type checking and casting. Key modifications include updates to arithmetic operations, with a shift from 32-bit to 64-bit representations for better precision. The Changes
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Actionable comments posted: 11
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📒 Files selected for processing (4)
- src/crab/ebpf_domain.cpp (19 hunks)
- src/crab/interval.cpp (9 hunks)
- src/crab/interval.hpp (9 hunks)
- src/crab_utils/bignums.hpp (6 hunks)
🔇 Additional comments not posted (37)
src/crab/interval.cpp (8)
32-33: LGTM: Consistent type usageThe change from
z_boundtobound_timproves type consistency within theinterval_tclass. This modification aligns with the overall goal of using explicit width for finite width parameters.
37-38: LGTM: Consistent type usage continuedThe replacement of
z_boundwithbound_tcontinues in this segment, maintaining consistency with the previous changes. This modification further enhances the type consistency within theinterval_tclass.
50-50: LGTM: Improved syntax for bound determinationThe use of
std::minandstd::maxwith initializer lists is a good improvement. It simplifies the syntax, makes the code more concise, and leverages modern C++ features. This change enhances readability while maintaining the same functionality.
79-80: LGTM: Consistent type usage in SDiv methodThe replacement of
z_boundwithbound_tin theSDivmethod maintains consistency with the changes made in other parts of the class. This continued effort to use explicit width for finite width parameters enhances the overall type consistency of theinterval_tclass.Also applies to: 84-85
97-97: LGTM: Consistent improvement in bound determinationThe use of
std::minandstd::maxwith initializer lists in theSDivmethod is consistent with the changes made in the operator/ method. This modification continues to simplify the syntax, enhance readability, and leverage modern C++ features while maintaining the same functionality.
215-216: LGTM: Consistent type usage in URem methodThe replacement of
z_boundwithbound_tin theURemmethod maintains consistency with the changes made throughout theinterval_tclass. This continued effort to use explicit width for finite width parameters further enhances the overall type consistency of the class.Also applies to: 220-221
269-269: LGTM: Simplified minimum value determinationThe use of
std::mininstead of a ternary operator is a good improvement. It simplifies the syntax, makes the code more concise, and is consistent with the use ofstd::minin other parts of the class. This change enhances readability while maintaining the same functionality.
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1-424: Overall assessment: Consistent improvements in type usage and syntaxThe changes in this file consistently replace
z_boundwithbound_t, improving type consistency throughout theinterval_tclass. Additionally, the use ofstd::minandstd::maxwith initializer lists simplifies the syntax for bound determination in several methods. These modifications align well with the PR objective of using explicit width for finite width parameters, enhance code consistency, and leverage modern C++ features. The changes maintain the existing functionality while improving code readability and maintainability.src/crab_utils/bignums.hpp (5)
38-38: No action needed for access specifier placement.The
public:access specifier is correctly placed, ensuring proper access control in the class.
86-90: Well-implemented genericfits<T>()method.The addition of the
fits<T>()template method enhances the flexibility and reusability of the code by allowing checks for any integral typeT. Good use of C++20 concepts withstd::integraland the[[nodiscard]]attribute to prevent unintentional ignoring of the return value.
94-109: Refactoredfits_*()methods improve maintainability.The methods
fits_sint32(),fits_uint32(),fits_sint64(), andfits_uint64()now leverage the genericfits<T>()template method. This change reduces code duplication and enhances maintainability.
212-215: Extended truncation to support 8-bit and 16-bit signed widths.Adding cases for 8-bit and 16-bit widths in
truncate_to_signed_finite_width()enhances functionality by allowing truncation to smaller signed types, increasing flexibility.
226-229: Extended truncation to support 8-bit and 16-bit unsigned widths.The inclusion of 8-bit and 16-bit cases in
truncate_to_unsigned_finite_width()improves the method's utility by supporting a wider range of unsigned truncation widths.src/crab/interval.hpp (4)
139-140: Ensure correct handling of negative bounds when casting touint64_tCasting negative numbers to
uint64_tin unsigned division may lead to unexpected large positive values due to modulo arithmetic. In theUDivmethod, please verify that casting_nandx._ntouint64_twhen they are negative is intentional and that the bound calculations handle negative values correctly.
154-155: Ensure correct handling of negative bounds when casting touint64_tinUModSimilar to the
UDivmethod, casting negative numbers touint64_tin theUModmethod may result in unexpected values. Please confirm that this casting is intentional and that the modulo operation behaves correctly with negative bounds.
402-402: Verify compatibility with C++ standards forstd::minandstd::maxwith initializer listsThe use of
std::minandstd::maxwith an initializer list in the expressionstd::min({ll, lu, ul, uu})requires C++11 or higher. Ensure that the project is compiled with a compatible C++ standard (C++11 or later) to support this syntax.
655-655: Confirmnoexceptusage into_stringfunctionThe
noexceptspecifier has been added to theto_stringfunction:std::string to_string(const crab::interval_t& interval) noexcept;Ensure that all operations within the
to_stringimplementation are exception-safe and do not throw, to adhere to thenoexceptguarantee.src/crab/ebpf_domain.cpp (20)
134-136: Correct Handling of Nonnegative 64-bit IntervalsThe modification at line 134 changes the condition to explicitly use
crab::interval_t::nonnegative(64)instead of the implicit 32-bit default. This ensures that when dealing with 64-bit signed equalities, the nonnegative interval is accurately represented.
209-210: Truncating Intervals to 32-bit Signed IntegersAt lines 209-210, the code truncates intervals to 32-bit signed integers using
truncate_to_sint(32)when they exceed the 32-bit signed range. This ensures proper handling of intervals that could cause overflow in 32-bit operations.
218-219: Correct Splitting of Left Interval into Positive and Negative PartsLines 218-219 correctly split
left_intervalintoleft_interval_positiveandleft_interval_negativebased on the 64-bit nonnegative and negative intervals. This allows for proper handling of signed intervals in subsequent computations.
225-227: Handling of Signed Intervals with Unsigned RepresentationsIn lines 225-227, when the signed interval is
topbut the unsigned interval is precise, the code splits the interval into positive and negative parts accordingly. This ensures accurate analysis even when the signed interval lacks precision.
236-237: Ensuring Intervals Fit Within 64-bit Signed IntegersLines 236-237 truncate any intervals that do not fit within 64-bit signed integers using
truncate_to_sint(64). This prevents potential overflow issues and maintains consistency in interval representations.
255-256: Adjustments for 32-bit and 64-bit Unsigned IntervalsAt lines 255-256 and 261-262 in
get_unsigned_intervals, the code checks whether the intervals fit within 32-bit nonnegative ranges and setsis64accordingly. Intervals not fitting within 32-bit are truncated to 32-bit unsigned integers. This logic ensures proper handling of unsigned intervals based on their bit-width.Also applies to: 261-262
270-271: Splitting Left Interval into Low and High Unsigned PartsLines 270-271 appropriately split
left_intervalintoleft_interval_lowandleft_interval_highfor 64-bit unsigned integers. This allows for accurate comparison and analysis of unsigned intervals across their full range.
277-278: Handling Precise Signed Intervals Represented as UnsignedAt lines 277-278, when the unsigned interval is
topbut the signed interval is precise, the code creates unsigned intervals from the signed bounds. This ensures that the analysis does not lose precision when dealing with values that can only be accurately represented in one form.
286-287: Truncating Intervals to 64-bit Unsigned IntegersLines 286-287 ensure that all intervals are truncated to fit within 64-bit unsigned integers using
truncate_to_uint(64). This maintains consistency and prevents potential overflows in unsigned arithmetic.
300-305: Improved Comparison Logic inassume_signed_64bit_ltLines 300-305 enhance the logic for signed less-than comparisons in 64-bit intervals. The code correctly handles cases when the right interval is negative or nonnegative, ensuring accurate constraints are applied based on the sign and range of the intervals.
323-332: Refinement of 32-bit Signed Less-Than ComparisonsAt lines 323-332 and 340-341, the code refines the handling of 32-bit signed less-than comparisons in
assume_signed_32bit_lt. The updated conditions account for the signedness and bounds of the intervals, improving the correctness of the analysis.Also applies to: 340-341
358-369: Enhancements in Signed Greater-Than Comparisons for 64-bitLines 358-369 in
assume_signed_64bit_gtimprove the handling of signed greater-than comparisons for 64-bit intervals, ensuring that both positive and negative ranges are correctly considered and that appropriate constraints are applied.
389-407: Improvements in Signed Greater-Than Comparisons for 32-bitLines 389-407 refine the logic in
assume_signed_32bit_gtfor 32-bit signed greater-than comparisons. The updated code ensures accurate handling of different interval ranges and applies correct relational constraints.
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491-519: Enhanced Unsigned Less-Than Comparisons in 64-bit ContextLines 491-519 and 523 improve the logic in
assume_unsigned_64bit_ltfor unsigned less-than comparisons. The code correctly handles various cases, including intervals representable as both signed and unsigned values, ensuring proper constraint application.Also applies to: 523-523
540-551: Refined Unsigned Less-Than Comparisons for 32-bitAt lines 540-551, the code in
assume_unsigned_32bit_ltis updated to more accurately handle 32-bit unsigned less-than comparisons, considering the signedness and bounds of the intervals involved.
569-583: Improvements in Unsigned Greater-Than Comparisons for 64-bitLines 569-583 in
assume_unsigned_64bit_gtenhance the handling of unsigned greater-than comparisons for 64-bit intervals, ensuring that constraints reflect the correct relationships between intervals in different ranges.
601-606: Refinement of Unsigned Greater-Than Comparisons for 32-bitLines 601-606 update
assume_unsigned_32bit_gtto handle 32-bit unsigned greater-than comparisons more accurately, taking into account different interval representations and ensuring correct constraint applications.
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633-654: Handling of Unsigned Not-Equal and Comparison OperationsLines 633-654 in
assume_unsigned_cst_intervaladdress the logic for handling unsigned not-equal, less-than, and greater-than comparisons. The code ensures that proper relational constraints are derived based on whether the intervals are singleton values and the specific comparison operation.
738-741: Correct Handling of 64-bit Equality ComparisonsLines 738-741 in
assume_cst_regcorrectly handle equality comparisons for 64-bit values, ensuring that both signed and unsigned intervals are considered when applying constraints.
203-204: Potential Confusion in is64 Flag AssignmentAt lines 203-204, the condition checks if both
left_intervalandright_intervalare within 32-bit nonnegative or negative ranges, and then setsis64 = true. This seems counterintuitive, as one might expectis64to remainfalsewhen both intervals fit within 32-bit. Please verify that settingis64 = truein this case is intentional and aligns with the desired behavior.You can run the following script to review all occurrences of
is64assignments and their contexts:This can help ensure that the logic for handling 32-bit and 64-bit intervals is implemented as intended.
Signed-off-by: Elazar Gershuni <[email protected]>
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Actionable comments posted: 10
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📒 Files selected for processing (2)
- src/crab/interval.hpp (9 hunks)
- src/crab_utils/bignums.hpp (8 hunks)
🧰 Additional context used
📓 Learnings (1)
src/crab/interval.hpp (1)
Learnt from: elazarg PR: vbpf/ebpf-verifier#687 File: src/crab/interval.hpp:256-262 Timestamp: 2024-09-25T11:00:29.008Z Learning: When comparing two unsigned integral types of the same size using '>', the comparison behaves correctly without needing special handling.
🔇 Additional comments not posted (7)
src/crab_utils/bignums.hpp (3)
106-111: Refactor improves code maintainability via templatedfits<T>()The introduction of the templated
fits<T>()method enhances code reuse and reduces duplication in thefits_*()methods. This change improves maintainability and eases future expansions to support additional integral types.
29-35: 🛠️ Refactor suggestionConsider integrating
truncate_to_coderabbitwith existingtruncate_to<T>()The new
truncate_to_coderabbitfunction for unsigned integral types appears to duplicate the functionality of the existingtruncate_to<T>()template function. To avoid redundancy and improve maintainability, consider integrating this implementation intotruncate_to<T>()or replacing the existing function if the new implementation addresses previous issues.⛔ Skipped due to learnings
Learnt from: elazarg PR: vbpf/ebpf-verifier#685 File: src/crab_utils/bignums.hpp:22-27 Timestamp: 2024-09-24T10:52:52.162Z Learning: In the `truncate_to` function, suggestions that result in the original code after inlining variables are unnecessary refactorings.
149-162: Verify correctness of casting logic incast_to<U>()The
cast_to<U>()function for unsigned integral types includes logic to handle cases where the value fits into the signed counterpartS. Please ensure that this casting logic correctly handles all edge cases, particularly when casting negative values or values that exceed the limits ofU.To confirm the correctness, you could check the behavior with test cases covering boundary values:
✅ Verification successful
Casting Logic in
cast_to<U>()Verified CorrectThe
cast_to<U>()function appropriately handles edge cases by verifying that values fit into the target unsigned type or its signed counterpart before casting. All usages in the codebase include necessary checks to prevent invalid casts of negative or oversized values.🏁 Scripts executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash # Description: Identify usages of `cast_to<U>()` and ensure they are correctly handling edge cases. # Test: Search for calls to `cast_to<U>()` in the codebase. rg --type cpp 'cast_to<.*>()'Length of output: 523
Script:
#!/bin/bash # Description: Extract surrounding lines of each `cast_to<U>()` usage to analyze handling of edge cases. # Extract lines with `cast_to<U>()` along with 3 lines before and after for context. rg --type cpp -C 3 'cast_to<.*>()' src/crab_utils/bignums.hpp src/crab/interval.hppLength of output: 1747
src/crab/interval.hpp (4)
256-262: Ensure correct initialization in templated constructorThe templated constructor for
interval_tmay not correctly initialize the interval whenlb > ub. Currently, it sets_lbto0and_ubto-1, representing a bottom interval. Ensure that this approach aligns with the representation of an empty interval in your implementation.Verify that setting
_lbto0and_ubto-1correctly represents a bottom interval within the codebase. You might want to check if other parts of the code interpret this representation as intended.
484-492: Consistent handling of invalid widths intruncate_to_sintIn the
truncate_to_sintmethod, thedefaultcase in theswitchstatement callsCRAB_ERROR("Invalid width ", width);. Verify thatCRAB_ERRORappropriately handles this error scenario (e.g., throws an exception or terminates the program) and that the function does not continue execution after this call.Ensure that
CRAB_ERRORis properly defined to handle errors and consider documenting its behavior for clarity.
496-504: Consistent handling of invalid widths intruncate_to_uintSimilar to
truncate_to_sint, in thetruncate_to_uintmethod, confirm that thedefaultcase andCRAB_ERRORusage correctly handle invalid width values.Ensure consistent error handling across both methods and that
CRAB_ERRORprevents further execution when an invalid width is provided.
651-651: Use ofnoexceptspecifier into_stringfunctionThe addition of the
noexceptspecifier to theto_stringfunction is appropriate if the function is guaranteed not to throw exceptions. Ensure that all code within the function adheres to this guarantee.
Signed-off-by: Elazar Gershuni <[email protected]>
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- src/crab/interval.hpp (9 hunks)
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📓 Learnings (1)
src/crab/interval.hpp (1)
Learnt from: elazarg PR: vbpf/ebpf-verifier#687 File: src/crab/interval.hpp:256-262 Timestamp: 2024-09-25T11:00:29.008Z Learning: When comparing two unsigned integral types of the same size using '>', the comparison behaves correctly without needing special handling.
🔇 Additional comments not posted (13)
src/crab/interval.hpp (13)
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23-28: Constructor Implementation Looks GoodThe implementation of the
bound_tconstructor correctly initializes the object and ensures proper handling of infinite bounds.
139-140: Potential Incorrect Handling of Negative Numbers inUDiv
154-155: Potential Incorrect Handling of Negative Numbers inUMod
256-262: Correct Implementation of Templatedinterval_tConstructorThe templated constructor for
interval_tcorrectly initializes the interval and handles cases wherelb > ubby setting the interval to bottom.
319-319: Correct Use ofstd::minandstd::maxin Union OperationThe use of
std::minandstd::maxcorrectly computes the bounds for the interval union in theoperator|method.
327-327: Correct Use ofstd::maxandstd::minin Intersection OperationThe use of
std::maxandstd::mincorrectly computes the bounds for the interval intersection in theoperator&method.
402-402: Efficient Computation of Interval Bounds in MultiplicationThe use of
std::minandstd::maxwith initializer lists efficiently computes the bounds after multiplication in theoperator*method.
486-492: Updatedtruncate_to_sintFunction Correctly Uses Width ParameterThe
truncate_to_sintfunction now accepts an integerwidthand correctly handles truncation based on the provided width.
498-504: Updatedtruncate_to_uintFunction Correctly Uses Width ParameterThe
truncate_to_uintfunction now accepts an integerwidthand correctly handles truncation based on the provided width.
508-524: Template Functiontruncate_toCorrectly Handles TruncationThe templated
truncate_tofunction accurately truncates the interval to the specified type, ensuring correct representation or returning the full range of the type if necessary.
530-536: Updatedsigned_intFunction for Specified WidthsThe
signed_intstatic function now accepts an integerwidthand correctly returns the full interval for the specified signed integer type.
543-551: Updatedunsigned_intFunction for Specified WidthsThe
unsigned_intstatic function now accepts an integerwidthand correctly returns the full interval for the specified unsigned integer type.
653-653: Addition ofnoexceptSpecifier toto_stringFunctionMarking the
to_stringfunction withnoexceptindicates that it does not throw exceptions, which can improve reliability and allow for certain compiler optimizations.
Signed-off-by: Elazar Gershuni <[email protected]>
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Actionable comments posted: 14
🧹 Outside diff range comments (3)
src/crab/interval.cpp (3)
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56-93: LGTM! Consistent improvements with operator/.The changes to the
SDivmethod mirror the improvements made tooperator/, enhancing readability and robustness.For consistency with the
operator/method, consider adding a similar comment explaining the rationale for division by 0:} else { // The eBPF ISA defines division by 0 as resulting in 0. + // This is a specific behavior of eBPF, different from traditional arithmetic. return interval_t(number_t(0)); }
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101-139: LGTM! Consistent improvements with operator/ and SDiv.The changes to the
UDivmethod align with the improvements made tooperator/andSDiv, enhancing readability and robustness.For consistency with the
operator/andSDivmethods, consider adding a similar comment explaining the rationale for division by 0:} else { // The eBPF ISA defines division by 0 as resulting in 0. + // This is a specific behavior of eBPF, different from traditional arithmetic. return interval_t(number_t(0)); }
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148-182: LGTM! Improved handling of edge cases.The changes to the
SRemmethod have improved its readability and robustness, particularly in handling edge cases like modulo by zero.Consider adding a comment to explain the behavior when the divisor contains zero:
if (x.contains(0)) { // The divisor contains 0. + // In this case, we split the interval and handle non-zero cases separately. + // We also include the original dividend as a possible result for x = 0. interval_t l(x._lb, bound_t(-1)); interval_t u(bound_t(1), x._ub); return SRem(l) | SRem(u) | *this; }
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📒 Files selected for processing (4)
- src/crab/ebpf_domain.cpp (20 hunks)
- src/crab/interval.cpp (6 hunks)
- src/crab/interval.hpp (10 hunks)
- src/crab_utils/bignums.hpp (8 hunks)
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📓 Learnings (1)
src/crab/interval.hpp (3)
Learnt from: elazarg PR: vbpf/ebpf-verifier#687 File: src/crab/interval.hpp:568-569 Timestamp: 2024-09-25T13:22:39.531Z Learning: In this project, 'svalue' and 'uvalue' are standard terms and should be used as is.Learnt from: elazarg PR: vbpf/ebpf-verifier#687 File: src/crab/interval.hpp:412-417 Timestamp: 2024-09-25T13:23:50.545Z Learning: In the `interval_t` class, the `size()` method may return infinite size when the interval has infinite bounds, and this is acceptable behavior.Learnt from: elazarg PR: vbpf/ebpf-verifier#687 File: src/crab/interval.hpp:256-262 Timestamp: 2024-09-25T11:00:29.008Z Learning: When comparing two unsigned integral types of the same size using '>', the comparison behaves correctly without needing special handling.
🔇 Additional comments not posted (56)
src/crab/interval.cpp (3)
268-283: LGTM! Minor readability improvements.The changes to the
Ormethod have improved its readability through the use ofconst autofor singleton checks.
289-295: LGTM! Minor readability improvements.The changes to the
Xormethod have improved its readability through the use ofconst autofor singleton checks.
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1-367: Overall, excellent improvements to readability and robustness.The changes in this file consistently enhance the readability and robustness of the
interval_tclass operations. Key improvements include:
- Consistent use of
const autofor singleton checks across all methods.- Improved handling of edge cases, particularly for division and modulo operations.
- More explicit and easier-to-understand logic for operations involving zero.
- Use of
std::minandstd::maxwith initializer lists for more concise and less error-prone code.- Enhanced precision for bitwise operations, especially for 32-bit scenarios.
These changes contribute to a more maintainable and reliable codebase. The minor suggestions provided in the review comments, if implemented, will further improve code clarity and consistency.
src/crab_utils/bignums.hpp (2)
232-235: Add support for 8-bit and 16-bit signed truncationIn the
truncate_to_signed_finite_width(int finite_width)function, cases for 8-bit and 16-bit widths have been added. This enhancement allows truncation to smaller signed widths, which can be useful for certain applications.
246-249: Add support for 8-bit and 16-bit unsigned truncationSimilarly, in the
truncate_to_unsigned_finite_width(int finite_width)function, cases for 8-bit and 16-bit widths have been added. This addition provides flexibility for truncating to smaller unsigned widths.src/crab/interval.hpp (15)
23-23: Acknowledged parameter modificationThe use of
constqualifiers on parameters passed by value, such asconst bool is_infinite, is acceptable and indicates that the parameter is not mutated within the function.
85-94: Correct handling of finite and infinite bounds inoperator+The updated implementation of
operator+in thebound_tclass properly handles combinations of finite and infinite bounds, including error handling for undefined operations like-oo + +oo.
253-259: Template constructor forinterval_tenhances flexibilityThe addition of the templated constructor allows
interval_tto be constructed with any integral typeT, improving the class's usability. The constructor correctly handles cases wherelb > ubby setting the interval to bottom.
316-316: Efficient union operation usingstd::minandstd::maxThe use of
std::minandstd::maxwithbound_tobjects in theoperator|method enhances code readability and ensures correct computation of interval bounds during the union operation.
324-324: Accurate intersection operation inoperator&The
operator&method correctly computes the intersection of intervals by usingstd::maxfor lower bounds andstd::minfor upper bounds.
399-399: Optimized multiplication result calculationThe consolidation of possible products using
std::minandstd::maxover an initializer list in theoperator*method efficiently determines the resulting interval bounds after multiplication.
504-520: Proper handling of optional finite sizes intruncate_toThe
truncate_totemplate method correctly checks for a finite size before proceeding, ensuring that optional values are safely dereferenced. This prevents potential runtime errors due to undefined optional values.
480-501: Refactored truncation methods enhance clarityReplacing
bool is64withint widthintruncate_to_sintandtruncate_to_uintmethods improves code clarity and flexibility, allowing for explicit width specifications.
526-532: Updatedsigned_intmethod with explicit widthsThe
signed_intstatic method now accepts anint widthparameter, aligning it with modern coding practices and improving the explicitness of width specifications for signed intervals.
539-547: Consistent width handling inunsigned_intmethodThe
unsigned_intmethod follows the same pattern assigned_int, using anint widthparameter to specify the bit width of the unsigned interval, enhancing consistency across the codebase.
549-560: Clarified nonnegative interval constructionThe
nonnegativemethod correctly generates intervals representing non-negative numbers within a specified width, using anint widthparameter for explicitness.
562-571: Correct implementation ofnegativemethodThe
negativemethod provides intervals representing negative numbers within the given width. The method and comments accurately reflect its functionality.
585-589: Addition offull<T>template method for complete intervalsThe
full<T>method offers a convenient way to create an interval covering the entire range of a given integral typeT, enhancing the utility of theinterval_tclass.
590-595: Introduction ofhigh<T>method for upper interval rangesThe
high<T>method generates intervals representing high ranges in unsigned integral types, specifically fromINT_MAX + 1toUINT_MAX, which is useful for certain unsigned computations.
649-649: Addednoexceptspecifier toto_stringfunctionThe addition of the
noexceptspecifier to theto_stringfunction indicates that the function is guaranteed not to throw exceptions, which can improve performance and reliability.src/crab/ebpf_domain.cpp (36)
134-134: Specified explicit 64-bit width in interval comparisonBy adding
64tocrab::interval_t::nonnegative(64), the code now explicitly handles 64-bit intervals, enhancing accuracy in the comparison operation.
203-204: Used explicit 32-bit widths in signed interval checksThe inclusion of
32ininterval_t::nonnegative(32)andinterval_t::negative(32)ensures correct handling of 32-bit signed intervals during comparisons.
209-210: Truncated intervals to 32-bit signed integersBy checking
*interval <= interval_t::signed_int(32)and truncating withtruncate_to_sint(32), the code accurately manages 32-bit signed integer intervals, preventing potential overflow issues.
218-219: Intersected intervals using explicit 64-bit nonnegative intervalUsing
interval_t::nonnegative(64)for intersection ensures that the positive intervals are correctly bounded within 64 bits.
225-227: Handled upper bounds with explicit 64-bit truncationTruncating the upper bound to 64 bits using
truncate_to_signed_finite_width(64)in line 227 ensures that interval calculations remain within the correct finite-width range.
230-231: Initialized intervals with explicit 64-bit widthsSetting
left_interval_positivetointerval_t::nonnegative(64)andleft_interval_negativetointerval_t::negative(64)explicitly defines the intervals within 64-bit bounds.
236-237: Ensured intervals are within 64-bit signed integer rangeBy truncating intervals exceeding
interval_t::signed_int(64)to 64 bits usingtruncate_to_sint(64), the code maintains accurate interval representations.
255-256: Used explicit 32-bit widths in unsigned interval checksThe replacement of implicit widths with
interval_t::nonnegative(32)andinterval_t::unsigned_high(32)ensures correct handling of 32-bit unsigned intervals.
261-262: Truncated intervals to 32-bit unsigned integersBy truncating intervals not within
interval_t::unsigned_int(32)usingtruncate_to_uint(32), the code properly manages 32-bit unsigned integer ranges.
270-271: Split unsigned intervals using explicit 64-bit boundsInitializing
left_interval_lowwithinterval_t::nonnegative(64)ensures accurate splitting of unsigned intervals for 64-bit analysis.
286-287: Truncated intervals to 64-bit unsigned integers when necessaryEnsuring that intervals exceeding
interval_t::unsigned_int(64)are truncated usingtruncate_to_uint(64)maintains correct interval bounds.
300-305: Handled 64-bit negative intervals in signed less-than comparisonBy explicitly checking for
interval_t::negative(64)and using 64-bit bounds, the code accurately manages comparisons involving negative intervals.
323-330: Managed 32-bit negative intervals in signed less-than comparisonIncluding explicit 32-bit width checks with
interval_t::negative(32)andinterval_t::nonnegative(32)ensures correct behavior in 32-bit signed comparisons.
340-341: Handled intervals within 32-bit signed integer rangeBy verifying that intervals are within
interval_t::signed_int(32), the code accurately processes 32-bit signed integers in comparisons.
358-360: Managed 64-bit nonnegative intervals in signed greater-than comparisonUsing
interval_t::nonnegative(64)and truncating upper bounds withtruncate_to_sint(64)ensures precise handling of positive intervals in 64-bit comparisons.
368-369: Handled 64-bit negative intervals in signed greater-than comparisonBy explicitly checking for
interval_t::negative(64), the code accurately processes negative intervals in 64-bit signed greater-than comparisons.
389-391: Managed 32-bit nonnegative intervals in signed greater-than comparisonIncluding checks for
interval_t::nonnegative(32)and truncating withtruncate_to_sint(32), the code correctly handles positive intervals in 32-bit comparisons.
399-400: Handled 32-bit negative intervals in signed greater-than comparisonUsing explicit checks for
interval_t::negative(32), the code ensures accurate processing of negative intervals in 32-bit signed comparisons.
406-407: Verified intervals within 32-bit signed integer rangeBy confirming intervals are within
interval_t::signed_int(32), the code properly manages 32-bit signed integer comparisons.
491-492: Truncated low interval bounds to 64-bit unsigned integersUsing
truncate_to_uint(64)onleft_interval_lowbefore accessing the lower bound ensures accurate interval calculations in unsigned comparisons.
502-503: Truncated high interval bounds to 64-bit unsigned integersBy truncating
left_interval_highwithtruncate_to_uint(64), the code correctly processes high intervals in 64-bit unsigned comparisons.
513-515: Handled 64-bit signed intervals in unsigned less-than comparisonChecking
right_interval <= interval_t::signed_int(64)and truncating upper bounds withtruncate_to_uint(64)ensures proper handling of signed intervals as unsigned.
519-523: Addressed edge cases in unsigned 64-bit interval comparisonsThe conditions handle scenarios where
left_interval_lowis bottom and when intervals equalinterval_t::unsigned_int(64), ensuring correctness in edge cases.
540-541: Managed 32-bit nonnegative intervals in unsigned less-than comparisonBy checking if intervals are within
interval_t::nonnegative(32), the code accurately handles 32-bit unsigned comparisons.
545-546: Handled 32-bit negative intervals in unsigned less-than comparisonIncluding checks for
interval_t::negative(32)allows for correct processing of negative intervals in unsigned comparisons, which may represent high unsigned values due to wrapping.
550-551: Ensured intervals are within 32-bit unsigned integer rangeBy verifying intervals are within
interval_t::unsigned_int(32), the code properly manages 32-bit unsigned integer comparisons.
569-572: Computed bounds for unsigned greater-than comparisonBy evaluating
right_interval.lb(), and truncating bounds withtruncate_to_uint(64), the code calculates accurate intervals for comparison.
578-578: Handled low interval out-of-range scenariosThe condition checks if
llubis less thanrlb, ensuring correct handling when the low interval is out of range in unsigned comparisons.
601-601: Managed 32-bit unsigned high intervals in greater-than comparisonBy checking
right_interval <= interval_t::unsigned_high(32), the code accurately processes high unsigned intervals in 32-bit comparisons.
605-606: Ensured intervals are within 32-bit unsigned integer rangeVerifying that both
left_uvalueandright_uvalueare withininterval_t::unsigned_int(32)ensures correct handling in unsigned greater-than comparisons.
633-633: Compared intervals with explicit finite widthsUsing
left_interval.truncate_to_uint(is64 ? 64 : 32)ensures that the comparison operates on intervals truncated to the correct finite width based onis64.
738-738: Evaluated source interval with explicit variableRetrieving
src_intervalusinginv.eval_interval(src_svalue)explicitly handles the source variable in interval calculations.
2060-2060: Checked interval containment with context descriptorsBy assessing whether
intervalcontainsdesc->data,desc->meta, ordesc->end, the code determines if pointers may be touched, enhancing safety checks.
2736-2736: Determined finite width based onis64flagSetting
finite_widthto64or32depending onbin.is64ensures that subsequent operations consider the correct bit width.
2753-2753: Handled unsigned overflow with explicit finite widthUsing
bin.is64 ? 64 : 32inoverflow_unsignedaccurately addresses potential overflows in unsigned arithmetic based on the operand size.
3024-3025: Optimized conditional check with explicit finite widthBy using
interval_t::unsigned_int(bin.is64 ? 64 : 32), the code clearly defines the interval range for the evaluation, enhancing readability.
Signed-off-by: Elazar Gershuni <[email protected]>
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Actionable comments posted: 10
🧹 Outside diff range comments (2)
src/crab/interval.cpp (1)
Line range hint
148-181: Clarify behavior when divisor is zero inSRemmethodIn the
SRem(signed remainder) method, when the divisor is zero, the function returns the dividend interval unchanged. This behavior might not be immediately clear to readers.Add a comment to explain this specific case:
if (*divisor == 0) { return interval_t(*dividend); + // In eBPF, modulo by zero results in the dividend unchanged. }src/crab/ebpf_domain.cpp (1)
Line range hint
738-744: Potential inefficiency in equality comparisonThe code checks if
src_intervalis not a singleton and if it is less than or equal to a non-negative 64-bit interval before adding constraints. This may be unnecessarily restrictive and could lead to inefficiencies in constraint handling.Consider simplifying the condition or reevaluating the necessity of the check to improve performance.
Apply this diff to streamline the condition:
-if (!src_interval.is_singleton() && (src_interval <= crab::interval_t::nonnegative(64))) { +if (src_interval <= crab::interval_t::nonnegative(64)) { return {eq(dst_svalue, src_svalue), eq(dst_uvalue, src_uvalue), eq(dst_svalue, dst_uvalue)}; } else { return {eq(dst_svalue, src_svalue), eq(dst_uvalue, src_uvalue)}; }
📜 Review details
Configuration used: CodeRabbit UI
Review profile: ASSERTIVE
📒 Files selected for processing (8)
- src/crab/array_domain.cpp (4 hunks)
- src/crab/ebpf_domain.cpp (33 hunks)
- src/crab/interval.cpp (6 hunks)
- src/crab/split_dbm.cpp (2 hunks)
- src/crab/var_factory.cpp (1 hunks)
- src/crab_utils/bignums.hpp (5 hunks)
- src/crab_verifier.cpp (1 hunks)
- src/test/conformance_check.cpp (1 hunks)
🧰 Additional context used
📓 Learnings (1)
src/crab/ebpf_domain.cpp (1)
Learnt from: elazarg PR: vbpf/ebpf-verifier#687 File: src/crab/interval.hpp:256-262 Timestamp: 2024-09-25T11:00:29.008Z Learning: When comparing two unsigned integral types of the same size using '>', the comparison behaves correctly without needing special handling.
🔇 Additional comments not posted (24)
src/test/conformance_check.cpp (1)
84-85: Approve: Improved type safety with explicit width parametersThe changes in these lines enhance type safety and code clarity by using templated functions with explicit type parameters:
fits_cast_to<int64_t>()instead offits_cast_to_int64()cast_to<uint64_t>()instead ofcast_to_uint64()These modifications align with modern C++ practices and make the code more maintainable. They also contribute to the PR's objective of using explicit width for finite width parameters.
src/crab/var_factory.cpp (1)
179-179: LGTM! Verify the behavior of the new casting method.The change from
offset.cast_to_uint64()tooffset.cast_to<uint64_t>()looks good. This template-based approach might provide better type safety or flexibility.To ensure the change doesn't introduce any unexpected behavior, please run the following verification:
src/crab_verifier.cpp (1)
51-52: Approve: Improved type safety and consistencyThe changes to
get_max_loop_countmethod enhance type safety and consistency:
- Replacing
fits_sint32()withfits<int32_t>()andcast_to_sint32()withcast_to<int32_t>()makes the target type explicit, improving code clarity.- This change likely aligns with a broader effort to use template-based type checking and casting throughout the codebase, promoting consistency.
- The functionality remains the same, ensuring backward compatibility.
These updates contribute to better maintainability and readability of the code.
src/crab/array_domain.cpp (5)
586-587: Improved type checking for better safety and readabilityThe change from
fits_sint32()tofits<int32_t>()is a good improvement. It uses a more standard C++ template approach for type checking, which enhances type safety and makes the code more readable. This change aligns well with modern C++ practices.
604-605: Consistent improvement in type checkingThis change is consistent with the previous modification, replacing
fits_sint32()withfits<int32_t>(). This consistency across the codebase enhances maintainability and reinforces the use of modern C++ practices. Good job on maintaining a uniform approach to type checking.
619-620: Enhanced type casting for improved flexibilityThe change from
cast_to_uint64()tocast_to<uint64_t>()is a positive improvement. This generic template approach for type casting enhances the flexibility of the code, allowing for easier adaptation to different types if needed in the future. It also maintains consistency with the other changes in this file, contributing to a more uniform and maintainable codebase.
754-755: Consistent type checking improvement throughout the fileThe change from
fits_uint32()tofits<uint32_t>()is consistent with the previous modifications in this file. This uniform approach to type checking enhances the overall code quality by improving type safety and maintainability. It's commendable to see this consistency maintained throughout the entire file, as it makes the code easier to understand and modify in the future.
Line range hint
586-755: Overall improvement in type handling and code consistencyThe changes made throughout this file represent a significant improvement in type handling and code consistency. By replacing custom functions like
fits_sint32(),fits_uint32(), andcast_to_uint64()with more standard C++ template approaches (fits<int32_t>(),fits<uint32_t>(), andcast_to<uint64_t>()), the code now benefits from:
- Enhanced type safety
- Improved readability
- Better maintainability
- Increased flexibility for future modifications
- Alignment with modern C++ practices
These consistent changes across the file demonstrate a thoughtful approach to code improvement. They make the codebase more robust and easier to work with in the long term. Great job on implementing these enhancements!
src/crab/split_dbm.cpp (2)
50-50: Improved type checking with template-based approachThe change from
n.fits_sint64()ton.fits<int64_t>()is a good improvement. It introduces a more generic, template-based approach for type checking, which enhances type safety and flexibility. This change will make it easier to adapt the code to different integer types in the future if needed.
1034-1034: Consistent improvement in type castingThe change from
k.cast_to_uint64()tok.cast_to<uint64_t>()is a positive improvement. It introduces a template-based casting method, which is more generic and aligns with modern C++ practices. This change enhances type safety and flexibility, making it consistent with the earlier modification in the file. It will make the code more adaptable to potential future changes in data types.src/crab_utils/bignums.hpp (4)
106-109: Great addition of templatedfits<T>()methodThe introduction of the templated
fits<T>()method enhances the code by providing a generic way to check if the internal value_nfits into any integral typeT, reducing code redundancy and improving maintainability.
120-128: Implementation ofcast_to<U>()improves type safetyThe new templated
cast_to<U>()method for unsigned integral types provides a type-safe way of casting the internal value_nto typeU, with appropriate fit checks to ensure correctness before casting. This enhances the robustness of the casting operations.
131-141: Enhanced casting withcast_to<S>()methodThe templated
cast_to<S>()method for signed integral types allows safe casting of the internal value_nto typeS, with necessary checks in place to prevent overflow or undefined behavior. This addition improves the flexibility and safety of the class.
170-173: Unified truncation usingtruncate_to<T>()The addition of the templated
truncate_to<T>()method provides a unified approach to truncating the internal value_nto any integral typeT. This generalization simplifies the code and eliminates the need for multiple specialized truncation functions.src/crab/ebpf_domain.cpp (10)
106-108: Proper check before casting toint64_tThe code correctly checks whether
dst_nis initialized and whetherdst_n.value()fits into anint64_tbefore casting, preventing potential overflows or undefined behavior.
Line range hint
134-138: Correct handling of equality constraints for signed and unsigned valuesThe code appropriately adds
eq(left_svalue, left_uvalue)whenright_intervalis non-negative and not a singleton, ensuring consistency between signed and unsigned representations.
236-237: Ensure intervals are correctly truncated to 64-bit signed integersThe code checks if the intervals exceed a 64-bit signed integer range and truncates them accordingly. This prevents potential overflow issues during subsequent computations.
261-262: Proper truncation of intervals to 32-bit unsigned integersThe code correctly truncates intervals to 32-bit unsigned integers when they exceed the 32-bit range, ensuring accurate interval analysis for 32-bit computations.
1517-1518: Check forfits_cast_to<int64_t>before castingThe code correctly checks if
n->fits_cast_to<int64_t>()before casting, preventing potential overflows or undefined behavior when performing the cast.
1666-1668: Proper handling of helper function IDsThe code ensures that the helper function ID fits into a 32-bit integer before proceeding, which is essential for compatibility with the eBPF helper function ID specifications.
2060-2062: Efficient computation ofmay_touch_ptrThe variable
may_touch_ptraggregates the results ofinterval.contains(desc->data),desc->meta, anddesc->end, determining if the interval may affect pointer values.
2481-2483: Handling dynamic helper function IDsThe code attempts to process dynamic helper function IDs where the ID is stored in a register. It checks if the ID fits into a 32-bit integer before processing.
2699-2700: Correct masking of shift amount to prevent undefined behaviorThe code masks
immwith(finite_width - 1)to ensure that the shift amount is within the valid range, preventing undefined behavior due to shifting by an amount equal to or greater than the bit-width.
2959-2960: Duplicate comment identifiedA previous review comment already addressed the issue regarding the potential need to truncate to
uint64. Ensure that the previous comment has been considered before making further changes.
| @@ -47,7 +47,7 @@ SplitDBM::vert_id SplitDBM::get_vert(variable_t v) { | |||
| **/ | |||
| SafeInt64DefaultParams::Weight SafeInt64DefaultParams::convert_NtoW(const z_number& n, bool& overflow) { | |||
| overflow = false; | |||
| if (!n.fits_sint64()) { | |||
| if (!n.fits<int64_t>()) { | |||
There was a problem hiding this comment.
🧹 Nitpick (assertive)
Summary: Improved type handling with template-based approaches
The two changes in this file consistently improve type checking and casting operations by introducing template-based approaches. These modifications enhance type safety, flexibility, and align the code with modern C++ practices. The changes appear to be part of a larger effort to modernize the codebase and improve its maintainability.
To fully leverage these improvements:
- Consider reviewing other parts of the codebase for similar type checking and casting operations that could benefit from this template-based approach.
- Ensure that the new template-based methods are properly documented, especially if they are part of a public API.
- If not already done, update any relevant unit tests to cover these new template-based methods.
Also applies to: 1034-1034
| } | ||
| if (const auto n = x.singleton()) { | ||
| // Divisor is a singleton: | ||
| // the linear interval solver can perform many divisions where | ||
| // the divisor is a singleton interval. We optimize for this case. | ||
| if (std::optional<number_t> n = x.singleton()) { | ||
| number_t c = *n; | ||
| if (c > number_t{0}) { | ||
| return interval_t(_lb.UMod(bound_t{c}), _ub.UMod(bound_t{c})); | ||
| } else { | ||
| // The eBPF ISA defines modulo 0 as being unchanged. | ||
| return *this; | ||
| } | ||
| number_t c = *n; | ||
| if (c > number_t{0}) { | ||
| return interval_t(_lb.URem(bound_t{c}), _ub.URem(bound_t{c})); | ||
| } | ||
| // Divisor is not a singleton | ||
| using z_interval = interval_t; | ||
| if (x[0]) { | ||
| // The divisor contains 0. | ||
| z_interval l(x._lb, z_bound(-1)); | ||
| z_interval u(z_bound(1), x._ub); | ||
| return (URem(l) | URem(u) | *this); | ||
| } else if (operator[](0)) { | ||
| // The dividend contains 0. | ||
| z_interval l(_lb, z_bound(-1)); | ||
| z_interval u(z_bound(1), _ub); | ||
| return (l.URem(x) | u.URem(x) | *this); | ||
| // The eBPF ISA defines modulo 0 as being unchanged. | ||
| return *this; | ||
| } | ||
| if (x.contains(0)) { | ||
| // The divisor contains 0. | ||
| interval_t l(x._lb, bound_t(-1)); | ||
| interval_t u(bound_t(1), x._ub); | ||
| return URem(l) | URem(u) | *this; | ||
| } else if (contains(0)) { | ||
| // The dividend contains 0. | ||
| interval_t l(_lb, bound_t(-1)); | ||
| interval_t u(bound_t(1), _ub); | ||
| return l.URem(x) | u.URem(x) | *this; | ||
| } else { | ||
| // Neither the dividend nor the divisor contains 0 | ||
| if (x._lb.is_infinite() || x._ub.is_infinite()) { | ||
| // Divisor is infinite. A "negative" dividend could result in anything except | ||
| // a value between the upper bound and 0, so set to top. A "positive" dividend | ||
| // could result in anything between 0 and the dividend - 1. | ||
| return (_ub < number_t{0}) ? top() : ((*this - interval_t(number_t{1})) | interval_t(number_t(0))); | ||
| } else if (_ub.is_finite() && (_ub.number()->cast_to<uint64_t>() < x._lb.number()->cast_to<uint64_t>())) { | ||
| // Dividend lower than divisor, so the dividend is the remainder. | ||
| return *this; | ||
| } else { | ||
| // Neither the dividend nor the divisor contains 0 | ||
| if (x._lb.is_infinite() || x._ub.is_infinite()) { | ||
| // Divisor is infinite. A "negative" dividend could result in anything except | ||
| // a value between the upper bound and 0, so set to top. A "positive" dividend | ||
| // could result in anything between 0 and the dividend - 1. | ||
| return (_ub < number_t{0}) ? top() : ((*this - interval_t(number_t{1})) | interval_t(number_t(0))); | ||
| } else if (_ub.is_finite() && (_ub.number()->cast_to_uint64() < x._lb.number()->cast_to_uint64())) { | ||
| // Dividend lower than divisor, so the dividend is the remainder. | ||
| return *this; | ||
| } else { | ||
| number_t max_divisor{x._ub.number()->cast_to_uint64()}; | ||
| return interval_t(number_t{0}, max_divisor - 1); | ||
| } | ||
| number_t max_divisor{x._ub.number()->cast_to<uint64_t>()}; | ||
| return interval_t(number_t{0}, max_divisor - 1); |
There was a problem hiding this comment.
🛠️ Refactor suggestion
Refactor common modulo logic to enhance code reuse
The SRem and URem methods have overlapping logic, particularly in handling singleton divisors and zero checks. To improve code clarity and reduce duplication, consider refactoring the shared logic into a helper function.
This change promotes reusability and aligns with best practices.
| } | ||
| assert(is_top() || (lb() >= number_t{0})); | ||
| assert(x.is_top() || (x.lb() >= number_t{0})); | ||
|
|
||
| if (left_op && right_op) { | ||
| return interval_t((*left_op) & (*right_op)); | ||
| } else if (right_op && right_op.value().fits_uint32() && right_op.value().cast_to_uint32() == UINT32_MAX) { | ||
| // Handle bitwise-AND with UINT32_MAX, which we do for 32-bit operations. | ||
| if (auto width = finite_size()) { | ||
| number_t lb32_n = (uint32_t)lb().number()->cast_to_uint64(); | ||
| number_t ub32_n = (uint32_t)ub().number()->cast_to_uint64(); | ||
| number_t width32_n = (uint32_t)width->cast_to_uint64(); | ||
| if ((width->cast_to_uint64() <= UINT32_MAX) && (lb32_n < ub32_n) && (lb32_n + width32_n == ub32_n)) { | ||
| return interval_t{lb32_n, ub32_n}; | ||
| } | ||
| if (const auto left = singleton()) { | ||
| if (const auto right = x.singleton()) { | ||
| return interval_t(*left & *right); | ||
| } | ||
| } | ||
| if (x == interval_t{std::numeric_limits<uint32_t>::max()}) { | ||
| // Handle bitwise-AND with UINT32_MAX, which we do for 32-bit operations. | ||
| if (const auto width = finite_size()) { | ||
| const number_t lb32_n = lb().number()->truncate_to<uint32_t>(); | ||
| const number_t ub32_n = ub().number()->truncate_to<uint32_t>(); | ||
| if (width->fits<uint32_t>() && lb32_n < ub32_n && lb32_n + width->truncate_to<uint32_t>() == ub32_n) { | ||
| return interval_t{lb32_n, ub32_n}; | ||
| } | ||
|
|
||
| // Return the full range of all 32-bit numbers. Use unsigned bounds to | ||
| // avoid setting other bits via sign extension. | ||
| return interval_t{number_t{0}, number_t{UINT32_MAX}}; | ||
| } else if (!is_top() && !x.is_top()) { | ||
| return interval_t(number_t{0}, bound_t::min(ub(), x.ub())); | ||
| } else if (!x.is_top()) { | ||
| return interval_t(number_t{0}, x.ub()); | ||
| } else if (!is_top()) { | ||
| return interval_t(number_t{0}, ub()); | ||
| } else { | ||
| return top(); | ||
| } | ||
| return full<uint32_t>(); | ||
| } | ||
| if (x.contains(std::numeric_limits<uint64_t>::max())) { | ||
| return truncate_to<uint64_t>(); | ||
| } else if (!is_top() && !x.is_top()) { | ||
| return interval_t(number_t{0}, std::min(ub(), x.ub())); | ||
| } else if (!x.is_top()) { | ||
| return interval_t(number_t{0}, x.ub()); | ||
| } else if (!is_top()) { | ||
| return interval_t(number_t{0}, ub()); | ||
| } else { | ||
| return top(); |
There was a problem hiding this comment.
🛠️ Refactor suggestion
Optimize And operation with known masks
In the And method, when dealing with masks like UINT32_MAX and UINT64_MAX, there's special handling to improve precision for 32-bit and 64-bit operations. To further optimize performance, consider leveraging bitwise properties or creating specialized methods for common masks.
This could enhance efficiency when performing bitwise operations with standard masks.
| const number_t k = *shift; | ||
| if (k < number_t{0}) { | ||
| // CRAB_ERROR("lshr shift operand cannot be negative"); | ||
| return top(); | ||
| } | ||
| // Some crazy linux drivers generate shl instructions with | ||
| // huge shifts. We limit the number of times the loop is run | ||
| // to avoid wasting too much time on it. | ||
| if (k <= 128) { | ||
| number_t factor = 1; | ||
| for (int i = 0; k > i; i++) { | ||
| factor *= 2; | ||
| } | ||
| return this->operator*(interval_t{factor}); | ||
| } | ||
| return top(); | ||
| } | ||
| return top(); | ||
| } | ||
|
|
||
| interval_t interval_t::AShr(const interval_t& x) const { | ||
| if (is_bottom() || x.is_bottom()) { | ||
| return bottom(); | ||
| } else { | ||
| if (std::optional<number_t> shift = x.singleton()) { | ||
| number_t k = *shift; | ||
| if (k < number_t{0}) { | ||
| // CRAB_ERROR("ashr shift operand cannot be negative"); | ||
| return top(); | ||
| } | ||
| // Some crazy linux drivers generate ashr instructions with | ||
| // huge shifts. We limit the number of times the loop is run | ||
| // to avoid wasting too much time on it. | ||
| if (k <= 128) { | ||
| number_t factor = 1; | ||
| for (int i = 0; k > i; i++) { | ||
| factor *= 2; | ||
| } | ||
| return this->operator/(interval_t{factor}); | ||
| } | ||
| if (const auto shift = x.singleton()) { | ||
| const number_t k = *shift; | ||
| if (k < number_t{0}) { | ||
| // CRAB_ERROR("ashr shift operand cannot be negative"); | ||
| return top(); | ||
| } | ||
| // Some crazy linux drivers generate ashr instructions with | ||
| // huge shifts. We limit the number of times the loop is run | ||
| // to avoid wasting too much time on it. | ||
| if (k <= 128) { | ||
| number_t factor = 1; | ||
| for (int i = 0; k > i; i++) { | ||
| factor *= 2; | ||
| } | ||
| return this->operator/(interval_t{factor}); | ||
| } | ||
| return top(); | ||
| } | ||
| return top(); | ||
| } | ||
|
|
||
| interval_t interval_t::LShr(const interval_t& x) const { | ||
| if (is_bottom() || x.is_bottom()) { | ||
| return bottom(); | ||
| } else { | ||
| if (std::optional<number_t> shift = x.singleton()) { | ||
| number_t k = *shift; | ||
| if (k < number_t{0}) { | ||
| // CRAB_ERROR("lshr shift operand cannot be negative"); | ||
| return top(); | ||
| } | ||
| // Some crazy linux drivers generate lshr instructions with | ||
| // huge shifts. We limit the number of times the loop is run | ||
| // to avoid wasting too much time on it. | ||
| if (k <= 128) { | ||
| if (lb() >= number_t{0} && ub().is_finite() && shift) { | ||
| number_t lb = *this->lb().number(); | ||
| number_t ub = *this->ub().number(); | ||
| return interval_t(lb >> k, ub >> k); | ||
| } | ||
| } | ||
| if (const auto shift = x.singleton()) { | ||
| const number_t k = *shift; | ||
| if (k < number_t{0}) { | ||
| // CRAB_ERROR("lshr shift operand cannot be negative"); | ||
| return top(); | ||
| } | ||
| // Some crazy linux drivers generate lshr instructions with | ||
| // huge shifts. We limit the number of times the loop is run | ||
| // to avoid wasting too much time on it. | ||
| if (k <= 128) { | ||
| if (lb() >= number_t{0} && ub().is_finite() && shift) { | ||
| const number_t lb = *this->lb().number(); | ||
| const number_t ub = *this->ub().number(); | ||
| return interval_t(lb >> k, ub >> k); | ||
| } | ||
| } | ||
| return top(); | ||
| } | ||
| return top(); |
There was a problem hiding this comment.
🧹 Nitpick (assertive)
Ensure consistent limit checks in shift operations
The Shl, AShr, and LShr methods enforce a limit on the shift amount (k <= 128) to prevent excessive computation. However, the comments and implementation details vary slightly between these methods.
For consistency, align the comments and structure across all shift methods:
-// Some crazy linux drivers generate shl instructions with
-// huge shifts. We limit the number of times the loop is run
-// to avoid wasting too much time on it.
+// Limit the shift amount to prevent excessive computation
if (k <= 128) {
// Existing logic
} else {
return top();
}Apply similar changes to AShr and LShr methods to maintain uniformity.
Committable suggestion was skipped due to low confidence.
| } | ||
| if (const auto n = x.singleton()) { | ||
| // Divisor is a singleton: | ||
| // the linear interval solver can perform many divisions where | ||
| // the divisor is a singleton interval. We optimize for this case. | ||
| if (std::optional<number_t> n = x.singleton()) { | ||
| number_t c = *n; | ||
| if (c == number_t{1}) { | ||
| return *this; | ||
| } else if (c > number_t{0}) { | ||
| return interval_t(_lb / bound_t{c}, _ub / bound_t{c}); | ||
| } else if (c < number_t{0}) { | ||
| return interval_t(_ub / bound_t{c}, _lb / bound_t{c}); | ||
| } else { | ||
| // The eBPF ISA defines division by 0 as resulting in 0. | ||
| return interval_t(number_t(0)); | ||
| } | ||
| } | ||
| // Divisor is not a singleton | ||
| using z_interval = interval_t; | ||
| if (x[0]) { | ||
| // The divisor contains 0. | ||
| z_interval l(x._lb, z_bound(-1)); | ||
| z_interval u(z_bound(1), x._ub); | ||
| return (operator/(l) | operator/(u) | z_interval(number_t(0))); | ||
| } else if (operator[](0)) { | ||
| // The dividend contains 0. | ||
| z_interval l(_lb, z_bound(-1)); | ||
| z_interval u(z_bound(1), _ub); | ||
| return ((l / x) | (u / x) | z_interval(number_t(0))); | ||
| number_t c = *n; | ||
| if (c == number_t{1}) { | ||
| return *this; | ||
| } else if (c > number_t{0}) { | ||
| return interval_t(_lb / bound_t{c}, _ub / bound_t{c}); | ||
| } else if (c < number_t{0}) { | ||
| return interval_t(_ub / bound_t{c}, _lb / bound_t{c}); | ||
| } else { | ||
| // Neither the dividend nor the divisor contains 0 | ||
| z_interval a = | ||
| (_ub < number_t{0}) | ||
| ? (*this + ((x._ub < number_t{0}) ? (x + z_interval(number_t(1))) : (z_interval(number_t(1)) - x))) | ||
| : *this; | ||
| bound_t ll = a._lb / x._lb; | ||
| bound_t lu = a._lb / x._ub; | ||
| bound_t ul = a._ub / x._lb; | ||
| bound_t uu = a._ub / x._ub; | ||
| return interval_t(bound_t::min(ll, lu, ul, uu), bound_t::max(ll, lu, ul, uu)); | ||
| // The eBPF ISA defines division by 0 as resulting in 0. | ||
| return interval_t(number_t(0)); | ||
| } | ||
| } | ||
| if (x.contains(0)) { | ||
| // The divisor contains 0. | ||
| interval_t l(x._lb, bound_t(-1)); | ||
| interval_t u(bound_t(1), x._ub); | ||
| return (operator/(l) | operator/(u) | interval_t(number_t(0))); | ||
| } else if (contains(0)) { | ||
| // The dividend contains 0. | ||
| interval_t l(_lb, bound_t(-1)); | ||
| interval_t u(bound_t(1), _ub); | ||
| return ((l / x) | (u / x) | interval_t(number_t(0))); | ||
| } else { | ||
| // Neither the dividend nor the divisor contains 0 | ||
| interval_t a = | ||
| (_ub < number_t{0}) | ||
| ? (*this + ((x._ub < number_t{0}) ? (x + interval_t(number_t(1))) : (interval_t(number_t(1)) - x))) | ||
| : *this; | ||
| bound_t ll = a._lb / x._lb; | ||
| bound_t lu = a._lb / x._ub; | ||
| bound_t ul = a._ub / x._lb; | ||
| bound_t uu = a._ub / x._ub; | ||
| return interval_t(std::min({ll, lu, ul, uu}), std::max({ll, lu, ul, uu})); | ||
| } |
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🛠️ Refactor suggestion
Refactor common division logic to improve maintainability
The operator/, SDiv, and UDiv methods share similar logic for handling division cases, including singleton divisors and zero checks. To adhere to the DRY (Don't Repeat Yourself) principle and enhance code maintainability, consider refactoring the shared logic into a common helper function.
You can create a private helper function like divide_interval to encapsulate the common logic:
+// Helper function for division operations
+interval_t interval_t::divide_interval(const interval_t& x, bool is_signed) const {
+ // Implement shared division logic here
+}
interval_t interval_t::operator/(const interval_t& x) const {
- // Existing division logic
+ return divide_interval(x, /*is_signed=*/true);
}
interval_t interval_t::SDiv(const interval_t& x) const {
- // Existing signed division logic
+ return divide_interval(x, /*is_signed=*/true);
}
interval_t interval_t::UDiv(const interval_t& x) const {
- // Existing unsigned division logic
+ return divide_interval(x, /*is_signed=*/false);
}Committable suggestion was skipped due to low confidence.
| if (!src_n || !src_n->fits_cast_to<int64_t>()) { | ||
| return {}; | ||
| } |
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Potential issue when casting negative values to uint64_t
After ensuring src_n.value() fits into an int64_t, the code casts it to uint64_t. If src_n.value() is negative, casting it to uint64_t may lead to unintended large positive values due to two's complement representation.
Consider checking if src_n.value() is non-negative before casting to uint64_t, or adjust the logic to handle negative values appropriately.
Also applies to: 114-117
| auto lllb = left_interval_low.truncate_to_uint(64).lb(); | ||
| if ((right_interval <= interval_t::nonnegative(64)) && (strict ? (lllb >= rub) : (lllb > rub))) { |
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Potential use of uninitialized variable lllb
The variable lllb is assigned using left_interval_low.truncate_to_uint(64).lb(), but there is no check to ensure that this lower bound is not infinite or undefined, which may lead to unexpected behavior.
Add a check to ensure lllb.number() is valid before using it in comparisons.
Apply this diff to address the issue:
auto lllb = left_interval_low.truncate_to_uint(64).lb();
+if (!lllb.number()) {
+ // Handle the case where the lower bound number is null
+ return {};
+}
if ((right_interval <= interval_t::nonnegative(64)) && (strict ? (lllb >= rub) : (lllb > rub))) {📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| auto lllb = left_interval_low.truncate_to_uint(64).lb(); | |
| if ((right_interval <= interval_t::nonnegative(64)) && (strict ? (lllb >= rub) : (lllb > rub))) { | |
| auto lllb = left_interval_low.truncate_to_uint(64).lb(); | |
| if (!lllb.number()) { | |
| // Handle the case where the lower bound number is null | |
| return {}; | |
| } | |
| if ((right_interval <= interval_t::nonnegative(64)) && (strict ? (lllb >= rub) : (lllb > rub))) { |
| int64_t lb = inv.eval_interval(left_svalue).lb().number()->cast_to<int64_t>(); | ||
|
|
||
| // Use the high 32-bits from the left lower bound and the low 32-bits from the right singleton. |
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Possible null pointer dereference of inv.eval_interval(left_svalue).lb().number()
The code assumes inv.eval_interval(left_svalue).lb().number() is not nullptr. If lb().number() is nullptr (e.g., if the lower bound is infinite), dereferencing it will cause a null pointer exception.
Add a check to ensure inv.eval_interval(left_svalue).lb().number() is not nullptr before dereferencing.
Apply this diff to address the issue:
int64_t lb = inv.eval_interval(left_svalue).lb().number()->cast_to<int64_t>();
+if (!inv.eval_interval(left_svalue).lb().number()) {
+ // Handle the case where the lower bound number is null
+ return {};
+}Committable suggestion was skipped due to low confidence.
| int64_t ub = inv.eval_interval(left_svalue).ub().number()->cast_to<int64_t>(); | ||
|
|
||
| // Use the high 32-bits from the left upper bound and the low 32-bits from the right singleton. |
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Possible null pointer dereference of inv.eval_interval(left_svalue).ub().number()
Similar to the lower bound, assuming inv.eval_interval(left_svalue).ub().number() is not nullptr may lead to a null pointer exception if the upper bound is infinite.
Add a check to ensure inv.eval_interval(left_svalue).ub().number() is not nullptr before dereferencing.
Apply this diff to address the issue:
int64_t ub = inv.eval_interval(left_svalue).ub().number()->cast_to<int64_t>();
+if (!inv.eval_interval(left_svalue).ub().number()) {
+ // Handle the case where the upper bound number is null
+ return {};
+}Committable suggestion was skipped due to low confidence.
Summary by CodeRabbit
New Features
z_numberclass for improved type casting and fitting checks.Bug Fixes
Refactor
bound_tandinterval_tclasses by simplifying method signatures and enhancing type safety.z_numberclass to utilize templates for integral type handling, improving readability and usability.