[Clang] Ignore empty FieldDecls when asking for the field number (#100040)

A FieldDecl that's an empty struct may not show up in CGRecordLayout. Go
ahead and ignore such a field as it shouldn't make a difference to these
calculations.

Fixes: 1f6f97e ("[Clang] Loop over FieldDecls instead of all Decls (#99574)")
Co-authored-by: Eli Friedman <[email protected]>

Author: 2 people

clang/lib/CodeGen/CGExpr.cpp

@@ -1076,6 +1076,11 @@ static bool getGEPIndicesToField(CodeGenFunction &CGF, const RecordDecl *RD,
   const CGRecordLayout &Layout = CGF.CGM.getTypes().getCGRecordLayout(RD);
   int64_t FieldNo = -1;
   for (const FieldDecl *FD : RD->fields()) {
+    if (!Layout.containsFieldDecl(FD))
+      // This could happen if the field has a struct type that's empty. I don't
+      // know why either.
+      continue;
+
     FieldNo = Layout.getLLVMFieldNo(FD);
     if (FD == Field) {
       Indices.emplace_back(std::make_pair(RD, CGF.Builder.getInt32(FieldNo)));

clang/lib/CodeGen/CGRecordLayout.h

@@ -193,6 +193,10 @@ class CGRecordLayout {
     return IsZeroInitializableAsBase;
   }
 
+  bool containsFieldDecl(const FieldDecl *FD) const {
+    return FieldInfo.count(FD) != 0;
+  }
+
   /// Return llvm::StructType element number that corresponds to the
   /// field FD.
   unsigned getLLVMFieldNo(const FieldDecl *FD) const {

clang/test/CodeGen/attr-counted-by.c

@@ -1906,3 +1906,51 @@ struct test30_struct {
 void test30(struct test30_struct *ptr, int idx) {
   ptr->pcpu_refcnt.__padding[idx] = __builtin_dynamic_object_size(ptr, 1);
 }
+
+struct test31_empty {};
+
+struct test31_struct {
+  struct test31_empty y;
+  int s;
+  int x[] __counted_by(s);
+};
+
+// SANITIZE-WITH-ATTR-LABEL: define dso_local i32 @test31(
+// SANITIZE-WITH-ATTR-SAME: ptr nocapture noundef readonly [[PTR:%.*]], i32 noundef [[IDX:%.*]]) local_unnamed_addr #[[ATTR2]] {
+// SANITIZE-WITH-ATTR-NEXT:  entry:
+// SANITIZE-WITH-ATTR-NEXT:    [[DOT_COUNTED_BY_LOAD:%.*]] = load i32, ptr [[PTR]], align 4
+// SANITIZE-WITH-ATTR-NEXT:    [[TMP0:%.*]] = sext i32 [[DOT_COUNTED_BY_LOAD]] to i64
+// SANITIZE-WITH-ATTR-NEXT:    [[TMP1:%.*]] = shl nsw i64 [[TMP0]], 2
+// SANITIZE-WITH-ATTR-NEXT:    [[TMP2:%.*]] = tail call i64 @llvm.smax.i64(i64 [[TMP1]], i64 0)
+// SANITIZE-WITH-ATTR-NEXT:    [[TMP3:%.*]] = trunc i64 [[TMP2]] to i32
+// SANITIZE-WITH-ATTR-NEXT:    [[TMP4:%.*]] = add i32 [[TMP3]], 4
+// SANITIZE-WITH-ATTR-NEXT:    [[DOTINV:%.*]] = icmp slt i32 [[DOT_COUNTED_BY_LOAD]], 0
+// SANITIZE-WITH-ATTR-NEXT:    [[CONV:%.*]] = select i1 [[DOTINV]], i32 0, i32 [[TMP4]]
+// SANITIZE-WITH-ATTR-NEXT:    ret i32 [[CONV]]
+//
+// NO-SANITIZE-WITH-ATTR-LABEL: define dso_local i32 @test31(
+// NO-SANITIZE-WITH-ATTR-SAME: ptr nocapture noundef readonly [[PTR:%.*]], i32 noundef [[IDX:%.*]]) local_unnamed_addr #[[ATTR2]] {
+// NO-SANITIZE-WITH-ATTR-NEXT:  entry:
+// NO-SANITIZE-WITH-ATTR-NEXT:    [[DOT_COUNTED_BY_LOAD:%.*]] = load i32, ptr [[PTR]], align 4
+// NO-SANITIZE-WITH-ATTR-NEXT:    [[TMP0:%.*]] = sext i32 [[DOT_COUNTED_BY_LOAD]] to i64
+// NO-SANITIZE-WITH-ATTR-NEXT:    [[TMP1:%.*]] = shl nsw i64 [[TMP0]], 2
+// NO-SANITIZE-WITH-ATTR-NEXT:    [[TMP2:%.*]] = tail call i64 @llvm.smax.i64(i64 [[TMP1]], i64 0)
+// NO-SANITIZE-WITH-ATTR-NEXT:    [[TMP3:%.*]] = trunc i64 [[TMP2]] to i32
+// NO-SANITIZE-WITH-ATTR-NEXT:    [[TMP4:%.*]] = add i32 [[TMP3]], 4
+// NO-SANITIZE-WITH-ATTR-NEXT:    [[DOTINV:%.*]] = icmp slt i32 [[DOT_COUNTED_BY_LOAD]], 0
+// NO-SANITIZE-WITH-ATTR-NEXT:    [[CONV:%.*]] = select i1 [[DOTINV]], i32 0, i32 [[TMP4]]
+// NO-SANITIZE-WITH-ATTR-NEXT:    ret i32 [[CONV]]
+//
+// SANITIZE-WITHOUT-ATTR-LABEL: define dso_local i32 @test31(
+// SANITIZE-WITHOUT-ATTR-SAME: ptr noundef [[PTR:%.*]], i32 noundef [[IDX:%.*]]) local_unnamed_addr #[[ATTR2]] {
+// SANITIZE-WITHOUT-ATTR-NEXT:  entry:
+// SANITIZE-WITHOUT-ATTR-NEXT:    ret i32 -1
+//
+// NO-SANITIZE-WITHOUT-ATTR-LABEL: define dso_local i32 @test31(
+// NO-SANITIZE-WITHOUT-ATTR-SAME: ptr noundef [[PTR:%.*]], i32 noundef [[IDX:%.*]]) local_unnamed_addr #[[ATTR1]] {
+// NO-SANITIZE-WITHOUT-ATTR-NEXT:  entry:
+// NO-SANITIZE-WITHOUT-ATTR-NEXT:    ret i32 -1
+//
+int test31(struct test31_struct *ptr, int idx) {
+  return __builtin_dynamic_object_size(ptr, 0);
+}