Remove special handling of zero registers in relation analysis

Signed-off-by: Hernan Ponce de Leon <[email protected]>

Author: hernanponcedeleon

dartagnan/src/main/java/com/dat3m/dartagnan/wmm/analysis/LazyRelationAnalysis.java

@@ -9,7 +9,6 @@
 import com.dat3m.dartagnan.program.analysis.ReachingDefinitionsAnalysis;
 import com.dat3m.dartagnan.program.analysis.alias.AliasAnalysis;
 import com.dat3m.dartagnan.program.event.Event;
-import com.dat3m.dartagnan.program.event.RegReader;
 import com.dat3m.dartagnan.program.event.Tag;
 import com.dat3m.dartagnan.program.event.core.*;
 import com.dat3m.dartagnan.program.filter.Filter;
@@ -33,7 +32,6 @@
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.stream.Collectors;
 
-import static com.dat3m.dartagnan.configuration.Arch.RISCV;
 import static com.dat3m.dartagnan.program.Register.UsageType.*;
 import static com.dat3m.dartagnan.program.event.Tag.FENCE;
 import static com.dat3m.dartagnan.program.event.Tag.VISIBLE;
@@ -233,24 +231,6 @@ public RelationAnalysis.Knowledge visitInternalDataDependency(DirectDataDependen
 
         private EventGraph computeInternalDependencies(Set<Register.UsageType> usageTypes) {
             Map<Event, Set<Event>> data = new HashMap<>();
-            program.getThreadEvents(RegReader.class).forEach(reader -> {
-                ReachingDefinitionsAnalysis.Writers state = definitions.getWriters(reader);
-                reader.getRegisterReads().forEach(read -> {
-                    if (usageTypes.contains(read.usageType())) {
-                        Register register = read.register();
-                        // TODO: Update after this is merged
-                        //  https://github.com/hernanponcedeleon/Dat3M/pull/741
-                        // Register x0 is hardwired to the constant 0 in RISCV
-                        // https://en.wikichip.org/wiki/risc-v/registers,
-                        // and thus it generates no dependency, see
-                        // https://github.com/herd/herdtools7/issues/408
-                        if (!program.getArch().equals(RISCV) || !register.getName().equals("x0")) {
-                            state.ofRegister(register).getMayWriters().forEach(writer ->
-                                    data.computeIfAbsent(writer, x -> new HashSet<>()).add(reader));
-                        }
-                    }
-                });
-            });
             if (usageTypes.contains(DATA)) {
                 program.getThreadEvents(ExecutionStatus.class).forEach(execStatus -> {
                     if (execStatus.doesTrackDep()) {

dartagnan/src/main/java/com/dat3m/dartagnan/wmm/analysis/NativeRelationAnalysis.java

@@ -40,7 +40,6 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-import static com.dat3m.dartagnan.configuration.Arch.RISCV;
 import static com.dat3m.dartagnan.program.Register.UsageType.*;
 import static com.dat3m.dartagnan.program.event.Tag.*;
 import static com.google.common.base.Preconditions.checkArgument;
@@ -915,16 +914,6 @@ private MutableKnowledge computeInternalDependencies(Set<UsageType> usageTypes)
                         continue;
                     }
                     final Register register = regRead.register();
-                    // TODO: Update after this is merged
-                    //  https://github.com/hernanponcedeleon/Dat3M/pull/741
-                    // Register x0 is hardwired to the constant 0 in RISCV
-                    // https://en.wikichip.org/wiki/risc-v/registers,
-                    // and thus it generates no dependency, see
-                    // https://github.com/herd/herdtools7/issues/408
-                    // TODO: Can't we just replace all reads of "x0" by 0 in RISC-specific preprocessing?
-                    if (program.getArch().equals(RISCV) && register.getName().equals("x0")) {
-                        continue;
-                    }
                     final List<? extends Event> writers = state.ofRegister(register).getMayWriters();
                     for (Event regWriter : writers) {
                         may.add(regWriter, regReader);