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[CodeGen] Fix hashing for MO_ExternalSymbol MachineOperands. 

We were hashing the string pointer, not the string, so two instructions
could be identical (isIdenticalTo), but have different hash codes.

This showed up as a very rare, non-deterministic assertion failure
rehashing a DenseMap constructed by MachineOutliner.  So there's no
"real" testcase, just a unittest which checks that the hash function
behaves correctly.

I'm a little scared fixing this is going to cause a regression in
outlining or MachineCSE, but hopefully we won't run into any issues.

Differential Revision: https://reviews.llvm.org/D61975

llvm-svn: 362281
This commit is contained in:
Eli Friedman 2019-06-01 00:08:54 +00:00
parent eb4d6142dc
commit d8e8722791
2 changed files with 11 additions and 1 deletions
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2
llvm/lib/CodeGen/MachineOperand.cpp
View File

@ -361,7 +361,7 @@ hash_code llvm::hash_value(const MachineOperand &MO) {
return hash_combine(MO.getType(), MO.getTargetFlags(), MO.getIndex());
case MachineOperand::MO_ExternalSymbol:
return hash_combine(MO.getType(), MO.getTargetFlags(), MO.getOffset(),
MO.getSymbolName());
StringRef(MO.getSymbolName()));
case MachineOperand::MO_GlobalAddress:
return hash_combine(MO.getType(), MO.getTargetFlags(), MO.getGlobal(),
MO.getOffset());

10
llvm/unittests/CodeGen/MachineOperandTest.cpp
View File

@ -398,4 +398,14 @@ TEST(MachineOperandTest, PrintPredicate) {
ASSERT_TRUE(OS.str() == "intpred(eq)");
}
TEST(MachineOperandTest, HashValue) {
char SymName1[] = "test";
char SymName2[] = "test";
MachineOperand MO1 = MachineOperand::CreateES(SymName1);
MachineOperand MO2 = MachineOperand::CreateES(SymName2);
ASSERT_NE(SymName1, SymName2);
ASSERT_EQ(hash_value(MO1), hash_value(MO2));
ASSERT_TRUE(MO1.isIdenticalTo(MO2));
}
} // end namespace