[llvm] r216939 - Fix a logic bug when copying fast-math flags.
Sanjay Patel
spatel at rotateright.com
Tue Sep 2 13:03:00 PDT 2014
Author: spatel
Date: Tue Sep 2 15:03:00 2014
New Revision: 216939
URL: http://llvm.org/viewvc/llvm-project?rev=216939&view=rev
Log:
Fix a logic bug when copying fast-math flags.
"Setting" does not equal "copying". This bug has sat dormant for 2 reasons:
1. The unit test was not adequate.
2. Every current user of the "copyFastMathFlags" API is operating on a new instruction.
(ie, all existing fast-math flags are off). If you copy flags to an existing
instruction that has some flags on already, you will not necessarily turn them off
as expected.
I uncovered this bug while trying to implement a fix for PR20802.
Modified:
llvm/trunk/include/llvm/IR/InstrTypes.h
llvm/trunk/include/llvm/IR/Instruction.h
llvm/trunk/include/llvm/IR/Operator.h
llvm/trunk/lib/IR/Instruction.cpp
llvm/trunk/lib/IR/Instructions.cpp
llvm/trunk/unittests/IR/IRBuilderTest.cpp
Modified: llvm/trunk/include/llvm/IR/InstrTypes.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/InstrTypes.h?rev=216939&r1=216938&r2=216939&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/InstrTypes.h (original)
+++ llvm/trunk/include/llvm/IR/InstrTypes.h Tue Sep 2 15:03:00 2014
@@ -358,7 +358,7 @@ public:
/// isExact - Determine whether the exact flag is set.
bool isExact() const;
- /// Convenience method to copy wrapping, exact, and fast-math flag values
+ /// Convenience method to copy supported wrapping, exact, and fast-math flags
/// from V to this instruction.
void copyFlags(const Value *V);
Modified: llvm/trunk/include/llvm/IR/Instruction.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Instruction.h?rev=216939&r1=216938&r2=216939&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/Instruction.h (original)
+++ llvm/trunk/include/llvm/IR/Instruction.h Tue Sep 2 15:03:00 2014
@@ -230,11 +230,16 @@ public:
/// this flag.
void setHasAllowReciprocal(bool B);
- /// Convenience function for setting all the fast-math flags on this
+ /// Convenience function for setting multiple fast-math flags on this
/// instruction, which must be an operator which supports these flags. See
/// LangRef.html for the meaning of these flags.
void setFastMathFlags(FastMathFlags FMF);
+ /// Convenience function for transferring all fast-math flag values to this
+ /// instruction, which must be an operator which supports these flags. See
+ /// LangRef.html for the meaning of these flags.
+ void copyFastMathFlags(FastMathFlags FMF);
+
/// Determine whether the unsafe-algebra flag is set.
bool hasUnsafeAlgebra() const;
Modified: llvm/trunk/include/llvm/IR/Operator.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Operator.h?rev=216939&r1=216938&r2=216939&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/Operator.h (original)
+++ llvm/trunk/include/llvm/IR/Operator.h Tue Sep 2 15:03:00 2014
@@ -257,11 +257,18 @@ private:
(B * FastMathFlags::AllowReciprocal);
}
- /// Convenience function for setting all the fast-math flags
+ /// Convenience function for setting multiple fast-math flags.
+ /// FMF is a mask of the bits to set.
void setFastMathFlags(FastMathFlags FMF) {
SubclassOptionalData |= FMF.Flags;
}
+ /// Convenience function for copying all fast-math flags.
+ /// All values in FMF are transferred to this operator.
+ void copyFastMathFlags(FastMathFlags FMF) {
+ SubclassOptionalData = FMF.Flags;
+ }
+
public:
/// Test whether this operation is permitted to be
/// algebraically transformed, aka the 'A' fast-math property.
Modified: llvm/trunk/lib/IR/Instruction.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Instruction.cpp?rev=216939&r1=216938&r2=216939&view=diff
==============================================================================
--- llvm/trunk/lib/IR/Instruction.cpp (original)
+++ llvm/trunk/lib/IR/Instruction.cpp Tue Sep 2 15:03:00 2014
@@ -143,6 +143,11 @@ void Instruction::setFastMathFlags(FastM
cast<FPMathOperator>(this)->setFastMathFlags(FMF);
}
+void Instruction::copyFastMathFlags(FastMathFlags FMF) {
+ assert(isa<FPMathOperator>(this) && "copying fast-math flag on invalid op");
+ cast<FPMathOperator>(this)->copyFastMathFlags(FMF);
+}
+
/// Determine whether the unsafe-algebra flag is set.
bool Instruction::hasUnsafeAlgebra() const {
assert(isa<FPMathOperator>(this) && "getting fast-math flag on invalid op");
@@ -183,7 +188,7 @@ FastMathFlags Instruction::getFastMathFl
/// Copy I's fast-math flags
void Instruction::copyFastMathFlags(const Instruction *I) {
- setFastMathFlags(I->getFastMathFlags());
+ copyFastMathFlags(I->getFastMathFlags());
}
Modified: llvm/trunk/lib/IR/Instructions.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Instructions.cpp?rev=216939&r1=216938&r2=216939&view=diff
==============================================================================
--- llvm/trunk/lib/IR/Instructions.cpp (original)
+++ llvm/trunk/lib/IR/Instructions.cpp Tue Sep 2 15:03:00 2014
@@ -2043,7 +2043,7 @@ void BinaryOperator::copyFlags(const Val
// Copy the fast-math flags.
if (auto *FP = dyn_cast<FPMathOperator>(V))
- setFastMathFlags(FP->getFastMathFlags());
+ copyFastMathFlags(FP->getFastMathFlags());
}
//===----------------------------------------------------------------------===//
Modified: llvm/trunk/unittests/IR/IRBuilderTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/IR/IRBuilderTest.cpp?rev=216939&r1=216938&r2=216939&view=diff
==============================================================================
--- llvm/trunk/unittests/IR/IRBuilderTest.cpp (original)
+++ llvm/trunk/unittests/IR/IRBuilderTest.cpp Tue Sep 2 15:03:00 2014
@@ -189,12 +189,16 @@ TEST_F(IRBuilderTest, FastMathFlags) {
Builder.clearFastMathFlags();
+ // To test a copy, make sure that a '0' and a '1' change state.
F = Builder.CreateFDiv(F, F);
ASSERT_TRUE(isa<Instruction>(F));
FDiv = cast<Instruction>(F);
EXPECT_FALSE(FDiv->getFastMathFlags().any());
+ FDiv->setHasAllowReciprocal(true);
+ FAdd->setHasAllowReciprocal(false);
FDiv->copyFastMathFlags(FAdd);
EXPECT_TRUE(FDiv->hasNoNaNs());
+ EXPECT_FALSE(FDiv->hasAllowReciprocal());
}
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