InstSimplify: Eliminate fabs on known positive
llvm-svn: 291624
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 8da2f09..73dcd71 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4308,10 +4308,21 @@
return nullptr;
// Unary Ops
- if (NumOperands == 1)
- if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(*ArgBegin))
+ if (NumOperands == 1) {
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(*ArgBegin)) {
if (II->getIntrinsicID() == IID)
return II;
+ }
+
+ switch (IID) {
+ case Intrinsic::fabs: {
+ if (SignBitMustBeZero(*ArgBegin, Q.TLI))
+ return *ArgBegin;
+ }
+ default:
+ break;
+ }
+ }
return nullptr;
}
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index d31472c..b98c962 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2580,51 +2580,70 @@
return false;
}
-bool llvm::CannotBeOrderedLessThanZero(const Value *V,
- const TargetLibraryInfo *TLI,
- unsigned Depth) {
- if (const ConstantFP *CFP = dyn_cast<ConstantFP>(V))
- return !CFP->getValueAPF().isNegative() || CFP->getValueAPF().isZero();
+/// If \p SignBitOnly is true, test for a known 0 sign bit rather than a
+/// standard ordered compare. e.g. make -0.0 olt 0.0 be true because of the sign
+/// bit despite comparing equal.
+static bool cannotBeOrderedLessThanZeroImpl(const Value *V,
+ const TargetLibraryInfo *TLI,
+ bool SignBitOnly,
+ unsigned Depth) {
+ if (const ConstantFP *CFP = dyn_cast<ConstantFP>(V)) {
+ return !CFP->getValueAPF().isNegative() ||
+ (!SignBitOnly && CFP->getValueAPF().isZero());
+ }
if (Depth == MaxDepth)
- return false; // Limit search depth.
+ return false; // Limit search depth.
const Operator *I = dyn_cast<Operator>(V);
- if (!I) return false;
+ if (!I)
+ return false;
switch (I->getOpcode()) {
- default: break;
+ default:
+ break;
// Unsigned integers are always nonnegative.
case Instruction::UIToFP:
return true;
case Instruction::FMul:
// x*x is always non-negative or a NaN.
- if (I->getOperand(0) == I->getOperand(1))
+ if (I->getOperand(0) == I->getOperand(1) &&
+ (!SignBitOnly || cast<FPMathOperator>(I)->hasNoNaNs()))
return true;
+
LLVM_FALLTHROUGH;
case Instruction::FAdd:
case Instruction::FDiv:
case Instruction::FRem:
- return CannotBeOrderedLessThanZero(I->getOperand(0), TLI, Depth + 1) &&
- CannotBeOrderedLessThanZero(I->getOperand(1), TLI, Depth + 1);
+ return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
+ Depth + 1) &&
+ cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
+ Depth + 1);
case Instruction::Select:
- return CannotBeOrderedLessThanZero(I->getOperand(1), TLI, Depth + 1) &&
- CannotBeOrderedLessThanZero(I->getOperand(2), TLI, Depth + 1);
+ return cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
+ Depth + 1) &&
+ cannotBeOrderedLessThanZeroImpl(I->getOperand(2), TLI, SignBitOnly,
+ Depth + 1);
case Instruction::FPExt:
case Instruction::FPTrunc:
// Widening/narrowing never change sign.
- return CannotBeOrderedLessThanZero(I->getOperand(0), TLI, Depth + 1);
+ return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
+ Depth + 1);
case Instruction::Call:
Intrinsic::ID IID = getIntrinsicForCallSite(cast<CallInst>(I), TLI);
switch (IID) {
default:
break;
case Intrinsic::maxnum:
- return CannotBeOrderedLessThanZero(I->getOperand(0), TLI, Depth + 1) ||
- CannotBeOrderedLessThanZero(I->getOperand(1), TLI, Depth + 1);
+ return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
+ Depth + 1) ||
+ cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
+ Depth + 1);
case Intrinsic::minnum:
- return CannotBeOrderedLessThanZero(I->getOperand(0), TLI, Depth + 1) &&
- CannotBeOrderedLessThanZero(I->getOperand(1), TLI, Depth + 1);
+ return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
+ Depth + 1) &&
+ cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
+ Depth + 1);
case Intrinsic::exp:
case Intrinsic::exp2:
case Intrinsic::fabs:
@@ -2636,18 +2655,30 @@
if (CI->getBitWidth() <= 64 && CI->getSExtValue() % 2u == 0)
return true;
}
- return CannotBeOrderedLessThanZero(I->getOperand(0), TLI, Depth + 1);
+ return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
+ Depth + 1);
case Intrinsic::fma:
case Intrinsic::fmuladd:
// x*x+y is non-negative if y is non-negative.
return I->getOperand(0) == I->getOperand(1) &&
- CannotBeOrderedLessThanZero(I->getOperand(2), TLI, Depth + 1);
+ (!SignBitOnly || cast<FPMathOperator>(I)->hasNoNaNs()) &&
+ cannotBeOrderedLessThanZeroImpl(I->getOperand(2), TLI, SignBitOnly,
+ Depth + 1);
}
break;
}
return false;
}
+bool llvm::CannotBeOrderedLessThanZero(const Value *V,
+ const TargetLibraryInfo *TLI) {
+ return cannotBeOrderedLessThanZeroImpl(V, TLI, false, 0);
+}
+
+bool llvm::SignBitMustBeZero(const Value *V, const TargetLibraryInfo *TLI) {
+ return cannotBeOrderedLessThanZeroImpl(V, TLI, true, 0);
+}
+
/// If the specified value can be set by repeating the same byte in memory,
/// return the i8 value that it is represented with. This is
/// true for all i8 values obviously, but is also true for i32 0, i32 -1,