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Fast-math optimization: fold multiply by zero

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Added in first optimization using fast-math flags to serve as an example for following optimizations. SimplifyInstruction will now try to optimize an fmul observing its FastMathFlags to see if it can fold multiply by zero when 'nnan' and 'nsz' flags are set.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168648 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Ilseman 2012-11-27 00:46:26 +00:00
parent a52f3ae45c
commit eb61c920f1
2 changed files with 48 additions and 0 deletions
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9
include/llvm/Analysis/InstructionSimplify.h
View File

@ -25,6 +25,7 @@ namespace llvm {
class DominatorTree;
class Instruction;
class DataLayout;
struct FastMathFlags;
class TargetLibraryInfo;
class Type;
class Value;
@ -43,6 +44,14 @@ namespace llvm {
const TargetLibraryInfo *TLI = 0,
const DominatorTree *DT = 0);
/// Given operands for an FMul, see if we can fold the result. If not, this
/// returns null.
Value *SimplifyFMulInst(Value *LHS, Value *RHS,
FastMathFlags FMF,
const DataLayout *TD = 0,
const TargetLibraryInfo *TLI = 0,
const DominatorTree *DT = 0);
/// SimplifyMulInst - Given operands for a Mul, see if we can
/// fold the result. If not, this returns null.
Value *SimplifyMulInst(Value *LHS, Value *RHS, const DataLayout *TD = 0,

39
lib/Analysis/InstructionSimplify.cpp
View File

@ -886,6 +886,33 @@ Value *llvm::SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
RecursionLimit);
}
/// Given the operands for an FMul, see if we can fold the result
static Value *SimplifyFMulInst(Value *Op0, Value *Op1,
FastMathFlags FMF,
const Query &Q,
unsigned MaxRecurse) {
if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
Constant *Ops[] = { CLHS, CRHS };
return ConstantFoldInstOperands(Instruction::FMul, CLHS->getType(),
Ops, Q.TD, Q.TLI);
}
}
// Check for some fast-math optimizations
if (FMF.NoNaNs) {
if (FMF.NoSignedZeros) {
// fmul N S 0, x ==> 0
if (match(Op0, m_Zero()))
return Op0;
if (match(Op1, m_Zero()))
return Op1;
}
}
return 0;
}
/// SimplifyMulInst - Given operands for a Mul, see if we can
/// fold the result. If not, this returns null.
static Value *SimplifyMulInst(Value *Op0, Value *Op1, const Query &Q,
@ -951,6 +978,14 @@ static Value *SimplifyMulInst(Value *Op0, Value *Op1, const Query &Q,
return 0;
}
Value *llvm::SimplifyFMulInst(Value *Op0, Value *Op1,
FastMathFlags FMF,
const DataLayout *TD,
const TargetLibraryInfo *TLI,
const DominatorTree *DT) {
return ::SimplifyFMulInst(Op0, Op1, FMF, Query (TD, TLI, DT), RecursionLimit);
}
Value *llvm::SimplifyMulInst(Value *Op0, Value *Op1, const DataLayout *TD,
const TargetLibraryInfo *TLI,
const DominatorTree *DT) {
@ -2799,6 +2834,10 @@ Value *llvm::SimplifyInstruction(Instruction *I, const DataLayout *TD,
cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
TD, TLI, DT);
break;
case Instruction::FMul:
Result = SimplifyFMulInst(I->getOperand(0), I->getOperand(1),
I->getFastMathFlags(), TD, TLI, DT);
break;
case Instruction::Mul:
Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT);
break;