//===----------------------------------------------------------------------===//
#include "InstCombine.h"
-#include "llvm/IntrinsicInst.h"
#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Support/PatternMatch.h"
using namespace llvm;
using namespace PatternMatch;
return Changed ? &I : 0;
}
+//
+// Detect pattern:
+//
+// log2(Y*0.5)
+//
+// And check for corresponding fast math flags
+//
+
+static void detectLog2OfHalf(Value *&Op, Value *&Y, IntrinsicInst *&Log2) {
+
+ if (!Op->hasOneUse())
+ return;
+
+ IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op);
+ if (!II)
+ return;
+ if (II->getIntrinsicID() != Intrinsic::log2 || !II->hasUnsafeAlgebra())
+ return;
+ Log2 = II;
+
+ Value *OpLog2Of = II->getArgOperand(0);
+ if (!OpLog2Of->hasOneUse())
+ return;
+
+ Instruction *I = dyn_cast<Instruction>(OpLog2Of);
+ if (!I)
+ return;
+ if (I->getOpcode() != Instruction::FMul || !I->hasUnsafeAlgebra())
+ return;
+
+ ConstantFP *CFP = dyn_cast<ConstantFP>(I->getOperand(0));
+ if (CFP && CFP->isExactlyValue(0.5)) {
+ Y = I->getOperand(1);
+ return;
+ }
+ CFP = dyn_cast<ConstantFP>(I->getOperand(1));
+ if (CFP && CFP->isExactlyValue(0.5))
+ Y = I->getOperand(0);
+}
+
Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
bool Changed = SimplifyAssociativeOrCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Value *Op1v = dyn_castFNegVal(Op1))
return BinaryOperator::CreateFMul(Op0v, Op1v);
+ // Under unsafe algebra do:
+ // X * log2(0.5*Y) = X*log2(Y) - X
+ if (I.hasUnsafeAlgebra()) {
+ Value *OpX = NULL;
+ Value *OpY = NULL;
+ IntrinsicInst *Log2;
+ detectLog2OfHalf(Op0, OpY, Log2);
+ if (OpY) {
+ OpX = Op1;
+ } else {
+ detectLog2OfHalf(Op1, OpY, Log2);
+ if (OpY) {
+ OpX = Op0;
+ }
+ }
+ // if pattern detected emit alternate sequence
+ if (OpX && OpY) {
+ Log2->setArgOperand(0, OpY);
+ Value *FMulVal = Builder->CreateFMul(OpX, Log2);
+ Instruction *FMul = cast<Instruction>(FMulVal);
+ FMul->copyFastMathFlags(Log2);
+ Instruction *FSub = BinaryOperator::CreateFSub(FMulVal, OpX);
+ FSub->copyFastMathFlags(Log2);
+ return FSub;
+ }
+ }
+
return Changed ? &I : 0;
}