[SystemZ::TTI] Improved cost values for comparison against memory.
Single instructions exist for i8 and i16 comparisons of memory against a small immediate. This patch makes sure that if the load in these cases has a single user (the ICmp), it gets a 0 cost (folded), and also that the ICmp gets a cost of 1. Review: Ulrich Weigand https://reviews.llvm.org/D54897 llvm-svn: 347733
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@ -835,8 +835,17 @@ int SystemZTTIImpl::getCmpSelInstrCost(unsigned Opcode, Type *ValTy,
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switch (Opcode) {
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case Instruction::ICmp: {
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unsigned Cost = 1;
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if (ValTy->isIntegerTy() && ValTy->getScalarSizeInBits() <= 16)
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if (ValTy->isIntegerTy() && ValTy->getScalarSizeInBits() <= 16) {
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if (I != nullptr) {
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// Single instruction for comparison of memory with a small immediate.
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if (const LoadInst* Ld = dyn_cast<LoadInst>(I->getOperand(0))) {
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const Instruction *FoldedValue = nullptr;
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if (isFoldableLoad(Ld, FoldedValue))
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return Cost;
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}
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}
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Cost += 2; // extend both operands
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}
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return Cost;
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}
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case Instruction::Select:
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@ -932,6 +941,12 @@ isFoldableLoad(const LoadInst *Ld, const Instruction *&FoldedValue) {
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if (SExtBits || ZExtBits)
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return false;
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// Comparison between memory and immediate.
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if (UserI->getOpcode() == Instruction::ICmp)
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if (ConstantInt *CI = dyn_cast<ConstantInt>(UserI->getOperand(1)))
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if (isUInt<16>(CI->getZExtValue()))
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return true;
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unsigned LoadOrTruncBits = (TruncBits ? TruncBits : LoadedBits);
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return (LoadOrTruncBits == 32 || LoadOrTruncBits == 64);
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break;
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@ -0,0 +1,27 @@
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; RUN: opt < %s -cost-model -analyze -mtriple=systemz-unknown -mcpu=z13 | FileCheck %s
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;
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; Test costs for i8 and i16 comparisons against memory with a small immediate.
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define i32 @fun0(i8* %Src, i8* %Dst, i8 %Val) {
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; CHECK: Printing analysis 'Cost Model Analysis' for function 'fun0':
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; CHECK: Cost Model: Found an estimated cost of 0 for instruction: %Ld = load i8, i8* %Src
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; CHECK: Cost Model: Found an estimated cost of 1 for instruction: %Cmp = icmp eq i8 %Ld, 123
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; CHECK: Cost Model: Found an estimated cost of 2 for instruction: %Ret = zext i1 %Cmp to i32
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; CHECK: Cost Model: Found an estimated cost of 0 for instruction: ret i32 %Ret
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%Ld = load i8, i8* %Src
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%Cmp = icmp eq i8 %Ld, 123
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%Ret = zext i1 %Cmp to i32
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ret i32 %Ret
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}
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define i32 @fun1(i16* %Src, i16* %Dst, i16 %Val) {
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; CHECK: Printing analysis 'Cost Model Analysis' for function 'fun1':
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; CHECK: Cost Model: Found an estimated cost of 0 for instruction: %Ld = load i16, i16* %Src
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; CHECK: Cost Model: Found an estimated cost of 1 for instruction: %Cmp = icmp eq i16
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; CHECK: Cost Model: Found an estimated cost of 2 for instruction: %Ret = zext i1 %Cmp to i32
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; CHECK: Cost Model: Found an estimated cost of 0 for instruction: ret i32 %Ret
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%Ld = load i16, i16* %Src
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%Cmp = icmp eq i16 %Ld, 1234
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%Ret = zext i1 %Cmp to i32
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ret i32 %Ret
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}
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