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There are some cases where icmp(add) can be folded into a new icmp. Handle them.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46687 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -45,6 +45,7 @@
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/Support/ConstantRange.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/GetElementPtrTypeIterator.h"
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#include "llvm/Support/InstVisitor.h"
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@ -5704,6 +5705,37 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
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DivRHS))
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return R;
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break;
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case Instruction::Add:
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// Fold: icmp pred (add, X, C1), C2
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if (!ICI.isEquality()) {
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ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(1));
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if (!LHSC) break;
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const APInt &LHSV = LHSC->getValue();
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ConstantRange CR = ICI.makeConstantRange(ICI.getPredicate(), RHSV)
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.subtract(LHSV);
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if (ICI.isSignedPredicate()) {
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if (CR.getLower().isSignBit()) {
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return new ICmpInst(ICmpInst::ICMP_SLT, LHSI->getOperand(0),
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ConstantInt::get(CR.getUpper()));
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} else if (CR.getUpper().isSignBit()) {
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return new ICmpInst(ICmpInst::ICMP_SGE, LHSI->getOperand(0),
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ConstantInt::get(CR.getLower()));
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}
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} else {
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if (CR.getLower().isMinValue()) {
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return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0),
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ConstantInt::get(CR.getUpper()));
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} else if (CR.getUpper().isMinValue()) {
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return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0),
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ConstantInt::get(CR.getLower()));
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}
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}
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}
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break;
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}
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// Simplify icmp_eq and icmp_ne instructions with integer constant RHS.
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19
test/Transforms/InstCombine/2008-01-29-AddICmp.ll
Normal file
19
test/Transforms/InstCombine/2008-01-29-AddICmp.ll
Normal file
@ -0,0 +1,19 @@
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; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep {a.off}
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define i1 @test1(i32 %a) {
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%a.off = add i32 %a, 4 ; <i32> [#uses=1]
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%C = icmp ult i32 %a.off, 4 ; <i1> [#uses=1]
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ret i1 %C
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}
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define i1 @test2(i32 %a) {
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%a.off = sub i32 %a, 4 ; <i32> [#uses=1]
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%C = icmp ugt i32 %a.off, -5 ; <i1> [#uses=1]
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ret i1 %C
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}
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define i1 @test3(i32 %a) {
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%a.off = add i32 %a, 4 ; <i32> [#uses=1]
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%C = icmp slt i32 %a.off, 2147483652 ; <i1> [#uses=1]
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ret i1 %C
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}
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