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[InstCombine] Fix PR24605.
PR24605 is caused due to an incorrect insert point in instcombine's IR builder. When simplifying %t = add X Y ... %m = icmp ... %t the replacement for %t should be placed before %t, not before %m, as there could be a use of %t between %t and %m. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246315 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -2140,6 +2140,12 @@ bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
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return true;
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};
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// If the overflow check was an add followed by a compare, the insertion point
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// may be pointing to the compare. We want to insert the new instructions
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// before the add in case there are uses of the add between the add and the
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// compare.
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Builder->SetInsertPoint(&OrigI);
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switch (OCF) {
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case OCF_INVALID:
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llvm_unreachable("bad overflow check kind!");
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@ -360,6 +360,11 @@ private:
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/// \brief Try to optimize a sequence of instructions checking if an operation
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/// on LHS and RHS overflows.
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///
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/// If this overflow check is done via one of the overflow check intrinsics,
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/// then CtxI has to be the call instruction calling that intrinsic. If this
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/// overflow check is done by arithmetic followed by a compare, then CtxI has
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/// to be the arithmetic instruction.
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///
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/// If a simplification is possible, stores the simplified result of the
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/// operation in OperationResult and result of the overflow check in
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/// OverflowResult, and return true. If no simplification is possible,
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15
test/Transforms/InstCombine/pr24605.ll
Normal file
15
test/Transforms/InstCombine/pr24605.ll
Normal file
@ -0,0 +1,15 @@
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; RUN: opt -S -instcombine < %s | FileCheck %s
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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define i1 @f(i8* %a, i8 %b) {
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; CHECK-LABEL: @f(
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entry:
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%or = or i8 %b, -117
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%sub = add i8 %or, -1
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store i8 %sub, i8* %a, align 1
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%cmp = icmp ugt i8 %or, %sub
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ret i1 %cmp
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; CHECK: ret i1 true
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}
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