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Don't duplicate the work done by a gep into a "bitcast" if the gep has

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more than one use.

Fixes PR10322.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134883 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2011-07-11 03:43:47 +00:00
parent f75ae4c977
commit b5a12dd12f
2 changed files with 24 additions and 0 deletions
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8
lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -785,6 +785,14 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// getelementptr instructions into a single instruction.
//
if (GEPOperator *Src = dyn_cast<GEPOperator>(PtrOp)) {
// If this GEP has only 0 indices, it is the same pointer as
// Src. If Src is not a trivial GEP too, don't combine
// the indices.
if (GEP.hasAllZeroIndices() && !Src->hasAllZeroIndices() &&
!Src->hasOneUse())
return 0;
// Note that if our source is a gep chain itself that we wait for that
// chain to be resolved before we perform this transformation. This
// avoids us creating a TON of code in some cases.

16
test/Transforms/InstCombine/getelementptr.ll
View File

@ -456,3 +456,19 @@ define i32* @test38(i32* %I, i32 %n) {
; CHECK: = sext i32 %n to i64
; CHECK: %A = getelementptr i32* %I, i64 %
}
; Test that we don't duplicate work when the second gep is a "bitcast".
%pr10322_t = type { i8* }
declare void @pr10322_f2(%pr10322_t*)
declare void @pr10322_f3(i8**)
define void @pr10322_f1(%pr10322_t* %foo) {
entry:
%arrayidx8 = getelementptr inbounds %pr10322_t* %foo, i64 2
call void @pr10322_f2(%pr10322_t* %arrayidx8) nounwind
%tmp2 = getelementptr inbounds %pr10322_t* %arrayidx8, i64 0, i32 0
call void @pr10322_f3(i8** %tmp2) nounwind
ret void
; CHECK: @pr10322_f1
; CHECK: %tmp2 = getelementptr inbounds %pr10322_t* %arrayidx8, i64 0, i32 0
}