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fix instcombine merging GEPs through a PHI to only make the 

result inbounds if all of the inputs are inbounds.

llvm-svn: 125785
This commit is contained in:
Chris Lattner 2011-02-17 22:21:26 +00:00
parent fb59c7c7d8
commit abb8eb2c63
2 changed files with 10 additions and 5 deletions
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10
llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
View File

@ -118,6 +118,8 @@ Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) {
// especially bad when the PHIs are in the header of a loop. // especially bad when the PHIs are in the header of a loop.
bool NeededPhi = false; bool NeededPhi = false;
bool AllInBounds = true;
// Scan to see if all operands are the same opcode, and all have one use. // Scan to see if all operands are the same opcode, and all have one use.
for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) { for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) {
GetElementPtrInst *GEP= dyn_cast<GetElementPtrInst>(PN.getIncomingValue(i)); GetElementPtrInst *GEP= dyn_cast<GetElementPtrInst>(PN.getIncomingValue(i));
@ -125,6 +127,8 @@ Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) {
GEP->getNumOperands() != FirstInst->getNumOperands()) GEP->getNumOperands() != FirstInst->getNumOperands())
return 0; return 0;
AllInBounds &= GEP->isInBounds();
// Keep track of whether or not all GEPs are of alloca pointers. // Keep track of whether or not all GEPs are of alloca pointers.
if (AllBasePointersAreAllocas && if (AllBasePointersAreAllocas &&
(!isa<AllocaInst>(GEP->getOperand(0)) || (!isa<AllocaInst>(GEP->getOperand(0)) ||
@ -202,11 +206,11 @@ Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) {
} }
Value *Base = FixedOperands[0]; Value *Base = FixedOperands[0];
return cast<GEPOperator>(FirstInst)->isInBounds() ? GetElementPtrInst *NewGEP =
GetElementPtrInst::CreateInBounds(Base, FixedOperands.begin()+1,
FixedOperands.end()) :
GetElementPtrInst::Create(Base, FixedOperands.begin()+1, GetElementPtrInst::Create(Base, FixedOperands.begin()+1,
FixedOperands.end()); FixedOperands.end());
if (AllInBounds) NewGEP->setIsInbounds();
return NewGEP;
} }

5
llvm/test/Transforms/InstCombine/phi.ll
View File

@ -125,7 +125,7 @@ Exit: ; preds = %Loop
define i32* @test8({ i32, i32 } *%A, i1 %b) { define i32* @test8({ i32, i32 } *%A, i1 %b) {
BB0: BB0:
%X = getelementptr { i32, i32 } *%A, i32 0, i32 1 %X = getelementptr inbounds { i32, i32 } *%A, i32 0, i32 1
br i1 %b, label %BB1, label %BB2 br i1 %b, label %BB1, label %BB2
BB1: BB1:
@ -139,7 +139,7 @@ BB2:
; CHECK: @test8 ; CHECK: @test8
; CHECK-NOT: phi ; CHECK-NOT: phi
; CHECK: BB2: ; CHECK: BB2:
; CHECK-NEXT: %B = getelementptr ; CHECK-NEXT: %B = getelementptr %0
; CHECK-NEXT: ret i32* %B ; CHECK-NEXT: ret i32* %B
} }
@ -525,3 +525,4 @@ Exit: ; preds = %Loop
; CHECK: Exit: ; CHECK: Exit:
; CHECK-NEXT: ret i32 %B ; CHECK-NEXT: ret i32 %B
} }