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GEPs with all zero indices are trivially coalesced by fast-isel. For example,

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%arrayidx135 = getelementptr inbounds [4 x [4 x [4 x [4 x i32]]]]* %M0, i32 0, i64 0
%arrayidx136 = getelementptr inbounds [4 x [4 x [4 x i32]]]* %arrayidx135, i32 0, i64 %idxprom134

Prior to this commit, the GEP instruction that defines %arrayidx136 thought that 
%arrayidx135 was a trivial kill.  The GEP that defines %arrayidx135 doesn't 
generate any code and thus %M0 gets folded into the second GEP.  Thus, we need
to look through GEPs with all zero indices.
rdar://10443319

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144730 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chad Rosier
2011-11-15 23:34:05 +00:00
parent e43862b6a6
commit 22b34cce4d
1 changed files with 5 additions and 0 deletions
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5
lib/CodeGen/SelectionDAG/FastISel.cpp
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@@ -96,6 +96,11 @@ bool FastISel::hasTrivialKill(const Value *V) const {
!hasTrivialKill(Cast->getOperand(0))) !hasTrivialKill(Cast->getOperand(0)))
return false; return false;
// GEPs with all zero indices are trivially coalesced by fast-isel.
if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I))
if (GEP->hasAllZeroIndices() && !hasTrivialKill(GEP->getOperand(0)))
return false;
// Only instructions with a single use in the same basic block are considered // Only instructions with a single use in the same basic block are considered
// to have trivial kills. // to have trivial kills.
return I->hasOneUse() && return I->hasOneUse() &&