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

%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

llvm-svn: 144730
This commit is contained in:
Chad Rosier 2011-11-15 23:34:05 +00:00
parent 78286b24fd
commit 291ce47db7
1 changed files with 5 additions and 0 deletions
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5
llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
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@ -96,6 +96,11 @@ bool FastISel::hasTrivialKill(const Value *V) const {
!hasTrivialKill(Cast->getOperand(0)))
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
// to have trivial kills.
return I->hasOneUse() &&