diff options
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstructionCombining.cpp | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp index 52519acb33f..94a7a4c5030 100644 --- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp +++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -1670,6 +1670,23 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) { if (!shouldMergeGEPs(*cast<GEPOperator>(&GEP), *Src)) return nullptr; + // Try to reassociate loop invariant GEP chains to enable LICM. + if (LI && Src->getNumOperands() == 2 && GEP.getNumOperands() == 2 && + Src->hasOneUse()) { + if (Loop *L = LI->getLoopFor(GEP.getParent())) { + Value *GO1 = GEP.getOperand(1); + Value *SO1 = Src->getOperand(1); + // Reassociate the two GEPs if SO1 is variant in the loop and GO1 is + // invariant: this breaks the dependence between GEPs and allows LICM + // to hoist the invariant part out of the loop. + if (L->isLoopInvariant(GO1) && !L->isLoopInvariant(SO1)) { + Src->setOperand(1, GO1); + GEP.setOperand(1, SO1); + return &GEP; + } + } + } + // Note that if our source is a gep chain itself then we wait for that // chain to be resolved before we perform this transformation. This // avoids us creating a TON of code in some cases. |
