nikic added inline comments.
================
Comment at: llvm/lib/Transforms/InstCombine/InstructionCombining.cpp:2336
+ // Try to reassociate loop invariant index calculations to enable LICM.
+ if (Idx && (Idx->getOpcode() == Instruction::Add)) {
+ Value *Ptr = GEP.getOperand(0);
----------------
This needs a one-use check. The transform is not profitable if we have to keep
*both* the add and the gep.
Can also use `match(GEP.getOperand(1), m_Add(...))` here.
================
Comment at: llvm/lib/Transforms/InstCombine/InstructionCombining.cpp:2339
+ Value *InvIdx = Idx->getOperand(0);
+ Value *NonInvIdx = Idx->getOperand(1);
+
----------------
This no longer checks for loop invariance, so we should remove any
invariance-related terminology.
================
Comment at: llvm/lib/Transforms/InstCombine/InstructionCombining.cpp:2351
+ NewPtr, NonInvIdx);
+ NewGEP->setIsInBounds(GEP.isInBounds());
+ return NewGEP;
----------------
This inbounds preservation is incorrect: https://alive2.llvm.org/ce/z/bJZvQG
It's even incorrect if the add is also nsw.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D155688/new/
https://reviews.llvm.org/D155688
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