[PATCH] D94470: [LSR] Don't break a critical edge if parent ends with "callbr"

[Bill Wendling via Phabricator via llvm-commits]

void added inline comments.


================
Comment at: llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:5594-5595
+
+       // Also bail out if we have a PHI with a value from a block ending in a
+       // CallBrInst, because those also can't be split for similar reasons.
+       for (BasicBlock *PredBB : PN->blocks())
----------------
nickdesaulniers wrote:
> MaskRay wrote:
> > void wrote:
> > > nickdesaulniers wrote:
> > > > Can this comment be made more precise, I don't think what's described is what's being tested?
> > > It's pretty accurate as is. :) I'm not sure how else to word it.
> > The change only affects `llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp`, not any codegen part, so I hope this can be tested with opt. Usually this should check the produced instructions.
> > 
> > If the resulting IR is correct but codegen somehow crashes, then it is probably a codegen bug which should be separately fixed. If the output IR is actually incorrect, then the IR verifier should be fixed instead.
> > 
> > Anyway I think the test should be added in an appropriate place and if this uncovers other issues those other issues should be reported as well.
> Ah, yes sorry, I was looking at the first `phi` thinking WTF; didn't notice the second `phi` until just now.
It appears that this pass is added only during code-gen:

```
llvm/lib/CodeGen/TargetPassConfig.cpp:      addPass(createLoopStrengthReducePass());
llvm/lib/Passes/PassBuilder.cpp:#include "llvm/Transforms/Scalar/LoopStrengthReduce.h"
llvm/lib/Passes/PassRegistry.def:LOOP_PASS("loop-reduce", LoopStrengthReducePass())
llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp:/// (LoopStrengthReduce.cpp) and memory optimization for address mode
llvm/lib/Target/NVPTX/NVPTXISelLowering.h:  /// reduction (LoopStrengthReduce.cpp) and memory optimization for
llvm/lib/Transforms/Scalar/CMakeLists.txt:  LoopStrengthReduce.cpp
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp://===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===//
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:#include "llvm/Transforms/Scalar/LoopStrengthReduce.h"
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:class LoopStrengthReduce : public LoopPass {
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:  LoopStrengthReduce();
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) {
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:  initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:PreservedAnalyses LoopStrengthReducePass::run(Loop &L, LoopAnalysisManager &AM,
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:char LoopStrengthReduce::ID = 0;
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:Pass *llvm::createLoopStrengthReducePass() { return new LoopStrengthReduce(); }
llvm/lib/Transforms/Scalar/Scalar.cpp:  initializeLoopStrengthReducePass(Registry);
```


Repository:
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  https://reviews.llvm.org/D94470/new/

https://reviews.llvm.org/D94470