[PATCH] D87479: [InstCombine] Don't sink the fdiv from (fmul (fdiv 1.0, %x), %y) if the fdiv isn't in the same basic block as the fmul

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

In D87479#2267835 <https://reviews.llvm.org/D87479#2267835>, @spatel wrote:

> In D87479#2266829 <https://reviews.llvm.org/D87479#2266829>, @craig.topper wrote:
>
>> We don't seem to run LICM after InstCombine in the LTO pipeline if I'm reading the pass manager correctly.
>
> That seems like the root bug...although a 1st hack at changing that didn't result in any regression test fails in llvm/test/Other/* .
> If we are inverting this fdiv pattern, then aren't we doing that to all kinds of other loop invariant opportunities too?

Actually, we do have some coverage for the new pass manager at least. I got that to wiggle with:

  diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
  index bae84784628..acc937cb202 100644
  --- a/llvm/lib/Passes/PassBuilder.cpp
  +++ b/llvm/lib/Passes/PassBuilder.cpp
  @@ -1576,6 +1576,9 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level, bool DebugLogging,
     MainFPM.addPass(InstCombinePass());
     invokePeepholeEPCallbacks(MainFPM, Level);
     MainFPM.addPass(JumpThreadingPass(/*InsertFreezeWhenUnfoldingSelect*/ true));
  +  MainFPM.addPass(createFunctionToLoopPassAdaptor(
  +      LICMPass(PTO.LicmMssaOptCap, PTO.LicmMssaNoAccForPromotionCap),
  +      EnableMSSALoopDependency, DebugLogging));
     MPM.addPass(createModuleToFunctionPassAdaptor(std::move(MainFPM)));
   
     // Create a function that performs CFI checks for cross-DSO calls with


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https://reviews.llvm.org/D87479