[PATCH] D157495: [WIP] Run SimplifyCFG from Atomic-Expand on CAS loop blocks.

[Pravin Jagtap via Phabricator via llvm-commits]

pravinjagtap added inline comments.


================
Comment at: llvm/lib/CodeGen/AtomicExpandPass.cpp:1524
       BB->splitBasicBlock(Builder.GetInsertPoint(), "atomicrmw.end");
+  CmpXchgLoopBlocks.push_back(ExitBB);
   BasicBlock *LoopBB = BasicBlock::Create(Ctx, "atomicrmw.start", F, ExitBB);
----------------
rovka wrote:
> Why are we only keeping track of these blocks? There seem to be lots of other places in this file that split blocks and create new ones. Shouldn't we call simplifyCFG for all of them?
> Why are we only keeping track of these blocks? There seem to be lots of other places in this file that split blocks and create new ones. Shouldn't we call simplifyCFG for all of them?

Targets can configure this simplification using separate pass run e.g. Aarch64 is running simplifyCFG after atomic expand pass https://github.com/llvm/llvm-project/blob/57c090b2ea03937e7c6a08a594532788d01bb813/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp#L557

We think, having separate pass run will be expensive, therefore, for AMDGPU usecase, we are interested in running it on local changes done by atomic-expand. Do you think, calling `simplifyCFG` on entire functions makes much more sense ?




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https://reviews.llvm.org/D157495