[PATCH] D158759: [RISCV] Add a pass to rewrite rd to x0 for AMO instrs whose return values are unused

[Yingwei Zheng via Phabricator via llvm-commits]

dtcxzyw added inline comments.


================
Comment at: llvm/lib/Target/RISCV/RISCVTargetMachine.cpp:398
   insertPass(&DetectDeadLanesID, &RISCVInitUndefID);
-
+  insertPass(&DetectDeadLanesID, &RISCVOptAMOInstrsID);
   TargetPassConfig::addOptimizedRegAlloc();
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craig.topper wrote:
> Does this depend on DetectDeadLanes?
> 
> AArch64 has a pass called AArch64DeadRegisterDefinitions that is inserted in addPreRegAlloc.
Yes, it currently depends on DetectDeadLanes to mark dead defs.
AArch64DeadRegisterDefinitions is better than this implementation.
I will update the implementation soon. Thank you!



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  https://reviews.llvm.org/D158759/new/

https://reviews.llvm.org/D158759