[PATCH] D113017: [AMDGPU] Avoid copying dead subregisters in copyPhysReg

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

I wonder if we would be better off trying to break these copies into individual subregister pieces before we discard liveness information. Recomputing physreg liveness all over the place isn't exactly cheap



================
Comment at: llvm/lib/Target/AMDGPU/SIInstrInfo.cpp:909-910
+
+    if (LiveRegs.available(MRI, SrcSubReg))
+      continue;
+
----------------
I don't understand how you can simply skip here


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  https://reviews.llvm.org/D113017/new/

https://reviews.llvm.org/D113017