[llvm] [AMDGPU] LiveRegOptimizer: fix PHI same-BB filter; consider i8/i16 binops on SDWA (PR #155800)

[via llvm-commits]

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@@ -126,7 +126,37 @@ class LiveRegOptimizer {
     return LK.first != TargetLoweringBase::TypeLegal;
   }
 
-  bool isOpLegal(Instruction *I) { return isa<StoreInst, IntrinsicInst>(I); }
+  bool isOpLegal(Instruction *I) {
+    if (auto *Intr = dyn_cast<IntrinsicInst>(I))
+      return true; // FIXME: narrow to known native intrinsics (DOT/MFMA/tbuffer) or use TTI cost.
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michaelselehov wrote:

Thanks. I'll look what TTI can provide. If TTI already provides a reliable signal for these cases, I’ll switch the gate to be TTI-only. If it doesn’t, I'm not sure if the change to TTI should be a part of this PR.

https://github.com/llvm/llvm-project/pull/155800