[llvm] [AMDGPU] LiveRegOptimizer: fix PHI same-BB filter; consider i8/i16 binops on SDWA (PR #155800)
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llvm-commits at lists.llvm.org
Thu Sep 11 04:38:45 PDT 2025
================
@@ -150,7 +184,12 @@ class LiveRegOptimizer {
if (!CVisited.insert(CII).second)
continue;
- if (CII->getParent() == II->getParent() && !IsLookThru(II))
+ // Allow same-BB non-lookthrough users when the def is a PHI:
+ // loop headers frequently consume the carried value in the header block
+ // (e.g. byte-wise vector binops). We *do* want to coerce across the
+ // backedge in that common case to enable packed i32 + SDWA lowering.
+ if (CII->getParent() == II->getParent() && !IsLookThru(CII) &&
+ !isa<PHINode>(II))
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michaelselehov wrote:
Sure, I can. Given this PR will be for isOpLegal/isProfitableSink improvement, what would you like to see separated? II->CII fix? PHI exception? Or maybe two separate PRs, one for each?
https://github.com/llvm/llvm-project/pull/155800
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