[PATCH] D156164: [HACK] X86: Disable isCopyInstrImpl for undef subregister defs

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


================
Comment at: llvm/lib/Target/X86/X86InstrInfo.cpp:3657
+      return std::nullopt;
+
     return DestSourcePair{MI.getOperand(0), MI.getOperand(1)};
----------------
I should have a more general fix ready tomorrow which adds an implicit-def during coalescing. The handling here then needs to guard against implicit-defs (and report the full def super register intsead of the physical subreg undef def)


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  https://reviews.llvm.org/D156164/new/

https://reviews.llvm.org/D156164