[PATCH] D118037: [DAGCombine] Consider SETULT as carry flag

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


================
Comment at: llvm/test/CodeGen/X86/addcarry.ll:1029
 ; CHECK-NEXT:    cmpl %ecx, %edx
-; CHECK-NEXT:    adcl $0, %eax
+; CHECK-NEXT:    adcl %esi, %eax
 ; CHECK-NEXT:    retq
----------------
This case looks like an easy X86 backend peephole.

X86ISD::ADC with an unused flag result, 0 for RHS, LHS is a single use ADD. If so fold the ADD operands into a new X86ISD::ADC.

I'm not sure about the @add_U320_without_i128_add case without staring at it for a lot longer.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D118037/new/

https://reviews.llvm.org/D118037