[PATCH] D64174: [DAGCombine] Do several rounds of combine for addcarry nodes.

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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Comment at: test/CodeGen/X86/addcarry.ll:326
+; CHECK-NEXT:    adcq %rdi, %rbx
+; CHECK-NEXT:    addq %r10, %rdx
+; CHECK-NEXT:    adcq %rdi, %rcx
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deadalnix wrote:
> craig.topper wrote:
> > Doesn't this add and adc compute the same result as line 321 and 325?
> There is a lot of duplication that is generated by this. But once the carry propagation is "linearized" because you removed all the diamonds, then a simple set of optimization can get rid of it all. See D57317 for that specific case.
Would adding X86ISD::ADD to X86TargetLowering::isCommutativeBinOp help with this?


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  rL LLVM

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  https://reviews.llvm.org/D64174/new/

https://reviews.llvm.org/D64174