[PATCH] D83153: [DAGCombiner] Prevent regression in isMulAddWithConstProfitable

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


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Comment at: llvm/test/CodeGen/AArch64/urem-seteq-nonzero.ll:7-10
+; CHECK-NEXT:    mov w9, #43691
+; CHECK-NEXT:    sub w8, w0, #1 // =1
+; CHECK-NEXT:    movk w9, #43690, lsl #16
+; CHECK-NEXT:    mul w8, w8, w9
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spatel wrote:
> I think we need to hear from someone with more AArch knowledge if this is an improvement or acceptable. cc @dmgreen @efriedma @fhahn 
The new code is worse; madd is essentially the same cost as mul, so the new code has one more arithmetic instruction.  Better to spend an extra instruction materializing a constant, particularly if the code is in a loop.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D83153/new/

https://reviews.llvm.org/D83153