[llvm] [LegalizeTypes] Create an ISD::ADD instead of an ISD::UADDO with unused overflow result. (PR #100647)

[Craig Topper via llvm-commits]

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@@ -115,7 +115,7 @@ define i128 @knownbits_mask_addc_shl(i64 %a0, i64 %a1, i64 %a2) nounwind {
 ; X64-NEXT:    andq $-1024, %rdi # imm = 0xFC00
 ; X64-NEXT:    andq $-1024, %rsi # imm = 0xFC00
 ; X64-NEXT:    addq %rdi, %rsi
-; X64-NEXT:    adcq $0, %rdx
+; X64-NEXT:    adcl $0, %edx
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topperc wrote:

There's a fshl+add combine that gets triggered now that reduces the size of the add. The uaddo eventually got turned into add, but it was later and something else changed that prevented the fshl+add combine from running at that point.

https://github.com/llvm/llvm-project/pull/100647