llvm-project

ea2de9aa - [X86] Fold generic ADD/SUB with constants to X86ISD::SUB/ADD (#164316)

[X86] Fold generic ADD/SUB with constants to X86ISD::SUB/ADD (#164316) Fix #163125 This PR enhances `combineX86AddSub` so that it can handle `X86ISD::SUB(X,Constant)` with `add(X,-Constant)` and other similar cases: - `X86ISD::ADD(LHS, C)` will fold `sub(-C, LHS)` - `X86ISD::SUB(LHS, C)` will fold `add(LHS, -C)` - `X86ISD::SUB(C, RHS)` will fold `add(RHS, -C)` `CodeGen/X86/dag-update-nodetomatch.ll` is updated because following IR is folded: ```llvm for.body2: ; ...... ; This generates `add t6, Constant:i64<1>` %indvars.iv.next = add nsw i64 %indvars.iv, 1; ; This generates `X86ISD::SUB t6, Constant:i64<-1>` and folds the previous `add` %cmp = icmp slt i64 %indvars.iv, -1; br i1 %cmp, label %for.body2, label %for.cond1.for.inc3_crit_edge.loopexit ``` ```diff - ; CHECK-NEXT: movq (%r15), %rax - ; CHECK-NEXT: movq %rax, (%r12,%r13,8) - ; CHECK-NEXT: leaq 1(%r13), %rdx - ; CHECK-NEXT: cmpq $-1, %r13 - ; CHECK-NEXT: movq %rdx, %r13 + ; CHECK-NEXT: movq (%r12), %rax + ; CHECK-NEXT: movq %rax, (%r13,%r9,8) + ; CHECK-NEXT: incq %r9 ```