[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
```

0 files changed, 0 insertions, 0 deletions