[llvm] [InstCombine] When -A + B both have nsw flag, set nsw flag. (PR #72127)

[via llvm-commits]

================
@@ -1487,7 +1487,11 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
       return BinaryOperator::CreateNeg(Builder.CreateAdd(A, B));
 
     // -A + B --> B - A
-    return BinaryOperator::CreateSub(RHS, A);
+    auto *Sub = BinaryOperator::CreateSub(RHS, A);
+    auto *OB0 = dyn_cast<OverflowingBinaryOperator>(LHS);
+    Sub->setHasNoSignedWrap(I.hasNoSignedWrap() && OB0->hasNoSignedWrap());
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Z572 wrote:

https://alive2.llvm.org/ce/z/7nnL25

if only `I.hasNoSignedWrap()`

```
define i32 @test5_add_nsw(i32 %A, i32 %B) {
  %C = sub i32 0, %A
  %D = add nsw i32 %C, %B
  ret i32 %D
}
```
--> 
```
define i32 @test5_add_nsw(i32 %A, i32 %B) {
  %D = sub nsw i32 %B, %A
  ret i32 %D
}
```

is error

https://github.com/llvm/llvm-project/pull/72127