[llvm] [GlobalISel] port rewrite from SelectionDAG to GlobalISel (PR #181486)

[Osman Yasar via llvm-commits]

================
@@ -1879,6 +1879,16 @@ def APlusBMinusCMinusB : GICombineRule<
           (G_SUB $root, $add1, $B)),
    (apply (G_SUB $root, $A, $C))>;
 
+// fold ((A+(B+C))-B) -> A+C
+def APlusBPlusCMinusB : GICombineRule<
+  (defs root:$root),
+  (match (G_ADD $add1, $B, $C),
+         (G_ADD $add2, $A, $add1),
+         (G_SUB $root, $add2, $B),
+             [{ return MRI.hasOneNonDBGUse(${add1}.getReg()) &&
+                       MRI.hasOneNonDBGUse(${add2}.getReg()); }]),
+  (apply (G_ADD $root, $x, $n))>;
----------------
osmanyasar05 wrote:

```suggestion
  (apply (G_ADD $root, $A, $C))>;
```

https://github.com/llvm/llvm-project/pull/181486