[llvm] [X86] Honor rewrite semantics of `contract` in X86ISel combines (PR #174440)

[Simon Pilgrim via llvm-commits]

================
@@ -55287,20 +55287,21 @@ static SDValue combineFaddCFmul(SDNode *N, SelectionDAG &DAG,
     return false;
   };
 
-  if (GetCFmulFrom(LHS))
+  if (GetCFmulFrom(LHS)) {
+    FAddOp0 = LHS;
     FAddOp1 = RHS;
-  else if (GetCFmulFrom(RHS))
+  } else if (GetCFmulFrom(RHS)) {
+    FAddOp0 = RHS;
     FAddOp1 = LHS;
-  else
+  } else
----------------
RKSimon wrote:

(style) uniform braces in if-else chains
```
} else {
  return SDValue();
}
```
https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements

https://github.com/llvm/llvm-project/pull/174440