[llvm] [InstCombine] Extend bitmask mul combine to handle independent operands (PR #142503)

[Yingwei Zheng via llvm-commits]

================
@@ -3659,6 +3665,64 @@ static std::optional<DecomposedBitMaskMul> matchBitmaskMul(Value *V) {
   return std::nullopt;
 }
 
+/// (A & N) * C + (A & M) * C -> (A & (N + M)) & C
+/// This also accepts the equivalent select form of (A & N) * C
+/// expressions i.e. !(A & N) ? 0 : N * C)
+static Value *foldBitmaskMul(Value *Op0, Value *Op1,
+                             InstCombiner::BuilderTy &Builder) {
+  auto Decomp1 = matchBitmaskMul(Op1);
+
+  if (Decomp1) {
+    auto Decomp0 = matchBitmaskMul(Op0);
+
+    if (Decomp0) {
----------------
dtcxzyw wrote:

```suggestion
  auto Decomp1 = matchBitmaskMul(Op1);
  if (!Decomp1) return nullptr;

  auto Decomp0 = matchBitmaskMul(Op0);
  if (!Decomp0) return nullptr;
```

https://github.com/llvm/llvm-project/pull/142503