[llvm] [DirectX] Legalize memcpy (PR #139173)

[Greg Roth via llvm-commits]

================
@@ -296,6 +351,30 @@ static void emitMemsetExpansion(IRBuilder<> &Builder, Value *Dst, Value *Val,
   }
 }
 
+static void removeMemCpy(Instruction &I,
----------------
pow2clk wrote:

```suggestion
// Expands the instruction `I` into corresponding loads and stores if it is a memcpy call.
// In that case, the call instruction is added to the `ToRemove` vector.
// `ReplacedValues` is unused.
static void legalizeMemCpy(Instruction &I,
```

https://github.com/llvm/llvm-project/pull/139173