[llvm] [PreISelIntrinsicLowering] Look through ptrtoint for a constant (e.g. global ptr) when trying to produce memset_pattern16 (PR #129220)

[Nikita Popov via llvm-commits]

================
@@ -254,10 +254,18 @@ static Constant *getMemSetPattern16Value(MemSetPatternInst *Inst,
   if (!isLibFuncEmittable(M, &TLI, LibFunc_memset_pattern16))
     return nullptr;
 
+  // Look through a ptrtoint cast for a candidate constant. This could be
+  // extended to look through other casts, but the assumption is earlier
+  // passes that introduced memset.pattern intrinsic would have just emitted
+  // the integer argument directly for CosntantFP or ConstantInt cases.
----------------
nikic wrote:

```suggestion
  // the integer argument directly for ConstantFP or ConstantInt cases.
```

https://github.com/llvm/llvm-project/pull/129220