[LoopIdiomRecognizer] creates memset_pattern16 with incorrect size type with custom dl #57679

Take, e.g., Transforms/LoopIdiom/unroll-custom-dl.ll. It creates this call:

; 64-bit size, 32-bit offset
target datalayout = "e-p:64:64:64:32-..."

  call void @memset_pattern16(i8* %f1, i8* bitcast ([4 x i32]* @.memset_pattern to i8*), i32 %3)

TargetLibraryInfo.def has this:

/// void memset_pattern16(void *b, const void *pattern16, size_t len);
TLI_DEFINE_ENUM_INTERNAL(memset_pattern16)
TLI_DEFINE_STRING_INTERNAL("memset_pattern16")
TLI_DEFINE_SIG_INTERNAL(Void, Ptr, Ptr, SizeT)

The end result is that the function isn't recognized as a libcall as there's a mismatch.
I believe the code shouldn't be using the index type for the last argument.