[IR] Allow llvm.experimental.memset.pattern to take any sized type as the pattern argument

I initially thought starting with a more narrow definition and later
expanding would make more sense. But as pointed out in review for
PR #129220, this restriction is generating additional unnecessary work.

This patch alters the intrinsic to accept patterns of any type. Future
patches will update LoopIdiomRecognize and PreISelIntrinsicLowering to
take advantage of this. The verifier will complain if an unsized type is
used. I've additionally taken the opportunity to remove a comment from
the LangRef about some bit widths potentially not being supported by the
target. I don't think this is any more true than it is for arbitrary
width loads/stores which don't carry a similar warning that I can see.

Author: asb

llvm/docs/LangRef.rst

@@ -15640,8 +15640,8 @@ Syntax:
 """""""
 
 This is an overloaded intrinsic. You can use
-``llvm.experimental.memset.pattern`` on any integer bit width and for
-different address spaces. Not all targets support all bit widths however.
+``llvm.experimental.memset.pattern`` on any sized type for different address
+spaces.
 
 ::
 

llvm/include/llvm/IR/Intrinsics.td

@@ -1025,7 +1025,7 @@ def int_memset_inline
 def int_experimental_memset_pattern
     : Intrinsic<[],
       [llvm_anyptr_ty, // Destination.
-       llvm_anyint_ty, // Pattern value.
+       llvm_any_ty,    // Pattern value.
        llvm_anyint_ty, // Count (number of times to fill value).
        llvm_i1_ty],    // IsVolatile.
       [IntrWriteMem, IntrArgMemOnly, IntrWillReturn, IntrNoFree, IntrNoCallback,

llvm/lib/IR/Verifier.cpp

@@ -5583,7 +5583,11 @@ void Verifier::visitIntrinsicCall(Intrinsic::ID ID, CallBase &Call) {
   case Intrinsic::memmove:
   case Intrinsic::memset:
   case Intrinsic::memset_inline:
+    break;
   case Intrinsic::experimental_memset_pattern: {
+    const auto Memset = cast<MemSetPatternInst>(&Call);
+    Check(Memset->getValue()->getType()->isSized(),
+          "unsized types cannot be used as memset patterns", Call);
     break;
   }
   case Intrinsic::memcpy_element_unordered_atomic:

llvm/test/Verifier/memset-pattern-unsized.ll

@@ -0,0 +1,10 @@
+; RUN: not opt -passes=verify < %s 2>&1 | FileCheck %s
+
+; CHECK: unsized types cannot be used as memset patterns
+
+%X = type opaque
+define void @bar(ptr %P, %X %value) {
+  call void @llvm.experimental.memset.pattern.p0.s_s.i32.0(ptr %P, %X %value, i32 4, i1 false)
+  ret void
+}
+declare void @llvm.experimental.memset.pattern.p0.s_s.i32.0(ptr nocapture, %X, i32, i1) nounwind