[DSE] Remove uninitialized from allockind when creating dummy zeroed variant function (#149336)

cc llvm/llvm-project#138299

rustc sets `allockind("uninitialized")` - if we copy the attributes
as-is when creating a dummy function, Verify complains about
`allockind("uninitialized,zeroed")` conflicting, so we need to clear the
flag.

Co-authored-by: Jamie Hill-Daniel <jamie@osec.io>

Author: clubby789

llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp

@@ -2079,6 +2079,7 @@ struct DSEState {
       AllocFnKind AllocKind =
           Attrs.getFnAttr(Attribute::AllocKind).getAllocKind() |
           AllocFnKind::Zeroed;
+      AllocKind &= ~AllocFnKind::Uninitialized;
       Attrs =
           Attrs.addFnAttribute(Ctx, Attribute::getWithAllocKind(Ctx, AllocKind))
               .removeFnAttribute(Ctx, "alloc-variant-zeroed");

llvm/test/Transforms/DeadStoreElimination/zeroed-missing.ll

@@ -12,6 +12,6 @@ define ptr @undeclared_customalloc(i64 %size, i64 %align) {
   ret ptr %call
 }
 
-declare ptr @customalloc2(i64, i64) allockind("alloc") "alloc-family"="customalloc2" "alloc-variant-zeroed"="customalloc2_zeroed"
+declare ptr @customalloc2(i64, i64) allockind("alloc,uninitialized") "alloc-family"="customalloc2" "alloc-variant-zeroed"="customalloc2_zeroed"
 ; CHECK-DAG: declare ptr @customalloc2_zeroed(i64, i64) #[[CA2ATTR:[0-9]+]]
 ; CHECK-DAG: attributes #[[CA2ATTR]] = { allockind("alloc,zeroed") "alloc-family"="customalloc2" }