[llvm] [LLVM] Add 'ExpandVariadicsPass' to LTO default pipeline (PR #100479)

[Matt Arsenault via llvm-commits]

================
@@ -0,0 +1,48 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -mtriple=amdgcn-- -S -passes='lto<O2>' < %s | FileCheck %s
+target triple = "amdgcn-amd-amdhsa"
+
+; We use the ExpandVariadics pass to lower variadic functions so they can be
+; inlined.
+
+define i32 @foo() {
+; CHECK-LABEL: define i32 @foo(
+; CHECK-SAME: ) local_unnamed_addr #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    ret i32 6
+;
+entry:
+  %call = tail call i32 (i32, ...) @vararg(i32 poison, i32 noundef 1, i32 noundef 2, i32 noundef 3)
+  ret i32 %call
+}
+
+define internal i32 @vararg(i32 %first, ...) {
+entry:
+  %vlist = alloca ptr, align 8, addrspace(5)
+  %vlist.ascast = addrspacecast ptr addrspace(5) %vlist to ptr
----------------
arsenm wrote:

We shouldn't have these addrspacecasts. if clang is still emitting these, that really should be fixed 

https://github.com/llvm/llvm-project/pull/100479