Auto merge of #115260 - scottmcm:not-quite-so-cold, r=WaffleLapkin

Use `preserve_mostcc` for `extern "rust-cold"`

As experimentation in #115242 has shown looks better than `coldcc`.  Notably, clang exposes `preserve_most` (https://clang.llvm.org/docs/AttributeReference.html#preserve-most) but not `cold`, so this change should put us on a better-supported path.

And *don't* use a different convention for cold on Windows, because that actually ends up making things worse. (See comment in the code.)

cc tracking issue #97544

1 files changed, 11 insertions, 2 deletions

diff --git a/tests/codegen/cold-call-declare-and-call.rs b/tests/codegen/cold-call-declare-and-call.rs
index 71d49478bfc..572dc407f51 100644
--- a/tests/codegen/cold-call-declare-and-call.rs
+++ b/tests/codegen/cold-call-declare-and-call.rs
@@ -1,12 +1,21 @@
+// revisions: NORMAL WINDOWS
 // compile-flags: -C no-prepopulate-passes
+//[NORMAL] ignore-windows
+//[WINDOWS] only-windows
+//[WINDOWS] only-x86_64
 
 #![crate_type = "lib"]
 #![feature(rust_cold_cc)]
 
 // wasm marks the definition as `dso_local`, so allow that as optional.
 
-// CHECK: define{{( dso_local)?}} coldcc void @this_should_never_happen(i16
-// CHECK: call coldcc void @this_should_never_happen(i16
+// NORMAL: define{{( dso_local)?}} preserve_mostcc void @this_should_never_happen(i16
+// NORMAL: call preserve_mostcc void @this_should_never_happen(i16
+
+// See the comment in `Target::adjust_abi` for why this differs
+
+// WINDOWS: define void @this_should_never_happen(i16
+// WINDOWS: call void @this_should_never_happen(i16
 
 #[no_mangle]
 pub extern "rust-cold" fn this_should_never_happen(x: u16) {}