From 754f488d46fa33387c3dca3b08d3f3ec2fe02d3f Mon Sep 17 00:00:00 2001
From: Scott McMurray <scottmcm@users.noreply.github.com>
Date: Sat, 26 Aug 2023 17:42:59 -0700
Subject: Use `preserve_mostcc` for `extern "rust-cold"`

As experimentation in 115242 has shown looks better than `coldcc`.

And *don't* use a different convention for cold on Windows, because that actually ends up making things worse.

cc tracking issue 97544
---
 compiler/rustc_codegen_llvm/src/abi.rs      | 4 +++-
 compiler/rustc_codegen_llvm/src/llvm/ffi.rs | 5 +++++
 2 files changed, 8 insertions(+), 1 deletion(-)

(limited to 'compiler/rustc_codegen_llvm/src')

diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs
index c6a7dc95d77..863cb7068f8 100644
--- a/compiler/rustc_codegen_llvm/src/abi.rs
+++ b/compiler/rustc_codegen_llvm/src/abi.rs
@@ -571,7 +571,9 @@ impl From<Conv> for llvm::CallConv {
             Conv::C | Conv::Rust | Conv::CCmseNonSecureCall | Conv::RiscvInterrupt { .. } => {
                 llvm::CCallConv
             }
-            Conv::RustCold => llvm::ColdCallConv,
+            Conv::Cold => llvm::ColdCallConv,
+            Conv::PreserveMost => llvm::PreserveMost,
+            Conv::PreserveAll => llvm::PreserveAll,
             Conv::AmdGpuKernel => llvm::AmdGpuKernel,
             Conv::AvrInterrupt => llvm::AvrInterrupt,
             Conv::AvrNonBlockingInterrupt => llvm::AvrNonBlockingInterrupt,
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 84157d1e25c..01cbf7d3b11 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -83,12 +83,17 @@ pub enum LLVMModFlagBehavior {
 // Consts for the LLVM CallConv type, pre-cast to usize.
 
 /// LLVM CallingConv::ID. Should we wrap this?
+///
+/// See <https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/IR/CallingConv.h>
 #[derive(Copy, Clone, PartialEq, Debug)]
 #[repr(C)]
 pub enum CallConv {
     CCallConv = 0,
     FastCallConv = 8,
     ColdCallConv = 9,
+    PreserveMost = 14,
+    PreserveAll = 15,
+    Tail = 18,
     X86StdcallCallConv = 64,
     X86FastcallCallConv = 65,
     ArmAapcsCallConv = 67,
-- 
cgit 1.4.1-3-g733a5