From df04fd6fba2e1b2b85a108e3ec7e56c731456ba9 Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Wed, 1 Feb 2023 13:55:28 +0000
Subject: [PATCH] Don't force many scalar pair values to the stack in
 write_cvalue_maybe_transmute

Sometimes it is necessary for handling vector to scalar pair transmutes,
but if the types are the same there is no need for this.

This improves runtime performance on simple-raytracer by 12%.
---
 src/abi/comments.rs    |  4 ++--
 src/value_and_place.rs | 11 +++++++----
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/abi/comments.rs b/src/abi/comments.rs
index 7f4619b5c940..abf63e33c353 100644
--- a/src/abi/comments.rs
+++ b/src/abi/comments.rs
@@ -98,12 +98,12 @@ pub(super) fn add_local_place_comments<'tcx>(
         }
         CPlaceInner::VarPair(place_local, var1, var2) => {
             assert_eq!(local, place_local);
-            ("ssa", Cow::Owned(format!(",var=({}, {})", var1.index(), var2.index())))
+            ("ssa", Cow::Owned(format!("var=({}, {})", var1.index(), var2.index())))
         }
         CPlaceInner::VarLane(_local, _var, _lane) => unreachable!(),
         CPlaceInner::Addr(ptr, meta) => {
             let meta = if let Some(meta) = meta {
-                Cow::Owned(format!(",meta={}", meta))
+                Cow::Owned(format!("meta={}", meta))
             } else {
                 Cow::Borrowed("")
             };
diff --git a/src/value_and_place.rs b/src/value_and_place.rs
index fa06d6c3ba7f..cc4493d442f7 100644
--- a/src/value_and_place.rs
+++ b/src/value_and_place.rs
@@ -588,10 +588,13 @@ fn transmute_value<'tcx>(
                 return;
             }
             CPlaceInner::VarPair(_local, var1, var2) => {
-                let (ptr, meta) = from.force_stack(fx);
-                assert!(meta.is_none());
-                let (data1, data2) =
-                    CValue(CValueInner::ByRef(ptr, None), dst_layout).load_scalar_pair(fx);
+                let (data1, data2) = if self.layout().ty == dst_layout.ty {
+                    CValue(from.0, dst_layout).load_scalar_pair(fx)
+                } else {
+                    let (ptr, meta) = from.force_stack(fx);
+                    assert!(meta.is_none());
+                    CValue(CValueInner::ByRef(ptr, None), dst_layout).load_scalar_pair(fx)
+                };
                 let (dst_ty1, dst_ty2) = fx.clif_pair_type(self.layout().ty).unwrap();
                 transmute_value(fx, var1, data1, dst_ty1);
                 transmute_value(fx, var2, data2, dst_ty2);