Auto merge of #56358 - nikic:mergefunc-aliases, r=rkruppe

Enable -mergefunc-use-aliases

If the Rust LLVM fork is used, enable the -mergefunc-use-aliases
flag, which will create aliases for merged functions, rather than
inserting a call from one to the other.

A number of codegen tests needed to be adjusted, because functions
that previously fell below the thunk limit are now being merged.
Merging is prevented in various ways now.

I expect that this is going to break something, somewhere, because
it isn't able to deal with aliases properly, but we won't find out
until we try :)

This fixes #52651.

r? @rkruppe

4 files changed, 8 insertions, 5 deletions

diff --git a/src/test/codegen/export-no-mangle.rs b/src/test/codegen/export-no-mangle.rs
index 3546284f9a3..95587d9d84c 100644
--- a/src/test/codegen/export-no-mangle.rs
+++ b/src/test/codegen/export-no-mangle.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// compile-flags: -C no-prepopulate-passes
+
 #![crate_type = "lib"]
 
 mod private {
diff --git a/src/test/codegen/external-no-mangle-fns.rs b/src/test/codegen/external-no-mangle-fns.rs
index 3f092b802f9..58232852596 100644
--- a/src/test/codegen/external-no-mangle-fns.rs
+++ b/src/test/codegen/external-no-mangle-fns.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: -O
+// compile-flags: -C no-prepopulate-passes
 // `#[no_mangle]`d functions always have external linkage, i.e. no `internal` in their `define`s
 
 #![crate_type = "lib"]
@@ -43,7 +43,7 @@ const HIDDEN: () = {
 };
 
 // The surrounding item should not accidentally become external
-// CHECK: define internal {{.*}} void @_ZN22external_no_mangle_fns1x
+// CHECK: define internal{{.*}} void @_ZN22external_no_mangle_fns1x
 #[inline(never)]
 fn x() {
     // CHECK: define void @g()
diff --git a/src/test/codegen/issue-45222.rs b/src/test/codegen/issue-45222.rs
index 30a03243f01..3544786e2e6 100644
--- a/src/test/codegen/issue-45222.rs
+++ b/src/test/codegen/issue-45222.rs
@@ -69,6 +69,6 @@ fn foo3r(n: u64) -> u64 {
 // CHECK-LABEL: @check_foo3r
 #[no_mangle]
 pub fn check_foo3r() -> u64 {
-    // CHECK: ret i64 500005000000000
-    foo3r(100000)
+    // CHECK: ret i64 500050000000
+    foo3r(10000)
 }
diff --git a/src/test/codegen/match-optimizes-away.rs b/src/test/codegen/match-optimizes-away.rs
index d7b77937431..2136b176eac 100644
--- a/src/test/codegen/match-optimizes-away.rs
+++ b/src/test/codegen/match-optimizes-away.rs
@@ -14,6 +14,7 @@
 
 pub enum Three { A, B, C }
 
+#[repr(u16)]
 pub enum Four { A, B, C, D }
 
 #[no_mangle]
@@ -32,7 +33,7 @@ pub fn three_valued(x: Three) -> Three {
 pub fn four_valued(x: Four) -> Four {
     // CHECK-LABEL: @four_valued
     // CHECK-NEXT: {{^.*:$}}
-    // CHECK-NEXT: ret i8 %0
+    // CHECK-NEXT: ret i16 %0
     match x {
         Four::A => Four::A,
         Four::B => Four::B,