Auto merge of #138503 - bjorn3:string_merging, r=tmiasko

Avoid wrapping constant allocations in packed structs when not necessary

This way LLVM will set the string merging flag if the alloc is a nul terminated string, reducing binary sizes.

try-job: armhf-gnu

src/allocator.rs

diff --git a/src/allocator.rs b/src/allocator.rs
index 416f323..f4ebd42 100644
--- a/src/allocator.rs
+++ b/src/allocator.rs
@@ -8,6 +8,7 @@
 use rustc_middle::bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::OomStrategy;
+use rustc_symbol_mangling::mangle_internal_symbol;
 
 use crate::GccContext;
 #[cfg(feature = "master")]
@@ -53,8 +54,8 @@
                     panic!("invalid allocator output")
                 }
             };
-            let from_name = global_fn_name(method.name);
-            let to_name = default_fn_name(method.name);
+            let from_name = mangle_internal_symbol(tcx, &global_fn_name(method.name));
+            let to_name = mangle_internal_symbol(tcx, &default_fn_name(method.name));
 
             create_wrapper_function(tcx, context, &from_name, &to_name, &types, output);
         }
@@ -64,13 +65,13 @@
     create_wrapper_function(
         tcx,
         context,
-        "__rust_alloc_error_handler",
-        alloc_error_handler_name(alloc_error_handler_kind),
+        &mangle_internal_symbol(tcx, "__rust_alloc_error_handler"),
+        &mangle_internal_symbol(tcx, alloc_error_handler_name(alloc_error_handler_kind)),
         &[usize, usize],
         None,
     );
 
-    let name = OomStrategy::SYMBOL.to_string();
+    let name = mangle_internal_symbol(tcx, OomStrategy::SYMBOL);
     let global = context.new_global(None, GlobalKind::Exported, i8, name);
     #[cfg(feature = "master")]
     global.add_attribute(VarAttribute::Visibility(symbol_visibility_to_gcc(
@@ -80,7 +81,7 @@
     let value = context.new_rvalue_from_int(i8, value as i32);
     global.global_set_initializer_rvalue(value);
 
-    let name = NO_ALLOC_SHIM_IS_UNSTABLE.to_string();
+    let name = mangle_internal_symbol(tcx, NO_ALLOC_SHIM_IS_UNSTABLE);
     let global = context.new_global(None, GlobalKind::Exported, i8, name);
     #[cfg(feature = "master")]
     global.add_attribute(VarAttribute::Visibility(symbol_visibility_to_gcc(

src/lib.rs

diff --git a/src/lib.rs b/src/lib.rs
index d478b2a..bfa2317 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -52,6 +52,7 @@
 extern crate rustc_middle;
 extern crate rustc_session;
 extern crate rustc_span;
+extern crate rustc_symbol_mangling;
 extern crate rustc_target;
 
 // This prevents duplicating functions and statics that are already part of the host rustc process.