Rollup merge of #130586 - dpaoliello:fixrawdylib, r=wesleywiser

Set "symbol name" in raw-dylib import libraries to the decorated name

`windows-rs` received a bug report that mixing raw-dylib generated and the Windows SDK import libraries was causing linker failures: <https://github.com/microsoft/windows-rs/issues/3285>

The root cause turned out to be #124958, that is we are not including the decorated name in the import library and so the import name type is also not being correctly set.

This change modifies the generation of import libraries to set the "symbol name" to the fully decorated name and correctly marks the import as being data vs function.

Note that this also required some changes to how the symbol is named within Rust: for MSVC we now need to use the decorated name but for MinGW we still need to use partially decorated (or undecorated) name.

Fixes #124958

Passing i686 MSVC and MinGW build: <https://github.com/rust-lang/rust/actions/runs/11000433888?pr=130586>

r? `@ChrisDenton`

1 files changed, 16 insertions, 9 deletions

diff --git a/compiler/rustc_codegen_llvm/src/callee.rs b/compiler/rustc_codegen_llvm/src/callee.rs
index 25037b97375..dcea9d3b391 100644
--- a/compiler/rustc_codegen_llvm/src/callee.rs
+++ b/compiler/rustc_codegen_llvm/src/callee.rs
@@ -44,6 +44,22 @@ pub(crate) fn get_fn<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'t
         let llfn = if tcx.sess.target.arch == "x86"
             && let Some(dllimport) = crate::common::get_dllimport(tcx, instance_def_id, sym)
         {
+            // When calling functions in generated import libraries, MSVC needs
+            // the fully decorated name (as would have been in the declaring
+            // object file), but MinGW wants the name as exported (as would be
+            // in the def file) which may be missing decorations.
+            let mingw_gnu_toolchain = common::is_mingw_gnu_toolchain(&tcx.sess.target);
+            let llfn = cx.declare_fn(
+                &common::i686_decorated_name(
+                    dllimport,
+                    mingw_gnu_toolchain,
+                    true,
+                    !mingw_gnu_toolchain,
+                ),
+                fn_abi,
+                Some(instance),
+            );
+
             // Fix for https://github.com/rust-lang/rust/issues/104453
             // On x86 Windows, LLVM uses 'L' as the prefix for any private
             // global symbols, so when we create an undecorated function symbol
@@ -55,15 +71,6 @@ pub(crate) fn get_fn<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'t
             // LLVM will prefix the name with `__imp_`. Ideally, we'd like the
             // existing logic below to set the Storage Class, but it has an
             // exemption for MinGW for backwards compatibility.
-            let llfn = cx.declare_fn(
-                &common::i686_decorated_name(
-                    dllimport,
-                    common::is_mingw_gnu_toolchain(&tcx.sess.target),
-                    true,
-                ),
-                fn_abi,
-                Some(instance),
-            );
             unsafe {
                 llvm::LLVMSetDLLStorageClass(llfn, llvm::DLLStorageClass::DllImport);
             }