[clang] [CodeGen][ObjC] Initial WebAssembly Support for GNUstep (PR #169043)

[Hugo Melder via cfe-commits]

https://github.com/hmelder updated https://github.com/llvm/llvm-project/pull/169043

>From a07542b0e2274e36a9276ce034697ebcd0d0fee8 Mon Sep 17 00:00:00 2001
From: hmelder <service at hugomelder.com>
Date: Fri, 21 Nov 2025 10:42:47 +0000
Subject: [PATCH 1/4] [clang] Whitelist wasm when targeting GNUstep 2.x

---
 clang/lib/Driver/ToolChains/Clang.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 30d3e5293a31b..6cbec5e17ae1a 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -8001,7 +8001,8 @@ ObjCRuntime Clang::AddObjCRuntimeArgs(const ArgList &args,
     if ((runtime.getKind() == ObjCRuntime::GNUstep) &&
         (runtime.getVersion() >= VersionTuple(2, 0)))
       if (!getToolChain().getTriple().isOSBinFormatELF() &&
-          !getToolChain().getTriple().isOSBinFormatCOFF()) {
+          !getToolChain().getTriple().isOSBinFormatCOFF() &&
+          !getToolChain().getTriple().isOSBinFormatWasm()) {
         getToolChain().getDriver().Diag(
             diag::err_drv_gnustep_objc_runtime_incompatible_binary)
           << runtime.getVersion().getMajor();

>From 0ee0356c3675722c8903cd4ba760b074b5c46561 Mon Sep 17 00:00:00 2001
From: hmelder <service at hugomelder.com>
Date: Fri, 21 Nov 2025 10:50:35 +0000
Subject: [PATCH 2/4] [CodeGen][ObjC] Mangle public symbols for wasm

Emscripten requires that exported symbols. See
https://github.com/emscripten-core/emscripten/pull/23563.
---
 clang/lib/CodeGen/CGObjCGNU.cpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/clang/lib/CodeGen/CGObjCGNU.cpp b/clang/lib/CodeGen/CGObjCGNU.cpp
index 06643d4bdc211..ab57e934dd6b5 100644
--- a/clang/lib/CodeGen/CGObjCGNU.cpp
+++ b/clang/lib/CodeGen/CGObjCGNU.cpp
@@ -179,8 +179,16 @@ class CGObjCGNU : public CGObjCRuntime {
       (R.getVersion() >= VersionTuple(major, minor));
   }
 
-  std::string ManglePublicSymbol(StringRef Name) {
-    return (StringRef(CGM.getTriple().isOSBinFormatCOFF() ? "$_" : "._") + Name).str();
+  const std::string ManglePublicSymbol(StringRef Name) {
+    StringRef prefix = "._";
+
+    // Exported symbols in Emscripten must be a valid Javascript identifier.
+    auto triple = CGM.getTriple();
+    if (triple.isOSBinFormatCOFF() || triple.isOSBinFormatWasm()) {
+      prefix = "$_";
+    }
+
+    return (prefix + Name).str();
   }
 
   std::string SymbolForProtocol(Twine Name) {

>From 45e7f4413b2583ca7ab8f17ca351babe101a9966 Mon Sep 17 00:00:00 2001
From: hmelder <service at hugomelder.com>
Date: Fri, 21 Nov 2025 13:04:33 +0000
Subject: [PATCH 3/4] [CodeGen][ObjC] Fix class_registerAlias_np signature

---
 clang/lib/CodeGen/CGObjCGNU.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/clang/lib/CodeGen/CGObjCGNU.cpp b/clang/lib/CodeGen/CGObjCGNU.cpp
index ab57e934dd6b5..9b30ab3cb94b3 100644
--- a/clang/lib/CodeGen/CGObjCGNU.cpp
+++ b/clang/lib/CodeGen/CGObjCGNU.cpp
@@ -4114,8 +4114,7 @@ llvm::Function *CGObjCGNU::ModuleInitFunction() {
   if (!ClassAliases.empty()) {
     llvm::Type *ArgTypes[2] = {PtrTy, PtrToInt8Ty};
     llvm::FunctionType *RegisterAliasTy =
-      llvm::FunctionType::get(Builder.getVoidTy(),
-                              ArgTypes, false);
+        llvm::FunctionType::get(BoolTy, ArgTypes, false);
     llvm::Function *RegisterAlias = llvm::Function::Create(
       RegisterAliasTy,
       llvm::GlobalValue::ExternalWeakLinkage, "class_registerAlias_np",

>From 8ad5d2460ae0538feccb83f92f00e305bb6f41ea Mon Sep 17 00:00:00 2001
From: hmelder <service at hugomelder.com>
Date: Fri, 28 Nov 2025 16:28:35 +0000
Subject: [PATCH 4/4] [CodeGen][ObjC] Add WASM symbol mangling test

---
 .../CodeGenObjC/gnustep2-wasm32-symbols.m     | 23 +++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 clang/test/CodeGenObjC/gnustep2-wasm32-symbols.m

diff --git a/clang/test/CodeGenObjC/gnustep2-wasm32-symbols.m b/clang/test/CodeGenObjC/gnustep2-wasm32-symbols.m
new file mode 100644
index 0000000000000..7da73b8f1903e
--- /dev/null
+++ b/clang/test/CodeGenObjC/gnustep2-wasm32-symbols.m
@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -triple wasm32-unknown-emscripten -emit-llvm -fobjc-runtime=gnustep-2.2 -o - %s | FileCheck %s
+
+ at class NSString;
+
+ at protocol AProtocol
+- (void) meth;
+ at end
+
+ at interface AClass <AProtocol>
+ at end
+
+ at implementation AClass
+- (void) meth {}
+ at end
+
+// Make sure that all public symbols are mangled correctly. All exported symbols
+// must be valid Javascript identifiers in Emscripten.
+// CHECK: $"$_OBJC_PROTOCOL_AProtocol" = comdat any
+// CHECK: @"$_OBJC_METACLASS_AClass"
+// CHECK: @"$_OBJC_PROTOCOL_AProtocol"
+// CHECK: @"$_OBJC_CLASS_AClass"
+// CHECK: @"$_OBJC_REF_CLASS_AClass"
+// CHECK: @"$_OBJC_INIT_CLASS_AClass"