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

[Hugo Melder via llvm-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 1/5] [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 90a6ea80ab587a670040c6ec7c574ae29419fb02 Mon Sep 17 00:00:00 2001
From: hmelder <service at hugomelder.com>
Date: Fri, 21 Nov 2025 10:50:35 +0000
Subject: [PATCH 2/5] [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 | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/clang/lib/CodeGen/CGObjCGNU.cpp b/clang/lib/CodeGen/CGObjCGNU.cpp
index 06643d4bdc211..d86aed0d977fa 100644
--- a/clang/lib/CodeGen/CGObjCGNU.cpp
+++ b/clang/lib/CodeGen/CGObjCGNU.cpp
@@ -179,8 +179,15 @@ class CGObjCGNU : public CGObjCRuntime {
       (R.getVersion() >= VersionTuple(major, minor));
   }
 
-  std::string ManglePublicSymbol(StringRef Name) {
-    return (StringRef(CGM.getTriple().isOSBinFormatCOFF() ? "$_" : "._") + Name).str();
+  const std::string ManglePublicSymbol(StringRef Name) {
+    auto triple = CGM.getTriple();
+
+    // Exported symbols in Emscripten must be a valid Javascript identifier.
+    if (triple.isOSBinFormatCOFF() || triple.isOSBinFormatWasm()) {
+      return (StringRef("$_") + Name).str();
+    } else {
+      return (StringRef("._") + Name).str();
+    }
   }
 
   std::string SymbolForProtocol(Twine Name) {

>From c1b0453c01e3a1a4f41b413eb6b1c6dfd61dc828 Mon Sep 17 00:00:00 2001
From: hmelder <service at hugomelder.com>
Date: Fri, 21 Nov 2025 13:04:33 +0000
Subject: [PATCH 3/5] [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 d86aed0d977fa..3b9f9f306829d 100644
--- a/clang/lib/CodeGen/CGObjCGNU.cpp
+++ b/clang/lib/CodeGen/CGObjCGNU.cpp
@@ -4113,8 +4113,7 @@ 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 0233bd22d901de804558cd40435a7c6c0fa770c7 Mon Sep 17 00:00:00 2001
From: hmelder <service at hugomelder.com>
Date: Fri, 21 Nov 2025 13:07:10 +0000
Subject: [PATCH 4/5] [Wasm] HACK: Do not export hidden symbols

---
 llvm/lib/MC/WasmObjectWriter.cpp | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index 15590b31fd07f..d882146e21b8a 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -1794,9 +1794,6 @@ uint64_t WasmObjectWriter::writeOneObject(MCAssembler &Asm,
       Flags |= wasm::WASM_SYMBOL_UNDEFINED;
     if (WS.isNoStrip()) {
       Flags |= wasm::WASM_SYMBOL_NO_STRIP;
-      if (isEmscripten()) {
-        Flags |= wasm::WASM_SYMBOL_EXPORTED;
-      }
     }
     if (WS.hasImportName())
       Flags |= wasm::WASM_SYMBOL_EXPLICIT_NAME;

>From 1b37875e1c00259731d4099c1ae2c9a89681060d Mon Sep 17 00:00:00 2001
From: Hugo Melder <service at hugomelder.com>
Date: Fri, 28 Nov 2025 14:09:55 +0100
Subject: [PATCH 5/5] Update clang/lib/CodeGen/CGObjCGNU.cpp

Co-authored-by: David Chisnall <davidchisnall at users.noreply.github.com>
---
 clang/lib/CodeGen/CGObjCGNU.cpp | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/clang/lib/CodeGen/CGObjCGNU.cpp b/clang/lib/CodeGen/CGObjCGNU.cpp
index 3b9f9f306829d..1427cc40d2914 100644
--- a/clang/lib/CodeGen/CGObjCGNU.cpp
+++ b/clang/lib/CodeGen/CGObjCGNU.cpp
@@ -180,14 +180,13 @@ class CGObjCGNU : public CGObjCRuntime {
   }
 
   const std::string ManglePublicSymbol(StringRef Name) {
-    auto triple = CGM.getTriple();
+    StringRef prefix = "._"
 
     // Exported symbols in Emscripten must be a valid Javascript identifier.
+    auto triple = CGM.getTriple();
     if (triple.isOSBinFormatCOFF() || triple.isOSBinFormatWasm()) {
-      return (StringRef("$_") + Name).str();
-    } else {
-      return (StringRef("._") + Name).str();
-    }
+      prefix = "$_";
+    return (prefix + Name).str();
   }
 
   std::string SymbolForProtocol(Twine Name) {