[clang] [CodeGen][ObjC] Initial WebAssembly Support for GNUstep (PR #169043)
Hugo Melder via cfe-commits
cfe-commits at lists.llvm.org
Mon Jan 26 02:51:23 PST 2026
https://github.com/hmelder updated https://github.com/llvm/llvm-project/pull/169043
>From 38fb99534154f37f43a69318407550db2dbe45f5 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 ab671d032644b..6f583af41999e 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -8091,7 +8091,8 @@ 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 6e135cdab416fb5c03ab3f78a61a575a1a6644ed 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 | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/clang/lib/CodeGen/CGObjCGNU.cpp b/clang/lib/CodeGen/CGObjCGNU.cpp
index 32fd6b760ed11..698fe16df7b85 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 90ce962fd0b450eef7670fc2ad07165cff2a555a 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 698fe16df7b85..080b263e5fd4d 100644
--- a/clang/lib/CodeGen/CGObjCGNU.cpp
+++ b/clang/lib/CodeGen/CGObjCGNU.cpp
@@ -4119,8 +4119,7 @@ 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 2a9692a67daf099e97d10daa3c5e7c691717e81f Mon Sep 17 00:00:00 2001
From: hmelder <service at hugomelder.com>
Date: Fri, 28 Nov 2025 16:28:35 +0000
Subject: [PATCH 4/5] [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"
>From 912f59824d1b4ec4b96fbe85c62d8782e1f3d516 Mon Sep 17 00:00:00 2001
From: hmelder <service at hugomelder.com>
Date: Wed, 14 Jan 2026 10:23:18 +0000
Subject: [PATCH 5/5] [CodeGen][ObjC] Use C++-based EH for WASM targets
The Wasm EH implementation in Clang pretty much hard-codes
__gxx_wasm_personality_v0 by calling the veneer function
_Unwind_CallPersonality instead of calling the personality function
directly.
While it is possible to remove _Unwind_CallPersonality and instead
generate its body in CG, this will add a couple of instructions in each
catch block. Doable, but we can also do the following:
Since we already have C++-based EH for MinGW in CGObjCGNU, reusing it
for Wasm saves us from implementing our own personality function
and objc_begin_catch/objc_end_catch functions.
---
clang/lib/CodeGen/CGException.cpp | 13 ++++++++++---
clang/lib/CodeGen/CGObjCGNU.cpp | 9 ++++-----
2 files changed, 14 insertions(+), 8 deletions(-)
diff --git a/clang/lib/CodeGen/CGException.cpp b/clang/lib/CodeGen/CGException.cpp
index e9d20672ce185..749dde5a92dcd 100644
--- a/clang/lib/CodeGen/CGException.cpp
+++ b/clang/lib/CodeGen/CGException.cpp
@@ -161,6 +161,8 @@ static const EHPersonality &getObjCPersonality(const TargetInfo &Target,
case ObjCRuntime::GNUstep:
if (T.isOSCygMing())
return EHPersonality::GNU_CPlusPlus_SEH;
+ else if (T.isWasm())
+ return EHPersonality::GNU_Wasm_CPlusPlus;
else if (L.ObjCRuntime.getVersion() >= VersionTuple(1, 7))
return EHPersonality::GNUstep_ObjC;
[[fallthrough]];
@@ -200,7 +202,8 @@ static const EHPersonality &getCXXPersonality(const TargetInfo &Target,
static const EHPersonality &getObjCXXPersonality(const TargetInfo &Target,
const CodeGenOptions &CGOpts,
const LangOptions &L) {
- if (Target.getTriple().isWindowsMSVCEnvironment())
+ auto Triple = Target.getTriple();
+ if (Triple.isWindowsMSVCEnvironment())
return EHPersonality::MSVC_CxxFrameHandler3;
switch (L.ObjCRuntime.getKind()) {
@@ -218,8 +221,12 @@ static const EHPersonality &getObjCXXPersonality(const TargetInfo &Target,
return getObjCPersonality(Target, CGOpts, L);
case ObjCRuntime::GNUstep:
- return Target.getTriple().isOSCygMing() ? EHPersonality::GNU_CPlusPlus_SEH
- : EHPersonality::GNU_ObjCXX;
+ if (Triple.isWasm())
+ return EHPersonality::GNU_Wasm_CPlusPlus;
+ else if (Triple.isOSCygMing())
+ return EHPersonality::GNU_CPlusPlus_SEH;
+ else
+ return EHPersonality::GNU_ObjCXX;
// The GCC runtime's personality function inherently doesn't support
// mixed EH. Use the ObjC personality just to avoid returning null.
diff --git a/clang/lib/CodeGen/CGObjCGNU.cpp b/clang/lib/CodeGen/CGObjCGNU.cpp
index 080b263e5fd4d..f9835703a68a9 100644
--- a/clang/lib/CodeGen/CGObjCGNU.cpp
+++ b/clang/lib/CodeGen/CGObjCGNU.cpp
@@ -2368,12 +2368,11 @@ CGObjCGNU::CGObjCGNU(CodeGenModule &cgm, unsigned runtimeABIVersion,
MetaClassPtrAlias(nullptr), RuntimeVersion(runtimeABIVersion),
ProtocolVersion(protocolClassVersion), ClassABIVersion(classABI) {
+ auto Triple = cgm.getContext().getTargetInfo().getTriple();
+
msgSendMDKind = VMContext.getMDKindID("GNUObjCMessageSend");
- usesSEHExceptions =
- cgm.getContext().getTargetInfo().getTriple().isWindowsMSVCEnvironment();
- usesCxxExceptions =
- cgm.getContext().getTargetInfo().getTriple().isOSCygMing() &&
- isRuntime(ObjCRuntime::GNUstep, 2);
+ usesSEHExceptions = Triple.isWindowsMSVCEnvironment();
+ usesCxxExceptions = (Triple.isOSCygMing() && isRuntime(ObjCRuntime::GNUstep, 2)) || Triple.isWasm();
CodeGenTypes &Types = CGM.getTypes();
IntTy = cast<llvm::IntegerType>(
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