[clang][WebAssembly] Support reftypes & varargs in test_function_pointer_signature (#150921)

hoodmane · web-flow · commit b9c328480cc5 · 2025-08-07T13:07:04.000-07:00
I fixed support for varargs functions
(previously it didn't crash but the codegen was incorrect).

I added tests for structs and unions which already work. With the
multivalue abi they crash in the backend, so I added a sema check that
rejects structs and unions for that abi.

It will also crash in the backend if passed an int128 or float128 type.
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -13234,9 +13234,9 @@ def err_wasm_builtin_arg_must_match_table_element_type : Error <
   "%ordinal0 argument must match the element type of the WebAssembly table in the %ordinal1 argument">;
 def err_wasm_builtin_arg_must_be_integer_type : Error <
   "%ordinal0 argument must be an integer">;
-def err_wasm_builtin_test_fp_sig_cannot_include_reference_type
-    : Error<"not supported for "
-            "function pointers with a reference type %select{return "
+def err_wasm_builtin_test_fp_sig_cannot_include_struct_or_union
+    : Error<"not supported with the multivalue ABI for "
+            "function pointers with a struct/union as %select{return "
             "value|parameter}0">;
 
 // OpenACC diagnostics.
diff --git a/clang/include/clang/Sema/SemaWasm.h b/clang/include/clang/Sema/SemaWasm.h
@@ -37,7 +37,8 @@ class SemaWasm : public SemaBase {
   bool BuiltinWasmTableGrow(CallExpr *TheCall);
   bool BuiltinWasmTableFill(CallExpr *TheCall);
   bool BuiltinWasmTableCopy(CallExpr *TheCall);
-  bool BuiltinWasmTestFunctionPointerSignature(CallExpr *TheCall);
+  bool BuiltinWasmTestFunctionPointerSignature(const TargetInfo &TI,
+                                               CallExpr *TheCall);
 
   WebAssemblyImportNameAttr *
   mergeImportNameAttr(Decl *D, const WebAssemblyImportNameAttr &AL);
diff --git a/clang/lib/CodeGen/TargetBuiltins/WebAssembly.cpp b/clang/lib/CodeGen/TargetBuiltins/WebAssembly.cpp
@@ -246,35 +246,26 @@ Value *CodeGenFunction::EmitWebAssemblyBuiltinExpr(unsigned BuiltinID,
     llvm::FunctionType *LLVMFuncTy =
         cast<llvm::FunctionType>(ConvertType(QualType(FuncTy, 0)));
 
+    bool VarArg = LLVMFuncTy->isVarArg();
     unsigned NParams = LLVMFuncTy->getNumParams();
     std::vector<Value *> Args;
-    Args.reserve(NParams + 3);
+    Args.reserve(NParams + 3 + VarArg);
     // The only real argument is the FuncRef
     Args.push_back(FuncRef);
 
     // Add the type information
-    auto addType = [this, &Args](llvm::Type *T) {
-      if (T->isVoidTy()) {
-        // Do nothing
-      } else if (T->isFloatingPointTy()) {
-        Args.push_back(ConstantFP::get(T, 0));
-      } else if (T->isIntegerTy()) {
-        Args.push_back(ConstantInt::get(T, 0));
-      } else if (T->isPointerTy()) {
-        Args.push_back(ConstantPointerNull::get(llvm::PointerType::get(
-            getLLVMContext(), T->getPointerAddressSpace())));
-      } else {
-        // TODO: Handle reference types. For now, we reject them in Sema.
-        llvm_unreachable("Unhandled type");
-      }
-    };
-
-    addType(LLVMFuncTy->getReturnType());
+    llvm::Type *RetType = LLVMFuncTy->getReturnType();
+    if (!RetType->isVoidTy()) {
+      Args.push_back(PoisonValue::get(RetType));
+    }
     // The token type indicates the boundary between return types and param
     // types.
     Args.push_back(PoisonValue::get(llvm::Type::getTokenTy(getLLVMContext())));
     for (unsigned i = 0; i < NParams; i++) {
-      addType(LLVMFuncTy->getParamType(i));
+      Args.push_back(PoisonValue::get(LLVMFuncTy->getParamType(i)));
+    }
+    if (VarArg) {
+      Args.push_back(PoisonValue::get(Builder.getPtrTy()));
     }
     Function *Callee = CGM.getIntrinsic(Intrinsic::wasm_ref_test_func);
     return Builder.CreateCall(Callee, Args);
diff --git a/clang/lib/Sema/SemaWasm.cpp b/clang/lib/Sema/SemaWasm.cpp
@@ -17,6 +17,7 @@
 #include "clang/Basic/AddressSpaces.h"
 #include "clang/Basic/DiagnosticSema.h"
 #include "clang/Basic/TargetBuiltins.h"
+#include "clang/Basic/TargetInfo.h"
 #include "clang/Sema/Attr.h"
 #include "clang/Sema/Sema.h"
 
@@ -227,7 +228,8 @@ bool SemaWasm::BuiltinWasmTableCopy(CallExpr *TheCall) {
   return false;
 }
 
-bool SemaWasm::BuiltinWasmTestFunctionPointerSignature(CallExpr *TheCall) {
+bool SemaWasm::BuiltinWasmTestFunctionPointerSignature(const TargetInfo &TI,
+                                                       CallExpr *TheCall) {
   if (SemaRef.checkArgCount(TheCall, 1))
     return true;
 
@@ -250,27 +252,31 @@ bool SemaWasm::BuiltinWasmTestFunctionPointerSignature(CallExpr *TheCall) {
            << ArgType << FuncPtrArg->getSourceRange();
   }
 
-  // Check that the function pointer doesn't use reference types
-  if (FuncTy->getReturnType().isWebAssemblyReferenceType()) {
-    return Diag(
-               FuncPtrArg->getBeginLoc(),
-               diag::err_wasm_builtin_test_fp_sig_cannot_include_reference_type)
-           << 0 << FuncTy->getReturnType() << FuncPtrArg->getSourceRange();
-  }
-  auto NParams = FuncTy->getNumParams();
-  for (unsigned I = 0; I < NParams; I++) {
-    if (FuncTy->getParamType(I).isWebAssemblyReferenceType()) {
+  if (TI.getABI() == "experimental-mv") {
+    auto isStructOrUnion = [](QualType T) {
+      return T->isUnionType() || T->isStructureType();
+    };
+    if (isStructOrUnion(FuncTy->getReturnType())) {
       return Diag(
                  FuncPtrArg->getBeginLoc(),
                  diag::
-                     err_wasm_builtin_test_fp_sig_cannot_include_reference_type)
-             << 1 << FuncPtrArg->getSourceRange();
+                     err_wasm_builtin_test_fp_sig_cannot_include_struct_or_union)
+             << 0 << FuncTy->getReturnType() << FuncPtrArg->getSourceRange();
+    }
+    auto NParams = FuncTy->getNumParams();
+    for (unsigned I = 0; I < NParams; I++) {
+      if (isStructOrUnion(FuncTy->getParamType(I))) {
+        return Diag(
+                   FuncPtrArg->getBeginLoc(),
+                   diag::
+                       err_wasm_builtin_test_fp_sig_cannot_include_struct_or_union)
+               << 1 << FuncPtrArg->getSourceRange();
+      }
     }
   }
 
   // Set return type to int (the result of the test)
   TheCall->setType(getASTContext().IntTy);
-
   return false;
 }
 
@@ -297,7 +303,7 @@ bool SemaWasm::CheckWebAssemblyBuiltinFunctionCall(const TargetInfo &TI,
   case WebAssembly::BI__builtin_wasm_table_copy:
     return BuiltinWasmTableCopy(TheCall);
   case WebAssembly::BI__builtin_wasm_test_function_pointer_signature:
-    return BuiltinWasmTestFunctionPointerSignature(TheCall);
+    return BuiltinWasmTestFunctionPointerSignature(TI, TheCall);
   }
 
   return false;
diff --git a/clang/test/CodeGen/WebAssembly/builtins-test-fp-sig.c b/clang/test/CodeGen/WebAssembly/builtins-test-fp-sig.c
@@ -0,0 +1,70 @@
+// RUN: %clang_cc1 -triple wasm32-unknown-unknown -target-feature +gc -O3 -emit-llvm -DSINGLE_VALUE -o - %s | FileCheck %s -check-prefixes WEBASSEMBLY,WEBASSEMBLY-SV
+// RUN: %clang_cc1 -triple wasm64-unknown-unknown -target-feature +gc -O3 -emit-llvm -DSINGLE_VALUE -o - %s | FileCheck %s -check-prefixes WEBASSEMBLY,WEBASSEMBLY-SV
+// RUN: %clang_cc1 -triple wasm64-unknown-unknown -target-feature +gc -target-abi experimental-mv -O3 -emit-llvm  -o - %s 2>&1 | FileCheck %s -check-prefixes WEBASSEMBLY
+// RUN: not %clang_cc1 -triple wasm64-unknown-unknown -O3 -emit-llvm -o - %s 2>&1 | FileCheck %s -check-prefixes MISSING-GC
+
+void use(int);
+
+typedef void (*Fvoid)(void);
+void test_function_pointer_signature_void(Fvoid func) {
+  // MISSING-GC: error: '__builtin_wasm_test_function_pointer_signature' needs target feature gc
+  // WEBASSEMBLY:  %0 = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, token poison)
+  use(__builtin_wasm_test_function_pointer_signature(func));
+}
+
+typedef float (*Ffloats)(float, double, int);
+void test_function_pointer_signature_floats(Ffloats func) {
+  // WEBASSEMBLY:  %0 = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, float poison, token poison, float poison, double poison, i32 poison)
+  use(__builtin_wasm_test_function_pointer_signature(func));
+}
+
+typedef void (*Fpointers)(Fvoid, Ffloats, void*, int*, int***, char[5]);
+void test_function_pointer_signature_pointers(Fpointers func) {
+  // WEBASSEMBLY:  %0 = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, token poison, ptr poison, ptr poison, ptr poison, ptr poison, ptr poison, ptr poison)
+  use(__builtin_wasm_test_function_pointer_signature(func));
+}
+
+typedef void (*FVarArgs)(int, ...);
+void test_function_pointer_signature_varargs(FVarArgs func) {
+  // WEBASSEMBLY:  %0 = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, token poison, i32 poison, ptr poison)
+  use(__builtin_wasm_test_function_pointer_signature(func));
+}
+
+typedef __externref_t (*FExternRef)(__externref_t, __externref_t);
+void test_function_pointer_externref(FExternRef func) {
+  // WEBASSEMBLY:  %0 = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, ptr addrspace(10) poison, token poison, ptr addrspace(10) poison, ptr addrspace(10) poison)
+  use(__builtin_wasm_test_function_pointer_signature(func));
+}
+
+typedef __funcref Fpointers (*FFuncRef)(__funcref Fvoid, __funcref Ffloats);
+void test_function_pointer_funcref(FFuncRef func) {
+  // WEBASSEMBLY:  %0 = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, ptr addrspace(20) poison, token poison, ptr addrspace(20) poison, ptr addrspace(20) poison)
+  use(__builtin_wasm_test_function_pointer_signature(func));
+}
+
+#ifdef SINGLE_VALUE
+// Some tests that we get struct ABIs correct. There is no special code in
+// __builtin_wasm_test_function_pointer_signature for this, it gets handled by
+// the normal type lowering code.
+// Single element structs are unboxed, multi element structs are passed on
+// stack.
+typedef struct {double x;} (*Fstructs1)(struct {double x;}, struct {float x;}, struct {double x; float y;});
+void test_function_pointer_structs1(Fstructs1 func) {
+  // WEBASSEMBLY-SV:  %0 = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, double poison, token poison, double poison, float poison, ptr poison)
+  use(__builtin_wasm_test_function_pointer_signature(func));
+}
+
+// Two element return struct ==> return ptr on stack
+typedef struct {double x; double y;} (*Fstructs2)(void);
+void test_function_pointer_structs2(Fstructs2 func) {
+  // WEBASSEMBLY-SV:  %0 = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, token poison, ptr poison)
+  use(__builtin_wasm_test_function_pointer_signature(func));
+}
+
+// Return union ==> return ptr on stack, one element union => unboxed
+typedef union {double x; float y;} (*FUnions)(union {double x; float y;}, union {double x;});
+void test_function_pointer_unions(FUnions func) {
+  // WEBASSEMBLY-SV:  %0 = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, token poison, ptr poison, ptr poison, double poison)
+  use(__builtin_wasm_test_function_pointer_signature(func));
+}
+#endif
diff --git a/clang/test/CodeGen/builtins-wasm.c b/clang/test/CodeGen/builtins-wasm.c
@@ -751,24 +751,3 @@ void *tp (void) {
   return __builtin_thread_pointer ();
   // WEBASSEMBLY: call {{.*}} @llvm.thread.pointer.p0()
 }
-
-typedef void (*Fvoid)(void);
-typedef float (*Ffloats)(float, double, int);
-typedef void (*Fpointers)(Fvoid, Ffloats, void*, int*, int***, char[5]);
-
-void use(int);
-
-void test_function_pointer_signature_void(Fvoid func) {
-  // WEBASSEMBLY:  %0 = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, token poison)
-  use(__builtin_wasm_test_function_pointer_signature(func));
-}
-
-void test_function_pointer_signature_floats(Ffloats func) {
-  // WEBASSEMBLY:  tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, float 0.000000e+00, token poison, float 0.000000e+00, double 0.000000e+00, i32 0)
-  use(__builtin_wasm_test_function_pointer_signature(func));
-}
-
-void test_function_pointer_signature_pointers(Fpointers func) {
-  // WEBASSEMBLY:  %0 = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, token poison, ptr null, ptr null, ptr null, ptr null, ptr null, ptr null)
-  use(__builtin_wasm_test_function_pointer_signature(func));
-}
diff --git a/clang/test/Sema/builtins-wasm.c b/clang/test/Sema/builtins-wasm.c
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -triple wasm32 -target-feature +reference-types %s
+// RUN: %clang_cc1 -fsyntax-only -verify -triple wasm32 -target-abi experimental-mv -DMULTIVALUE -target-feature +reference-types %s
 
 #define EXPR_HAS_TYPE(expr, type) _Generic((expr), type : 1, default : 0)
 
@@ -57,8 +58,8 @@ void test_table_copy(int dst_idx, int src_idx, int nelem) {
 
 typedef void (*F1)(void);
 typedef int (*F2)(int);
-typedef int (*F3)(__externref_t);
-typedef __externref_t (*F4)(int);
+typedef void (*F3)(struct {int x; double y;});
+typedef struct {int x; double y;} (*F4)(void);
 
 void test_function_pointer_signature() {
   // Test argument count validation
@@ -68,13 +69,21 @@ void test_function_pointer_signature() {
   // // Test argument type validation - should require function pointer
   (void)__builtin_wasm_test_function_pointer_signature((void*)0); // expected-error {{used type 'void *' where function pointer is required}}
   (void)__builtin_wasm_test_function_pointer_signature((int)0);   // expected-error {{used type 'int' where function pointer is required}}
-  (void)__builtin_wasm_test_function_pointer_signature((F3)0);   // expected-error {{not supported for function pointers with a reference type parameter}}
-  (void)__builtin_wasm_test_function_pointer_signature((F4)0);   // expected-error {{not supported for function pointers with a reference type return value}}
 
   // // Test valid usage
   int res = __builtin_wasm_test_function_pointer_signature((F1)0);
   res = __builtin_wasm_test_function_pointer_signature((F2)0);
 
   // Test return type
   _Static_assert(EXPR_HAS_TYPE(__builtin_wasm_test_function_pointer_signature((F1)0), int), "");
+
+#ifdef MULTIVALUE
+  // Test that struct arguments and returns are rejected with multivalue abi
+  (void)__builtin_wasm_test_function_pointer_signature((F3)0); // expected-error {{not supported with the multivalue ABI for function pointers with a struct/union as parameter}}
+  (void)__builtin_wasm_test_function_pointer_signature((F4)0); // expected-error {{not supported with the multivalue ABI for function pointers with a struct/union as return value}}
+#else
+  // with default abi they are fine
+  (void)__builtin_wasm_test_function_pointer_signature((F3)0);
+  (void)__builtin_wasm_test_function_pointer_signature((F4)0);
+#endif
 }
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISelDAGToDAG.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyISelDAGToDAG.cpp
@@ -136,6 +136,15 @@ static APInt encodeFunctionSignature(SelectionDAG *DAG, SDLoc &DL,
     if (VT == MVT::f64) {
       return wasm::ValType::F64;
     }
+    if (VT == MVT::externref) {
+      return wasm::ValType::EXTERNREF;
+    }
+    if (VT == MVT::funcref) {
+      return wasm::ValType::FUNCREF;
+    }
+    if (VT == MVT::exnref) {
+      return wasm::ValType::EXNREF;
+    }
     LLVM_DEBUG(errs() << "Unhandled type for llvm.wasm.ref.test.func: " << VT
                       << "\n");
     llvm_unreachable("Unhandled type for llvm.wasm.ref.test.func");
diff --git a/llvm/test/CodeGen/WebAssembly/ref-test-func.ll b/llvm/test/CodeGen/WebAssembly/ref-test-func.ll
@@ -31,7 +31,7 @@ define void @test_fpsig_return_i32(ptr noundef %func) local_unnamed_addr #0 {
 ; CHECK-NEXT:    call use
 ; CHECK-NEXT:    # fallthrough-return
 entry:
-  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, i32 0)
+  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, i32 poison)
   tail call void @use(i32 noundef %res) #3
   ret void
 }
@@ -48,7 +48,7 @@ define void @test_fpsig_return_i64(ptr noundef %func) local_unnamed_addr #0 {
 ; CHECK-NEXT:    call use
 ; CHECK-NEXT:    # fallthrough-return
 entry:
-  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, i64 0)
+  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, i64 poison)
   tail call void @use(i32 noundef %res) #3
   ret void
 }
@@ -65,7 +65,7 @@ define void @test_fpsig_return_f32(ptr noundef %func) local_unnamed_addr #0 {
 ; CHECK-NEXT:    call use
 ; CHECK-NEXT:    # fallthrough-return
 entry:
-  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, float 0.)
+  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, float poison)
   tail call void @use(i32 noundef %res) #3
   ret void
 }
@@ -82,7 +82,7 @@ define void @test_fpsig_return_f64(ptr noundef %func) local_unnamed_addr #0 {
 ; CHECK-NEXT:    call use
 ; CHECK-NEXT:    # fallthrough-return
 entry:
-  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, double 0.)
+  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, double poison)
   tail call void @use(i32 noundef %res) #3
   ret void
 }
@@ -100,7 +100,7 @@ define void @test_fpsig_param_i32(ptr noundef %func) local_unnamed_addr #0 {
 ; CHECK-NEXT:    call use
 ; CHECK-NEXT:    # fallthrough-return
 entry:
-  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, token poison, double 0.)
+  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, token poison, double poison)
   tail call void @use(i32 noundef %res) #3
   ret void
 }
@@ -118,7 +118,7 @@ define void @test_fpsig_multiple_params_and_returns(ptr noundef %func) local_unn
 ; CHECK-NEXT:    call use
 ; CHECK-NEXT:    # fallthrough-return
 entry:
-  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, i32 0, i64 0, float 0., double 0., token poison, i64 0, float 0., i64 0)
+  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, i32 poison, i64 poison, float poison, double poison, token poison, i64 poison, float poison, i64 poison)
   tail call void @use(i32 noundef %res) #3
   ret void
 }
@@ -137,10 +137,26 @@ define void @test_fpsig_ptrs(ptr noundef %func) local_unnamed_addr #0 {
 ; CHECK-NEXT:    call use
 ; CHECK-NEXT:    # fallthrough-return
 entry:
-  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, ptr null, token poison, ptr null, ptr null)
+  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, ptr poison, token poison, ptr poison, ptr poison)
   tail call void @use(i32 noundef %res) #3
   ret void
 }
 
+define void @test_reference_types(ptr noundef %func) local_unnamed_addr #0 {
+; CHECK-LABEL: test_reference_types:
+; CHK32:         .functype test_reference_types (i32) -> ()
+; CHK64:         .functype test_reference_types (i64) -> ()
+; CHECK-NEXT:  # %bb.0: # %entry
+; CHECK-NEXT:    local.get 0
+; CHK64-NEXT:    i32.wrap_i64
+; CHECK-NEXT:    table.get __indirect_function_table
+; CHECK-NEXT:    ref.test (funcref, externref) -> (externref)
+; CHECK-NEXT:    call use
+; CHECK-NEXT:    # fallthrough-return
+entry:
+  %res = tail call i32 (ptr, ...) @llvm.wasm.ref.test.func(ptr %func, ptr addrspace(10) poison, token poison, ptr addrspace(20) poison, ptr addrspace(10) poison)
+  tail call void @use(i32 noundef %res) #3
+  ret void
+}
 
 declare void @use(i32 noundef) local_unnamed_addr #1
