[wasm] Migrate from catch_all to catch in the jiterpreter and destroy exceptions (#91364)

* Expose the cxa catch functions to jiterp
* Import the exception tag type from dotnet.wasm when generating jiterpreter modules
* Properly free C++ exceptions in do_jit_call_indirect_js and don't trap non-C++ exceptions
* Properly clean up exceptions in the fallback trampoline invoke routine (though this shouldn't be necessary)
* Call begin_catch/end_catch in generated jitcall trampolines
* Remove the jiterpreter_do_jit_call machinery, it is no longer useful
* Reuse loader feature detection for SIMD and EH

Author: kg

src/mono/CMakeLists.txt

@@ -655,7 +655,12 @@ if(LLVM_PREFIX)
 
   # llvm-config --cflags
   set(llvm_cflags "-I${LLVM_PREFIX}/include -D__STDC_CONSTANT_MACROS -D__STD_FORMAT_MACROS -D__STDC_LIMIT_MACROS")
-  set(llvm_cxxflags "-I${LLVM_PREFIX}/include ${MONO_cxx_include} ${MONO_cxx_std_version} ${MONO_stdlib} -fno-exceptions -fno-rtti -D__STDC_CONSTANT_MACROS -D__STD_FORMAT_MACROS -D__STDC_LIMIT_MACROS")
+
+  if (HOST_BROWSER)
+    set(llvm_cxxflags "-I${LLVM_PREFIX}/include ${MONO_cxx_include} ${MONO_cxx_std_version} ${MONO_stdlib} -fno-rtti -D__STDC_CONSTANT_MACROS -D__STD_FORMAT_MACROS -D__STDC_LIMIT_MACROS")
+  else()
+    set(llvm_cxxflags "-I${LLVM_PREFIX}/include ${MONO_cxx_include} ${MONO_cxx_std_version} ${MONO_stdlib} -fno-exceptions -fno-rtti -D__STDC_CONSTANT_MACROS -D__STD_FORMAT_MACROS -D__STDC_LIMIT_MACROS")
+  endif()
   set(llvm_includedir "${LLVM_PREFIX}/include")
 
   if(HOST_LINUX)
@@ -694,6 +699,10 @@ if(LLVM_PREFIX)
     string(REPLACE "/EHs-c-" "" llvm_cxxflags "${llvm_cxxflags}")
     # /GR- already enabled and inherited from LLVM flags. Corresponds to -fno-rtti.
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${llvm_cxxflags}")
+  elseif(HOST_BROWSER)
+    # emscripten's handling of the different exception modes is complex, so having multiple flags
+    # passed during a single compile is undesirable. we need to set them elsewhere.
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${llvm_cxxflags} -fno-rtti")
   else()
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${llvm_cxxflags} -fexceptions -fno-rtti")
   endif()

src/mono/mono.proj

@@ -207,7 +207,7 @@
       <ActualWasiSdkVersion>%(_ActualVersionLines.Identity)</ActualWasiSdkVersion>
       <ExpectedWasiSdkVersion>%(_ExpectedVersionLines.Identity)</ExpectedWasiSdkVersion>
     </PropertyGroup>
-    <Error Text="Expected and actual version of WASI SDK does not match. Please delete $(WASI_SDK_PATH) folder to provision a new version." 
+    <Error Text="Expected and actual version of WASI SDK does not match. Please delete $(WASI_SDK_PATH) folder to provision a new version."
       Condition="'$(ActualWasiSdkVersion)' != '$(ExpectedWasiSdkVersion)'" />
   </Target>
 
@@ -417,10 +417,8 @@
       <_MonoCMakeArgs Include="-DENABLE_ICALL_EXPORT=1"/>
       <_MonoCMakeArgs Include="-DENABLE_LAZY_GC_THREAD_CREATION=1"/>
       <_MonoCMakeArgs Include="-DENABLE_WEBCIL=1"/>
-      <_MonoCFLAGS Include="-fexceptions"/>
       <_MonoCFLAGS Condition="'$(MonoWasmThreads)' == 'true'" Include="-pthread"/>
       <_MonoCFLAGS Condition="'$(MonoWasmThreads)' == 'true'" Include="-D_GNU_SOURCE=1" />
-      <_MonoCXXFLAGS Include="-fexceptions"/>
       <_MonoCXXFLAGS Condition="'$(MonoWasmThreads)' == 'true'" Include="-pthread"/>
       <_MonoCXXFLAGS Condition="'$(MonoWasmThreads)' == 'true'" Include="-D_GNU_SOURCE=1" />
     </ItemGroup>
@@ -434,8 +432,8 @@
     </ItemGroup>
     <!-- WASI specific options -->
     <ItemGroup Condition="'$(TargetsWasi)' == 'true'">
-      <!-- TODOWASI 
-      use $(CrossToolchainFile) and eng/common/cross/toolchain.cmake ? 
+      <!-- TODOWASI
+      use $(CrossToolchainFile) and eng/common/cross/toolchain.cmake ?
       sockets,eventpipe, DENABLE_LLVM_RUNTIME
       -->
       <_MonoCFLAGS Include="$(EscapedQuoteW)-I$([MSBuild]::NormalizePath('$(MonoProjectRoot)', 'wasi', 'include').Replace('\','/'))$(EscapedQuoteW)"/>

src/mono/mono/mini/CMakeLists.txt

@@ -503,10 +503,14 @@ if(HOST_BROWSER)
   # This is the only source file which contains a c++ throw or catch
   add_library(mono-wasm-eh-js STATIC llvm-runtime.cpp)
   target_link_libraries (mono-wasm-eh-js PRIVATE monoapi eglib_api)
+  set_target_properties(mono-wasm-eh-js PROPERTIES COMPILE_FLAGS "-fexceptions")
+  set_target_properties(mono-wasm-eh-js PROPERTIES LINK_FLAGS "-fexceptions -s EXPORT_EXCEPTION_HANDLING_HELPERS=1")
   install(TARGETS mono-wasm-eh-js LIBRARY)
+
   add_library(mono-wasm-eh-wasm STATIC llvm-runtime.cpp)
   target_link_libraries (mono-wasm-eh-wasm PRIVATE monoapi eglib_api)
   set_target_properties(mono-wasm-eh-wasm PROPERTIES COMPILE_FLAGS "-fwasm-exceptions")
+  set_target_properties(mono-wasm-eh-wasm PROPERTIES LINK_FLAGS "-fwasm-exceptions -s EXPORT_EXCEPTION_HANDLING_HELPERS=1")
   install(TARGETS mono-wasm-eh-wasm LIBRARY)
 endif()
 

src/mono/mono/mini/interp/interp.c

@@ -2707,21 +2707,8 @@ do_jit_call (ThreadContext *context, stackval *ret_sp, stackval *sp, InterpFrame
 	interp_push_lmf (&ext, frame);
 
 	if (mono_aot_mode == MONO_AOT_MODE_LLVMONLY_INTERP) {
-#if JITERPRETER_ENABLE_SPECIALIZED_JIT_CALL
-		/*
-		 * invoke jit_call_cb via a single indirect function call that dispatches to
-		 *  either a specialized JS implementation or a specialized WASM EH version
-		 * see jiterpreter-jit-call.ts and do-jit-call.wat
-		 * NOTE: the first argument must ALWAYS be jit_call_cb for the specialization.
-		 *  the actual implementation cannot verify this at runtime, so get it right
-		 * this is faster than mono_llvm_cpp_catch_exception by avoiding the use of
-		 *  emscripten invoke_vi to find and invoke jit_call_cb indirectly
-		 */
-		jiterpreter_do_jit_call (jit_call_cb, &cb_data, &thrown);
-#else
 		/* Catch the exception thrown by the native code using a try-catch */
 		mono_llvm_cpp_catch_exception (jit_call_cb, &cb_data, &thrown);
-#endif
 	} else {
 		jit_call_cb (&cb_data);
 	}

src/mono/mono/mini/interp/jiterpreter.c

@@ -60,10 +60,6 @@ void jiterp_preserve_module (void);
 static gint32 jiterpreter_abort_counts[MINT_LASTOP + 1] = { 0 };
 static int64_t jiterp_trace_bailout_counts[256] = { 0 };
 
-// This function pointer is used by interp.c to invoke jit_call_cb for exception handling purposes
-// See jiterpreter-jit-call.ts mono_jiterp_do_jit_call_indirect
-WasmDoJitCall jiterpreter_do_jit_call = mono_jiterp_do_jit_call_indirect;
-
 // We disable this diagnostic because EMSCRIPTEN_KEEPALIVE makes it a false alarm, the keepalive
 //  functions are being used externally. Having a bunch of prototypes is pointless since these
 //  functions are not consumed by C anywhere else
@@ -1021,20 +1017,6 @@ mono_jiterp_get_options_as_json ()
 	return mono_options_get_as_json ();
 }
 
-EMSCRIPTEN_KEEPALIVE void
-mono_jiterp_update_jit_call_dispatcher (WasmDoJitCall dispatcher)
-{
-	// If we received a 0 dispatcher that means the TS side failed to compile
-	//  any kind of dispatcher - this likely indicates that content security policy
-	//  blocked the use of Module.addFunction
-	if (!dispatcher)
-		dispatcher = (WasmDoJitCall)mono_llvm_cpp_catch_exception;
-	else if (((int)(void*)dispatcher)==-1)
-		dispatcher = mono_jiterp_do_jit_call_indirect;
-
-	jiterpreter_do_jit_call = dispatcher;
-}
-
 EMSCRIPTEN_KEEPALIVE int
 mono_jiterp_object_has_component_size (MonoObject ** ppObj)
 {

src/mono/mono/mini/interp/jiterpreter.h

@@ -5,12 +5,8 @@
 
 #ifdef DISABLE_THREADS
 #define JITERPRETER_ENABLE_JIT_CALL_TRAMPOLINES 1
-// enables specialized mono_llvm_cpp_catch_exception replacement (see jiterpreter-jit-call.ts)
-// works even if the jiterpreter is otherwise disabled.
-#define JITERPRETER_ENABLE_SPECIALIZED_JIT_CALL 1
 #else
 #define JITERPRETER_ENABLE_JIT_CALL_TRAMPOLINES 0
-#define JITERPRETER_ENABLE_SPECIALIZED_JIT_CALL 0
 #endif // DISABLE_THREADS
 
 // mono_interp_tier_prepare_jiterpreter will return these special values if it doesn't
@@ -49,9 +45,8 @@ __attribute__ ((__packed__, __aligned__(2)))
 // Keep in sync with JiterpreterTable in jiterpreter-enums.ts
 enum {
 	JITERPRETER_TABLE_TRACE = 0,
-	JITERPRETER_TABLE_DO_JIT_CALL = 1,
-	JITERPRETER_TABLE_JIT_CALL = 2,
-	JITERPRETER_TABLE_INTERP_ENTRY_STATIC_0 = 3,
+	JITERPRETER_TABLE_JIT_CALL = 1,
+	JITERPRETER_TABLE_INTERP_ENTRY_STATIC_0 = 2,
 	JITERPRETER_TABLE_INTERP_ENTRY_STATIC_1,
 	JITERPRETER_TABLE_INTERP_ENTRY_STATIC_2,
 	JITERPRETER_TABLE_INTERP_ENTRY_STATIC_3,
@@ -165,11 +160,6 @@ mono_interp_invoke_wasm_jit_call_trampoline (
 	void *ftndesc, gboolean *thrown
 );
 
-extern void
-mono_jiterp_do_jit_call_indirect (
-	gpointer cb, gpointer arg, gboolean *out_thrown
-);
-
 #ifdef __MONO_MINI_INTERPRETER_INTERNALS_H__
 
 extern void
@@ -247,8 +237,6 @@ mono_jiterp_tlqueue_purge_all (gpointer item);
 
 #endif // __MONO_MINI_INTERPRETER_INTERNALS_H__
 
-extern WasmDoJitCall jiterpreter_do_jit_call;
-
 #endif // HOST_BROWSER
 
 #endif // __MONO_MINI_JITERPRETER_H__

src/mono/mono/mini/llvm-runtime.cpp

@@ -47,4 +47,22 @@ mono_llvm_cpp_catch_exception (MonoLLVMInvokeCallback cb, gpointer arg, gboolean
 	}
 }
 
+#ifdef HOST_WASM
+
+// https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html
+void *__cxa_begin_catch (void *exceptionObject);
+void __cxa_end_catch (void);
+
+EMSCRIPTEN_KEEPALIVE void
+mono_jiterp_begin_catch (void *exception_object) {
+	__cxa_begin_catch (exception_object);
+}
+
+EMSCRIPTEN_KEEPALIVE void
+mono_jiterp_end_catch (void) {
+	return __cxa_end_catch ();
+}
+
+#endif
+
 }

src/mono/wasm/build/WasmApp.Native.targets

@@ -26,6 +26,8 @@
       _ReadEmccProps
     </_BeforeWasmBuildAppDependsOn>
 
+    <_EmccDefaultFlags Condition="'$(WasmEnableExceptionHandling)' == 'false'">-fexceptions</_EmccDefaultFlags>
+    <_EmccDefaultFlags Condition="'$(WasmEnableExceptionHandling)' != 'false'">-fwasm-exceptions</_EmccDefaultFlags>
     <_EmccDefaultFlags Condition="'$(WasmEnableSIMD)' == 'true'">-msimd128</_EmccDefaultFlags>
     <_ExeExt Condition="$([MSBuild]::IsOSPlatform('WINDOWS'))">.exe</_ExeExt>
     <WasmUseEMSDK_PATH Condition="'$(WasmUseEMSDK_PATH)' == '' and '$(EMSDK_PATH)' != '' and Exists('$(MSBuildThisFileDirectory)WasmApp.InTree.targets')">true</WasmUseEMSDK_PATH>
@@ -254,6 +256,7 @@
       <_EmccLDFlags Include="$(EmccLinkOptimizationFlag)" />
       <_EmccLDFlags Include="@(_EmccCommonFlags)" />
       <_EmccLDFlags Include="-s EXPORT_ES6=1" />
+      <_EmccLDFlags Condition="'$(WasmEnableExceptionHandling)' != 'false'" Include="-s EXPORT_EXCEPTION_HANDLING_HELPERS=1"   />
 
       <_DriverCDependencies Include="$(_WasmPInvokeHPath);$(_WasmICallTablePath)" />
       <_DriverCDependencies Include="$(_DriverGenCPath)" Condition="'$(_DriverGenCNeeded)' == 'true'" />

src/mono/wasm/runtime/cwraps.ts

@@ -118,7 +118,6 @@ const fn_signatures: SigLine[] = [
     [true, "mono_jiterp_adjust_abort_count", "number", ["number", "number"]],
     [true, "mono_jiterp_register_jit_call_thunk", "void", ["number", "number"]],
     [true, "mono_jiterp_type_get_raw_value_size", "number", ["number"]],
-    [true, "mono_jiterp_update_jit_call_dispatcher", "void", ["number"]],
     [true, "mono_jiterp_get_signature_has_this", "number", ["number"]],
     [true, "mono_jiterp_get_signature_return_type", "number", ["number"]],
     [true, "mono_jiterp_get_signature_param_count", "number", ["number"]],
@@ -147,6 +146,8 @@ const fn_signatures: SigLine[] = [
     [true, "mono_jiterp_tlqueue_next", "number", ["number"]],
     [true, "mono_jiterp_tlqueue_add", "number", ["number", "number"]],
     [true, "mono_jiterp_tlqueue_clear", "void", ["number"]],
+    [true, "mono_jiterp_begin_catch", "void", ["number"]],
+    [true, "mono_jiterp_end_catch", "void", []],
 
     ...diagnostics_cwraps,
     ...legacy_interop_cwraps
@@ -259,7 +260,6 @@ export interface t_Cwraps {
     mono_jiterp_get_options_version(): number;
     mono_jiterp_adjust_abort_count(opcode: number, delta: number): number;
     mono_jiterp_register_jit_call_thunk(cinfo: number, func: number): void;
-    mono_jiterp_update_jit_call_dispatcher(fn: number): void;
     mono_jiterp_get_signature_has_this(sig: VoidPtr): number;
     mono_jiterp_get_signature_return_type(sig: VoidPtr): MonoType;
     mono_jiterp_get_signature_param_count(sig: VoidPtr): number;
@@ -291,6 +291,8 @@ export interface t_Cwraps {
     // returns new size of queue after add
     mono_jiterp_tlqueue_add(queue: number, value: VoidPtr): number;
     mono_jiterp_tlqueue_clear(queue: number): void;
+    mono_jiterp_begin_catch(ptr: number): void;
+    mono_jiterp_end_catch(): void;
 }
 
 const wrapped_c_functions: t_Cwraps = <any>{};

src/mono/wasm/runtime/exports-binding.ts

@@ -10,7 +10,7 @@ import { mono_wasm_bind_cs_function } from "./invoke-cs";
 import { mono_wasm_bind_js_function, mono_wasm_invoke_bound_function, mono_wasm_invoke_import } from "./invoke-js";
 import { mono_interp_tier_prepare_jiterpreter, mono_jiterp_free_method_data_js } from "./jiterpreter";
 import { mono_interp_jit_wasm_entry_trampoline, mono_interp_record_interp_entry } from "./jiterpreter-interp-entry";
-import { mono_interp_jit_wasm_jit_call_trampoline, mono_interp_invoke_wasm_jit_call_trampoline, mono_interp_flush_jitcall_queue, mono_jiterp_do_jit_call_indirect } from "./jiterpreter-jit-call";
+import { mono_interp_jit_wasm_jit_call_trampoline, mono_interp_invoke_wasm_jit_call_trampoline, mono_interp_flush_jitcall_queue } from "./jiterpreter-jit-call";
 import { mono_wasm_marshal_promise } from "./marshal-to-js";
 import { mono_wasm_eventloop_has_unsettled_interop_promises } from "./pthreads/shared/eventloop";
 import { mono_wasm_pthread_on_pthread_attached, mono_wasm_pthread_on_pthread_detached } from "./pthreads/worker";
@@ -88,7 +88,6 @@ export const mono_wasm_imports = [
     mono_interp_jit_wasm_jit_call_trampoline,
     mono_interp_invoke_wasm_jit_call_trampoline,
     mono_interp_flush_jitcall_queue,
-    mono_jiterp_do_jit_call_indirect,
     mono_jiterp_free_method_data_js,
 
     mono_wasm_profiler_enter,