[WebAssembly] Add -fwasm-exceptions for wasm EH

Summary:
This adds `-fwasm-exceptions` (in similar fashion with
`-fdwarf-exceptions` or `-fsjlj-exceptions`) that turns on everything
with wasm exception handling from the frontend to the backend.

We currently have `-mexception-handling` in clang frontend, but this is
only about the architecture capability and does not turn on other
necessary options such as the exception model in the backend. (This can
be turned on with `llc -exception-model=wasm`, but llc is not invoked
separately as a command line tool, so this option has to be transferred
from clang.)

Turning on `-fwasm-exceptions` in clang also turns on
`-mexception-handling` if not specified, and will error out if
`-mno-exception-handling` is specified.

Reviewers: dschuff, tlively, sbc100

Subscribers: aprantl, jgravelle-google, sunfish, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D67208

llvm-svn: 371708

clang/include/clang/Basic/LangOptions.def

@@ -128,6 +128,7 @@ LANGOPT(CXXExceptions     , 1, 0, "C++ exceptions")
 LANGOPT(DWARFExceptions   , 1, 0, "dwarf exception handling")
 LANGOPT(SjLjExceptions    , 1, 0, "setjmp-longjump exception handling")
 LANGOPT(SEHExceptions     , 1, 0, "SEH .xdata exception handling")
+LANGOPT(WasmExceptions    , 1, 0, "WebAssembly exception handling")
 LANGOPT(ExternCNoUnwind   , 1, 0, "Assume extern C functions don't unwind")
 LANGOPT(TraditionalCPP    , 1, 0, "traditional CPP emulation")
 LANGOPT(RTTI              , 1, 1, "run-time type information")

clang/include/clang/Driver/Options.td

@@ -904,6 +904,8 @@ def fsjlj_exceptions : Flag<["-"], "fsjlj-exceptions">, Group<f_Group>,
   Flags<[CC1Option]>, HelpText<"Use SjLj style exceptions">;
 def fseh_exceptions : Flag<["-"], "fseh-exceptions">, Group<f_Group>,
   Flags<[CC1Option]>, HelpText<"Use SEH style exceptions">;
+def fwasm_exceptions : Flag<["-"], "fwasm-exceptions">, Group<f_Group>,
+  Flags<[CC1Option]>, HelpText<"Use WebAssembly style exceptions">;
 def fexcess_precision_EQ : Joined<["-"], "fexcess-precision=">,
     Group<clang_ignored_gcc_optimization_f_Group>;
 def : Flag<["-"], "fexpensive-optimizations">, Group<clang_ignored_gcc_optimization_f_Group>;

clang/lib/CodeGen/BackendUtil.cpp

@@ -468,6 +468,8 @@ static void initTargetOptions(llvm::TargetOptions &Options,
     Options.ExceptionModel = llvm::ExceptionHandling::WinEH;
   if (LangOpts.DWARFExceptions)
     Options.ExceptionModel = llvm::ExceptionHandling::DwarfCFI;
+  if (LangOpts.WasmExceptions)
+    Options.ExceptionModel = llvm::ExceptionHandling::Wasm;
 
   Options.NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
   Options.NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;

clang/lib/CodeGen/CGException.cpp

@@ -165,10 +165,7 @@ static const EHPersonality &getCXXPersonality(const TargetInfo &Target,
     return EHPersonality::GNU_CPlusPlus;
   if (L.SEHExceptions)
     return EHPersonality::GNU_CPlusPlus_SEH;
-  // Wasm EH is a non-MVP feature for now.
+  if (L.WasmExceptions)
-  if (Target.hasFeature("exception-handling") &&
-      (T.getArch() == llvm::Triple::wasm32 ||
-       T.getArch() == llvm::Triple::wasm64))
     return EHPersonality::GNU_Wasm_CPlusPlus;
   return EHPersonality::GNU_CPlusPlus;
 }

clang/lib/Driver/ToolChains/Clang.cpp

@@ -4981,9 +4981,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     addExceptionArgs(Args, InputType, TC, KernelOrKext, Runtime, CmdArgs);
 
   // Handle exception personalities
-  Arg *A = Args.getLastArg(options::OPT_fsjlj_exceptions,
+  Arg *A = Args.getLastArg(
-                           options::OPT_fseh_exceptions,
+      options::OPT_fsjlj_exceptions, options::OPT_fseh_exceptions,
-                           options::OPT_fdwarf_exceptions);
+      options::OPT_fdwarf_exceptions, options::OPT_fwasm_exceptions);
   if (A) {
     const Option &Opt = A->getOption();
     if (Opt.matches(options::OPT_fsjlj_exceptions))
@@ -4992,6 +4992,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       CmdArgs.push_back("-fseh-exceptions");
     if (Opt.matches(options::OPT_fdwarf_exceptions))
       CmdArgs.push_back("-fdwarf-exceptions");
+    if (Opt.matches(options::OPT_fwasm_exceptions))
+      CmdArgs.push_back("-fwasm-exceptions");
   } else {
     switch (TC.GetExceptionModel(Args)) {
     default:

clang/lib/Driver/ToolChains/WebAssembly.cpp

@@ -166,6 +166,26 @@ void WebAssembly::addClangTargetOptions(const ArgList &DriverArgs,
     CC1Args.push_back("-target-feature");
     CC1Args.push_back("+mutable-globals");
   }
+
+  if (DriverArgs.getLastArg(options::OPT_fwasm_exceptions)) {
+    // '-fwasm-exceptions' is not compatible with '-mno-exception-handling'
+    if (DriverArgs.hasFlag(options::OPT_mno_exception_handing,
+                           options::OPT_mexception_handing, false))
+      getDriver().Diag(diag::err_drv_argument_not_allowed_with)
+          << "-fwasm-exceptions"
+          << "-mno-exception-handling";
+    // '-fwasm-exceptions' is not compatible with
+    // '-mllvm -enable-emscripten-cxx-exceptions'
+    for (const Arg *A : DriverArgs.filtered(options::OPT_mllvm)) {
+      if (StringRef(A->getValue(0)) == "-enable-emscripten-cxx-exceptions")
+        getDriver().Diag(diag::err_drv_argument_not_allowed_with)
+            << "-fwasm-exceptions"
+            << "-mllvm -enable-emscripten-cxx-exceptions";
+    }
+    // '-fwasm-exceptions' implies exception-handling
+    CC1Args.push_back("-target-feature");
+    CC1Args.push_back("+exception-handling");
+  }
 }
 
 ToolChain::RuntimeLibType WebAssembly::GetDefaultRuntimeLibType() const {

clang/lib/Frontend/CompilerInvocation.cpp

@@ -2686,9 +2686,9 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
       Opts.FixedPoint;
 
   // Handle exception personalities
-  Arg *A = Args.getLastArg(options::OPT_fsjlj_exceptions,
+  Arg *A = Args.getLastArg(
-                           options::OPT_fseh_exceptions,
+      options::OPT_fsjlj_exceptions, options::OPT_fseh_exceptions,
-                           options::OPT_fdwarf_exceptions);
+      options::OPT_fdwarf_exceptions, options::OPT_fwasm_exceptions);
   if (A) {
     const Option &Opt = A->getOption();
     llvm::Triple T(TargetOpts.Triple);
@@ -2699,6 +2699,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
     Opts.SjLjExceptions = Opt.matches(options::OPT_fsjlj_exceptions);
     Opts.SEHExceptions = Opt.matches(options::OPT_fseh_exceptions);
     Opts.DWARFExceptions = Opt.matches(options::OPT_fdwarf_exceptions);
+    Opts.WasmExceptions = Opt.matches(options::OPT_fwasm_exceptions);
   }
 
   Opts.ExternCNoUnwind = Args.hasArg(OPT_fexternc_nounwind);

clang/test/CodeGenCXX/wasm-eh.cpp

@@ -1,5 +1,6 @@
-// RUN: %clang_cc1 %s -triple wasm32-unknown-unknown -fms-extensions -fexceptions -fcxx-exceptions -target-feature +exception-handling -emit-llvm -o - -std=c++11 | FileCheck %s
+// RUN: %clang_cc1 %s -triple wasm32-unknown-unknown -fms-extensions -fexceptions -fcxx-exceptions -fwasm-exceptions -target-feature +exception-handling -emit-llvm -o - -std=c++11 | FileCheck %s
-// RUN: %clang_cc1 %s -triple wasm64-unknown-unknown -fms-extensions -fexceptions -fcxx-exceptions -target-feature +exception-handling -emit-llvm -o - -std=c++11 | FileCheck %s
+// RUN: %clang_cc1 %s -triple wasm64-unknown-unknown -fms-extensions -fexceptions -fcxx-exceptions -fwasm-exceptions -target-feature +exception-handling -emit-llvm -o - -std=c++11 | FileCheck %s
+// RUN: %clang_cc1 %s -triple wasm32-unknown-unknown -fms-extensions -fexceptions -fcxx-exceptions -fwasm-exceptions -target-feature +exception-handling -S -o - -std=c++11 | FileCheck %s --check-prefix=ASSEMBLY
 
 void may_throw();
 void dont_throw() noexcept;
@@ -382,3 +383,11 @@ void test8() {
 // CHECK:   cleanupret from %[[CLEANUPPAD1]] unwind to caller
 
 // CHECK:   unreachable
+
+// Here we only check if the command enables wasm exception handling in the
+// backend so that exception handling instructions can be generated in .s file.
+
+// ASSEMBLY: try
+// ASSEMBLY: catch
+// ASSEMBLY: rethrow
+// ASSEMBLY: end_try

clang/test/Driver/wasm-toolchain.c

@@ -73,6 +73,25 @@
 // RUN:   | FileCheck -check-prefix=PTHREAD_NO_MUT_GLOBALS %s
 // PTHREAD_NO_MUT_GLOBALS: invalid argument '-pthread' not allowed with '-mno-mutable-globals'
 
+// '-fwasm-exceptions' sets +exception-handling
+// RUN: %clang -### -no-canonical-prefixes -target wasm32-unknown-unknown \
+// RUN:    --sysroot=/foo %s -fwasm-exceptions 2>&1 \
+// RUN:  | FileCheck -check-prefix=WASM_EXCEPTIONS %s
+// WASM_EXCEPTIONS: clang{{.*}}" "-cc1" {{.*}} "-target-feature" "+exception-handling"
+
+// '-fwasm-exceptions' not allowed with '-mno-exception-handling'
+// RUN: %clang -### -no-canonical-prefixes -target wasm32-unknown-unknown \
+// RUN:     --sysroot=/foo %s -fwasm-exceptions -mno-exception-handling 2>&1 \
+// RUN:   | FileCheck -check-prefix=WASM_EXCEPTIONS_NO_EH %s
+// WASM_EXCEPTIONS_NO_EH: invalid argument '-fwasm-exceptions' not allowed with '-mno-exception-handling'
+
+// '-fwasm-exceptions' not allowed with
+// '-mllvm -enable-emscripten-cxx-exceptions'
+// RUN: %clang -### -no-canonical-prefixes -target wasm32-unknown-unknown \
+// RUN:     --sysroot=/foo %s -fwasm-exceptions -mllvm -enable-emscripten-cxx-exceptions 2>&1 \
+// RUN:   | FileCheck -check-prefix=WASM_EXCEPTIONS_EMSCRIPTEN_EH %s
+// WASM_EXCEPTIONS_EMSCRIPTEN_EH: invalid argument '-fwasm-exceptions' not allowed with '-mllvm -enable-emscripten-cxx-exceptions'
+
 // RUN: %clang %s -### -fsanitize=address -target wasm32-unknown-emscripten 2>&1 | FileCheck -check-prefix=CHECK-ASAN-EMSCRIPTEN %s
 // CHECK-ASAN-EMSCRIPTEN: "-fsanitize=address"
 // CHECK-ASAN-EMSCRIPTEN: "-fsanitize-address-globals-dead-stripping"