[WebAssembly] Add Wasm SjLj option support for clang

[aheejin]

Summary

This adds support for Wasm SjLj in clang. Also this sets the new
-mllvm -wasm-enable-eh option for Wasm EH.

Note there is a little unfortunate inconsistency there: Wasm EH is
enabled by a clang option -fwasm-exceptions, which sets
-mllvm -wasm-enable-eh in the backend options. It also sets
-exception-model=wasm but this is done in the common code.

Wasm SjLj doesn't have a clang-level option like -fwasm-exceptions.
-fwasm-exceptions was added because each exception model has its
corresponding -f***-exceptions, but I'm not sure if adding a new
option like -fwasm-sjlj or something is a good idea.

So the current plan is Emscripten sets -mllvm -wasm-enable-sjlj if
Wasm SJLj is enabled in its settings.js, as it does for Emscripten
EH/SjLj (it sets -mllvm -enable-emscripten-cxx-exceptions for
Emscripten EH and -mllvm -enable-emscripten-sjlj for Emscripten SjLj).
And setting this enables the exception handling feature, and also sets
-exception-model=wasm, but this time this is not done in the common
code so we do it ourselves. It also sets the multivalue feature, because
for longjmp we throw two values and catch two values: the setjmp
buffer and the return value. So catch instruction will produce two
values.

Also note that other exception models have 1-to-1 correspondance with
their -f***-exceptions flag and their -exception-model=*** flag, but
because we use -exception-model=wasm also for Wasm SjLj while
-fwasm-exceptions still means Wasm EH, there is also a little
inconsistency there, but I think it is manageable.

Also this adds various error checking and tests.

[aheejin]

Oh, I fortot I made this currently set +multivalue feature... Maybe we have to rethink that.

[aheejin]

Oh sorry I clicked the wrong button....

[aheejin]

As we discussed offline, I'll remove +multivalue part for now; it doesn't have reliable support in the Wasm LLVM backend and Binaryen yet.

[aheejin]

Remove multivalue setting

clang/lib/Driver/ToolChains/WebAssembly.cpp

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 feature
     CC1Args.push_back("-target-feature");
     CC1Args.push_back("+exception-handling");
+    // Backend needs -wasm-enable-eh to enable Wasm EH
+    CC1Args.push_back("-mllvm");
+    CC1Args.push_back("-wasm-enable-eh");
   }
 
   for (const Arg *A : DriverArgs.filtered(options::OPT_mllvm)) {
     StringRef Opt = A->getValue(0);
     if (Opt.startswith("-emscripten-cxx-exceptions-allowed")) {
       // '-mllvm -emscripten-cxx-exceptions-allowed' should be used with
       // '-mllvm -enable-emscripten-cxx-exceptions'
-      bool EmExceptionArgExists = false;
+      bool EmEHArgExists = false;
       for (const Arg *A : DriverArgs.filtered(options::OPT_mllvm)) {
         if (StringRef(A->getValue(0)) == "-enable-emscripten-cxx-exceptions") {
-          EmExceptionArgExists = true;
+          EmEHArgExists = true;
           break;
         }
       }
-      if (!EmExceptionArgExists)
+      if (!EmEHArgExists)
         getDriver().Diag(diag::err_drv_argument_only_allowed_with)
             << "-mllvm -emscripten-cxx-exceptions-allowed"
             << "-mllvm -enable-emscripten-cxx-exceptions";
 
       // Prevent functions specified in -emscripten-cxx-exceptions-allowed list
       // from being inlined before reaching the wasm backend.
       StringRef FuncNamesStr = Opt.split('=').second;
       SmallVector<StringRef, 4> FuncNames;
       FuncNamesStr.split(FuncNames, ',');
       for (auto Name : FuncNames) {
         CC1Args.push_back("-mllvm");
         CC1Args.push_back(DriverArgs.MakeArgString("--force-attribute=" + Name +
                                                    ":noinline"));
       }
     }
+
+    if (Opt.startswith("-wasm-enable-sjlj")) {
+      // '-mllvm -wasm-enable-sjlj' 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)
+            << "-mllvm -wasm-enable-sjlj"
+            << "-mno-exception-handling";
+      // '-mllvm -wasm-enable-sjlj' is not compatible with
+      // '-mllvm -enable-emscripten-cxx-exceptions'
+      // because we don't allow Emscripten EH + Wasm SjLj
+      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)
+              << "-mllvm -wasm-enable-sjlj"
+              << "-mllvm -enable-emscripten-cxx-exceptions";
+      }
+      // '-mllvm -wasm-enable-sjlj' is not compatible with
+      // '-mllvm -enable-emscripten-sjlj'
+      for (const Arg *A : DriverArgs.filtered(options::OPT_mllvm)) {
+        if (StringRef(A->getValue(0)) == "-enable-emscripten-sjlj")
+          getDriver().Diag(diag::err_drv_argument_not_allowed_with)
+              << "-mllvm -wasm-enable-sjlj"
+              << "-mllvm -enable-emscripten-sjlj";
+      }
+      // '-mllvm -wasm-enable-sjlj' implies exception-handling feature
+      CC1Args.push_back("-target-feature");
+      CC1Args.push_back("+exception-handling");
+      // Backend needs '-exception-model=wasm' to use Wasm EH instructions
+      CC1Args.push_back("-exception-model=wasm");
+    }
   }
 }
 
 ToolChain::RuntimeLibType WebAssembly::GetDefaultRuntimeLibType() const {
   return ToolChain::RLT_CompilerRT;
 }
 
 ToolChain::CXXStdlibType

clang/test/Driver/wasm-toolchain.c

 
 // '-mllvm -emscripten-cxx-exceptions-allowed' only allowed with
 // '-mllvm -enable-emscripten-cxx-exceptions'
 // RUN: %clang -### -no-canonical-prefixes -target wasm32-unknown-unknown \
 // RUN:     --sysroot=/foo %s -mllvm -emscripten-cxx-exceptions-allowed 2>&1 \
 // RUN:   | FileCheck -check-prefix=EMSCRIPTEN_EH_ALLOWED_WO_ENABLE %s
 // EMSCRIPTEN_EH_ALLOWED_WO_ENABLE: invalid argument '-mllvm -emscripten-cxx-exceptions-allowed' only allowed with '-mllvm -enable-emscripten-cxx-exceptions'
 
-// '-fwasm-exceptions' sets +exception-handling
+// '-fwasm-exceptions' sets +exception-handling and '-mllvm -wasm-enable-eh'
 // 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"
+// WASM_EXCEPTIONS: clang{{.*}}" "-cc1" {{.*}} "-target-feature" "+exception-handling" "-mllvm" "-wasm-enable-eh"
 
 // '-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'
+// '-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:     --sysroot=/foo %s -fwasm-exceptions \
+// RUN:     -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'
 
+// '-mllvm -wasm-enable-sjlj' sets +exception-handling and
+// '-exception-model=wasm'
+// RUN: %clang -### -no-canonical-prefixes -target wasm32-unknown-unknown \
+// RUN:    --sysroot=/foo %s -mllvm -wasm-enable-sjlj 2>&1 \
+// RUN:  | FileCheck -check-prefix=WASM_SJLJ %s
+// WASM_SJLJ: clang{{.*}}" "-cc1" {{.*}} "-target-feature" "+exception-handling" "-exception-model=wasm"
+
+// '-mllvm -wasm-enable-sjlj' not allowed with '-mno-exception-handling'
+// RUN: %clang -### -no-canonical-prefixes -target wasm32-unknown-unknown \
+// RUN:     --sysroot=/foo %s -mllvm -wasm-enable-sjlj -mno-exception-handling \
+// RUN:     2>&1 \
+// RUN:   | FileCheck -check-prefix=WASM_SJLJ_NO_EH %s
+// WASM_SJLJ_NO_EH: invalid argument '-mllvm -wasm-enable-sjlj' not allowed with '-mno-exception-handling'
+
+// '-mllvm -wasm-enable-sjlj' not allowed with
+// '-mllvm -enable-emscripten-cxx-exceptions'
+// RUN: %clang -### -no-canonical-prefixes -target wasm32-unknown-unknown \
+// RUN:     --sysroot=/foo %s -mllvm -wasm-enable-sjlj \
+// RUN:     -mllvm -enable-emscripten-cxx-exceptions 2>&1 \
+// RUN:   | FileCheck -check-prefix=WASM_SJLJ_EMSCRIPTEN_EH %s
+// WASM_SJLJ_EMSCRIPTEN_EH: invalid argument '-mllvm -wasm-enable-sjlj' not allowed with '-mllvm -enable-emscripten-cxx-exceptions'
+
+// '-mllvm -wasm-enable-sjlj' not allowed with '-mllvm -enable-emscripten-sjlj'
+// RUN: %clang -### -no-canonical-prefixes -target wasm32-unknown-unknown \
+// RUN:     --sysroot=/foo %s -mllvm -wasm-enable-sjlj \
+// RUN:     -mllvm -enable-emscripten-sjlj 2>&1 \
+// RUN:   | FileCheck -check-prefix=WASM_SJLJ_EMSCRIPTEN_SJLJ %s
+// WASM_SJLJ_EMSCRIPTEN_SJLJ: invalid argument '-mllvm -wasm-enable-sjlj' not allowed with '-mllvm -enable-emscripten-sjlj'
+
 // 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"
 
 // Basic exec-model tests.
 
 // RUN: %clang %s -### -no-canonical-prefixes -target wasm32-unknown-unknown --sysroot=%s/no-sysroot-there -mexec-model=command 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHECK-COMMAND %s