[V8][Wasm] Wasm throws.

This CL implements the throw wasm opcode. This is a pre-requisite for
implementing try-catches in wasm.

BUG=

Review-Url: https://codereview.chromium.org/2339053003
Cr-Commit-Position: refs/heads/master@{#39449}

src/compiler/wasm-compiler.cc

@@ -1703,6 +1703,29 @@ Node* WasmGraphBuilder::GrowMemory(Node* input) {
   return result;
 }
 
+Node* WasmGraphBuilder::Throw(Node* input) {
+  MachineOperatorBuilder* machine = jsgraph()->machine();
+
+  // Pass the thrown value as two SMIs:
+  //
+  // upper = static_cast<uint32_t>(input) >> 16;
+  // lower = input & 0xFFFF;
+  //
+  // This is needed because we can't safely call BuildChangeInt32ToTagged from
+  // this method.
+  //
+  // TODO(wasm): figure out how to properly pass this to the runtime function.
+  Node* upper = BuildChangeInt32ToSmi(
+      graph()->NewNode(machine->Word32Shr(), input, Int32Constant(16)));
+  Node* lower = BuildChangeInt32ToSmi(
+      graph()->NewNode(machine->Word32And(), input, Int32Constant(0xFFFFu)));
+
+  Node* parameters[] = {lower, upper};  // thrown value
+  return BuildCallToRuntime(Runtime::kWasmThrow, jsgraph(),
+                            module_->instance->context, parameters,
+                            arraysize(parameters), effect_, *control_);
+}
+
 Node* WasmGraphBuilder::BuildI32DivS(Node* left, Node* right,
                                      wasm::WasmCodePosition position) {
   MachineOperatorBuilder* m = jsgraph()->machine();

src/compiler/wasm-compiler.h

@@ -134,6 +134,7 @@ class WasmGraphBuilder {
   Node* Unop(wasm::WasmOpcode opcode, Node* input,
              wasm::WasmCodePosition position = wasm::kNoCodePosition);
   Node* GrowMemory(Node* input);
+  Node* Throw(Node* input);
   unsigned InputCount(Node* node);
   bool IsPhiWithMerge(Node* phi, Node* merge);
   void AppendToMerge(Node* merge, Node* from);
@@ -306,6 +307,7 @@ class WasmGraphBuilder {
 
   Node* BuildJavaScriptToNumber(Node* node, Node* context, Node* effect,
                                 Node* control);
+
   Node* BuildChangeInt32ToTagged(Node* value);
   Node* BuildChangeFloat64ToTagged(Node* value);
   Node* BuildChangeTaggedToFloat64(Node* value);

src/runtime/runtime-wasm.cc

@@ -21,8 +21,7 @@ namespace internal {
 RUNTIME_FUNCTION(Runtime_WasmGrowMemory) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
-  uint32_t delta_pages = 0;
-  CHECK(args[0]->ToUint32(&delta_pages));
+  CONVERT_UINT32_ARG_CHECKED(delta_pages, 0);
   Handle<JSObject> module_instance;
 
   {
@@ -118,5 +117,17 @@ RUNTIME_FUNCTION(Runtime_WasmThrowTypeError) {
   THROW_NEW_ERROR_RETURN_FAILURE(
       isolate, NewTypeError(MessageTemplate::kWasmTrapTypeError));
 }
+
+RUNTIME_FUNCTION(Runtime_WasmThrow) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(2, args.length());
+  CONVERT_SMI_ARG_CHECKED(lower, 0);
+  CONVERT_SMI_ARG_CHECKED(upper, 1);
+
+  const int32_t thrown_value = (upper << 16) | lower;
+
+  return isolate->Throw(*isolate->factory()->NewNumberFromInt(thrown_value));
+}
+
 }  // namespace internal
 }  // namespace v8

src/runtime/runtime.h

@@ -914,7 +914,8 @@ namespace internal {
 
 #define FOR_EACH_INTRINSIC_WASM(F) \
   F(WasmGrowMemory, 1, 1)          \
-  F(WasmThrowTypeError, 0, 1)
+  F(WasmThrowTypeError, 0, 1)      \
+  F(WasmThrow, 2, 1)
 
 #define FOR_EACH_INTRINSIC_RETURN_PAIR(F) \
   F(LoadLookupSlotForCall, 1, 2)

src/wasm/ast-decoder.cc

@@ -667,9 +667,8 @@ class WasmFullDecoder : public WasmDecoder {
           }
           case kExprThrow: {
             CHECK_PROTOTYPE_OPCODE(wasm_eh_prototype);
-            Pop(0, kAstI32);
-
-            // TODO(jpp): start exception propagation.
+            Value value = Pop(0, kAstI32);
+            BUILD(Throw, value.node);
             break;
           }
           case kExprTry: {

test/mjsunit/wasm/exceptions.js

@@ -0,0 +1,67 @@
+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --expose-wasm --wasm-eh-prototype
+
+load("test/mjsunit/wasm/wasm-constants.js");
+load("test/mjsunit/wasm/wasm-module-builder.js");
+
+var module = (function () {
+  var builder = new WasmModuleBuilder();
+
+  builder.addFunction("throw_param_if_not_zero", kSig_i_i)
+    .addBody([
+      kExprGetLocal, 0,
+      kExprI32Const, 0,
+      kExprI32Ne,
+      kExprIf,
+      kExprGetLocal, 0,
+      kExprThrow,
+      kExprEnd,
+      kExprI32Const, 1
+    ])
+    .exportFunc()
+
+  builder.addFunction("throw_20", kSig_v_v)
+    .addBody([
+      kExprI32Const, 20,
+      kExprThrow
+    ])
+    .exportFunc()
+
+  builder.addFunction("throw_expr_with_params", kSig_v_ddi)
+    .addBody([
+      // p2 * (p0 + min(p0, p1))|0 - 20
+      kExprGetLocal, 2,
+      kExprGetLocal, 0,
+      kExprGetLocal, 0,
+      kExprGetLocal, 1,
+      kExprF64Min,
+      kExprF64Add,
+      kExprI32SConvertF64,
+      kExprI32Mul,
+      kExprI32Const, 20,
+      kExprI32Sub,
+      kExprThrow
+    ])
+    .exportFunc()
+
+  return builder.instantiate();
+})();
+
+// Check the module exists.
+assertFalse(module === undefined);
+assertFalse(module === null);
+assertFalse(module === 0);
+assertEquals("object", typeof module.exports);
+assertEquals("function", typeof module.exports.throw_param_if_not_zero);
+
+assertEquals(1, module.exports.throw_param_if_not_zero(0));
+assertWasmThrows(10, function() { module.exports.throw_param_if_not_zero(10) });
+assertWasmThrows(-1, function() { module.exports.throw_param_if_not_zero(-1) });
+assertWasmThrows(20, module.exports.throw_20);
+assertWasmThrows(
+    -8, function() { module.exports.throw_expr_with_params(1.5, 2.5, 4); });
+assertWasmThrows(
+    12, function() { module.exports.throw_expr_with_params(5.7, 2.5, 4); });

test/mjsunit/wasm/wasm-constants.js

@@ -106,6 +106,7 @@ var kSig_v_ii = makeSig([kAstI32, kAstI32], []);
 var kSig_v_iii = makeSig([kAstI32, kAstI32, kAstI32], []);
 var kSig_v_d = makeSig([kAstF64], []);
 var kSig_v_dd = makeSig([kAstF64, kAstF64], []);
+var kSig_v_ddi = makeSig([kAstF64, kAstF64, kAstI32], []);
 
 function makeSig(params, results) {
   return {params: params, results: results};
@@ -143,6 +144,7 @@ var kExprBrIf = 0x07;
 var kExprBrTable = 0x08;
 var kExprReturn = 0x09;
 var kExprUnreachable = 0x0a;
+var kExprThrow = 0xfa;
 var kExprEnd = 0x0f;
 
 var kExprI32Const = 0x10;
@@ -348,3 +350,20 @@ function assertTraps(trap, code) {
     }
     throw new MjsUnitAssertionError("Did not trap, expected: " + kTrapMsgs[trap]);
 }
+
+function assertWasmThrows(value, code) {
+    assertEquals("number", typeof(value));
+    try {
+      if (typeof code === 'function') {
+        code();
+      } else {
+        eval(code);
+      }
+    } catch (e) {
+      assertEquals("number", typeof e);
+      assertEquals(value, e);
+      // Success.
+      return;
+    }
+    throw new MjsUnitAssertionError("Did not throw at all, expected: " + value);
+}