[WASM] Implements catch for the wasm low level exception mechanism.

src/compiler/wasm-compiler.cc

 // 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.
 
 #include "src/compiler/wasm-compiler.h"
 
 #include <memory>
 
 #include "src/isolate-inl.h"
 
@@ skipping 319 matching lines @@
 
 unsigned WasmGraphBuilder::InputCount(Node* node) {
   return static_cast<unsigned>(node->InputCount());
 }
 
 bool WasmGraphBuilder::IsPhiWithMerge(Node* phi, Node* merge) {
   return phi && IrOpcode::IsPhiOpcode(phi->opcode()) &&
          NodeProperties::GetControlInput(phi) == merge;
 }
 
+bool WasmGraphBuilder::ThrowsException(Node* node, Node** if_success,
+                                       Node** if_exception) {
+  if (node->op()->HasProperty(compiler::Operator::kNoThrow)) {
+    return false;
+  }
+
+  *if_success = graph()->NewNode(jsgraph()->common()->IfSuccess(), node);
+  *if_exception =
+      graph()->NewNode(jsgraph()->common()->IfException(), node, node);
+
+  return true;
+}
+
 void WasmGraphBuilder::AppendToMerge(Node* merge, Node* from) {
   DCHECK(IrOpcode::IsMergeOpcode(merge->opcode()));
   merge->AppendInput(jsgraph()->zone(), from);
   int new_size = merge->InputCount();
   NodeProperties::ChangeOp(
       merge, jsgraph()->common()->ResizeMergeOrPhi(merge->op(), new_size));
 }
 
 void WasmGraphBuilder::AppendToPhi(Node* phi, Node* from) {
   DCHECK(IrOpcode::IsPhiOpcode(phi->opcode()));
@@ skipping 1367 matching lines @@
       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::Catch(Node* input, wasm::WasmCodePosition position) {
+  CommonOperatorBuilder* common = jsgraph()->common();
+
+  Node* parameters[] = {input};  // caught value
+  Node* value =
+      BuildCallToRuntime(Runtime::kWasmGetCaughtExceptionValue, jsgraph(),
+                         module_->instance->context, parameters,
+                         arraysize(parameters), effect_, *control_);
+
+  Node* is_smi;
+  Node* is_heap;
+  Branch(BuildTestNotSmi(value), &is_heap, &is_smi);
+
+  // is_heap
+  Node* heap_f64 = BuildLoadHeapNumberValue(value, is_heap);
+  // *control_ needs to point to the current control dependency (is_heap) in
+  // case BuildI32SConvertF64 needs to insert nodes that depend on the "current"
+  // control node.
+  *control_ = is_heap;
+  Node* heap_i32 = BuildI32SConvertF64(heap_f64, position);
+  // *control_ contains the control node that should be used when merging the
+  // result for the catch clause. It may be different than *control_ because
+  // BuildI32SConvertF64 may introduce a new control node (used for trapping if
+  // heap_f64 cannot be converted to an i32.
+  is_heap = *control_;
+
+  // is_smi
+  Node* smi_i32 = BuildChangeSmiToInt32(value);
+
+  Node* merge = graph()->NewNode(common->Merge(2), is_heap, is_smi);
+  Node* value_i32 = graph()->NewNode(
+      common->Phi(MachineRepresentation::kWord32, 2), heap_i32, smi_i32, merge);
+
+  *control_ = merge;
+  return value_i32;
+}
+
 Node* WasmGraphBuilder::BuildI32DivS(Node* left, Node* right,
                                      wasm::WasmCodePosition position) {
   MachineOperatorBuilder* m = jsgraph()->machine();
   trap_->ZeroCheck32(wasm::kTrapDivByZero, right, position);
   Node* before = *control_;
   Node* denom_is_m1;
   Node* denom_is_not_m1;
   Branch(
       graph()->NewNode(m->Word32Equal(), right, jsgraph()->Int32Constant(-1)),
       &denom_is_m1, &denom_is_not_m1);
@@ skipping 248 matching lines @@
 
   CallDescriptor* desc =
       Linkage::GetSimplifiedCDescriptor(jsgraph()->zone(), sig);
 
   const Operator* op = jsgraph()->common()->Call(desc);
   Node* call = graph()->NewNode(op, static_cast<int>(count), args);
   *effect_ = call;
   return call;
 }
 
-Node** WasmGraphBuilder::BuildWasmCall(wasm::FunctionSig* sig, Node** args,
-                                       wasm::WasmCodePosition position) {
+Node* WasmGraphBuilder::BuildWasmCall(wasm::FunctionSig* sig, Node** args,

[titzer, 2016/09/29 13:33:59]

I think this would be cleaner if it returned the return value array as before
and took a double pointer to the call node.

[John, 2016/09/29 13:52:05]

I made this change because of the way this is used in ast-builder.

Essentially, BUILD() dispatches the returned value to CheckForException, which
in turn performs the exception handling wiring. I can change this, but then the
ast-builder's code for creating calls will not look like the rest. It will
become something like:

if (build()) {
  Node** call = nullptr;
  Node** rets = BUILD(CallDirect, ..., &call, ...);
  CheckForException(call);
}

Leaving as is, per offline discussion.

+                                      Node*** rets,
+                                      wasm::WasmCodePosition position) {
   const size_t params = sig->parameter_count();
   const size_t extra = 2;  // effect and control inputs.
   const size_t count = 1 + params + extra;
 
   // Reallocate the buffer to make space for extra inputs.
   args = Realloc(args, 1 + params, count);
 
   // Add effect and control inputs.
   args[params + 1] = *effect_;
   args[params + 2] = *control_;
 
   CallDescriptor* descriptor =
       wasm::ModuleEnv::GetWasmCallDescriptor(jsgraph()->zone(), sig);
   const Operator* op = jsgraph()->common()->Call(descriptor);
   Node* call = graph()->NewNode(op, static_cast<int>(count), args);
   SetSourcePosition(call, position);
 
   *effect_ = call;
   size_t ret_count = sig->return_count();
-  if (ret_count == 0) return nullptr;  // No return value.
+  if (ret_count == 0) return call;  // No return value.
 
-  Node** rets = Buffer(ret_count);
+  *rets = Buffer(ret_count);
   if (ret_count == 1) {
     // Only a single return value.
-    rets[0] = call;
+    (*rets)[0] = call;
   } else {
     // Create projections for all return values.
     for (size_t i = 0; i < ret_count; i++) {
-      rets[i] = graph()->NewNode(jsgraph()->common()->Projection(i), call,
-                                 graph()->start());
+      (*rets)[i] = graph()->NewNode(jsgraph()->common()->Projection(i), call,
+                                    graph()->start());
     }
   }
-  return rets;
+  return call;
 }
 
-Node** WasmGraphBuilder::CallDirect(uint32_t index, Node** args,
-                                    wasm::WasmCodePosition position) {
+Node* WasmGraphBuilder::CallDirect(uint32_t index, Node** args, Node*** rets,
+                                   wasm::WasmCodePosition position) {
   DCHECK_NULL(args[0]);
 
   // Add code object as constant.
   Handle<Code> code = module_->GetFunctionCode(index);
   DCHECK(!code.is_null());
   args[0] = HeapConstant(code);
   wasm::FunctionSig* sig = module_->GetFunctionSignature(index);
 
-  return BuildWasmCall(sig, args, position);
+  return BuildWasmCall(sig, args, rets, position);
 }
 
-Node** WasmGraphBuilder::CallIndirect(uint32_t index, Node** args,
-                                      wasm::WasmCodePosition position) {
+Node* WasmGraphBuilder::CallIndirect(uint32_t index, Node** args, Node*** rets,
+                                     wasm::WasmCodePosition position) {
   DCHECK_NOT_NULL(args[0]);
   DCHECK(module_ && module_->instance);
 
   MachineOperatorBuilder* machine = jsgraph()->machine();
 
   // Compute the code object by loading it from the function table.
   Node* key = args[0];
 
   // Assume only one table for now.
   DCHECK_LE(module_->instance->function_tables.size(), 1u);
   // Bounds check the index.
   uint32_t table_size =
       module_->IsValidTable(0) ? module_->GetTable(0)->max_size : 0;
   wasm::FunctionSig* sig = module_->GetSignature(index);
   if (table_size > 0) {
     // Bounds check against the table size.
     Node* size = Uint32Constant(table_size);
     Node* in_bounds = graph()->NewNode(machine->Uint32LessThan(), key, size);
     trap_->AddTrapIfFalse(wasm::kTrapFuncInvalid, in_bounds, position);
   } else {
     // No function table. Generate a trap and return a constant.
     trap_->AddTrapIfFalse(wasm::kTrapFuncInvalid, Int32Constant(0), position);
-    Node** rets = Buffer(sig->return_count());
+    (*rets) = Buffer(sig->return_count());
     for (size_t i = 0; i < sig->return_count(); i++) {
-      rets[i] = trap_->GetTrapValue(sig->GetReturn(i));
+      (*rets)[i] = trap_->GetTrapValue(sig->GetReturn(i));
     }
-    return rets;
+    return trap_->GetTrapValue(sig);
   }
   Node* table = FunctionTable(0);
 
   // Load signature from the table and check.
   // The table is a FixedArray; signatures are encoded as SMIs.
   // [sig1, sig2, sig3, ...., code1, code2, code3 ...]
   ElementAccess access = AccessBuilder::ForFixedArrayElement();
   const int fixed_offset = access.header_size - access.tag();
   {
     Node* load_sig = graph()->NewNode(
@@ skipping 13 matching lines @@
   uint32_t offset = fixed_offset + kPointerSize * table_size;
   Node* load_code = graph()->NewNode(
       machine->Load(MachineType::AnyTagged()), table,
       graph()->NewNode(machine->Int32Add(),
                        graph()->NewNode(machine->Word32Shl(), key,
                                         Int32Constant(kPointerSizeLog2)),
                        Uint32Constant(offset)),
       *effect_, *control_);
 
   args[0] = load_code;
-  return BuildWasmCall(sig, args, position);
+  return BuildWasmCall(sig, args, rets, position);
 }
 
 Node* WasmGraphBuilder::BuildI32Rol(Node* left, Node* right) {
   // Implement Rol by Ror since TurboFan does not have Rol opcode.
   // TODO(weiliang): support Word32Rol opcode in TurboFan.
   Int32Matcher m(right);
   if (m.HasValue()) {
     return Binop(wasm::kExprI32Ror, left,
                  jsgraph()->Int32Constant(32 - m.Value()));
   } else {
@@ skipping 1207 matching lines @@
                             function_->code_start_offset),
            compile_ms);
   }
 
   return code;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8