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

src/compiler/wasm-compiler.cc

Index: src/compiler/wasm-compiler.cc
diff --git a/src/compiler/wasm-compiler.cc b/src/compiler/wasm-compiler.cc
index 7837a64c9012562ece864f6e8810a07af6386e30..dac9eec7a75a9ee22c49e7ee7ec114822a7f86ef 100644
--- a/src/compiler/wasm-compiler.cc
+++ b/src/compiler/wasm-compiler.cc
@@ -337,6 +337,19 @@ bool WasmGraphBuilder::IsPhiWithMerge(Node* phi, Node* merge) {
          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);
@@ -1724,6 +1737,50 @@ Node* WasmGraphBuilder::Throw(Node* input) {
                             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;

[Mircea Trofin, 2016/09/30 16:00:44]

it'd be nice if these were initialized and DCHECK-ed on the BuildTestNotSmi,
thus clarifying the contract.

[John, 2016/09/30 16:07:17]

I agree, but I'd have to change every call to Branch(); I'll leave as is.

+  Node* is_heap;
+  Branch(BuildTestNotSmi(value), &is_heap, &is_smi);
+
+  // is_smi
+  Node* smi_i32 = BuildChangeSmiToInt32(value);
+  Node* is_smi_effect = *effect_;
+
+  // is_heap
+  *control_ = 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.
+  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_;
+  Node* is_heap_effect = *effect_;
+
+  Node* merge = graph()->NewNode(common->Merge(2), is_heap, is_smi);
+  Node* effect_merge = graph()->NewNode(common->EffectPhi(2), is_heap_effect,
+                                        is_smi_effect, merge);
+
+  Node* value_i32 = graph()->NewNode(
+      common->Phi(MachineRepresentation::kWord32, 2), heap_i32, smi_i32, merge);
+
+  *control_ = merge;
+  *effect_ = effect_merge;
+  return value_i32;
+}
+
 Node* WasmGraphBuilder::BuildI32DivS(Node* left, Node* right,
                                      wasm::WasmCodePosition position) {
   MachineOperatorBuilder* m = jsgraph()->machine();
@@ -1992,8 +2049,9 @@ Node* WasmGraphBuilder::BuildCCall(MachineSignature* sig, Node** args) {
   return call;
 }
 
-Node** WasmGraphBuilder::BuildWasmCall(wasm::FunctionSig* sig, Node** args,
-                                       wasm::WasmCodePosition position) {
+Node* WasmGraphBuilder::BuildWasmCall(wasm::FunctionSig* sig, Node** args,
+                                      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;
@@ -2013,24 +2071,24 @@ Node** WasmGraphBuilder::BuildWasmCall(wasm::FunctionSig* sig, Node** args,
 
   *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.
@@ -2039,11 +2097,11 @@ Node** WasmGraphBuilder::CallDirect(uint32_t index, Node** args,
   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);
 
@@ -2066,11 +2124,11 @@ Node** WasmGraphBuilder::CallIndirect(uint32_t index, Node** args,
   } 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);
 
@@ -2104,7 +2162,7 @@ Node** WasmGraphBuilder::CallIndirect(uint32_t index, Node** args,
       *effect_, *control_);
 
   args[0] = load_code;
-  return BuildWasmCall(sig, args, position);
+  return BuildWasmCall(sig, args, rets, position);
 }
 
 Node* WasmGraphBuilder::BuildI32Rol(Node* left, Node* right) {