[wasm] Fix location for error in asm.js ToNumber conversion

src/asmjs/asm-wasm-builder.cc

Index: src/asmjs/asm-wasm-builder.cc
diff --git a/src/asmjs/asm-wasm-builder.cc b/src/asmjs/asm-wasm-builder.cc
index 30eb0274f925820ed0e2be154ad9535a69323307..e11b31ef24cd33a846aa86e342efe18fc8ea29fe 100644
--- a/src/asmjs/asm-wasm-builder.cc
+++ b/src/asmjs/asm-wasm-builder.cc
@@ -35,6 +35,20 @@ namespace wasm {
     if (HasStackOverflow()) return; \
   } while (false)
 
+#ifdef DEBUG
+namespace {
+bool IsChild(Expression* parent, Expression* child) {

[bradnelson, 2016/12/07 19:19:06]

IsBinOpChild ?

[Clemens Hammacher, 2016/12/08 10:50:23]

I just removed the function completely :)
By storing a BinaryOperation* as parent, the condition is simple enough to be
inlined.

+  DCHECK_NOT_NULL(parent);
+  if (parent->IsBinaryOperation()) {
+    BinaryOperation* bin_op = static_cast<BinaryOperation*>(parent);
+    return bin_op->left() == child || bin_op->right() == child;
+  }
+  UNREACHABLE();
+  return false;
+}
+}  // namespace
+#endif
+
 enum AsmScope { kModuleScope, kInitScope, kFuncScope, kExportScope };
 enum ValueFate { kDrop, kLeaveOnStack };
 
@@ -71,7 +85,8 @@ class AsmWasmBuilderImpl final : public AstVisitor<AsmWasmBuilderImpl> {
         foreign_init_function_(nullptr),
         function_tables_(ZoneHashMap::kDefaultHashMapCapacity,
                          ZoneAllocationPolicy(zone)),
-        imported_function_table_(this) {
+        imported_function_table_(this),
+        parent_(nullptr) {
     InitializeAstVisitor(isolate);
   }
 
@@ -1396,6 +1411,10 @@ class AsmWasmBuilderImpl final : public AstVisitor<AsmWasmBuilderImpl> {
   bool VisitCallExpression(Call* expr) {
     Call::CallType call_type = expr->GetCallType();
     bool returns_value = true;
+
+    // Save the parent now, it might be overwritten in VisitCallArgs.
+    Expression* this_parent = parent_;
+
     switch (call_type) {
       case Call::OTHER_CALL: {
         VariableProxy* proxy = expr->expression()->AsVariableProxy();
@@ -1426,13 +1445,18 @@ class AsmWasmBuilderImpl final : public AstVisitor<AsmWasmBuilderImpl> {
           uint32_t index = imported_function_table_.LookupOrInsertImportUse(
               vp->var(), sig.Build());
           VisitCallArgs(expr);
-          current_function_builder_->AddAsmWasmOffset(expr->position());
+          // For non-void functions, we must know the parent node.
+          DCHECK_IMPLIES(returns_value, IsChild(this_parent, expr));
+          int pos = expr->position();
+          int parent_pos = returns_value ? this_parent->position() : pos;
+          current_function_builder_->AddAsmWasmOffset(pos, parent_pos);
           current_function_builder_->Emit(kExprCallFunction);
           current_function_builder_->EmitVarInt(index);
         } else {
           WasmFunctionBuilder* function = LookupOrInsertFunction(vp->var());
           VisitCallArgs(expr);
-          current_function_builder_->AddAsmWasmOffset(expr->position());
+          current_function_builder_->AddAsmWasmOffset(expr->position(),
+                                                      expr->position());
           current_function_builder_->Emit(kExprCallFunction);
           current_function_builder_->EmitDirectCallIndex(
               function->func_index());
@@ -1458,7 +1482,8 @@ class AsmWasmBuilderImpl final : public AstVisitor<AsmWasmBuilderImpl> {
         VisitCallArgs(expr);
 
         current_function_builder_->EmitGetLocal(tmp.index());
-        current_function_builder_->AddAsmWasmOffset(expr->position());
+        current_function_builder_->AddAsmWasmOffset(expr->position(),
+                                                    expr->position());
         current_function_builder_->Emit(kExprCallIndirect);
         current_function_builder_->EmitVarInt(indices->signature_index);
         current_function_builder_->EmitVarInt(0);  // table index
@@ -1630,6 +1655,7 @@ class AsmWasmBuilderImpl final : public AstVisitor<AsmWasmBuilderImpl> {
   void VisitBinaryOperation(BinaryOperation* expr) {
     ConvertOperation convertOperation = MatchBinaryOperation(expr);
     static const bool kDontIgnoreSign = false;
+    parent_ = expr;
     if (convertOperation == kToDouble) {
       RECURSE(Visit(expr->left()));
       TypeIndex type = TypeIndexOf(expr->left(), kDontIgnoreSign);
@@ -1933,6 +1959,9 @@ class AsmWasmBuilderImpl final : public AstVisitor<AsmWasmBuilderImpl> {
   uint32_t next_table_index_;
   ZoneHashMap function_tables_;
   ImportedFunctionTable imported_function_table_;
+  // Remember the parent node for reporting the correct location for ToNumber
+  // conversions after calls.
+  Expression* parent_;
 
   DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();