[v8-dev] Remove usages of alloca() according to style guide. (issue 535133002 by [email protected])

Wed, 03 Sep 2014 06:14:37 -0700 

Reviewers: Benedikt Meurer,

Message:
According to the C++ style guide all usages of alloca() are disallowed. Some of 
our existing usages even weren't bounded enough and hence might have already
lead to undefined behavior due to stack overflow.

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Variable-Length_Arrays_and_alloca__

Description:
Remove usages of alloca() according to style guide.

[email protected]

Please review this at https://codereview.chromium.org/535133002/

SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge

Affected files (+7, -12 lines):
  M src/compiler/ast-graph-builder.cc
  M src/compiler/graph-builder.cc
  M src/compiler/machine-node-factory.h
  M src/compiler/structured-machine-assembler.cc


Index: src/compiler/ast-graph-builder.cc
diff --git a/src/compiler/ast-graph-builder.cc b/src/compiler/ast-graph-builder.cc index afc58e91454b95a560c96ebdca3c57ca838b8bef..5ad8269ca9a19c1f6eec61fc86d2621870a509ab 100644 
--- a/src/compiler/ast-graph-builder.cc
+++ b/src/compiler/ast-graph-builder.cc
@@ -1652,7 +1652,7 @@ void AstGraphBuilder::VisitLogicalExpression(BinaryOperation* expr) { 

 Node* AstGraphBuilder::ProcessArguments(Operator* op, int arity) {
   DCHECK(environment()->stack_height() >= arity);
-  Node** all = info()->zone()->NewArray<Node*>(arity);  // XXX: alloca?
+  Node** all = info()->zone()->NewArray<Node*>(arity);
   for (int i = arity - 1; i >= 0; --i) {
     all[i] = environment()->Pop();
   }
Index: src/compiler/graph-builder.cc
diff --git a/src/compiler/graph-builder.cc b/src/compiler/graph-builder.cc
index 504d25ec2f00fe42801b0a4a12d71fe993ba3f58..c41fd6fac58d615d895694712d12f3dc413f9087 100644 
--- a/src/compiler/graph-builder.cc
+++ b/src/compiler/graph-builder.cc
@@ -49,8 +49,7 @@ Node* StructuredGraphBuilder::MakeNode(Operator* op, int value_input_count, 
     if (has_framestate) ++input_count_with_deps;
     if (has_control) ++input_count_with_deps;
     if (has_effect) ++input_count_with_deps;
-    void* raw_buffer = alloca(kPointerSize * input_count_with_deps);
-    Node** buffer = reinterpret_cast<Node**>(raw_buffer);
+    Node** buffer = zone()->NewArray<Node*>(input_count_with_deps);
     memcpy(buffer, value_inputs, kPointerSize * value_input_count);
     Node** current_input = buffer + value_input_count;
     if (has_context) {
@@ -163,8 +162,7 @@ void StructuredGraphBuilder::Environment::PrepareForLoop() {
Node* StructuredGraphBuilder::NewPhi(int count, Node* input, Node* control) { 
   Operator* phi_op = common()->Phi(count);
-  void* raw_buffer = alloca(kPointerSize * (count + 1));
-  Node** buffer = reinterpret_cast<Node**>(raw_buffer);
+  Node** buffer = zone()->NewArray<Node*>(count + 1);
   MemsetPointer(buffer, input, count);
   buffer[count] = control;
   return graph()->NewNode(phi_op, count + 1, buffer);
@@ -175,8 +173,7 @@ Node* StructuredGraphBuilder::NewPhi(int count, Node* input, Node* control) { 
 Node* StructuredGraphBuilder::NewEffectPhi(int count, Node* input,
                                            Node* control) {
   Operator* phi_op = common()->EffectPhi(count);
-  void* raw_buffer = alloca(kPointerSize * (count + 1));
-  Node** buffer = reinterpret_cast<Node**>(raw_buffer);
+  Node** buffer = zone()->NewArray<Node*>(count + 1);
   MemsetPointer(buffer, input, count);
   buffer[count] = control;
   return graph()->NewNode(phi_op, count + 1, buffer);
Index: src/compiler/machine-node-factory.h
diff --git a/src/compiler/machine-node-factory.h b/src/compiler/machine-node-factory.h index 7b2e5ff82b07dd9f93e4b841290ba4b3dd35f8a2..a2605d9fd21a7fd0db0028cfb22ae959d002a7ec 100644 
--- a/src/compiler/machine-node-factory.h
+++ b/src/compiler/machine-node-factory.h
@@ -349,8 +349,7 @@ class MachineNodeFactory {
               MachineType* arg_types, Node** args, int n_args) {
     CallDescriptor* descriptor =
         Linkage::GetSimplifiedCDescriptor(ZONE(), MACHINE_SIG());
-    Node** passed_args =
-        static_cast<Node**>(alloca((n_args + 1) * sizeof(args[0])));
+    Node** passed_args = ZONE()->NewArray<Node*>(n_args + 1);
     passed_args[0] = function_address;
     for (int i = 0; i < n_args; ++i) {
       passed_args[i + 1] = args[i];
Index: src/compiler/structured-machine-assembler.cc
diff --git a/src/compiler/structured-machine-assembler.cc b/src/compiler/structured-machine-assembler.cc index 6475809e0e8e2c0f52b77cf27000f593b870a712..432b84c64a9e8e89ed0a39e870efffbba97c0919 100644 
--- a/src/compiler/structured-machine-assembler.cc
+++ b/src/compiler/structured-machine-assembler.cc
@@ -213,8 +213,7 @@ void StructuredMachineAssembler::Merge(EnvironmentVector* environments, 
   vars.reserve(n_vars);
   Node** scratch = NULL;
   size_t n_envs = environments->size();
-  Environment** live_environments = reinterpret_cast<Environment**>(
-      alloca(sizeof(environments->at(0)) * n_envs));
+  Environment** live_environments = zone()->NewArray<Environment*>(n_envs);
   size_t n_live = 0;
   for (size_t i = 0; i < n_envs; i++) {
     if (environments->at(i)->is_dead_) continue;
@@ -250,7 +249,7 @@ void StructuredMachineAssembler::Merge(EnvironmentVector* environments, 
       CHECK(resolved != NULL);
       // Init scratch buffer.
       if (scratch == NULL) {
-        scratch = static_cast<Node**>(alloca(n_envs * sizeof(resolved)));
+        scratch = zone()->NewArray<Node*>(n_envs);
       }
       for (size_t k = 0; k < i; k++) {
         scratch[k] = resolved;


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