[wasm] Several unrelated cleanups

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 57185a5070a5752575fef14436a5b0d232e9e807..7bad1feb12ef9b6dbe6d90f9b0c97a9faf1f8d7d 100644
--- a/src/compiler/wasm-compiler.cc
+++ b/src/compiler/wasm-compiler.cc
@@ -179,22 +179,24 @@ class WasmTrapHelper : public ZoneObject {
   }
 
   Builtins::Name GetBuiltinIdForTrap(wasm::TrapReason reason) {
-    if (builder_->module_ && !builder_->module_->instance->context.is_null()) {
-      switch (reason) {
+    bool in_cctest =
+        !builder_->module_ || builder_->module_->instance->context.is_null();
+    if (in_cctest) {
+      // We use Builtins::builtin_count as a marker to tell the code generator
+      // to generate a call to a testing c-function instead of a runtime
+      // function. This code should only be called from a cctest.
+      return Builtins::builtin_count;
+    }
+
+    switch (reason) {
 #define TRAPREASON_TO_MESSAGE(name) \
   case wasm::k##name:               \
     return Builtins::kThrowWasm##name;
-        FOREACH_WASM_TRAPREASON(TRAPREASON_TO_MESSAGE)
+      FOREACH_WASM_TRAPREASON(TRAPREASON_TO_MESSAGE)
 #undef TRAPREASON_TO_MESSAGE
-        default:
-          UNREACHABLE();
-          return Builtins::builtin_count;
-      }
-    } else {
-      // We use Runtime::kNumFunctions as a marker to tell the code generator
-      // to generate a call to a testing c-function instead of a runtime
-      // function. This code should only be called from a cctest.
-      return Builtins::builtin_count;
+      default:
+        UNREACHABLE();
+        return Builtins::builtin_count;
     }
   }
 
@@ -367,10 +369,10 @@ WasmGraphBuilder::WasmGraphBuilder(
       trap_(new (zone) WasmTrapHelper(this)),
       sig_(sig),
       source_position_table_(source_position_table) {
-  for (size_t i = 0; i < sig->parameter_count(); i++) {
+  for (size_t i = 0, e = sig->parameter_count(); i < e && !has_simd_; ++i) {

[titzer, 2017/02/28 15:15:07]

You could also just iterate from sig->parameter_count() and iterate until
wraparound.

[Clemens Hammacher, 2017/03/01 16:41:11]

Done (iterate while > 0 and use "i-1" in the body, since i is unsigned).

     if (sig->GetParam(i) == wasm::kWasmS128) has_simd_ = true;

[titzer, 2017/02/28 15:15:07]

And could also just break if found, instead of checking every iteration.

[Clemens Hammacher, 2017/03/01 16:41:11]

I expect this to be eliminated by the compiler (SSA & jump threading). Adding an
explicit break would add three lines two times :(

   }
-  for (size_t i = 0; i < sig->return_count(); i++) {
+  for (size_t i = 0, e = sig->return_count(); i < e && !has_simd_; ++i) {
     if (sig->GetReturn(i) == wasm::kWasmS128) has_simd_ = true;
   }
   DCHECK_NOT_NULL(jsgraph_);
@@ -3050,13 +3052,12 @@ Node* WasmGraphBuilder::CurrentMemoryPages() {
   CallDescriptor* desc = Linkage::GetRuntimeCallDescriptor(
       jsgraph()->zone(), function_id, function->nargs, Operator::kNoThrow,
       CallDescriptor::kNoFlags);
-  wasm::ModuleEnv* module = module_;
   Node* inputs[] = {
       jsgraph()->CEntryStubConstant(function->result_size),  // C entry
       jsgraph()->ExternalConstant(
           ExternalReference(function_id, jsgraph()->isolate())),  // ref
       jsgraph()->Int32Constant(function->nargs),                  // arity
-      jsgraph()->HeapConstant(module->instance->context),         // context
+      jsgraph()->HeapConstant(module_->instance->context),        // context
       *effect_,
       *control_};
   Node* call = graph()->NewNode(jsgraph()->common()->Call(desc),