[wasm] Do float constant folding if the origin is not wasm

I removed some constant folding optimizations for float instruction in
https://codereview.chromium.org/2647353007 because they were incorrect
if the input was a signalling NaN. Removing these optimizations, however
had an unexpectedly big impact on asm.js performance. With this CL I
restore the optimizations again when the source origin is not wasm. In
JavaScript signalling NaNs are not observable and therefore the
optimizations are correct.

R=titzer@chromium.org
BUG=chromium:686654

Review-Url: https://codereview.chromium.org/2666903002
Cr-Commit-Position: refs/heads/master@{#42850}

src/compiler/machine-operator-reducer.cc

@@ -17,9 +17,9 @@ namespace v8 {
 namespace internal {
 namespace compiler {
 
-MachineOperatorReducer::MachineOperatorReducer(JSGraph* jsgraph)
-    : jsgraph_(jsgraph) {}
-
+MachineOperatorReducer::MachineOperatorReducer(JSGraph* jsgraph,
+                                               bool allow_signalling_nan)
+    : jsgraph_(jsgraph), allow_signalling_nan_(allow_signalling_nan) {}
 
 MachineOperatorReducer::~MachineOperatorReducer() {}
 
@@ -316,7 +316,10 @@ Reduction MachineOperatorReducer::Reduce(Node* node) {
     }
     case IrOpcode::kFloat32Sub: {
       Float32BinopMatcher m(node);
-      // TODO(ahaas): We could do x - 0.0 = x if we knew that x is not an sNaN.
+      if (allow_signalling_nan_ && m.right().Is(0) &&
+          (copysign(1.0, m.right().Value()) > 0)) {
+        return Replace(m.left().node());  // x - 0 => x
+      }
       if (m.right().IsNaN()) {  // x - NaN => NaN
         // Do some calculation to make a signalling NaN quiet.
         return ReplaceFloat32(m.right().Value() - m.right().Value());
@@ -360,7 +363,10 @@ Reduction MachineOperatorReducer::Reduce(Node* node) {
     }
     case IrOpcode::kFloat64Sub: {
       Float64BinopMatcher m(node);
-      // TODO(ahaas): We could do x - 0.0 = x if we knew that x is not an sNaN.
+      if (allow_signalling_nan_ && m.right().Is(0) &&
+          (Double(m.right().Value()).Sign() > 0)) {
+        return Replace(m.left().node());  // x - 0 => x
+      }
       if (m.right().IsNaN()) {  // x - NaN => NaN
         // Do some calculation to make a signalling NaN quiet.
         return ReplaceFloat64(m.right().Value() - m.right().Value());
@@ -393,7 +399,8 @@ Reduction MachineOperatorReducer::Reduce(Node* node) {
     }
     case IrOpcode::kFloat64Mul: {
       Float64BinopMatcher m(node);
-      // TODO(ahaas): We could do x * 1.0 = x if we knew that x is not an sNaN.
+      if (allow_signalling_nan_ && m.right().Is(1))
+        return Replace(m.left().node());  // x * 1.0 => x
       if (m.right().Is(-1)) {  // x * -1.0 => -0.0 - x
         node->ReplaceInput(0, Float64Constant(-0.0));
         node->ReplaceInput(1, m.left().node());
@@ -416,6 +423,8 @@ Reduction MachineOperatorReducer::Reduce(Node* node) {
     }
     case IrOpcode::kFloat64Div: {
       Float64BinopMatcher m(node);
+      if (allow_signalling_nan_ && m.right().Is(1))
+        return Replace(m.left().node());  // x / 1.0 => x
       // TODO(ahaas): We could do x / 1.0 = x if we knew that x is not an sNaN.
       if (m.right().IsNaN()) {                               // x / NaN => NaN
         // Do some calculation to make a signalling NaN quiet.

src/compiler/machine-operator-reducer.h

@@ -24,7 +24,8 @@ class JSGraph;
 class V8_EXPORT_PRIVATE MachineOperatorReducer final
     : public NON_EXPORTED_BASE(Reducer) {
  public:
-  explicit MachineOperatorReducer(JSGraph* jsgraph);
+  explicit MachineOperatorReducer(JSGraph* jsgraph,
+                                  bool allow_signalling_nan = true);
   ~MachineOperatorReducer();
 
   Reduction Reduce(Node* node) override;
@@ -104,6 +105,7 @@ class V8_EXPORT_PRIVATE MachineOperatorReducer final
   MachineOperatorBuilder* machine() const;
 
   JSGraph* jsgraph_;
+  bool allow_signalling_nan_;
 };
 
 }  // namespace compiler

src/compiler/pipeline.cc

@@ -640,13 +640,15 @@ class PipelineWasmCompilationJob final : public CompilationJob {
   explicit PipelineWasmCompilationJob(
       CompilationInfo* info, JSGraph* jsgraph, CallDescriptor* descriptor,
       SourcePositionTable* source_positions,
-      ZoneVector<trap_handler::ProtectedInstructionData>* protected_insts)
+      ZoneVector<trap_handler::ProtectedInstructionData>* protected_insts,
+      bool allow_signalling_nan)
       : CompilationJob(info->isolate(), info, "TurboFan",
                        State::kReadyToExecute),
         zone_stats_(info->isolate()->allocator()),
         data_(&zone_stats_, info, jsgraph, source_positions, protected_insts),
         pipeline_(&data_),
-        linkage_(descriptor) {}
+        linkage_(descriptor),
+        allow_signalling_nan_(allow_signalling_nan) {}
 
  protected:
   Status PrepareJobImpl() final;
@@ -658,6 +660,7 @@ class PipelineWasmCompilationJob final : public CompilationJob {
   PipelineData data_;
   PipelineImpl pipeline_;
   Linkage linkage_;
+  bool allow_signalling_nan_;
 };
 
 PipelineWasmCompilationJob::Status
@@ -682,7 +685,8 @@ PipelineWasmCompilationJob::ExecuteJobImpl() {
     DeadCodeElimination dead_code_elimination(&graph_reducer, data->graph(),
                                               data->common());
     ValueNumberingReducer value_numbering(scope.zone(), data->graph()->zone());
-    MachineOperatorReducer machine_reducer(data->jsgraph());
+    MachineOperatorReducer machine_reducer(data->jsgraph(),
+                                           allow_signalling_nan_);
     CommonOperatorReducer common_reducer(&graph_reducer, data->graph(),
                                          data->common(), data->machine());
     AddReducer(data, &graph_reducer, &dead_code_elimination);
@@ -1749,10 +1753,11 @@ CompilationJob* Pipeline::NewCompilationJob(Handle<JSFunction> function) {
 CompilationJob* Pipeline::NewWasmCompilationJob(
     CompilationInfo* info, JSGraph* jsgraph, CallDescriptor* descriptor,
     SourcePositionTable* source_positions,
-    ZoneVector<trap_handler::ProtectedInstructionData>*
-        protected_instructions) {
+    ZoneVector<trap_handler::ProtectedInstructionData>* protected_instructions,
+    bool allow_signalling_nan) {
   return new PipelineWasmCompilationJob(
-      info, jsgraph, descriptor, source_positions, protected_instructions);
+      info, jsgraph, descriptor, source_positions, protected_instructions,
+      allow_signalling_nan);
 }
 
 bool Pipeline::AllocateRegistersForTesting(const RegisterConfiguration* config,

src/compiler/pipeline.h

@@ -41,7 +41,8 @@ class Pipeline : public AllStatic {
       CompilationInfo* info, JSGraph* jsgraph, CallDescriptor* descriptor,
       SourcePositionTable* source_positions,
       ZoneVector<trap_handler::ProtectedInstructionData>*
-          protected_instructions);
+          protected_instructions,
+      bool wasm_origin);
 
   // Run the pipeline on a machine graph and generate code. The {schedule} must
   // be valid, hence the given {graph} does not need to be schedulable.

src/compiler/wasm-compiler.cc

@@ -3960,9 +3960,9 @@ void WasmCompilationUnit::ExecuteCompilation() {
     descriptor = module_env_->module_env.GetI32WasmCallDescriptor(
         &compilation_zone_, descriptor);
   }
-  job_.reset(Pipeline::NewWasmCompilationJob(&info_, jsgraph_, descriptor,
-                                             source_positions,
-                                             &protected_instructions_));
+  job_.reset(Pipeline::NewWasmCompilationJob(
+      &info_, jsgraph_, descriptor, source_positions, &protected_instructions_,
+      module_env_->module_env.module->origin != wasm::kWasmOrigin));
   ok_ = job_->ExecuteJob() == CompilationJob::SUCCEEDED;
   // TODO(bradnelson): Improve histogram handling of size_t.
   // TODO(ahaas): The counters are not thread-safe at the moment.

src/wasm/wasm-module.h

@@ -169,7 +169,7 @@ struct WasmExport {
   uint32_t index;         // index into the respective space.
 };
 
-enum ModuleOrigin { kWasmOrigin, kAsmJsOrigin };
+enum ModuleOrigin : uint8_t { kWasmOrigin, kAsmJsOrigin };
 struct ModuleWireBytes;
 
 // Static representation of a module.

test/cctest/wasm/wasm-run-utils.h

@@ -602,7 +602,7 @@ class WasmFunctionCompiler : private GraphAndBuilders {
     CompilationInfo info(CStrVector("wasm"), this->isolate(), this->zone(),
                          Code::ComputeFlags(Code::WASM_FUNCTION));
     std::unique_ptr<CompilationJob> job(Pipeline::NewWasmCompilationJob(
-        &info, &jsgraph, desc, &source_position_table_, nullptr));
+        &info, &jsgraph, desc, &source_position_table_, nullptr, false));
     if (job->ExecuteJob() != CompilationJob::SUCCEEDED ||
         job->FinalizeJob() != CompilationJob::SUCCEEDED)
       return Handle<Code>::null();