[wasm] Backoff implementation for F64Trunc using std::trunc.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/1638283004

Cr-Commit-Position: refs/heads/master@{#33670}

src/assembler.cc

@@ -34,6 +34,7 @@
 
 #include "src/assembler.h"
 
+#include <math.h>
 #include <cmath>
 #include "src/api.h"
 #include "src/base/cpu.h"
@@ -1131,6 +1132,12 @@ ExternalReference ExternalReference::compute_output_frames_function(
       Redirect(isolate, FUNCTION_ADDR(Deoptimizer::ComputeOutputFrames)));
 }
 
+static void trunc64_wrapper(double* param) { *param = trunc(*param); }
+
+ExternalReference ExternalReference::trunc64_wrapper_function(
+    Isolate* isolate) {
+  return ExternalReference(Redirect(isolate, FUNCTION_ADDR(trunc64_wrapper)));
+}
 
 ExternalReference ExternalReference::log_enter_external_function(
     Isolate* isolate) {

src/assembler.h

@@ -913,6 +913,8 @@ class ExternalReference BASE_EMBEDDED {
   static ExternalReference new_deoptimizer_function(Isolate* isolate);
   static ExternalReference compute_output_frames_function(Isolate* isolate);
 
+  static ExternalReference trunc64_wrapper_function(Isolate* isolate);
+
   // Log support.
   static ExternalReference log_enter_external_function(Isolate* isolate);
   static ExternalReference log_leave_external_function(Isolate* isolate);

src/compiler/wasm-compiler.cc

@@ -795,13 +795,9 @@ Node* WasmGraphBuilder::Unop(wasm::WasmOpcode opcode, Node* input) {
       }
     }
     case wasm::kExprF64Trunc: {
-      if (m->Float64RoundTruncate().IsSupported()) {
-        op = m->Float64RoundTruncate().op();
-        break;
-      } else {
-        op = UnsupportedOpcode(opcode);
-        break;
-      }
+      if (!m->Float64RoundTruncate().IsSupported()) return BuildF64Trunc(input);
+      op = m->Float64RoundTruncate().op();
+      break;
     }
     case wasm::kExprF64NearestInt: {
       if (m->Float64RoundTiesEven().IsSupported()) {
@@ -1436,6 +1432,60 @@ Node* WasmGraphBuilder::BuildF32Trunc(Node* input) {
   return Unop(wasm::kExprF32ReinterpretI32, result);
 }
 
+Node* WasmGraphBuilder::BuildF64Trunc(Node* input) {
+  // We do truncation by calling a C function which calculates the truncation
+  // for us. The input is passed to the C function as a double* to avoid double
+  // parameters. For this we reserve a slot on the stack, store the parameter in
+  // that slot, pass a pointer to the slot to the C function, and after calling
+  // the C function we collect the return value from the stack slot.
+
+  Node* stack_slot_param = graph()->NewNode(
+      jsgraph()->machine()->StackSlot(MachineRepresentation::kFloat64));
+
+  const Operator* store_op = jsgraph()->machine()->Store(
+      StoreRepresentation(MachineRepresentation::kFloat64, kNoWriteBarrier));
+  *effect_ =
+      graph()->NewNode(store_op, stack_slot_param, jsgraph()->Int32Constant(0),
+                       input, *effect_, *control_);
+
+  Signature<MachineType>::Builder sig_builder(jsgraph()->zone(), 0, 1);
+  sig_builder.AddParam(MachineType::Pointer());
+  Node* function = graph()->NewNode(jsgraph()->common()->ExternalConstant(
+      ExternalReference::trunc64_wrapper_function(jsgraph()->isolate())));
+
+  Node* args[] = {function, stack_slot_param};
+
+  BuildCCall(sig_builder.Build(), args);
+
+  const Operator* load_op = jsgraph()->machine()->Load(MachineType::Float64());
+
+  Node* load =
+      graph()->NewNode(load_op, stack_slot_param, jsgraph()->Int32Constant(0),
+                       *effect_, *control_);
+  *effect_ = load;
+  return load;
+}
+
+Node* WasmGraphBuilder::BuildCCall(MachineSignature* sig, Node** args) {
+  const size_t params = sig->parameter_count();
+  const size_t extra = 2;  // effect and control inputs.
+  const size_t count = 1 + params + extra;
+
+  // Reallocate the buffer to make space for extra inputs.
+  args = Realloc(args, count);
+
+  // Add effect and control inputs.
+  args[params + 1] = *effect_;
+  args[params + 2] = *control_;
+
+  CallDescriptor* desc =
+      Linkage::GetSimplifiedCDescriptor(jsgraph()->zone(), sig);
+
+  const Operator* op = jsgraph()->common()->Call(desc);
+  Node* call = graph()->NewNode(op, static_cast<int>(count), args);
+  *effect_ = call;
+  return call;
+}
 
 Node* WasmGraphBuilder::BuildWasmCall(wasm::FunctionSig* sig, Node** args) {
   const size_t params = sig->parameter_count();

src/compiler/wasm-compiler.h

@@ -159,6 +159,7 @@ class WasmGraphBuilder {
   Node* MemBuffer(uint32_t offset);
   void BoundsCheckMem(MachineType memtype, Node* index, uint32_t offset);
 
+  Node* BuildCCall(MachineSignature* sig, Node** args);
   Node* BuildWasmCall(wasm::FunctionSig* sig, Node** args);
   Node* BuildF32Neg(Node* input);
   Node* BuildF64Neg(Node* input);
@@ -177,6 +178,7 @@ class WasmGraphBuilder {
   Node* BuildI64Ctz(Node* input);
   Node* BuildI64Popcnt(Node* input);
   Node* BuildF32Trunc(Node* input);
+  Node* BuildF64Trunc(Node* input);
 
   Node** Realloc(Node** buffer, size_t count) {
     Node** buf = Buffer(count);

src/compiler/wasm-linkage.cc

@@ -264,6 +264,7 @@ CallDescriptor* ModuleEnv::GetWasmCallDescriptor(Zone* zone,
   // The target for WASM calls is always a code object.
   MachineType target_type = MachineType::AnyTagged();
   LinkageLocation target_loc = LinkageLocation::ForAnyRegister();
+
   return new (zone) CallDescriptor(       // --
       CallDescriptor::kCallCodeObject,    // kind
       target_type,                        // target MachineType

src/snapshot/serialize.cc

@@ -119,6 +119,8 @@ ExternalReferenceTable::ExternalReferenceTable(Isolate* isolate) {
       "InvokeFunctionCallback");
   Add(ExternalReference::invoke_accessor_getter_callback(isolate).address(),
       "InvokeAccessorGetterCallback");
+  Add(ExternalReference::trunc64_wrapper_function(isolate).address(),
+      "trunc64_wrapper");
   Add(ExternalReference::log_enter_external_function(isolate).address(),
       "Logger::EnterExternal");
   Add(ExternalReference::log_leave_external_function(isolate).address(),

test/cctest/compiler/test-run-machops.cc

@@ -5588,6 +5588,19 @@ TEST(RunCallCFunction8) {
 }
 #endif  // USE_SIMULATOR
 
+TEST(RunCallExternalReferenceF64Trunc) {
+  BufferedRawMachineAssemblerTester<double> m(MachineType::Float64());
+  Node* stack_slot = m.StackSlot(MachineRepresentation::kFloat64);
+  m.Store(MachineRepresentation::kFloat64, stack_slot, m.Parameter(0),
+          WriteBarrierKind::kNoWriteBarrier);
+  Node* function = m.ExternalConstant(
+      ExternalReference::trunc64_wrapper_function(m.isolate()));
+  m.CallCFunction1(MachineType::Pointer(), MachineType::Pointer(), function,
+                   stack_slot);
+  m.Return(m.Load(MachineType::Float64(), stack_slot));
+  FOR_FLOAT64_INPUTS(i) { CheckDoubleEq(trunc(*i), m.Call(*i)); }
+}
+
 #if V8_TARGET_ARCH_64_BIT
 // TODO(titzer): run int64 tests on all platforms when supported.
 TEST(RunCheckedLoadInt64) {

test/cctest/wasm/test-run-wasm.cc

@@ -3006,14 +3006,6 @@ TEST(Run_Wasm_F64Ceil) {
 }
 
 
-TEST(Run_Wasm_F64Trunc) {
-  WasmRunner<double> r(MachineType::Float64());
-  BUILD(r, WASM_F64_TRUNC(WASM_GET_LOCAL(0)));
-
-  FOR_FLOAT64_INPUTS(i) { CheckDoubleEq(trunc(*i), r.Call(*i)); }
-}
-
-
 TEST(Run_Wasm_F64NearestInt) {
   WasmRunner<double> r(MachineType::Float64());
   BUILD(r, WASM_F64_NEARESTINT(WASM_GET_LOCAL(0)));
@@ -3023,6 +3015,12 @@ TEST(Run_Wasm_F64NearestInt) {
 
 #endif
 
+TEST(Run_Wasm_F64Trunc) {
+  WasmRunner<double> r(MachineType::Float64());
+  BUILD(r, WASM_F64_TRUNC(WASM_GET_LOCAL(0)));
+
+  FOR_FLOAT64_INPUTS(i) { CheckDoubleEq(trunc(*i), r.Call(*i)); }
+}
 
 TEST(Run_Wasm_F32Min) {
   WasmRunner<float> r(MachineType::Float32(), MachineType::Float32());