[wasm] Fixed F32Neg and F64Neg for -0.0.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/1516143004

Cr-Commit-Position: refs/heads/master@{#32802}

src/compiler/wasm-compiler.cc

@@ -692,8 +692,8 @@ Node* WasmGraphBuilder::Unop(wasm::WasmOpcode opcode, Node* input) {
       op = m->Float32Abs();
       break;
     case wasm::kExprF32Neg:
-      op = m->Float32Sub();
-      return graph()->NewNode(op, jsgraph()->Float32Constant(0), input);
+      op = m->Float32Mul();
+      return graph()->NewNode(op, jsgraph()->Float32Constant(-1), input);
     case wasm::kExprF32Sqrt:
       op = m->Float32Sqrt();
       break;
@@ -701,8 +701,8 @@ Node* WasmGraphBuilder::Unop(wasm::WasmOpcode opcode, Node* input) {
       op = m->Float64Abs();
       break;
     case wasm::kExprF64Neg:
-      op = m->Float64Sub();
-      return graph()->NewNode(op, jsgraph()->Float64Constant(0), input);
+      op = m->Float64Mul();
+      return graph()->NewNode(op, jsgraph()->Float64Constant(-1), input);
     case wasm::kExprF64Sqrt:
       op = m->Float64Sqrt();
       break;

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

@@ -1153,6 +1153,30 @@ TEST(Run_WasmFloat64Unops) {
 }
 
 
+TEST(Run_WasmFloat32Neg) {
+  WasmRunner<float> r(MachineType::Float32());
+  BUILD(r, WASM_F32_NEG(WASM_GET_LOCAL(0)));
+
+  FOR_FLOAT32_INPUTS(i) { CheckFloatEq(-(*i), r.Call(*i)); }
+
+  // The difference between +0 and -0 matters here.
+  CHECK_EQ(bit_cast<uint32_t>(-0.0f), bit_cast<uint32_t>(r.Call(0.0f)));
+  CHECK_EQ(bit_cast<uint32_t>(0.0f), bit_cast<uint32_t>(r.Call(-0.0f)));
+}
+
+
+TEST(Run_WasmFloat64Neg) {
+  WasmRunner<double> r(MachineType::Float64());
+  BUILD(r, WASM_F64_NEG(WASM_GET_LOCAL(0)));
+
+  FOR_FLOAT64_INPUTS(i) { CheckDoubleEq(-(*i), r.Call(*i)); }
+
+  // The difference between +0 and -0 matters here.
+  CHECK_EQ(bit_cast<uint64_t>(-0.0), bit_cast<uint64_t>(r.Call(0.0)));
+  CHECK_EQ(bit_cast<uint64_t>(0.0), bit_cast<uint64_t>(r.Call(-0.0)));
+}
+
+
 TEST(Run_Wasm_IfElse_P) {
   WasmRunner<int32_t> r(MachineType::Int32());
   // if (p0) return 11; else return 22;