[turbofan] Implement rounding of floats on x64 and ia32 without sse4.1.

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

Index: test/cctest/compiler/test-run-machops.cc
diff --git a/test/cctest/compiler/test-run-machops.cc b/test/cctest/compiler/test-run-machops.cc
index 52672c8a89204cdf1fcc7d275311813bbeaf9a46..4569e3f4db7c800d5f0e9cbc7283ab89190a6857 100644
--- a/test/cctest/compiler/test-run-machops.cc
+++ b/test/cctest/compiler/test-run-machops.cc
@@ -5419,6 +5419,28 @@ TEST(RunFloat32RoundDown) {
 }
 
 
+TEST(RunFloat32RoundDownMinusZero) {
+  BufferedRawMachineAssemblerTester<float> m(MachineType::Float32());
+  if (!m.machine()->Float32RoundDown().IsSupported()) return;
+
+  m.Return(m.Float32RoundDown(m.Parameter(0)));
+  int32_t expected = bit_cast<int32_t>(-0.0f);
+  int32_t result = bit_cast<int32_t>(m.Call(-0.0f));
+  CHECK_EQ(expected, result);
+}
+
+
+TEST(RunFloat64RoundDownMinusZero) {
+  BufferedRawMachineAssemblerTester<double> m(MachineType::Float64());
+  if (!m.machine()->Float64RoundDown().IsSupported()) return;
+
+  m.Return(m.Float64RoundDown(m.Parameter(0)));
+  int64_t expected = bit_cast<int64_t>(-0.0);
+  int64_t result = bit_cast<int64_t>(m.Call(-0.0));
+  CHECK_EQ(expected, result);
+}
+
+
 TEST(RunFloat64RoundDown1) {
   BufferedRawMachineAssemblerTester<double> m(MachineType::Float64());
   if (!m.machine()->Float64RoundDown().IsSupported()) return;