X87: [TurboFan] enable the Float64RoundDown and Float64RoundTruncate operators in x87.

src/compiler/x87/instruction-selector-x87.cc

Index: src/compiler/x87/instruction-selector-x87.cc
diff --git a/src/compiler/x87/instruction-selector-x87.cc b/src/compiler/x87/instruction-selector-x87.cc
index 3c06979dc0987697f00fe12f43a50384cd7d32d1..192efd6800110bd64d72e88731a8a8f99fb67a52 100644
--- a/src/compiler/x87/instruction-selector-x87.cc
+++ b/src/compiler/x87/instruction-selector-x87.cc
@@ -1300,6 +1300,9 @@ InstructionSelector::SupportedMachineOperatorFlags() {
   if (CpuFeatures::IsSupported(POPCNT)) {
     flags |= MachineOperatorBuilder::kWord32Popcnt;
   }
+
+  flags |= MachineOperatorBuilder::kFloat64RoundDown |
+           MachineOperatorBuilder::kFloat64RoundTruncate;
   return flags;
 }