X87: [turbofan] Implemented the optional Float32RoundTruncate operator.

  port 19741ac9 (r32301)

  original commit message:
  The Float32RoundTruncate operator rounds float32 numbers towards zero.
  The operator is currently implemented on x64, ia32, arm, and arm64.

  Additionally I added support for the float32 vrintz, vrintn, and vrinta
  instructions to the arm simulator.

BUG=

Review URL: https://codereview.chromium.org/1493213002

Cr-Commit-Position: refs/heads/master@{#32537}

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

@@ -871,7 +871,9 @@ void InstructionSelector::VisitFloat64RoundUp(Node* node) {
 
 
 void InstructionSelector::VisitFloat32RoundTruncate(Node* node) {
-  UNREACHABLE();
+  X87OperandGenerator g(this);
+  Emit(kX87Float32Round | MiscField::encode(kRoundToZero),
+       g.UseFixed(node, stX_0), g.Use(node->InputAt(0)));
 }
 
 
@@ -1319,6 +1321,7 @@ InstructionSelector::SupportedMachineOperatorFlags() {
            MachineOperatorBuilder::kFloat64RoundDown |
            MachineOperatorBuilder::kFloat32RoundUp |
            MachineOperatorBuilder::kFloat64RoundUp |
+           MachineOperatorBuilder::kFloat32RoundTruncate |
            MachineOperatorBuilder::kFloat64RoundTruncate |
            MachineOperatorBuilder::kFloat64RoundTiesEven;
   return flags;