X87: [turbofan] Add TruncationMode for TruncateFloat64ToInt32.

port 4b38c158 (r29527).

original commit message:

    We actually need round to zero truncation to implement the counterpart
    of LDoubleToI in TurboFan, which tries to convert a double to an integer
    as required for keyed load/store optimizations.

    Drive-by-cleanup: Reduce some code duplication in the InstructionSelector
    implementations.

BUG=

Review URL: https://codereview.chromium.org/1227923003

Cr-Commit-Position: refs/heads/master@{#29629}

src/compiler/x87/code-generator-x87.cc

@@ -422,11 +422,13 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       __ mov(i.OutputRegister(), esp);
       break;
     case kArchTruncateDoubleToI: {
-      auto input = i.InputDoubleRegister(0);
-      USE(input);
-      DCHECK(input.code() == 0);
-      auto result_reg = i.OutputRegister();
-      __ TruncateX87TOSToI(result_reg);
+      if (!instr->InputAt(0)->IsDoubleRegister()) {
+        __ fld_d(i.InputOperand(0));
+      }
+      __ TruncateX87TOSToI(i.OutputRegister());
+      if (!instr->InputAt(0)->IsDoubleRegister()) {
+        __ fstp(0);
+      }
       break;
     }
     case kX87Add:

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

@@ -647,6 +647,23 @@ void InstructionSelector::VisitTruncateFloat64ToFloat32(Node* node) {
 }
 
 
+void InstructionSelector::VisitTruncateFloat64ToInt32(Node* node) {
+  X87OperandGenerator g(this);
+
+  switch (TruncationModeOf(node->op())) {
+    case TruncationMode::kJavaScript:
+      Emit(kArchTruncateDoubleToI, g.DefineAsRegister(node),
+           g.Use(node->InputAt(0)));
+      return;
+    case TruncationMode::kRoundToZero:
+      Emit(kX87Float64ToInt32, g.DefineAsRegister(node),
+           g.Use(node->InputAt(0)));
+      return;
+  }
+  UNREACHABLE();
+}
+
+
 void InstructionSelector::VisitFloat32Add(Node* node) {
   X87OperandGenerator g(this);
   Emit(kX87PushFloat32, g.NoOutput(), g.Use(node->InputAt(0)));