PPC64: [turbofan] Change TruncateFloat64ToUint64 to TryTruncateFloatToUint64.

Port c343f309

Original commit message:
    This operator now provides a second output which indicates whether the
    conversion from float64 to uint64 was successful or not. The second output
    returns 0 if the conversion fails, or something else if the conversion
    succeeds.

    The second output can be ignored, which means that the operator can be used
    the same as the original operator.

R=ahaas@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1512963002

Cr-Commit-Position: refs/heads/master@{#32728}

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

@@ -1188,11 +1188,24 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       break;
     }
 #if V8_TARGET_ARCH_PPC64
-    case kPPC_DoubleToUint64:
+    case kPPC_DoubleToUint64: {
+      bool check_conversion = (i.OutputCount() > 1);
+      if (check_conversion) {
+        __ mtfsb0(VXCVI);  // clear FPSCR:VXCVI bit
+      }
       __ ConvertDoubleToUnsignedInt64(i.InputDoubleRegister(0),
-                                      i.OutputRegister(), kScratchDoubleReg);
+                                      i.OutputRegister(0), kScratchDoubleReg);
+      if (check_conversion) {
+        // Set 2nd output to zero if conversion fails.
+        CRBit crbit = static_cast<CRBit>(VXCVI % CRWIDTH);
+        __ mcrfs(cr7, VXCVI);  // extract FPSCR field containing VXCVI into cr7
+        __ li(i.OutputRegister(1), Operand(1));
+        __ isel(i.OutputRegister(1), r0, i.OutputRegister(1),
+                v8::internal::Assembler::encode_crbit(cr7, crbit));
+      }
       DCHECK_EQ(LeaveRC, i.OutputRCBit());
       break;
+    }
 #endif
     case kPPC_DoubleToFloat32:
       ASSEMBLE_FLOAT_UNOP_RC(frsp);

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

@@ -955,11 +955,19 @@ void InstructionSelector::VisitTruncateFloat32ToUint64(Node* node) {
 
 
 void InstructionSelector::VisitTryTruncateFloat64ToUint64(Node* node) {
-  if (NodeProperties::FindProjection(node, 1)) {
-    // TODO(ppc): implement the second return value.
-    UNIMPLEMENTED();
+  PPCOperandGenerator g(this);
+
+  InstructionOperand inputs[] = {g.UseRegister(node->InputAt(0))};
+  InstructionOperand outputs[2];
+  size_t output_count = 0;
+  outputs[output_count++] = g.DefineAsRegister(node);
+
+  Node* success_output = NodeProperties::FindProjection(node, 1);
+  if (success_output) {
+    outputs[output_count++] = g.DefineAsRegister(success_output);
   }
-  VisitRR(this, kPPC_DoubleToUint64, node);
+
+  Emit(kPPC_DoubleToUint64, output_count, outputs, 1, inputs);
 }