PPC: [turbofan] Add new Float32Abs and Float64Abs operators.

Port 9af9f1d0

Original commit message:
These operators compute the absolute floating point value of some
arbitrary input, and are implemented without any branches (i.e. using
vabs on arm, and andps/andpd on x86).

R=mbrandy@us.ibm.com

BUG=

Review URL: https://codereview.chromium.org/1072963002

Cr-Commit-Position: refs/heads/master@{#27727}

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

@@ -857,6 +857,9 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
     case kPPC_MinDouble:
       ASSEMBLE_FLOAT_MIN(kScratchDoubleReg);
       break;
+    case kPPC_AbsDouble:
+      ASSEMBLE_FLOAT_UNOP_RC(fabs);
+      break;
     case kPPC_SqrtDouble:
       ASSEMBLE_FLOAT_UNOP_RC(fsqrt);
       break;

src/compiler/ppc/instruction-codes-ppc.h

@@ -60,6 +60,7 @@ namespace compiler {
   V(PPC_RoundDouble)               \
   V(PPC_MaxDouble)                 \
   V(PPC_MinDouble)                 \
+  V(PPC_AbsDouble)                 \
   V(PPC_Cntlz32)                   \
   V(PPC_Cmp32)                     \
   V(PPC_Cmp64)                     \

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

@@ -995,10 +995,14 @@ void InstructionSelector::VisitFloat64Min(Node* node) {
 }
 
 
-void InstructionSelector::VisitFloat32Abs(Node* node) { UNREACHABLE(); }
+void InstructionSelector::VisitFloat32Abs(Node* node) {
+  VisitRR(this, kPPC_AbsDouble, node);
+}
 
 
-void InstructionSelector::VisitFloat64Abs(Node* node) { UNREACHABLE(); }
+void InstructionSelector::VisitFloat64Abs(Node* node) {
+  VisitRR(this, kPPC_AbsDouble, node);
+}
 
 
 void InstructionSelector::VisitFloat32Sqrt(Node* node) {
@@ -1536,8 +1540,10 @@ void InstructionSelector::VisitFloat64InsertHighWord32(Node* node) {
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {
-  return MachineOperatorBuilder::kFloat32Max |
+  return MachineOperatorBuilder::kFloat32Abs |
+         MachineOperatorBuilder::kFloat32Max |
          MachineOperatorBuilder::kFloat32Min |
+         MachineOperatorBuilder::kFloat64Abs |
          MachineOperatorBuilder::kFloat64Max |
          MachineOperatorBuilder::kFloat64Min |
          MachineOperatorBuilder::kFloat64RoundDown |