[x86] Fix InstructionSelector::SupportedMachineOperatorFlags().

Word32 shifts are always safe on ia32 and x64, independent of whether
SSE4.1 is available.

R=dcarney@chromium.org

Review URL: https://codereview.chromium.org/975363002

Cr-Commit-Position: refs/heads/master@{#26984}

src/compiler/ia32/instruction-selector-ia32.cc

@@ -1071,13 +1071,14 @@ void InstructionSelector::VisitFloat64LessThanOrEqual(Node* node) {
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {
+  MachineOperatorBuilder::Flags flags =
+      MachineOperatorBuilder::kWord32ShiftIsSafe;
   if (CpuFeatures::IsSupported(SSE4_1)) {
-    return MachineOperatorBuilder::kFloat64Floor |
-           MachineOperatorBuilder::kFloat64Ceil |
-           MachineOperatorBuilder::kFloat64RoundTruncate |
-           MachineOperatorBuilder::kWord32ShiftIsSafe;
+    flags |= MachineOperatorBuilder::kFloat64Floor |
+             MachineOperatorBuilder::kFloat64Ceil |
+             MachineOperatorBuilder::kFloat64RoundTruncate;
   }
-  return MachineOperatorBuilder::Flag::kNoFlags;
+  return flags;
 }
 
 }  // namespace compiler

src/compiler/x64/instruction-selector-x64.cc

@@ -1374,13 +1374,14 @@ void InstructionSelector::VisitFloat64LessThanOrEqual(Node* node) {
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {
+  MachineOperatorBuilder::Flags flags =
+      MachineOperatorBuilder::kWord32ShiftIsSafe;
   if (CpuFeatures::IsSupported(SSE4_1)) {
-    return MachineOperatorBuilder::kFloat64Floor |
-           MachineOperatorBuilder::kFloat64Ceil |
-           MachineOperatorBuilder::kFloat64RoundTruncate |
-           MachineOperatorBuilder::kWord32ShiftIsSafe;
+    flags |= MachineOperatorBuilder::kFloat64Floor |
+             MachineOperatorBuilder::kFloat64Ceil |
+             MachineOperatorBuilder::kFloat64RoundTruncate;
   }
-  return MachineOperatorBuilder::kNoFlags;
+  return flags;
 }
 
 }  // namespace compiler