MIPS: [turbofan] Enable Word32 safe shifts.

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

Index: src/compiler/mips/instruction-selector-mips.cc
diff --git a/src/compiler/mips/instruction-selector-mips.cc b/src/compiler/mips/instruction-selector-mips.cc
index 0877e0005e4bf7a9a16196cbe11ddfc762df0f89..b97cdb6af2673a61b240661256746cfba3885e3b 100644
--- a/src/compiler/mips/instruction-selector-mips.cc
+++ b/src/compiler/mips/instruction-selector-mips.cc
@@ -1196,7 +1196,8 @@ InstructionSelector::SupportedMachineOperatorFlags() {
              MachineOperatorBuilder::kFloat64RoundTruncate |
              MachineOperatorBuilder::kFloat64RoundTiesEven;
   }
-  return flags | MachineOperatorBuilder::kFloat64Min |
+  return flags | MachineOperatorBuilder::kWord32ShiftIsSafe |
+         MachineOperatorBuilder::kFloat64Min |
          MachineOperatorBuilder::kFloat64Max |
          MachineOperatorBuilder::kFloat32Min |
          MachineOperatorBuilder::kFloat32Max;