MIPS: [turbofan] Optimize sign-extension patterns like Sar(Shl(x, a), b)).

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

Index: src/compiler/mips/instruction-codes-mips.h
diff --git a/src/compiler/mips/instruction-codes-mips.h b/src/compiler/mips/instruction-codes-mips.h
index 269ac0fed450b75b42bf39867d7c046e8f058237..1b052547ed4e3019df5924c3f3ac35ad3e3ae0a7 100644
--- a/src/compiler/mips/instruction-codes-mips.h
+++ b/src/compiler/mips/instruction-codes-mips.h
@@ -126,7 +126,9 @@ namespace compiler {
   V(MipsPush)                      \
   V(MipsStoreToStackSlot)          \
   V(MipsByteSwap32)                \
-  V(MipsStackClaim)
+  V(MipsStackClaim)                \
+  V(MipsSeb)                       \
+  V(MipsSeh)
 
 // Addressing modes represent the "shape" of inputs to an instruction.
 // Many instructions support multiple addressing modes. Addressing modes