Add assembler test.

src/mips64/simulator-mips64.cc

Index: src/mips64/simulator-mips64.cc
diff --git a/src/mips64/simulator-mips64.cc b/src/mips64/simulator-mips64.cc
index 42b9ee0ed301945433dcd52b5ed8c6b61041ad7b..f9b6dd856ae9bb7c961725c04758c56fdf65326b 100644
--- a/src/mips64/simulator-mips64.cc
+++ b/src/mips64/simulator-mips64.cc
@@ -3494,6 +3494,20 @@ void Simulator::DecodeTypeRegisterSPECIAL() {
     case DSRAV:
       SetResult(rd_reg(), rt() >> rs());
       break;
+    case LSA: {
+      DCHECK(kArchVariant == kMips64r6);
+      int8_t sa = lsa_sa() + 1;
+      int32_t _rt = static_cast<int32_t>(rt());
+      int32_t _rs = static_cast<int32_t>(rs());
+      int32_t res = _rs << sa;
+      res += _rt;
+      SetResult(rd_reg(), static_cast<int64_t>(res));
+      break;
+    }
+    case DLSA:
+      DCHECK(kArchVariant == kMips64r6);
+      SetResult(rd_reg(), (rs() << (lsa_sa() + 1)) + rt());
+      break;
     case MFHI:  // MFHI == CLZ on R6.
       if (kArchVariant != kMips64r6) {
         DCHECK(sa() == 0);