MIPS64: Fix rotate instructions in simulator

src/mips64/simulator-mips64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <limits.h>
 #include <stdarg.h>
 #include <stdlib.h>
 #include <cmath>
 
 #if V8_TARGET_ARCH_MIPS64
@@ skipping 3401 matching lines @@
       SetResult(rd_reg(), rt() << sa());
       break;
     case DSLL32:
       SetResult(rd_reg(), rt() << sa() << 32);
       break;
     case SRL:
       if (rs_reg() == 0) {
         // Regular logical right shift of a word by a fixed number of
         // bits instruction. RS field is always equal to 0.
         // Sign-extend the 32-bit result.
         alu_out = static_cast<int32_t>(static_cast<uint32_t>(rt_u()) >> sa());

[balazs.kilvady, 2016/04/12 13:14:33]

I see. A lot of unnecessary casting existed already, you just followed it. Yep,
there are quite much to clean-up. Sorry, could you fix the conversions here
also?

-      } else {
+      } else if (rs_reg() == 1) {
         // Logical right-rotate of a word by a fixed number of bits. This
         // is special case of SRL instruction, added in MIPS32 Release 2.
         // RS field is equal to 00001.
         alu_out = static_cast<int32_t>(
             base::bits::RotateRight32(static_cast<const uint32_t>(rt_u()),
                                       static_cast<const uint32_t>(sa())));

[balazs.kilvady, 2016/04/12 13:14:33]

I see. A lot of unecessary comment existed already, you just followed it. Yep,
there are quite much to clean-up. Sorry, could you fix the conversions here
also?

+      } else {
+        UNREACHABLE();
       }
       SetResult(rd_reg(), alu_out);
       break;
     case DSRL:
-      SetResult(rd_reg(), rt_u() >> sa());
+      if (rs_reg() == 0) {
+        // Regular logical right shift of a word by a fixed number of
+        // bits instruction. RS field is always equal to 0.
+        // Sign-extend the 64-bit result.
+        alu_out = static_cast<int64_t>(rt_u() >> sa());
+      } else if (rs_reg() == 1) {
+        // Logical right-rotate of a word by a fixed number of bits. This
+        // is special case of SRL instruction, added in MIPS32 Release 2.
+        // RS field is equal to 00001.
+        alu_out = static_cast<int64_t>(base::bits::RotateRight64(rt_u(), sa()));
+      } else {
+        UNREACHABLE();
+      }
+      SetResult(rd_reg(), alu_out);
       break;
     case DSRL32:
-      SetResult(rd_reg(), rt_u() >> sa() >> 32);
+      if (rs_reg() == 0) {
+        // Regular logical right shift of a word by a fixed number of
+        // bits instruction. RS field is always equal to 0.
+        // Sign-extend the 64-bit result.
+        alu_out = static_cast<int64_t>(rt_u() >> sa() >> 32);
+      } else if (rs_reg() == 1) {
+        // Logical right-rotate of a word by a fixed number of bits. This
+        // is special case of SRL instruction, added in MIPS32 Release 2.
+        // RS field is equal to 00001.
+        alu_out =
+            static_cast<int64_t>(base::bits::RotateRight64(rt_u(), sa() + 32));
+      } else {
+        UNREACHABLE();
+      }
+      SetResult(rd_reg(), alu_out);
       break;
     case SRA:
       SetResult(rd_reg(), (int32_t)rt() >> sa());
       break;
     case DSRA:
       SetResult(rd_reg(), rt() >> sa());
       break;
     case DSRA32:
       SetResult(rd_reg(), rt() >> sa() >> 32);
       break;
@@ skipping 15 matching lines @@
         alu_out = static_cast<int32_t>(
             base::bits::RotateRight32(static_cast<const uint32_t>(rt_u()),
                                       static_cast<const uint32_t>(rs_u())));
       }
       SetResult(rd_reg(), alu_out);
       break;
     case DSRLV:
       if (sa() == 0) {
         // Regular logical right-shift of a word by a variable number of
         // bits instruction. SA field is always equal to 0.
-        alu_out = rt_u() >> rs();
+        alu_out = static_cast<int64_t>(rt_u() >> rs());
       } else {
         // Logical right-rotate of a word by a variable number of bits.
         // This is special case od SRLV instruction, added in MIPS32
         // Release 2. SA field is equal to 00001.
-        alu_out = base::bits::RotateRight64(rt_u(), rs_u());
+        alu_out =
+            static_cast<int64_t>(base::bits::RotateRight64(rt_u(), rs_u()));
       }
       SetResult(rd_reg(), alu_out);
       break;
     case SRAV:
       SetResult(rd_reg(), (int32_t)rt() >> rs());
       break;
     case DSRAV:
       SetResult(rd_reg(), rt() >> rs());
       break;
     case LSA: {
@@ skipping 1357 matching lines @@
 }
 
 
 #undef UNSUPPORTED
 }  // namespace internal
 }  // namespace v8
 
 #endif  // USE_SIMULATOR
 
 #endif  // V8_TARGET_ARCH_MIPS64