MIPS: Improve Lsa/Dlsa implementations.

src/mips/assembler-mips.cc

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 1743 matching lines @@
   DCHECK(rd.is_valid() && rt.is_valid() && rs.is_valid());
   DCHECK(IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6));
   Instr instr = SPECIAL | (rs.code() << kRsShift) | (rt.code() << kRtShift)
      | (rd.code() << kRdShift) | (1 << kSaShift) | SRLV;
   emit(instr);
 }
 
 
 void Assembler::lsa(Register rd, Register rt, Register rs, uint8_t sa) {
   DCHECK(rd.is_valid() && rt.is_valid() && rs.is_valid());
-  DCHECK(sa < 5 && sa > 0);
+  DCHECK(sa <= 3);
   DCHECK(IsMipsArchVariant(kMips32r6));
-  Instr instr = SPECIAL | (rs.code() << kRsShift) | (rt.code() << kRtShift) |
-                (rd.code() << kRdShift) | (sa - 1) << kSaShift | LSA;
+  Instr instr = SPECIAL | rs.code() << kRsShift | rt.code() << kRtShift |
+                rd.code() << kRdShift | sa << kSaShift | LSA;
   emit(instr);
 }
 
 
 // ------------Memory-instructions-------------
 
 // Helper for base-reg + offset, when offset is larger than int16.
 void Assembler::LoadRegPlusOffsetToAt(const MemOperand& src) {
   DCHECK(!src.rm().is(at));
   lui(at, (src.offset_ >> kLuiShift) & kImm16Mask);
@@ skipping 1377 matching lines @@
 
   if (icache_flush_mode != SKIP_ICACHE_FLUSH) {
     Assembler::FlushICache(isolate, pc, 2 * sizeof(int32_t));
   }
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS