MIPS: Fix Sltu macro instruction.

src/mips/macro-assembler-mips.cc

 // Copyright 2012 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>  // For LONG_MIN, LONG_MAX.
 
 #if V8_TARGET_ARCH_MIPS
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
@@ skipping 1103 matching lines @@
       // li handles the relocation.
       DCHECK(!rs.is(at));
       li(at, rt);
       slt(rd, rs, at);
     }
   }
 }
 
 
 void MacroAssembler::Sltu(Register rd, Register rs, const Operand& rt) {
+  const uint32_t int16_min = std::numeric_limits<int16_t>::min();

[balazs.kilvady, 2016/09/30 17:45:19]

This should be in the else branch.

[akos.palfi.imgtec, 2016/09/30 17:55:10]

Acknowledged.

   if (rt.is_reg()) {
     sltu(rd, rs, rt.rm());
   } else {
-    if (is_uint16(rt.imm32_) && !MustUseReg(rt.rmode_)) {
+    if (is_uint15(rt.imm32_) && !MustUseReg(rt.rmode_)) {
+      // Imm range is: [0, 32767].
       sltiu(rd, rs, rt.imm32_);
+    } else if (is_uint15(rt.imm32_ - int16_min) && !MustUseReg(rt.rmode_)) {
+      // Imm range is: [max_unsigned-32767,max_unsigned].
+      sltiu(rd, rs, static_cast<uint16_t>(rt.imm32_));

[balazs.kilvady, 2016/09/30 17:45:19]

sltiu() expects int16 or uint16? Is this cast ok?

[akos.palfi.imgtec, 2016/09/30 17:55:10]

It expects int32. This casts [ffff8000, ffffffff] to [8000, ffff], I've checked
it with the debugger.

     } else {
       // li handles the relocation.
       DCHECK(!rs.is(at));
       li(at, rt);
       sltu(rd, rs, at);
     }
   }
 }
 
 
@@ skipping 5841 matching lines @@
   if (mag.shift > 0) sra(result, result, mag.shift);
   srl(at, dividend, 31);
   Addu(result, result, Operand(at));
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS