Use Rotate*() functions instead of doing this manually.

src/base/bits.h

 // Copyright 2014 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.
 
 #ifndef V8_BASE_BITS_H_
 #define V8_BASE_BITS_H_
 
 #include <stdint.h>
 #include "src/base/macros.h"
 #if V8_CC_MSVC
@@ skipping 130 matching lines @@
 // less than or equal to |value|. If you pass in a |value| that is already a
 // power of two, it is returned as is.
 inline uint32_t RoundDownToPowerOfTwo32(uint32_t value) {
   if (value > 0x80000000u) return 0x80000000u;
   uint32_t result = RoundUpToPowerOfTwo32(value);
   if (result > value) result >>= 1;
   return result;
 }
 
 
+// Precondition: 0 <= shift < 32

[hans, 2015/03/04 06:02:51]

Any reason the preconditions are not some kind of assert or check?

[Nico, 2015/03/04 06:21:10]

I was worried that this might be performance-critical and things might get very
slow in debug builds. I don't know if that's true.

 inline uint32_t RotateRight32(uint32_t value, uint32_t shift) {
   if (shift == 0) return value;
   return (value >> shift) | (value << (32 - shift));
 }
 
+// Precondition: 0 <= shift < 32
+inline uint32_t RotateLeft32(uint32_t value, uint32_t shift) {
+  if (shift == 0) return value;
+  return (value << shift) | (value >> (32 - shift));
+}
 
+// Precondition: 0 <= shift < 64
 inline uint64_t RotateRight64(uint64_t value, uint64_t shift) {
   if (shift == 0) return value;
   return (value >> shift) | (value << (64 - shift));
 }
 
+// Precondition: 0 <= shift < 64
+inline uint64_t RotateLeft64(uint64_t value, uint64_t shift) {
+  if (shift == 0) return value;
+  return (value << shift) | (value >> (64 - shift));
+}
+
 
 // SignedAddOverflow32(lhs,rhs,val) performs a signed summation of |lhs| and
 // |rhs| and stores the result into the variable pointed to by |val| and
 // returns true if the signed summation resulted in an overflow.
 inline bool SignedAddOverflow32(int32_t lhs, int32_t rhs, int32_t* val) {
 #if V8_HAS_BUILTIN_SADD_OVERFLOW
   return __builtin_sadd_overflow(lhs, rhs, val);
 #else
   uint32_t res = static_cast<uint32_t>(lhs) + static_cast<uint32_t>(rhs);
   *val = bit_cast<int32_t>(res);
@@ skipping 51 matching lines @@
 // truncated to uint32. If |rhs| is zero, then zero is returned.
 inline uint32_t UnsignedMod32(uint32_t lhs, uint32_t rhs) {
   return rhs ? lhs % rhs : 0u;
 }
 
 }  // namespace bits
 }  // namespace base
 }  // namespace v8
 
 #endif  // V8_BASE_BITS_H_