diff options
Diffstat (limited to 'compiler/optimizing/code_generator_utils.cc')
| -rw-r--r-- | compiler/optimizing/code_generator_utils.cc | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/compiler/optimizing/code_generator_utils.cc b/compiler/optimizing/code_generator_utils.cc index 26cab2ff09..921c1d86c2 100644 --- a/compiler/optimizing/code_generator_utils.cc +++ b/compiler/optimizing/code_generator_utils.cc @@ -18,13 +18,15 @@ #include "base/logging.h" +namespace art { + void CalculateMagicAndShiftForDivRem(int64_t divisor, bool is_long, int64_t* magic, int* shift) { // It does not make sense to calculate magic and shift for zero divisor. DCHECK_NE(divisor, 0); - /* According to implementation from H.S.Warren's "Hacker's Delight" (Addison Wesley, 2002) - * Chapter 10 and T,Grablund, P.L.Montogomery's "Division by Invariant Integers Using + /* Implementation according to H.S.Warren's "Hacker's Delight" (Addison Wesley, 2002) + * Chapter 10 and T.Grablund, P.L.Montogomery's "Division by Invariant Integers Using * Multiplication" (PLDI 1994). * The magic number M and shift S can be calculated in the following way: * Let nc be the most positive value of numerator(n) such that nc = kd - 1, @@ -39,11 +41,11 @@ void CalculateMagicAndShiftForDivRem(int64_t divisor, bool is_long, * 2^p > nc * (d - 2^p % d), where d >= 2 * 2^p > nc * (d + 2^p % d), where d <= -2. * - * The magic number M is calcuated by + * The magic number M is calculated by * M = (2^p + d - 2^p % d) / d, where d >= 2 * M = (2^p - d - 2^p % d) / d, where d <= -2. * - * Notice that p is always bigger than or equal to 32 (resp. 64), so we just return 32-p + * Notice that p is always bigger than or equal to 32 (resp. 64), so we just return 32 - p * (resp. 64 - p) as the shift number S. */ @@ -52,9 +54,10 @@ void CalculateMagicAndShiftForDivRem(int64_t divisor, bool is_long, // Initialize the computations. uint64_t abs_d = (divisor >= 0) ? divisor : -divisor; - uint64_t tmp = exp + (is_long ? static_cast<uint64_t>(divisor) >> 63 : - static_cast<uint32_t>(divisor) >> 31); - uint64_t abs_nc = tmp - 1 - tmp % abs_d; + uint64_t sign_bit = is_long ? static_cast<uint64_t>(divisor) >> 63 : + static_cast<uint32_t>(divisor) >> 31; + uint64_t tmp = exp + sign_bit; + uint64_t abs_nc = tmp - 1 - (tmp % abs_d); uint64_t quotient1 = exp / abs_nc; uint64_t remainder1 = exp % abs_nc; uint64_t quotient2 = exp / abs_d; @@ -91,3 +94,4 @@ void CalculateMagicAndShiftForDivRem(int64_t divisor, bool is_long, *shift = is_long ? p - 64 : p - 32; } +} // namespace art |