diff options
Diffstat (limited to 'compiler-rt/lib/builtins/ctzsi2.c')
| -rw-r--r-- | compiler-rt/lib/builtins/ctzsi2.c | 69 |
1 files changed, 34 insertions, 35 deletions
diff --git a/compiler-rt/lib/builtins/ctzsi2.c b/compiler-rt/lib/builtins/ctzsi2.c index d5dfe256893..405b2f771cd 100644 --- a/compiler-rt/lib/builtins/ctzsi2.c +++ b/compiler-rt/lib/builtins/ctzsi2.c @@ -17,40 +17,39 @@ /* Precondition: a != 0 */ -COMPILER_RT_ABI si_int -__ctzsi2(si_int a) -{ - su_int x = (su_int)a; - si_int t = ((x & 0x0000FFFF) == 0) << 4; /* if (x has no small bits) t = 16 else 0 */ - x >>= t; /* x = [0 - 0xFFFF] + higher garbage bits */ - su_int r = t; /* r = [0, 16] */ - /* return r + ctz(x) */ - t = ((x & 0x00FF) == 0) << 3; - x >>= t; /* x = [0 - 0xFF] + higher garbage bits */ - r += t; /* r = [0, 8, 16, 24] */ - /* return r + ctz(x) */ - t = ((x & 0x0F) == 0) << 2; - x >>= t; /* x = [0 - 0xF] + higher garbage bits */ - r += t; /* r = [0, 4, 8, 12, 16, 20, 24, 28] */ - /* return r + ctz(x) */ - t = ((x & 0x3) == 0) << 1; - x >>= t; - x &= 3; /* x = [0 - 3] */ - r += t; /* r = [0 - 30] and is even */ - /* return r + ctz(x) */ +COMPILER_RT_ABI si_int __ctzsi2(si_int a) { + su_int x = (su_int)a; + si_int t = ((x & 0x0000FFFF) == 0) + << 4; /* if (x has no small bits) t = 16 else 0 */ + x >>= t; /* x = [0 - 0xFFFF] + higher garbage bits */ + su_int r = t; /* r = [0, 16] */ + /* return r + ctz(x) */ + t = ((x & 0x00FF) == 0) << 3; + x >>= t; /* x = [0 - 0xFF] + higher garbage bits */ + r += t; /* r = [0, 8, 16, 24] */ + /* return r + ctz(x) */ + t = ((x & 0x0F) == 0) << 2; + x >>= t; /* x = [0 - 0xF] + higher garbage bits */ + r += t; /* r = [0, 4, 8, 12, 16, 20, 24, 28] */ + /* return r + ctz(x) */ + t = ((x & 0x3) == 0) << 1; + x >>= t; + x &= 3; /* x = [0 - 3] */ + r += t; /* r = [0 - 30] and is even */ + /* return r + ctz(x) */ -/* The branch-less return statement below is equivalent - * to the following switch statement: - * switch (x) - * { - * case 0: - * return r + 2; - * case 2: - * return r + 1; - * case 1: - * case 3: - * return r; - * } - */ - return r + ((2 - (x >> 1)) & -((x & 1) == 0)); + /* The branch-less return statement below is equivalent + * to the following switch statement: + * switch (x) + * { + * case 0: + * return r + 2; + * case 2: + * return r + 1; + * case 1: + * case 3: + * return r; + * } + */ + return r + ((2 - (x >> 1)) & -((x & 1) == 0)); } |

