diff options
author | dj <dj@138bc75d-0d04-0410-961f-82ee72b054a4> | 2004-06-08 19:24:07 +0000 |
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committer | dj <dj@138bc75d-0d04-0410-961f-82ee72b054a4> | 2004-06-08 19:24:07 +0000 |
commit | 2f8c398164724cd8cdc439c871cec8d3664d663e (patch) | |
tree | 887165390ca703d20364aad9a0a6ada538084ea9 | |
parent | 442ab8352a0a09b6da05f5079f9ee2bb2a246807 (diff) | |
download | gcc-2f8c398164724cd8cdc439c871cec8d3664d663e.tar.gz |
* toplev.c (floor_log2_wide): Replace loop with faster bit
operations.
(exact_log2_wide): Define in terms of the above.
* toplev.h (floor_log2): Use _builtin_clz family of builtins if
available.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@82778 138bc75d-0d04-0410-961f-82ee72b054a4
-rw-r--r-- | gcc/ChangeLog | 8 | ||||
-rw-r--r-- | gcc/toplev.c | 50 | ||||
-rw-r--r-- | gcc/toplev.h | 23 |
3 files changed, 62 insertions, 19 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index b251c45ad0c..d150c60822d 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +2004-06-08 DJ Delorie <dj@redhat.com> + + * toplev.c (floor_log2_wide): Replace loop with faster bit + operations. + (exact_log2_wide): Define in terms of the above. + * toplev.h (floor_log2): Use _builtin_clz family of builtins if + available. + 2004-06-08 Andrew Pinski <pinskia@physics.uc.edu> * config/rs6000/rs6000.c (print_operand, <case 'z'>): diff --git a/gcc/toplev.c b/gcc/toplev.c index 2741be5047f..e1803943d9c 100644 --- a/gcc/toplev.c +++ b/gcc/toplev.c @@ -1248,36 +1248,48 @@ read_integral_parameter (const char *p, const char *pname, const int defval) return atoi (p); } -/* Return the logarithm of X, base 2, considering X unsigned, - if X is a power of 2. Otherwise, returns -1. +/* Given X, an unsigned number, return the largest int Y such that 2**Y <= X. + If X is 0, return -1. - This should be used via the `exact_log2' macro. */ + This should be used via the floor_log2 macro. */ int -exact_log2_wide (unsigned HOST_WIDE_INT x) +floor_log2_wide (unsigned HOST_WIDE_INT x) { - int log = 0; - /* Test for 0 or a power of 2. */ - if (x == 0 || x != (x & -x)) + int t=0; + if (x == 0) return -1; - while ((x >>= 1) != 0) - log++; - return log; + if (sizeof (HOST_WIDE_INT)*8 > 64) + if (x >= (unsigned HOST_WIDE_INT)(1 << (t+64))) + t += 64; + if (sizeof (HOST_WIDE_INT)*8 > 32) + if (x >= (unsigned HOST_WIDE_INT)(1 << (t+32))) + t += 32; + if (x >= (unsigned HOST_WIDE_INT)(1 << (t+16))) + t += 16; + if (x >= (unsigned HOST_WIDE_INT)(1 << (t+8))) + t += 8; + if (x >= (unsigned HOST_WIDE_INT)(1 << (t+4))) + t += 4; + if (x >= (unsigned HOST_WIDE_INT)(1 << (t+2))) + t += 2; + if (x >= (unsigned HOST_WIDE_INT)(1 << (t+1))) + t += 1; + return t; } -/* Given X, an unsigned number, return the largest int Y such that 2**Y <= X. - If X is 0, return -1. +/* Return the logarithm of X, base 2, considering X unsigned, + if X is a power of 2. Otherwise, returns -1. - This should be used via the floor_log2 macro. */ + This should be used via the `exact_log2' macro. */ int -floor_log2_wide (unsigned HOST_WIDE_INT x) +exact_log2_wide (unsigned HOST_WIDE_INT x) { - int log = -1; - while (x != 0) - log++, - x >>= 1; - return log; + /* Test for 0 or a power of 2. */ + if (x == 0 || x != (x & -x)) + return -1; + return floor_log2_wide (x); } /* Handler for fatal signals, such as SIGSEGV. These are transformed diff --git a/gcc/toplev.h b/gcc/toplev.h index aca355771fb..f12102e9f7b 100644 --- a/gcc/toplev.h +++ b/gcc/toplev.h @@ -152,8 +152,31 @@ extern bool fast_math_flags_set_p (void); #ifndef exact_log2 #define exact_log2(N) exact_log2_wide ((unsigned HOST_WIDE_INT) (N)) + +#if (__GNUC__ * 1000 + __GNUC_MINOR__) >= 3004 +#if HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_LONGLONG +#define FL2T__ HOST_WIDE_INT +#define FL2T_CLZ__ __builtin_clzll +#else +#if HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_LONG +#define FL2T__ HOST_WIDE_INT +#define FL2T_CLZ__ __builtin_clzl +#else +#define FL2T__ int +#define FL2T_CLZ__ __builtin_clz +#endif +#endif +static inline int floor_log2(FL2T__ n) +{ + if (n) + return (sizeof(FL2T__)*8-1) - (int)FL2T_CLZ__(n); + return -1; +} +#else #define floor_log2(N) floor_log2_wide ((unsigned HOST_WIDE_INT) (N)) #endif + +#endif extern int exact_log2_wide (unsigned HOST_WIDE_INT); extern int floor_log2_wide (unsigned HOST_WIDE_INT); |