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add __likely branch prediction hints

make inlining work in the face of gcc in non-gnu c99 mode
master
Felix von Leitner 11 years ago
parent
commit
13bc4b6987
  1. 66
      rangecheck.h

66
rangecheck.h

@ -5,18 +5,58 @@
#include <inttypes.h>
#include <stddef.h>
/* return 0 for range error / overflow, 1 for ok */
/* We are trying to achieve that gcc has to inline the function and we
* don't want it to emit a copy of the function. This can be done with
* static inline or with extern inline. static inline tells gcc to not
* emit a copy unless someone is using & to take a pointer, which nobody
* is ever supposed to do. extern inline tells gcc to not ever emit a
* copy.
*
* Unfortunately, the C99 standard defines extern inline to mean "always
* emit a copy for external reference", so this causes duplicate symbol
* linking errors. gcc signals C99 inline expansion mode by defining
* __GNUC_STDC_INLINE__ and it then has an attribute gnu_inline to
* switch back to GNU behavior. So that's what we are doing. Taking
* the address of one of these functions is considered a user error.
*
* We are so anal about inlining here because these checks can in most
* cases be optimized away. In particular, if you call this function
* often, gcc can see that some of the basic checks are done repeatedly
* and not do them again. But this only works if the function is
* inlined. */
#if defined(__GNUC_STDC_INLINE__)
#define __gnuinline __attribute__((gnu_inline))
#else
#define __gnuinline
#endif
#if defined(__GNUC__) && defined(__OPTIMIZE__) && !defined(__clang__)
#if defined(__GNUC__) && !defined(__NO_INLINE__) && !defined(__clang__)
#define __static extern
#else
#define __static static
#endif
#if !defined(__GNUC__) || (__GNUC__ < 3)
#define __builtin_expect(foo,bar) (foo)
#define __expect(foo,bar) (foo)
#else
#define __expect(foo,bar) __builtin_expect((long)(foo),bar)
#endif
#if defined(__GNUC__) && !defined(__likely)
#define __likely(foo) __expect((foo),1)
#define __unlikely(foo) __expect((foo),0)
#endif
/* return 0 for range error / overflow, 1 for ok */
/* we assume the normal case is that the checked value is in range */
/* does ptr point to one of buf[0], buf[1], ... buf[len-1]? */
__static inline int range_ptrinbuf(const void* buf,size_t len,const void* ptr) {
__static inline __gnuinline int range_ptrinbuf(const void* buf,size_t len,const void* ptr) {
register const char* c=(const char*)buf; /* no pointer arithmetic on void* */
return (c && /* is buf non-NULL? */
return __likely(c && /* is buf non-NULL? */
((uintptr_t)c)+len>(uintptr_t)c && /* gcc 4.1 miscompiles without (uintptr_t) */
/* catch integer overflows and fail if buffer is 0 bytes long */
/* because then ptr can't point _in_ the buffer */
@ -28,30 +68,30 @@ __static inline int range_ptrinbuf(const void* buf,size_t len,const void* ptr) {
/* same thing, but the buffer is specified by a pointer to the first
* byte (Min) and a pointer after the last byte (Max). */
__static inline int range_ptrinbuf2(const void* Min,const void* Max,const void* ptr) {
return (Min && ptr>=Min && ptr<Max);
__static inline __gnuinline int range_ptrinbuf2(const void* Min,const void* Max,const void* ptr) {
return __likely(Min && ptr>=Min && ptr<Max);
/* Min <= Max is implicitly checked here */
}
/* Is this a plausible buffer?
* Check whether buf is NULL, and whether buf+len overflows.
* Does NOT check whether buf has a non-zero length! */
__static inline int range_validbuf(const void* buf,size_t len) {
return (buf && (uintptr_t)buf+len>=(uintptr_t)buf);
__static inline __gnuinline int range_validbuf(const void* buf,size_t len) {
return __likely(buf && (uintptr_t)buf+len>=(uintptr_t)buf);
}
/* same thing but buffer is given as pointer to first byte (Min) and
* pointer beyond last byte (Max). Again, an 0-size buffer is valid. */
__static inline int range_validbuf2(const void* Min,const void* Max) {
return (Min && Max>=Min);
__static inline __gnuinline int range_validbuf2(const void* Min,const void* Max) {
return __likely(Min && Max>=Min);
}
/* is buf2[0..len2-1] inside buf1[0..len-1]? */
__static inline int range_bufinbuf(const void* buf1,size_t len1,const void* buf2,size_t len2) {
__static inline __gnuinline int range_bufinbuf(const void* buf1,size_t len1,const void* buf2,size_t len2) {
return range_validbuf(buf1,len1) &&
range_validbuf(buf2,len2) &&
buf1<=buf2 &&
(ptrdiff_t)buf1+len1>=(ptrdiff_t)buf2+len2;
__likely(buf1<=buf2 &&
(ptrdiff_t)buf1+len1>=(ptrdiff_t)buf2+len2);
}
/* does an array of "elements" members of size "membersize" starting at

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