Re: [PATCH 2/1] bswap: convert get_be16, get_be32 and put_be32 to inline functions
On Sun, Jul 16, 2017 at 06:27:04AM -0400, Jeff King wrote: > On Sat, Jul 15, 2017 at 09:22:50PM +0200, René Scharfe wrote: > > > Simplify the implementation and allow callers to use expressions with > > side-effects by turning the macros get_be16, get_be32 and put_be32 into > > inline functions. > > > > Signed-off-by: Rene Scharfe > > --- > > All these redundant casts started to bother me, so I tried to come up > > with nice and clean inline functions. Successfully? You tell me. > > They are longer, but less cluttered. Would it punish -O0 builds? Is > > it all worth it? > > I do think the end result is a lot more readable. On gcc 6 at least, the > function seems[1] to end up inlined even with -O0. For my footnote. I was just going to show the test file I compiled: #include "git-compat-util.h" uint32_t foo(const char *x) { return get_be32(x); } It's possible the optimizer may behave differently on a more complicated input, but it does show that -O0 is still willing to inline. -Peff
Re: [PATCH 2/1] bswap: convert get_be16, get_be32 and put_be32 to inline functions
On Sat, Jul 15, 2017 at 09:22:50PM +0200, René Scharfe wrote: > Simplify the implementation and allow callers to use expressions with > side-effects by turning the macros get_be16, get_be32 and put_be32 into > inline functions. > > Signed-off-by: Rene Scharfe > --- > All these redundant casts started to bother me, so I tried to come up > with nice and clean inline functions. Successfully? You tell me. > They are longer, but less cluttered. Would it punish -O0 builds? Is > it all worth it? I do think the end result is a lot more readable. On gcc 6 at least, the function seems[1] to end up inlined even with -O0. Interestingly, at -O2 even with -DNO_UNALIGNED_LOADS, gcc converts the result to a movl and a bswap. Which is the same thing our unaligned-loads path is trying for. I wonder if we could/should just drop it (that _would_ punish -O0 on x86, though). -Peff
[PATCH 2/1] bswap: convert get_be16, get_be32 and put_be32 to inline functions
Simplify the implementation and allow callers to use expressions with side-effects by turning the macros get_be16, get_be32 and put_be32 into inline functions. Signed-off-by: Rene Scharfe --- All these redundant casts started to bother me, so I tried to come up with nice and clean inline functions. Successfully? You tell me. They are longer, but less cluttered. Would it punish -O0 builds? Is it all worth it? compat/bswap.h | 38 -- 1 file changed, 24 insertions(+), 14 deletions(-) diff --git a/compat/bswap.h b/compat/bswap.h index 4582c1107a..7d063e9e40 100644 --- a/compat/bswap.h +++ b/compat/bswap.h @@ -162,19 +162,29 @@ static inline uint64_t git_bswap64(uint64_t x) #else -#define get_be16(p)( \ - (*((unsigned char *)(p) + 0) << 8) | \ - (*((unsigned char *)(p) + 1) << 0) ) -#define get_be32(p)( \ - ((uint32_t)*((unsigned char *)(p) + 0) << 24) | \ - ((uint32_t)*((unsigned char *)(p) + 1) << 16) | \ - ((uint32_t)*((unsigned char *)(p) + 2) << 8) | \ - ((uint32_t)*((unsigned char *)(p) + 3) << 0) ) -#define put_be32(p, v) do { \ - unsigned int __v = (v); \ - *((unsigned char *)(p) + 0) = __v >> 24; \ - *((unsigned char *)(p) + 1) = __v >> 16; \ - *((unsigned char *)(p) + 2) = __v >> 8; \ - *((unsigned char *)(p) + 3) = __v >> 0; } while (0) +static inline uint16_t get_be16(const void *ptr) +{ + const unsigned char *p = ptr; + return (uint16_t)p[0] << 8 | + (uint16_t)p[1] << 0; +} + +static inline uint32_t get_be32(const void *ptr) +{ + const unsigned char *p = ptr; + return (uint32_t)p[0] << 24 | + (uint32_t)p[1] << 16 | + (uint32_t)p[2] << 8 | + (uint32_t)p[3] << 0; +} + +static inline void put_be32(void *ptr, uint32_t value) +{ + unsigned char *p = ptr; + p[0] = value >> 24; + p[1] = value >> 16; + p[2] = value >> 8; + p[3] = value >> 0; +} #endif -- 2.13.3