1. ffmpeg
  2. Commit f64c2e710fa1a7b59753224e717f57c48462076f
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bswap: make generic implementation more compiler-friendly

With these changes, gcc 4.5 and later recognise it as a bswap
and use the proper instructions on ARM and x86. On x86, the
16-bit bswap is recognised from gcc 4.1.

Signed-off-by: Mans Rullgard <mans@mansr.com>

Mans Rullgard authored on 2011/12/12 09:50:08
Showing 3 changed files
libavutil/arm/bswap.h
History View file @ f64c2e7
... ... 
@@ -51,6 +51,7 @@ static av_always_inline av_const unsigned av_bswap16(unsigned x)
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 }
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 #endif
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+#if !AV_GCC_VERSION_AT_LEAST(4,5)
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 #define av_bswap32 av_bswap32
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 static av_always_inline av_const uint32_t av_bswap32(uint32_t x)
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 {
... ... 
@@ -66,6 +67,7 @@ static av_always_inline av_const uint32_t av_bswap32(uint32_t x)
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 #endif /* HAVE_ARMV6 */
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     return x;
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 }
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+#endif /* !AV_GCC_VERSION_AT_LEAST(4,5) */
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 #endif /* __ARMCC_VERSION */
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libavutil/bswap.h
History View file @ f64c2e7
... ... 
@@ -65,23 +65,14 @@ static av_always_inline av_const uint16_t av_bswap16(uint16_t x)
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 #ifndef av_bswap32
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 static av_always_inline av_const uint32_t av_bswap32(uint32_t x)
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 {
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-    x= ((x<<8)&0xFF00FF00) | ((x>>8)&0x00FF00FF);
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-    x= (x>>16) | (x<<16);
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-    return x;
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+    return AV_BSWAP32C(x);
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 }
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 #endif
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 #ifndef av_bswap64
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 static inline uint64_t av_const av_bswap64(uint64_t x)
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 {
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-    union {
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-        uint64_t ll;
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-        uint32_t l[2];
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-    } w, r;
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-    w.ll = x;
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-    r.l[0] = av_bswap32 (w.l[1]);
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-    r.l[1] = av_bswap32 (w.l[0]);
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-    return r.ll;
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+    return (uint64_t)av_bswap32(x) << 32 | av_bswap32(x >> 32);
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 }
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 #endif
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libavutil/x86/bswap.h
History View file @ f64c2e7
... ... 
@@ -28,13 +28,16 @@
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 #include "config.h"
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 #include "libavutil/attributes.h"
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+#if !AV_GCC_VERSION_AT_LEAST(4,1)
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 #define av_bswap16 av_bswap16
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 static av_always_inline av_const unsigned av_bswap16(unsigned x)
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 {
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     __asm__("rorw $8, %w0" : "+r"(x));
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     return x;
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 }
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+#endif /* !AV_GCC_VERSION_AT_LEAST(4,1) */
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+#if !AV_GCC_VERSION_AT_LEAST(4,5)
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 #define av_bswap32 av_bswap32
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 static av_always_inline av_const uint32_t av_bswap32(uint32_t x)
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 {
... ... 
@@ -57,5 +60,6 @@ static inline uint64_t av_const av_bswap64(uint64_t x)
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     return x;
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 }
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 #endif
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+#endif /* !AV_GCC_VERSION_AT_LEAST(4,5) */
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 #endif /* AVUTIL_X86_BSWAP_H */