IMPORT: ebtree: rework the fls macros to better deal with arch-specific ones
The definitions were a bit of a mess and there wasn't even a fall back to __builtin_clz() on compilers supporting it. Now we instead define a macro for each implementation that is set on an arch-dependent case by case, and add the fall back ones only when not defined. This also allows the flsnz8() to automatically fall back to the 32-bit arch-specific version if available. This shows a consistent 33% speedup on arm for strings. This is cbtree commit c6075742e8d0a6924e7183d44bd93dec20ca8049. This is ebtree commit f452d0f83eca72f6c3484ccb138d341ed6fd27ed.
This commit is contained in:
Willy Tarreau
parent
fc421e5b3d
commit
1c46a07460
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@ -250,46 +250,83 @@
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#include <import/ebtree-t.h>
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#include <haproxy/api.h>
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static inline int flsnz8_generic(unsigned int x)
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/* returns clz from 7 to 0 for 0x01 to 0xFF. Returns 7 for 0 as well. */
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static inline unsigned int clz8(unsigned char c)
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{
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int ret = 0;
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if (x >> 4) { x >>= 4; ret += 4; }
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return ret + ((0xFFFFAA50U >> (x << 1)) & 3) + 1;
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unsigned int r = 4;
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if (c & 0xf0) {
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r = 0;
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c >>= 4;
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}
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return r + ((0x000055afU >> (c * 2)) & 0x3);
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}
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/* Note: we never need to run fls on null keys, so we can optimize the fls
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* function by removing a conditional jump.
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/* FLSNZ: find last set bit for non-zero value. "Last" here means the highest
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* one. It returns a value from 1 to 32 for 1<<0 to 1<<31.
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*/
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#if defined(__i386__) || defined(__x86_64__)
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/* this code is similar on 32 and 64 bit */
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static inline int flsnz(int x)
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#if (defined(__i386__) || defined(__x86_64__)) && !defined(__atom__)
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/* DO NOT USE ON ATOM! The instruction is emulated and is several times slower
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* than doing the math by hand.
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*/
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static inline int flsnz32(unsigned int x)
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{
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int r;
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__asm__("bsrl %1,%0\n"
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: "=r" (r) : "rm" (x));
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return r + 1;
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}
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#define flsnz32(x) flsnz32(x)
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static inline int flsnz8(unsigned char x)
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# if defined(__x86_64__)
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static inline int flsnz64(unsigned long long x)
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{
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int r;
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__asm__("movzbl %%al, %%eax\n"
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"bsrl %%eax,%0\n"
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: "=r" (r) : "a" (x));
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return r+1;
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}
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static inline long flsnz_long(unsigned long x)
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{
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long r;
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__asm__("bsr %1,%0\n"
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unsigned long long r;
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__asm__("bsrq %1,%0\n"
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: "=r" (r) : "rm" (x));
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return r + 1;
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}
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# define flsnz64(x) flsnz64(x)
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# endif
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#elif !defined(__atom__) && defined(__GNUC__) && ((__GNUC__ > 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 2)))
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/* gcc >= 4.2 brings __builtin_clz() and __builtin_clzl(), usable for non-x86 */
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static inline int flsnz32(unsigned int x)
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{
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return 32 - __builtin_clz(x);
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}
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# define flsnz32(x) flsnz32(x)
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# if defined(__SIZEOF_LONG__) && (__SIZEOF_LONG__ > 4)
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static inline int flsnz64(unsigned long x)
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{
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return (__SIZEOF_LONG__ * 8) - __builtin_clzl(x);
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}
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# define flsnz64(x) flsnz64(x)
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# endif
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#endif /* end of arch-specific implementations */
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/*** Fallback versions below ***/
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#ifndef flsnz8
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# if defined(flsnz32)
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# define flsnz8(x) flsnz32((unsigned char)x)
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# else
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// returns 1 to 32 for 1<<0 to 1<<31. Undefined for 0.
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#define flsnz(___a) ({ \
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static inline int flsnz8(unsigned int x)
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{
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int ret = 0;
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if (x >> 4) { x >>= 4; ret += 4; }
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return ret + ((0xFFFFAA50U >> (x << 1)) & 3) + 1;
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}
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# define flsnz8(x) flsnz8(x)
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# endif
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#endif
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#ifndef flsnz32
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# define flsnz32(___a) ({ \
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register int ___x, ___bits = 0; \
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___x = (___a); \
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if (___x & 0xffff0000) { ___x &= 0xffff0000; ___bits += 16;} \
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@ -299,17 +336,10 @@ static inline long flsnz_long(unsigned long x)
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if (___x & 0xaaaaaaaa) { ___x &= 0xaaaaaaaa; ___bits += 1;} \
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___bits + 1; \
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})
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static inline int flsnz8(unsigned int x)
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{
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return flsnz8_generic(x);
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}
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#define flsnz_long(x) ((sizeof(long) > 4) ? flsnz64(x) : flsnz32(x))
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#endif
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static inline int fls64(unsigned long long x)
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#ifndef flsnz64
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static inline int flsnz64(unsigned long long x)
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{
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unsigned int h;
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unsigned int bits = 32;
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@ -319,10 +349,21 @@ static inline int fls64(unsigned long long x)
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h = x;
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bits = 0;
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}
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return flsnz(h) + bits;
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return flsnz32(h) + bits;
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}
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# define flsnz64(x) flsnz64(x)
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#endif
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#define fls_auto(x) ((sizeof(x) > 4) ? fls64(x) : flsnz(x))
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#ifndef flsnz_long
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# define flsnz_long(x) ((sizeof(long) > 4) ? flsnz64(x) : flsnz32(x))
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#endif
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#ifndef flsnz
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# define flsnz(x) ((sizeof(x) > 4) ? flsnz64(x) : (sizeof(x) > 1) ? flsnz32(x) : flsnz8(x))
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#endif
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#define fls64(x) flsnz64(x)
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#define fls_auto(x) ((x) ? flsnz(x) : 0)
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/* Linux-like "container_of". It returns a pointer to the structure of type
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* <type> which has its member <name> stored at address <ptr>.
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