find_first_set_bit tweaks
Correct sizing in m68k asm. Make the gerneric version far more generic. Change-Id: I32945f7431771979b3fe0da5472bdb110fd054ae
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2 changed files with 9 additions and 24 deletions
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@ -21,9 +21,7 @@
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#include "config.h"
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#include "config.h"
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#include <inttypes.h>
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#include <inttypes.h>
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/* find_first_set_bit() - this is a C version of the ffs algorithm devised
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/*
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* by D.Seal and posted to comp.sys.arm on 16 Feb 1994.
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*
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* Find the index of the least significant set bit in the word.
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* Find the index of the least significant set bit in the word.
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* return values:
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* return values:
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* 0 - bit 0 is set
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* 0 - bit 0 is set
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@ -32,25 +30,12 @@
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* 31 - bit 31 is set
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* 31 - bit 31 is set
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* 32 - no bits set
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* 32 - no bits set
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*/
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*/
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/* Table shared with assembly code */
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const uint8_t L_ffs_table[64] ICONST_ATTR =
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{
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/* 0 1 2 3 4 5 6 7 */
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/* ----------------------------------------- */
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32, 0, 1, 12, 2, 6, 0, 13, /* 0- 7 */
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3, 0, 7, 0, 0, 0, 0, 14, /* 8-15 */
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10, 4, 0, 0, 8, 0, 0, 25, /* 16-23 */
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0, 0, 0, 0, 0, 21, 27, 15, /* 24-31 */
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31, 11, 5, 0, 0, 0, 0, 0, /* 32-39 */
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9, 0, 0, 24, 0, 0, 20, 26, /* 40-47 */
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30, 0, 0, 0, 0, 23, 0, 19, /* 48-55 */
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29, 0, 22, 18, 28, 17, 16, 0, /* 56-63 */
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};
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#if !defined(CPU_COLDFIRE)
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int find_first_set_bit(uint32_t val)
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int find_first_set_bit(uint32_t val)
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{
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{
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return L_ffs_table[((val & -val)*0x0450fbaf) >> 26];
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if (val == 0)
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return 32;
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/* __builtin_ffs(l(l)): Returns one plus the index of the least significant
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1-bit of x, or if x is zero, returns zero. */
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return __builtin_ffs(val) - 1;
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}
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}
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#endif
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@ -61,6 +61,7 @@ find_first_set_bit:
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| the top 24 bits of d0 are 0 so just load the value over it
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| the top 24 bits of d0 are 0 so just load the value over it
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move.b (%a0, %d1.l), %d0 |
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move.b (%a0, %d1.l), %d0 |
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rts |
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rts |
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.size find_first_set_bit, .-find_first_set_bit
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.section .irodata
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.section .irodata
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L_ffs_table:
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L_ffs_table:
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@ -74,5 +75,4 @@ L_ffs_table:
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.byte 9, 0, 0, 24, 0, 0, 20, 26 | 40-47
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.byte 9, 0, 0, 24, 0, 0, 20, 26 | 40-47
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.byte 30, 0, 0, 0, 0, 23, 0, 19 | 48-55
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.byte 30, 0, 0, 0, 0, 23, 0, 19 | 48-55
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.byte 29, 0, 22, 18, 28, 17, 16, 0 | 56-63
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.byte 29, 0, 22, 18, 28, 17, 16, 0 | 56-63
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.size L_ffs_table, .-L_ffs_table
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.size find_first_set_bit, .-find_first_set_bit
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