152 lines
4.6 KiB
C
152 lines
4.6 KiB
C
/*---------------------------------------------------------------------------+
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| wm_shrx.c |
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| 64 bit right shift functions |
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| Copyright (C) 1992,1995,1999 |
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| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
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| Australia. E-mail billm@melbpc.org.au |
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+---------------------------------------------------------------------------*/
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/*---------------------------------------------------------------------------+
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| unsigned FPU_shrx(void *arg1, unsigned arg2) |
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| Extended shift right function. |
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| Fastest for small shifts. |
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| Shifts the 64 bit quantity pointed to by the first arg (arg1) |
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| right by the number of bits specified by the second arg (arg2). |
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| Forms a 96 bit quantity from the 64 bit arg and eax: |
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| [ 64 bit arg ][ eax ] |
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| shift right ---------> |
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| The eax register is initialized to 0 before the shifting. |
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| Results returned in the 64 bit arg and eax. |
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+---------------------------------------------------------------------------*/
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#include "fpu_emu.h"
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unsigned FPU_shrx(void *arg1, u32 arg2)
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{
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u32 x;
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if ( arg2 >= 64 )
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{
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if ( arg2 >= 96 )
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{
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*(u64 *)arg1 = 0;
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return 0;
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}
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arg2 -= 64;
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x = (*(u64 *)arg1) >> 32;
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*(u64 *)arg1 = 0;
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if ( arg2 )
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return x >> arg2;
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else
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return x;
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}
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if ( arg2 < 32 )
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{
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if ( arg2 == 0 )
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return 0;
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x = (*(u64 *)arg1) << (32 - arg2);
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}
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else if ( arg2 > 32 )
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{
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x = (*(u64 *)arg1) >> (arg2 - 32);
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}
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else
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{
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/* arg2 == 32 */
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x = *(u64 *)arg1;
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}
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(*(u64 *)arg1) >>= arg2;
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return x;
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}
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/*---------------------------------------------------------------------------+
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| unsigned FPU_shrxs(void *arg1, unsigned arg2) |
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| Extended shift right function (optimized for small floating point |
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| integers). |
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| Shifts the 64 bit quantity pointed to by the first arg (arg1) |
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| right by the number of bits specified by the second arg (arg2). |
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| Forms a 96 bit quantity from the 64 bit arg and eax: |
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| [ 64 bit arg ][ eax ] |
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| shift right ---------> |
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| The eax register is initialized to 0 before the shifting. |
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| The lower 8 bits of eax are lost and replaced by a flag which is |
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| set (to 0x01) if any bit, apart from the first one, is set in the |
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| part which has been shifted out of the arg. |
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| Results returned in the 64 bit arg and eax. |
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+---------------------------------------------------------------------------*/
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unsigned FPU_shrxs(void *arg1, u32 arg2)
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{
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u32 x, bits;
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u64 lost;
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if ( arg2 >= 64 )
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{
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if ( arg2 >= 96 )
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{
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bits = *(u64 *)arg1 != 0;
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*(u64 *)arg1 = 0;
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return bits ? 1 : 0;
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}
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arg2 -= 64;
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lost = (*(u64 *)arg1) << (32 - arg2);
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x = (*(u64 *)arg1) >> 32;
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*(u64 *)arg1 = 0;
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if ( arg2 )
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x >>= arg2;
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if ( lost )
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x |= 1;
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return x;
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}
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if ( arg2 < 32 )
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{
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if ( arg2 == 0 )
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/* No bits are lost */
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return 0;
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/* No bits are lost */
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x = (*(u64 *)arg1) << (32 - arg2);
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}
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else if ( arg2 > 32 )
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{
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bits = (*(u64 *)arg1);
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bits <<= (64 - arg2);
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x = (*(u64 *)arg1) >> (arg2 - 32);
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if ( bits )
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x |= 1;
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}
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else
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{
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/* arg2 == 32 */
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/* No bits are lost */
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x = *(u64 *)arg1;
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}
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(*(u64 *)arg1) >>= arg2;
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if ( x & 0x7fffffff )
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x |= 1;
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return x;
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}
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