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207 lines
6.2 KiB
207 lines
6.2 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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.file "wm_shrx.S" |
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/*---------------------------------------------------------------------------+ |
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| wm_shrx.S | |
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| | |
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| 64 bit right shift functions | |
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| | |
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| Copyright (C) 1992,1995 | |
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| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, | |
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| Australia. E-mail billm@jacobi.maths.monash.edu.au | |
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| | |
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| Call from C as: | |
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| unsigned FPU_shrx(void *arg1, unsigned arg2) | |
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| and | |
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| unsigned FPU_shrxs(void *arg1, unsigned arg2) | |
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| | |
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+---------------------------------------------------------------------------*/ |
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#include "fpu_emu.h" |
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.text |
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/*---------------------------------------------------------------------------+ |
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| unsigned FPU_shrx(void *arg1, unsigned arg2) | |
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| | |
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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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SYM_FUNC_START(FPU_shrx) |
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push %ebp |
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movl %esp,%ebp |
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pushl %esi |
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movl PARAM2,%ecx |
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movl PARAM1,%esi |
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cmpl $32,%ecx /* shrd only works for 0..31 bits */ |
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jnc L_more_than_31 |
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/* less than 32 bits */ |
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pushl %ebx |
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movl (%esi),%ebx /* lsl */ |
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movl 4(%esi),%edx /* msl */ |
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xorl %eax,%eax /* extension */ |
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shrd %cl,%ebx,%eax |
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shrd %cl,%edx,%ebx |
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shr %cl,%edx |
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movl %ebx,(%esi) |
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movl %edx,4(%esi) |
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popl %ebx |
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popl %esi |
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leave |
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ret |
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L_more_than_31: |
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cmpl $64,%ecx |
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jnc L_more_than_63 |
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subb $32,%cl |
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movl (%esi),%eax /* lsl */ |
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movl 4(%esi),%edx /* msl */ |
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shrd %cl,%edx,%eax |
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shr %cl,%edx |
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movl %edx,(%esi) |
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movl $0,4(%esi) |
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popl %esi |
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leave |
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ret |
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L_more_than_63: |
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cmpl $96,%ecx |
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jnc L_more_than_95 |
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subb $64,%cl |
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movl 4(%esi),%eax /* msl */ |
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shr %cl,%eax |
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xorl %edx,%edx |
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movl %edx,(%esi) |
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movl %edx,4(%esi) |
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popl %esi |
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leave |
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ret |
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L_more_than_95: |
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xorl %eax,%eax |
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movl %eax,(%esi) |
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movl %eax,4(%esi) |
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popl %esi |
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leave |
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ret |
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SYM_FUNC_END(FPU_shrx) |
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/*---------------------------------------------------------------------------+ |
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| unsigned FPU_shrxs(void *arg1, unsigned arg2) | |
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| | |
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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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SYM_FUNC_START(FPU_shrxs) |
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push %ebp |
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movl %esp,%ebp |
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pushl %esi |
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pushl %ebx |
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movl PARAM2,%ecx |
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movl PARAM1,%esi |
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cmpl $64,%ecx /* shrd only works for 0..31 bits */ |
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jnc Ls_more_than_63 |
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cmpl $32,%ecx /* shrd only works for 0..31 bits */ |
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jc Ls_less_than_32 |
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/* We got here without jumps by assuming that the most common requirement |
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is for small integers */ |
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/* Shift by [32..63] bits */ |
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subb $32,%cl |
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movl (%esi),%eax /* lsl */ |
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movl 4(%esi),%edx /* msl */ |
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xorl %ebx,%ebx |
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shrd %cl,%eax,%ebx |
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shrd %cl,%edx,%eax |
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shr %cl,%edx |
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orl %ebx,%ebx /* test these 32 bits */ |
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setne %bl |
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test $0x7fffffff,%eax /* and 31 bits here */ |
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setne %bh |
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orw %bx,%bx /* Any of the 63 bit set ? */ |
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setne %al |
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movl %edx,(%esi) |
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movl $0,4(%esi) |
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popl %ebx |
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popl %esi |
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leave |
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ret |
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/* Shift by [0..31] bits */ |
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Ls_less_than_32: |
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movl (%esi),%ebx /* lsl */ |
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movl 4(%esi),%edx /* msl */ |
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xorl %eax,%eax /* extension */ |
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shrd %cl,%ebx,%eax |
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shrd %cl,%edx,%ebx |
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shr %cl,%edx |
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test $0x7fffffff,%eax /* only need to look at eax here */ |
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setne %al |
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movl %ebx,(%esi) |
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movl %edx,4(%esi) |
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popl %ebx |
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popl %esi |
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leave |
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ret |
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/* Shift by [64..95] bits */ |
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Ls_more_than_63: |
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cmpl $96,%ecx |
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jnc Ls_more_than_95 |
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subb $64,%cl |
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movl (%esi),%ebx /* lsl */ |
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movl 4(%esi),%eax /* msl */ |
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xorl %edx,%edx /* extension */ |
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shrd %cl,%ebx,%edx |
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shrd %cl,%eax,%ebx |
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shr %cl,%eax |
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orl %ebx,%edx |
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setne %bl |
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test $0x7fffffff,%eax /* only need to look at eax here */ |
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setne %bh |
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orw %bx,%bx |
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setne %al |
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xorl %edx,%edx |
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movl %edx,(%esi) /* set to zero */ |
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movl %edx,4(%esi) /* set to zero */ |
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popl %ebx |
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popl %esi |
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leave |
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ret |
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Ls_more_than_95: |
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/* Shift by [96..inf) bits */ |
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xorl %eax,%eax |
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movl (%esi),%ebx |
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orl 4(%esi),%ebx |
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setne %al |
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xorl %ebx,%ebx |
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movl %ebx,(%esi) |
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movl %ebx,4(%esi) |
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popl %ebx |
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popl %esi |
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leave |
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ret |
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SYM_FUNC_END(FPU_shrxs)
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