| 1 | /* mc68020 __mpn_rshift -- Shift right a low-level natural-number integer. |
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| 2 | |
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| 3 | Copyright (C) 1996-2024 Free Software Foundation, Inc. |
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| 4 | |
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| 5 | This file is part of the GNU MP Library. |
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| 6 | |
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| 7 | The GNU MP Library is free software; you can redistribute it and/or modify |
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| 8 | it under the terms of the GNU Lesser General Public License as published by |
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| 9 | the Free Software Foundation; either version 2.1 of the License, or (at your |
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| 10 | option) any later version. |
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| 11 | |
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| 12 | The GNU MP Library is distributed in the hope that it will be useful, but |
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| 13 | WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
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| 14 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
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| 15 | License for more details. |
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| 16 | |
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| 17 | You should have received a copy of the GNU Lesser General Public License |
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| 18 | along with the GNU MP Library. If not, see <https://www.gnu.org/licenses/>. */ |
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| 19 | |
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| 20 | /* |
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| 21 | INPUT PARAMETERS |
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| 22 | res_ptr (sp + 4) |
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| 23 | s_ptr (sp + 8) |
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| 24 | s_size (sp + 16) |
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| 25 | cnt (sp + 12) |
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| 26 | */ |
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| 27 | |
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| 28 | #include "sysdep.h" |
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| 29 | #include "asm-syntax.h" |
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| 30 | |
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| 31 | #define res_ptr a1 |
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| 32 | #define s_ptr a0 |
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| 33 | #define s_size d6 |
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| 34 | #define cnt d4 |
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| 35 | |
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| 36 | TEXT |
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| 37 | ENTRY(__mpn_rshift) |
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| 38 | /* Save used registers on the stack. */ |
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| 39 | moveml R(d2)-R(d6)/R(a2),MEM_PREDEC(sp) |
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| 40 | cfi_adjust_cfa_offset (6*4) |
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| 41 | cfi_rel_offset (R(d2), 0) |
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| 42 | cfi_rel_offset (R(d3), 4) |
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| 43 | cfi_rel_offset (R(d4), 8) |
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| 44 | cfi_rel_offset (R(d5), 12) |
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| 45 | cfi_rel_offset (R(d6), 16) |
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| 46 | cfi_rel_offset (R(a2), 20) |
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| 47 | |
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| 48 | /* Copy the arguments to registers. */ |
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| 49 | movel MEM_DISP(sp,28),R(res_ptr) |
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| 50 | movel MEM_DISP(sp,32),R(s_ptr) |
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| 51 | movel MEM_DISP(sp,36),R(s_size) |
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| 52 | movel MEM_DISP(sp,40),R(cnt) |
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| 53 | |
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| 54 | moveql #1,R(d5) |
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| 55 | cmpl R(d5),R(cnt) |
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| 56 | bne L(Lnormal) |
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| 57 | cmpl R(res_ptr),R(s_ptr) |
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| 58 | bls L(Lspecial) /* jump if res_ptr >= s_ptr */ |
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| 59 | #if M68K_SCALE_AVAILABLE |
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| 60 | lea MEM_INDX1(res_ptr,s_size,l,4),R(a2) |
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| 61 | #else |
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| 62 | movel R(s_size),R(d0) |
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| 63 | asll #2,R(d0) |
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| 64 | lea MEM_INDX(res_ptr,d0,l),R(a2) |
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| 65 | #endif |
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| 66 | cmpl R(s_ptr),R(a2) |
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| 67 | bls L(Lspecial) /* jump if s_ptr >= res_ptr + s_size */ |
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| 68 | |
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| 69 | L(Lnormal:) |
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| 70 | moveql #32,R(d5) |
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| 71 | subl R(cnt),R(d5) |
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| 72 | movel MEM_POSTINC(s_ptr),R(d2) |
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| 73 | movel R(d2),R(d0) |
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| 74 | lsll R(d5),R(d0) /* compute carry limb */ |
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| 75 | |
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| 76 | lsrl R(cnt),R(d2) |
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| 77 | movel R(d2),R(d1) |
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| 78 | subql #1,R(s_size) |
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| 79 | beq L(Lend) |
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| 80 | lsrl #1,R(s_size) |
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| 81 | bcs L(L1) |
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| 82 | subql #1,R(s_size) |
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| 83 | |
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| 84 | L(Loop:) |
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| 85 | movel MEM_POSTINC(s_ptr),R(d2) |
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| 86 | movel R(d2),R(d3) |
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| 87 | lsll R(d5),R(d3) |
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| 88 | orl R(d3),R(d1) |
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| 89 | movel R(d1),MEM_POSTINC(res_ptr) |
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| 90 | lsrl R(cnt),R(d2) |
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| 91 | L(L1:) |
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| 92 | movel MEM_POSTINC(s_ptr),R(d1) |
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| 93 | movel R(d1),R(d3) |
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| 94 | lsll R(d5),R(d3) |
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| 95 | orl R(d3),R(d2) |
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| 96 | movel R(d2),MEM_POSTINC(res_ptr) |
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| 97 | lsrl R(cnt),R(d1) |
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| 98 | |
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| 99 | dbf R(s_size),L(Loop) |
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| 100 | subl #0x10000,R(s_size) |
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| 101 | bcc L(Loop) |
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| 102 | |
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| 103 | L(Lend:) |
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| 104 | movel R(d1),MEM(res_ptr) /* store most significant limb */ |
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| 105 | |
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| 106 | /* Restore used registers from stack frame. */ |
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| 107 | moveml MEM_POSTINC(sp),R(d2)-R(d6)/R(a2) |
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| 108 | cfi_remember_state |
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| 109 | cfi_adjust_cfa_offset (-6*4) |
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| 110 | cfi_restore (R(d2)) |
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| 111 | cfi_restore (R(d3)) |
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| 112 | cfi_restore (R(d4)) |
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| 113 | cfi_restore (R(d5)) |
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| 114 | cfi_restore (R(d6)) |
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| 115 | cfi_restore (R(a2)) |
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| 116 | rts |
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| 117 | |
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| 118 | /* We loop from most significant end of the arrays, which is only |
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| 119 | permissible if the source and destination don't overlap, since the |
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| 120 | function is documented to work for overlapping source and destination. */ |
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| 121 | |
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| 122 | cfi_restore_state |
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| 123 | L(Lspecial:) |
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| 124 | #if M68K_SCALE_AVAILABLE |
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| 125 | lea MEM_INDX1(s_ptr,s_size,l,4),R(s_ptr) |
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| 126 | lea MEM_INDX1(res_ptr,s_size,l,4),R(res_ptr) |
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| 127 | #else |
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| 128 | movel R(s_size),R(d0) |
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| 129 | asll #2,R(d0) |
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| 130 | addl R(d0),R(s_ptr) |
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| 131 | addl R(d0),R(res_ptr) |
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| 132 | #endif |
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| 133 | |
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| 134 | clrl R(d0) /* initialize carry */ |
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| 135 | eorw #1,R(s_size) |
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| 136 | lsrl #1,R(s_size) |
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| 137 | bcc L(LL1) |
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| 138 | subql #1,R(s_size) |
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| 139 | |
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| 140 | L(LLoop:) |
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| 141 | movel MEM_PREDEC(s_ptr),R(d2) |
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| 142 | roxrl #1,R(d2) |
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| 143 | movel R(d2),MEM_PREDEC(res_ptr) |
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| 144 | L(LL1:) |
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| 145 | movel MEM_PREDEC(s_ptr),R(d2) |
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| 146 | roxrl #1,R(d2) |
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| 147 | movel R(d2),MEM_PREDEC(res_ptr) |
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| 148 | |
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| 149 | dbf R(s_size),L(LLoop) |
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| 150 | roxrl #1,R(d0) /* save cy in msb */ |
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| 151 | subl #0x10000,R(s_size) |
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| 152 | bcs L(LLend) |
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| 153 | addl R(d0),R(d0) /* restore cy */ |
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| 154 | bra L(LLoop) |
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| 155 | |
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| 156 | L(LLend:) |
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| 157 | /* Restore used registers from stack frame. */ |
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| 158 | moveml MEM_POSTINC(sp),R(d2)-R(d6)/R(a2) |
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| 159 | cfi_adjust_cfa_offset (-6*4) |
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| 160 | cfi_restore (R(d2)) |
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| 161 | cfi_restore (R(d3)) |
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| 162 | cfi_restore (R(d4)) |
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| 163 | cfi_restore (R(d5)) |
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| 164 | cfi_restore (R(d6)) |
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| 165 | cfi_restore (R(a2)) |
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| 166 | rts |
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| 167 | END(__mpn_rshift) |
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| 168 | |
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