1/* mips.s -- assembly support. */ 2 3/* 4 * QuickThreads -- Threads-building toolkit. 5 * Copyright (c) 1993 by David Keppel 6 * 7 * Permission to use, copy, modify and distribute this software and 8 * its documentation for any purpose and without fee is hereby 9 * granted, provided that the above copyright notice and this notice 10 * appear in all copies. This software is provided as a 11 * proof-of-concept and for demonstration purposes; there is no 12 * representation about the suitability of this software for any 13 * purpose. 14 */ 15 16/* Callee-save $16-$23, $30-$31. 17 * 18 * $25 is used as a procedure value pointer, used to discover constants 19 * in a callee. Thus, each caller here sets $25 before the call. 20 * 21 * On startup, restore regs so retpc === call to a function to start. 22 * We're going to call a function ($4) from within this routine. 23 * We're passing 3 args, therefore need to allocate 12 extra bytes on 24 * the stack for a save area. The start routine needs a like 16-byte 25 * save area. Must be doubleword aligned (_mips r3000 risc 26 * architecture_, gerry kane, pg d-23). 27 */ 28 29/* 30 * Modified by Assar Westerlund <assar@sics.se> to support Irix 5.x 31 * calling conventions for dynamically-linked code. 32 */ 33 34 /* Make this position-independent code. */ 35 .option pic2 36 37 .globl qt_block 38 .globl qt_blocki 39 .globl qt_abort 40 .globl qt_start 41 .globl qt_vstart 42 43 /* 44 ** $4: ptr to function to call once curr is suspended 45 ** and control is on $7's stack. 46 ** $5: 1'th arg to $4. 47 ** $6: 2'th arg to $4 48 ** $7: sp of thread to suspend. 49 ** 50 ** Totally gross hack: The MIPS calling convention reserves 51 ** 4 words on the stack for a0..a3. This routine "ought" to 52 ** allocate space for callee-save registers plus 4 words for 53 ** the helper function, but instead we use the 4 words 54 ** provided by the function that called us (we don't need to 55 ** save our argument registers). So what *appears* to be 56 ** allocating only 40 bytes is actually allocating 56, by 57 ** using the caller's 16 bytes. 58 ** 59 ** The helper routine returns a value that is passed on as the 60 ** return value from the blocking routine. Since we don't 61 ** touch $2 between the helper's return and the end of 62 ** function, we get this behavior for free. 63 */ 64qt_blocki: 65 sub $sp,$sp,40 /* Allocate reg save space. */ 66 sw $16, 0+16($sp) 67 sw $17, 4+16($sp) 68 sw $18, 8+16($sp) 69 sw $19,12+16($sp) 70 sw $20,16+16($sp) 71 sw $21,20+16($sp) 72 sw $22,24+16($sp) 73 sw $23,28+16($sp) 74 sw $30,32+16($sp) 75 sw $31,36+16($sp) 76 add $2, $sp,$0 /* $2 <= old sp to pass to func@$4. */ 77qt_abort: 78 add $sp, $7,$0 /* $sp <= new sp. */ 79 .set noreorder 80 add $25, $4,$0 /* Set helper function procedure value. */ 81 jal $31,$25 /* Call helper func@$4 . */ 82 add $4, $2,$0 /* $a0 <= pass old sp as a parameter. */ 83 .set reorder 84 lw $31,36+16($sp) /* Restore callee-save regs... */ 85 lw $30,32+16($sp) 86 lw $23,28+16($sp) 87 lw $22,24+16($sp) 88 lw $21,20+16($sp) 89 lw $20,16+16($sp) 90 lw $19,12+16($sp) 91 lw $18, 8+16($sp) 92 lw $17, 4+16($sp) 93 lw $16, 0+16($sp) /* Restore callee-save */ 94 95 add $sp,$sp,40 /* Deallocate reg save space. */ 96 j $31 /* Return to caller. */ 97 98 /* 99 ** Non-varargs thread startup. 100 ** Note: originally, 56 bytes were allocated on the stack. 101 ** The thread restore routine (_blocki/_abort) removed 40 102 ** of them, which means there is still 16 bytes for the 103 ** argument area required by the MIPS calling convention. 104 */ 105qt_start: 106 add $4, $16,$0 /* Load up user function pu. */ 107 add $5, $17,$0 /* ... user function pt. */ 108 add $6, $18,$0 /* ... user function userf. */ 109 add $25, $19,$0 /* Set `only' procedure value. */ 110 jal $31,$25 /* Call `only'. */ 111 la $25,qt_error /* Set `qt_error' procedure value. */ 112 j $25 113 114 115 /* 116 ** Save calle-save floating-point regs $f20-$f30 117 ** See comment in `qt_block' about calling conventinos and 118 ** reserved space. Use the same trick here, but here we 119 ** actually have to allocate all the bytes since we have to 120 ** leave 4 words leftover for `qt_blocki'. 121 ** 122 ** Return value from `qt_block' is the same as the return from 123 ** `qt_blocki'. We get that for free since we don't touch $2 124 ** between the return from `qt_blocki' and the return from 125 ** `qt_block'. 126 */ 127qt_block: 128 sub $sp, $sp,56 /* 6 8-byte regs, saved ret pc, aligned. */ 129 swc1 $f20, 0+16($sp) 130 swc1 $f22, 8+16($sp) 131 swc1 $f24, 16+16($sp) 132 swc1 $f26, 24+16($sp) 133 swc1 $f28, 32+16($sp) 134 swc1 $f30, 40+16($sp) 135 sw $31, 48+16($sp) 136 jal qt_blocki 137 lwc1 $f20, 0+16($sp) 138 lwc1 $f22, 8+16($sp) 139 lwc1 $f24, 16+16($sp) 140 lwc1 $f26, 24+16($sp) 141 lwc1 $f28, 32+16($sp) 142 lwc1 $f30, 40+16($sp) 143 lw $31, 48+16($sp) 144 add $sp, $sp,56 145 j $31 146 147 148 /* 149 ** First, call `startup' with the `pt' argument. 150 ** 151 ** Next, call the user's function with all arguments. 152 ** Note that we don't know whether args were passed in 153 ** integer regs, fp regs, or on the stack (See Gerry Kane 154 ** "MIPS R2000 RISC Architecture" pg D-22), so we reload 155 ** all the registers, possibly with garbage arguments. 156 ** 157 ** Finally, call `cleanup' with the `pt' argument and with 158 ** the return value from the user's function. It is an error 159 ** for `cleanup' to return. 160 */ 161qt_vstart: 162 add $4, $17,$0 /* `pt' is arg0 to `startup'. */ 163 add $25, $18,$0 /* Set `startup' procedure value. */ 164 jal $31, $25 /* Call `startup'. */ 165 166 add $sp, $sp,16 /* Free extra save space. */ 167 lw $4, 0($sp) /* Load up args. */ 168 lw $5, 4($sp) 169 lw $6, 8($sp) 170 lw $7, 12($sp) 171 lwc1 $f12, 0($sp) /* Load up fp args. */ 172 lwc1 $f14, 8($sp) 173 add $25, $19,$0 /* Set `userf' procedure value. */ 174 jal $31,$25 /* Call `userf'. */ 175 176 add $4, $17,$0 /* `pt' is arg0 to `cleanup'. */ 177 add $5, $2,$0 /* Ret. val is arg1 to `cleanup'. */ 178 add $25, $16,$0 /* Set `cleanup' procedure value. */ 179 jal $31, $25 /* Call `cleanup'. */ 180 181 la $25,qt_error /* Set `qt_error' procedure value. */ 182 j $25 183