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 * On startup, restore regs so retpc === call to a function to start. 19 * We're going to call a function ($4) from within this routine. 20 * We're passing 3 args, therefore need to allocate 12 extra bytes on 21 * the stack for a save area. The start routine needs a like 16-byte 22 * save area. Must be doubleword aligned (_mips r3000 risc 23 * architecture_, gerry kane, pg d-23). 24 */ 25 26 .globl qt_block 27 .globl qt_blocki 28 .globl qt_abort 29 .globl qt_start 30 .globl qt_vstart 31 32 /* 33 ** $4: ptr to function to call once curr is suspended 34 ** and control is on $7's stack. 35 ** $5: 1'th arg to $4. 36 ** $6: 2'th arg to $4 37 ** $7: sp of thread to suspend. 38 ** 39 ** Totally gross hack: The MIPS calling convention reserves 40 ** 4 words on the stack for a0..a3. This routine "ought" to 41 ** allocate space for callee-save registers plus 4 words for 42 ** the helper function, but instead we use the 4 words 43 ** provided by the function that called us (we don't need to 44 ** save our argument registers). So what *appears* to be 45 ** allocating only 40 bytes is actually allocating 56, by 46 ** using the caller's 16 bytes. 47 ** 48 ** The helper routine returns a value that is passed on as the 49 ** return value from the blocking routine. Since we don't 50 ** touch $2 between the helper's return and the end of 51 ** function, we get this behavior for free. 52 */ 53qt_blocki: 54 sub $sp,$sp,40 /* Allocate reg save space. */ 55 sw $16, 0+16($sp) 56 sw $17, 4+16($sp) 57 sw $18, 8+16($sp) 58 sw $19,12+16($sp) 59 sw $20,16+16($sp) 60 sw $21,20+16($sp) 61 sw $22,24+16($sp) 62 sw $23,28+16($sp) 63 sw $30,32+16($sp) 64 sw $31,36+16($sp) 65 add $2, $sp,$0 /* $2 <= old sp to pass to func@$4. */ 66qt_abort: 67 add $sp, $7,$0 /* $sp <= new sp. */ 68 .set noreorder 69 jal $31,$4 /* Call helper func@$4 . */ 70 add $4, $2,$0 /* $a0 <= pass old sp as a parameter. */ 71 .set reorder 72 lw $31,36+16($sp) /* Restore callee-save regs... */ 73 lw $30,32+16($sp) 74 lw $23,28+16($sp) 75 lw $22,24+16($sp) 76 lw $21,20+16($sp) 77 lw $20,16+16($sp) 78 lw $19,12+16($sp) 79 lw $18, 8+16($sp) 80 lw $17, 4+16($sp) 81 lw $16, 0+16($sp) /* Restore callee-save */ 82 83 add $sp,$sp,40 /* Deallocate reg save space. */ 84 j $31 /* Return to caller. */ 85 86 /* 87 ** Non-varargs thread startup. 88 ** Note: originally, 56 bytes were allocated on the stack. 89 ** The thread restore routine (_blocki/_abort) removed 40 90 ** of them, which means there is still 16 bytes for the 91 ** argument area required by the MIPS calling convention. 92 */ 93qt_start: 94 add $4, $16,$0 /* Load up user function pu. */ 95 add $5, $17,$0 /* ... user function pt. */ 96 add $6, $18,$0 /* ... user function userf. */ 97 jal $31,$19 /* Call `only'. */ 98 j qt_error 99 100 101 /* 102 ** Save calle-save floating-point regs $f20-$f30 103 ** See comment in `qt_block' about calling conventinos and 104 ** reserved space. Use the same trick here, but here we 105 ** actually have to allocate all the bytes since we have to 106 ** leave 4 words leftover for `qt_blocki'. 107 ** 108 ** Return value from `qt_block' is the same as the return from 109 ** `qt_blocki'. We get that for free since we don't touch $2 110 ** between the return from `qt_blocki' and the return from 111 ** `qt_block'. 112 */ 113qt_block: 114 sub $sp, $sp,56 /* 6 8-byte regs, saved ret pc, aligned. */ 115 swc1 $f20, 0+16($sp) 116 swc1 $f22, 8+16($sp) 117 swc1 $f24, 16+16($sp) 118 swc1 $f26, 24+16($sp) 119 swc1 $f28, 32+16($sp) 120 swc1 $f30, 40+16($sp) 121 sw $31, 48+16($sp) 122 jal qt_blocki 123 lwc1 $f20, 0+16($sp) 124 lwc1 $f22, 8+16($sp) 125 lwc1 $f24, 16+16($sp) 126 lwc1 $f26, 24+16($sp) 127 lwc1 $f28, 32+16($sp) 128 lwc1 $f30, 40+16($sp) 129 lw $31, 48+16($sp) 130 add $sp, $sp,56 131 j $31 132 133 134 /* 135 ** First, call `startup' with the `pt' argument. 136 ** 137 ** Next, call the user's function with all arguments. 138 ** Note that we don't know whether args were passed in 139 ** integer regs, fp regs, or on the stack (See Gerry Kane 140 ** "MIPS R2000 RISC Architecture" pg D-22), so we reload 141 ** all the registers, possibly with garbage arguments. 142 ** 143 ** Finally, call `cleanup' with the `pt' argument and with 144 ** the return value from the user's function. It is an error 145 ** for `cleanup' to return. 146 */ 147qt_vstart: 148 add $4, $17,$0 /* `pt' is arg0 to `startup'. */ 149 jal $31, $18 /* Call `startup'. */ 150 151 add $sp, $sp,16 /* Free extra save space. */ 152 lw $4, 0($sp) /* Load up args. */ 153 lw $5, 4($sp) 154 lw $6, 8($sp) 155 lw $7, 12($sp) 156 lwc1 $f12, 0($sp) /* Load up fp args. */ 157 lwc1 $f14, 8($sp) 158 jal $31,$19 /* Call `userf'. */ 159 160 add $4, $17,$0 /* `pt' is arg0 to `cleanup'. */ 161 add $5, $2,$0 /* Ret. val is arg1 to `cleanup'. */ 162 jal $31, $16 /* Call `cleanup'. */ 163 164 j qt_error 165