mu - Soul of a tiny new machine. More thorough tests → More comprehensible and rewrite-friendly software → More resilient society.

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <title>Mu - 076zero-out.subx</title> <meta name="Generator" content="Vim/8.1"> <meta name="plugin-version" content="vim8.1_v1"> <meta name="syntax" content="none"> <meta name="settings" content="number_lines,use_css,no_foldcolumn,expand_tabs,line_ids,prevent_copy="> <meta name="colorscheme" content="minimal-light"> <style type="text/css">  </style> <script type='text/javascript'>  </script> </head> <body onload='JumpToLine();'> <a href='https://github.com/akkartik/mu/blob/master/076zero-out.subx'>https://github.com/akkartik/mu/blob/master/076zero-out.subx</a> <pre id='vimCodeElement'> 1 # Fill a region of memory with zeroes. 2 3 == code 4 # instruction effective address register displacement immediate 5 # . op subop mod rm32 base index scale r32 6 # . 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes 7 8 zero-out: # start : address, len : int 9 # pseudocode: 10 # curr/esi = start 11 # i/ecx = 0 12 # while true 13 # if (i >= len) break 14 # *curr = 0 15 # ++curr 16 # ++i 17 # 18 # . prolog 19 55/push-ebp 20 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp 21 # . save registers 22 50/push-eax 23 51/push-ecx 24 52/push-edx 25 56/push-esi 26 # curr/esi = start 27 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 8/disp8 . # copy *(ebp+8) to esi 28 # i/ecx = 0 29 31/xor 3/mod/direct 1/rm32/ecx . . . 1/r32/ecx . . # clear ecx 30 # edx = len 31 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 2/r32/edx 0xc/disp8 . # copy *(ebp+12) to edx 32 $zero-out:loop: 33 # if (i >= len) break 34 39/compare 3/mod/direct 1/rm32/ecx . . . 2/r32/edx . . # compare ecx with edx 35 7d/jump-if-greater-or-equal $zero-out:end/disp8 36 # *curr = 0 37 c6 0/subop/copy 0/mod/direct 6/rm32/esi . . . . . 0/imm8 # copy byte to *esi 38 # ++curr 39 46/increment-esi 40 # ++i 41 41/increment-ecx 42 eb/jump $zero-out:loop/disp8 43 $zero-out:end: 44 # . restore registers 45 5e/pop-to-esi 46 5a/pop-to-edx 47 59/pop-to-ecx 48 58/pop-to-eax 49 # . epilog 50 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 51 5d/pop-to-ebp 52 c3/return 53 54 test-zero-out: 55 # . prolog 56 55/push-ebp 57 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp 58 # region/ecx = 34, 35, 36, 37 59 68/push 0x37363534/imm32 60 89/copy 3/mod/direct 1/rm32/ecx . . . 4/r32/esp . . # copy esp to ecx 61 # zero-out(ecx, 3) 62 # . . push args 63 68/push 3/imm32/len 64 51/push-ecx 65 # . . call 66 e8/call <a href='076zero-out.subx.html#L8'>zero-out</a>/disp32 67 # . . discard args 68 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp 69 # first 3 bytes cleared, fourth left alone 70 # . check-ints-equal(*ecx, 0x37000000, msg) 71 # . . push args 72 68/push "F - test-zero-out"/imm32 73 68/push 0x37000000/imm32 74 ff 6/subop/push 0/mod/indirect 1/rm32/ecx . . . . . . # push *ecx 75 # . . call 76 e8/call <a href='051test.subx.html#L24'>check-ints-equal</a>/disp32 77 # . . discard args 78 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp 79 # . epilog 80 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 81 5d/pop-to-ebp 82 c3/return 83 84 # . . vim:nowrap:textwidth=0 </pre> </body> </html>


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