Mu - subx/076zero-out.subx

From 6e1eeeebfb453fa7c871869c19375ce60fbd7413 Mon Sep 17 00:00:00 2001 From: Kartik Agaram Date: Sat, 27 Jul 2019 16:01:55 -0700 Subject: 5485 - promote SubX to top-level --- html/076zero-out.subx.html | 147 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 147 insertions(+) create mode 100644 html/076zero-out.subx.html (limited to 'html/076zero-out.subx.html') diff --git a/html/076zero-out.subx.html b/html/076zero-out.subx.html new file mode 100644 index 00000000..fcc42479 --- /dev/null +++ b/html/076zero-out.subx.html @@ -0,0 +1,147 @@ + + + + +Mu - subx/076zero-out.subx + + + + + + + + + + +https://github.com/akkartik/mu/blob/master/subx/076zero-out.subx +

+ 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  zero-out/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  check-ints-equal/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
+

+ + + -- cgit 1.4.1-2-gfad0