mu/055stream.subx

# streams: data structure for operating on arrays in a stateful manner
#
# A stream looks like this:
#   write : int  # index at which writes go
#   read : int  # index that we've read until
#   data : (array byte)  # prefixed by length as usual
#
# some primitives for operating on streams:
#   - clear-stream (clears everything but the data length)
#   - rewind-stream (resets read pointer)

== code
#   instruction                     effective address                                                   register    displacement    immediate
# . op          subop               mod             rm32          base        index         scale       r32
# . 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

clear-stream:  # f : (addr stream byte)
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    50/push-eax
    51/push-ecx
    # eax = f
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         0/r32/eax   8/disp8         .                 # copy *(ebp+8) to eax
    # var count/ecx : int = f->length
    8b/copy                         1/mod/*+disp8   0/rm32/eax    .           .             .           1/r32/ecx   8/disp8         .                 # copy *(eax+8) to ecx
    # var max/ecx : (addr byte) = &f->data[f->length]
    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    0/base/eax  1/index/ecx   .           1/r32/ecx   0xc/disp8       .                 # copy eax+ecx+12 to ecx
    # f->write = 0
    c7          0/subop/copy        0/mod/direct    0/rm32/eax    .           .             .           .           .               0/imm32           # copy to *eax
    # f->read = 0
    c7          0/subop/copy        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         0/imm32           # copy to *(eax+4)
    # var curr/eax : (addr byte) = f->data
    81          0/subop/add         3/mod/direct    0/rm32/eax    .           .             .           .           .               0xc/imm32         # add to eax
$clear-stream:loop:
    # if (curr >= max) break
    39/compare                      3/mod/direct    0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # compare eax with ecx
    73/jump-if-addr>=  $clear-stream:end/disp8
    # *curr = 0
    c6          0/subop/copy-byte   0/mod/direct    0/rm32/eax    .           .             .           .           .               0/imm8            # copy byte to *eax
    # ++curr
    40/increment-eax
    eb/jump  $clear-stream:loop/disp8
$clear-stream:end:
    # . restore registers
    59/pop-to-ecx
    58/pop-to-eax
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

rewind-stream:  # f : (addr stream byte)
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    50/push-eax
    # eax = f
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         0/r32/eax   8/disp8         .                 # copy *(ebp+8) to eax
    # f->read = 0
    c7          0/subop/copy        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         0/imm32           # copy to *(eax+4)
$rewind-stream:end:
    # . restore registers
    58/pop-to-eax
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

# . . vim:nowrap:textwidth=0
4949 2019-02-03 06:05:11 +00:00			`# streams: data structure for operating on arrays in a stateful manner`
			`#`
			`# A stream looks like this:`
			`# write : int # index at which writes go`
4951 Cleaner way to compare streams in tests. 2019-02-04 07:31:03 +00:00			`# read : int # index that we've read until`
5883 - drop the `ref` keyword When I created it I was conflating two things: a) needing to refer to just the start, rather than the whole, and b) counting indirections. Both are kinda ill-posed. Now Mu will have just `addr` and `handle` types. Normal types will translate implicitly to `addr` types, while `handle` will always require explicit handling. 2020-01-12 20:11:15 +00:00			`# data : (array byte) # prefixed by length as usual`
4949 2019-02-03 06:05:11 +00:00			`#`
4952 2019-02-06 07:29:15 +00:00			`# some primitives for operating on streams:`
4949 2019-02-03 06:05:11 +00:00			`# - clear-stream (clears everything but the data length)`
4952 2019-02-06 07:29:15 +00:00			`# - rewind-stream (resets read pointer)`
4949 2019-02-03 06:05:11 +00:00
			`== code`
			`# instruction effective address register displacement immediate`
			`# . op subop mod rm32 base index scale r32`
			`# . 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`

5876 - address -> addr 2020-01-03 09:36:34 +00:00			`clear-stream: # f : (addr stream byte)`
5698 Thanks Andrew Owen for reporting this typo. 2019-10-16 02:35:19 +00:00			`# . prologue`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`55/push-ebp`
			`89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp`
4949 2019-02-03 06:05:11 +00:00			`# . save registers`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`50/push-eax`
			`51/push-ecx`
			`# eax = f`
			`8b/copy 1/mod/+disp8 5/rm32/ebp . . 0/r32/eax 8/disp8 . # copy (ebp+8) to eax`
5804 Try to make the comments consistent with the type system we'll eventually have. 2019-12-08 21:56:46 +00:00			`# var count/ecx : int = f->length`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`8b/copy 1/mod/+disp8 0/rm32/eax . . . 1/r32/ecx 8/disp8 . # copy (eax+8) to ecx`
5876 - address -> addr 2020-01-03 09:36:34 +00:00			`# var max/ecx : (addr byte) = &f->data[f->length]`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`8d/copy-address 1/mod/*+disp8 4/rm32/sib 0/base/eax 1/index/ecx . 1/r32/ecx 0xc/disp8 . # copy eax+ecx+12 to ecx`
4949 2019-02-03 06:05:11 +00:00			`# f->write = 0`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`c7 0/subop/copy 0/mod/direct 0/rm32/eax . . . . . 0/imm32 # copy to *eax`
4949 2019-02-03 06:05:11 +00:00			`# f->read = 0`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`c7 0/subop/copy 1/mod/+disp8 0/rm32/eax . . . . 4/disp8 0/imm32 # copy to (eax+4)`
5876 - address -> addr 2020-01-03 09:36:34 +00:00			`# var curr/eax : (addr byte) = f->data`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`81 0/subop/add 3/mod/direct 0/rm32/eax . . . . . 0xc/imm32 # add to eax`
4949 2019-02-03 06:05:11 +00:00			`$clear-stream:loop:`
5804 Try to make the comments consistent with the type system we'll eventually have. 2019-12-08 21:56:46 +00:00			`# if (curr >= max) break`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`39/compare 3/mod/direct 0/rm32/eax . . . 1/r32/ecx . . # compare eax with ecx`
5897 - rename comparison instructions Signed and unsigned don't quite capture the essence of what the different combinations of x86 flags are doing for SubX. The crucial distinction is that one set of comparison operators is for integers and the second is for addresses. 2020-01-17 02:31:12 +00:00			`73/jump-if-addr>= $clear-stream:end/disp8`
5804 Try to make the comments consistent with the type system we'll eventually have. 2019-12-08 21:56:46 +00:00			`# *curr = 0`
5666 - start of sugar for structured control flow 2019-09-19 07:33:21 +00:00			`c6 0/subop/copy-byte 0/mod/direct 0/rm32/eax . . . . . 0/imm8 # copy byte to *eax`
5804 Try to make the comments consistent with the type system we'll eventually have. 2019-12-08 21:56:46 +00:00			`# ++curr`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`40/increment-eax`
4949 2019-02-03 06:05:11 +00:00			`eb/jump $clear-stream:loop/disp8`
			`$clear-stream:end:`
			`# . restore registers`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`59/pop-to-ecx`
			`58/pop-to-eax`
5698 Thanks Andrew Owen for reporting this typo. 2019-10-16 02:35:19 +00:00			`# . epilogue`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp`
			`5d/pop-to-ebp`
4949 2019-02-03 06:05:11 +00:00			`c3/return`
4952 2019-02-06 07:29:15 +00:00
5876 - address -> addr 2020-01-03 09:36:34 +00:00			`rewind-stream: # f : (addr stream byte)`
5698 Thanks Andrew Owen for reporting this typo. 2019-10-16 02:35:19 +00:00			`# . prologue`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`55/push-ebp`
			`89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp`
4952 2019-02-06 07:29:15 +00:00			`# . save registers`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`50/push-eax`
			`# eax = f`
			`8b/copy 1/mod/+disp8 5/rm32/ebp . . 0/r32/eax 8/disp8 . # copy (ebp+8) to eax`
4952 2019-02-06 07:29:15 +00:00			`# f->read = 0`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`c7 0/subop/copy 1/mod/+disp8 0/rm32/eax . . . . 4/disp8 0/imm32 # copy to (eax+4)`
4952 2019-02-06 07:29:15 +00:00			`$rewind-stream:end:`
			`# . restore registers`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`58/pop-to-eax`
5698 Thanks Andrew Owen for reporting this typo. 2019-10-16 02:35:19 +00:00			`# . epilogue`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp`
			`5d/pop-to-ebp`
4952 2019-02-06 07:29:15 +00:00			`c3/return`
4961 2019-02-15 00:24:20 +00:00
			`# . . vim:nowrap:textwidth=0`