diff options
| author | Kartik Agaram <vc@akkartik.com> | 2019-05-04 12:58:09 -0700 |
|---|---|---|
| committer | Kartik Agaram <vc@akkartik.com> | 2019-05-04 14:06:40 -0700 |
| commit | 02b105fee40399410e6aa05ee33d4ee2cef8fd4d (patch) | |
| tree | bd0c324c61a27ad5ba377ef12e3a30d016fe8fb4 /subx/074print-int-decimal.subx | |
| parent | 2d61d10eca7b7858588a4aa0eb40a7952120f527 (diff) | |
| download | mu-02b105fee40399410e6aa05ee33d4ee2cef8fd4d.tar.gz | |
5137
A few minor stylistic things that may ease reading, but not significantly
enough that I care to force others to follow them:
* no end-of-line comments for instructions without /rm32
* arguments either at tab stops or after 2 spaces
* compare 'with' when using in asymmetric tests (greater/lesser),
compare 'and' for symmetric equality checking
* prefix internal labels with function name
Diffstat (limited to 'subx/074print-int-decimal.subx')
| -rw-r--r-- | subx/074print-int-decimal.subx | 129 |
1 files changed, 52 insertions, 77 deletions
diff --git a/subx/074print-int-decimal.subx b/subx/074print-int-decimal.subx index 31999dcd..72c99495 100644 --- a/subx/074print-int-decimal.subx +++ b/subx/074print-int-decimal.subx @@ -14,24 +14,25 @@ #? cd/syscall 0x80/imm8 print-int32-decimal: # out : (address stream), n : int32 - # PSEUDOCODE - # based on K&R itoa: https://en.wikibooks.org/wiki/C_Programming/stdlib.h/itoa - # push SENTINAL - # if n >= 0: - # goto digit-encode - # else: - # n = -n - # negative = true - # while true: - # push n % 10 + '0' - # n = n / 10 - # break if n == 0 - # if negative: - # push '-' - # while true: - # EAX = pop - # break if EAX == SENTINAL - # out->data[out->write++] = EAX + # pseudocode: + # push sentinel + # EAX, negative? = abs(n), sign(n) + # while true + # sign-extend EAX into EDX + # EAX, EDX = EAX/10, EAX%10 + # EDX += '0' + # push EDX + # if (EAX == 0) break + # if negative? + # push '-' + # while true + # pop into EAX + # if (EAX == sentinel) break + # out->data[out->write] = AL + # ++out->write + # (based on K&R itoa: https://en.wikibooks.org/wiki/C_Programming/stdlib.h/itoa) + # (this pseudocode contains registers because operations like division + # require specific registers in x86) # # . prolog 55/push-EBP @@ -42,86 +43,60 @@ print-int32-decimal: # out : (address stream), n : int32 52/push-EDX 53/push-EBX 57/push-EDI - - # negative = false - bf/copy-to-EDI 0/imm32 # EDI = 0 - - # push sentinal for $append-loop - 68/push-sentinel 0/imm32 - - # EAX = n + # push sentinel + 68/push 0/imm32/sentinel + # EAX, negative?/EDI = abs(n), sign(n) + bf/copy-to-EDI 0/imm32/false 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 0/r32/EAX 0xc/disp8 . # EAX = *(EBP+12) - # if n >= 0 jump to digit-encode - 3d/compare-EAX-and 0/imm32 - 7d/jump-if-greater-eq $digit-encode:prelude/disp8 - # else - # n = -n - f7 3/subop/negate 3/mod/direct 0/rm32/EAX # EAX = -EAX - - # negative = true - bf/copy-to-EDI 1/imm32 # EDI = 1 - -$digit-encode:prelude: + 3d/compare-EAX-with 0/imm32 + 7d/jump-if-greater-or-equal $print-int32-decimal:read/disp8 + f7 3/subop/negate 3/mod/direct 0/rm32/EAX . . . . . . # negate EAX + bf/copy-to-EDI 1/imm32/true +$print-int32-decimal:read: # EBX = n 8b/copy 3/mod/direct 0/rm32/EAX . . . 3/r32/EBX . . # EBX = EAX - -$digit-encode-loop: +$print-int32-decimal:read-loop: # EAX = EBX(n) 89/copy 3/mod/direct 0/rm32/EAX . . . 3/r32/EBX . . # EAX = EBX - b9/copy-to-ECX 0xa/imm32 + b9/copy-to-ECX 0xa/imm32 + # EAX, EDX = EAX / 10, EAX % 10 99/sign-extend-EAX-into-EDX - # EDX:EAX(n) / ECX(10) - - # EDX, EAX = n % 10, n / 10 f7 7/subop/idiv 3/mod/direct 1/rm32/ECX . . . . . . # divide EDX:EAX by ECX, storing quotient in EAX and remainder in EDX - 81 0/subop/add 3/mod/direct 2/rm32/EDX . . . . . 0x30/imm32 # EDX += '0' (0x30) - - # push n % 10 + '0' + # EDX += '0' + 81 0/subop/add 3/mod/direct 2/rm32/EDX . . . . . 0x30/imm32 # add to EDX + # push EDX 52/push-EDX - # EBX = n / 10 89/copy 3/mod/direct 3/rm32/EBX . . . 0/r32/EAX . . # EBX = EAX - - # loop if n / 10 > 0 + # if (EAX == 0) break 3d/compare-EAX-and 0/imm32 - 7f/jump-if-greater $digit-encode-loop/disp8 - # else: - + 7f/jump-if-greater $print-int32-decimal:read-loop/disp8 +$print-int32-decimal:read-break: + # if (negative?) push('-') 8b/copy 3/mod/direct 7/rm32/EDI . . . 0/r32/EAX . . # EAX = EDX - # . if !negative: goto append-loop - 3d/compare-EAX-and 0/imm32 - 74/jump-if-equal $append-loop:prelude/disp8 - # . else - 68/push-negative 0x2d/imm32 # push '-' - -$append-loop:prelude: - # EBX = &out + 3d/compare-EAX-and 0/imm32 + 74/jump-if-equal $print-int32-decimal:write/disp8 + 68/push 0x2d/imm32/- +$print-int32-decimal:write: + # EBX = out 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 3/r32/EBX 8/disp8 . # copy *(EBP+8) to EBX - -$append-loop: - # EAX = next_character +$print-int32-decimal:write-loop: + # pop into EAX 58/pop-to-EAX - - 3d/compare-EAX . . . . . . . 0/imm32 # EAX == 0 - 74/jump-if-equal $append-loop:break/disp8 - - # ECX = out->write + # if (EAX == sentinel) break + 3d/compare-EAX-and 0/imm32/sentinel + 74/jump-if-equal $print-int32-decimal:end/disp8 + # out->data[out->write] = AL + # . ECX = out->write 8b/copy 0/mod/indirect 3/rm32/EBX . . . 1/r32/ECX . . # ECX = *EBX - - # out->data[out->write] = next_character # . ECX = &out->data[out->write] 8d/copy-address 1/mod/*+disp8 4/rm32/sib 3/base/EBX 1/index/ECX . 1/r32/ECX 0xc/disp8 . # copy EBX+ECX+12 to ECX # . out->data[out->write] = EAX 89/copy 0/mod/indirect 1/rm32/ECX . . . 0/r32/ECX . . # *ECX = EAX - # out->write++ - ff 0/subop/increment 0/mod/indirect 3/rm32/EBX . . . . . . # (*EBX)++ - eb/jump $append-loop/disp8 - -$append-loop:break: - + ff 0/subop/increment 0/mod/indirect 3/rm32/EBX . . . . . . # increment *EBX + eb/jump $print-int32-decimal:write-loop/disp8 $print-int32-decimal:end: - # . reclaim locals # . restore registers 57/pop-to-EDI 5b/pop-to-EBX |