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Diffstat (limited to 'subx/054string-equal.subx')
| -rw-r--r-- | subx/054string-equal.subx | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/subx/054string-equal.subx b/subx/054string-equal.subx new file mode 100644 index 00000000..fe6dd17b --- /dev/null +++ b/subx/054string-equal.subx @@ -0,0 +1,170 @@ +# Comparing 'regular' length-prefixed strings. + +== 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 + +# main: + # run-tests() + e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'. + # syscall(exit, Num-test-failures) + 8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/EBX Num-test-failures/disp32 # copy *Num-test-failures to EBX + b8/copy-to-EAX 1/imm32/exit + cd/syscall 0x80/imm8 + +string-equal: # s : string, benchmark : string -> EAX : boolean + # . prolog + 55/push-EBP + 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP + # . save registers + 51/push-ECX + 52/push-EDX + 53/push-EBX + 56/push-ESI + # pseudocode: + # if s->length != b->length return false + # for i = 0; i < s->length; ++i + # if s[i] != b[i] return false + # return true + # registers: + # i: ECX + # s->length: EDX + # b->length: EBX + # b[i]: EBX + # s[i]: EAX + # + # var s/EAX : (address array byte) + 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 0/r32/EAX 8/disp8 . # copy *(EBP+8) to EAX + # var benchmark/EBX : (address array byte) + 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 3/r32/EBX 0xc/disp8 . # copy *(EBP+12) to EBX + # if s->length != b->length return false + # EDX = s->length + 8b/copy 0/mod/indirect 0/rm32/EAX . . . 2/r32/EDX . . # copy *EAX to EDX + # compare s->length and b->length + 39/compare 0/mod/indirect 3/rm32/EBX . . . 2/r32/EDX . . # compare *EBX with EDX + 75/jump-if-not-equal $string-equal:false/disp8 +$string-equal:lengths: + # var i/ECX : int = 0 + b9/copy-to-ECX 0/imm32 + # EBX = &b[i] + 43/inc-EBX + # EAX = &s[i] + 40/inc-EAX +$string-equal:loop: + # if i >= s->length return true + 39/compare 3/mod/direct 1/rm32/ECX . . . 2/r32/EDX . . # compare ECX with EDX + 7d/jump-if-greater-or-equal $string-equal:true/disp8 + # if b[i] != s[i] return false + # ESI = s[i] + 8b/copy 0/mod/indirect 0/rm32/EAX . . . 6/r32/ESI . . # copy *EAX to ESI + # compare b[i] with ESI + 39/compare 0/mod/indirect 3/rm32/EBX . . . 6/r32/ESI . . # compare *EBX with ESI + 75/jump-if-not-equal $string-equal:false/disp8 + # ++i + 41/inc-ECX + 40/inc-EAX + 43/inc-EBX + # loop + eb/jump $string-equal:loop/disp8 +$string-equal:true: + # return true + b8/copy-to-EAX 1/imm32 + eb/jump $string-equal:end/disp8 +$string-equal:false: + # return false + b8/copy-to-EAX 0/imm32 +$string-equal:end: + # . restore registers + 5e/pop-to-ESI + 5b/pop-to-EBX + 5a/pop-to-EDX + 59/pop-to-ECX + # . epilog + 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP + 5d/pop-to-EBP + c3/return + +# - tests + +test-compare-empty-with-empty-string: + # EAX = string-equal("", "") + # . . push args + 68/push ""/imm32 + 68/push ""/imm32 + # . . call + e8/call string-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP + # check-ints-equal(EAX, 1, msg) + # . . push args + 68/push "F - test-compare-empty-with-empty-string"/imm32 + 68/push 1/imm32/true + 50/push-EAX + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + c3/return + +test-compare-empty-with-non-empty-string: # also checks length-mismatch code path + # EAX = string-equal("", "Abc") + # . . push args + 68/push "Abc"/imm32 + 68/push ""/imm32 + # . . call + e8/call string-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP + # check-ints-equal(EAX, 0, msg) + # . . push args + 68/push "F - test-compare-empty-with-non-empty-string"/imm32 + 68/push 0/imm32/false + 50/push-EAX + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + c3/return + +test-compare-equal-strings: + # EAX = string-equal("Abc", "Abc") + # . . push args + 68/push "Abc"/imm32 + 68/push "Abc"/imm32 + # . . call + e8/call string-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP + # check-ints-equal(EAX, 1, msg) + # . . push args + 68/push "F - test-compare-equal-strings"/imm32 + 68/push 1/imm32/true + 50/push-EAX + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + c3/return + +test-compare-inequal-strings-equal-lengths: + # EAX = string-equal("Abc", "Adc") + # . . push args + 68/push "Adc"/imm32 + 68/push "Abc"/imm32 + # . . call + e8/call string-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP + # check-ints-equal(EAX, 0, msg) + # . . push args + 68/push "F - test-compare-inequal-strings-equal-lengths"/imm32 + 68/push 0/imm32/false + 50/push-EAX + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + c3/return + +# . . vim:nowrap:textwidth=0 |