diff options
| author | Kartik Agaram <vc@akkartik.com> | 2019-08-25 00:24:03 -0700 |
|---|---|---|
| committer | Kartik Agaram <vc@akkartik.com> | 2019-08-25 00:27:42 -0700 |
| commit | d230393c924276a8bb3d9661dff688d5b07705ff (patch) | |
| tree | 4aa4271d75e49db304d75f6e5684e2baf3bb3f8f | |
| parent | be063736d0cd1f4141dc595361b575605683269d (diff) | |
| download | mu-d230393c924276a8bb3d9661dff688d5b07705ff.tar.gz | |
parsing *(reg+reg)
Turns out there's an ambiguity even in this simple one-line language: when you see 'base+' you don't know whether the next token is the index or displacement. (Whereas a '-' would be unambiguous but is still not handled.) Fixing this ambiguity adds 15 instructions worth of complexity.
| -rwxr-xr-x | apps/desugar | bin | 43605 -> 44097 bytes | |||
| -rw-r--r-- | apps/desugar.subx | 171 |
2 files changed, 150 insertions, 21 deletions
diff --git a/apps/desugar b/apps/desugar index 8b1eb786..88ba5534 100755 --- a/apps/desugar +++ b/apps/desugar Binary files differdiff --git a/apps/desugar.subx b/apps/desugar.subx index 6d2d607b..dc36f401 100644 --- a/apps/desugar.subx +++ b/apps/desugar.subx @@ -1497,6 +1497,7 @@ parse-effective-address: # word : (address slice) -> base/EAX, index/ECX, scale # if (*word->start != '+') goto error2 # ++word->start to skip '+' # skip whitespace + # if next 3 characters don't make a register, goto displacement # read register into index # skip whitespace # if (*word->start == ')') goto end @@ -1509,10 +1510,9 @@ parse-effective-address: # word : (address slice) -> base/EAX, index/ECX, scale # skip whitespace # if (*word->start == ')') goto end # } - # if (*word->start != '+') goto error4 - # ++word->start to skip '+' - # skip whitespace - # read register into disp + # if (*word->start not in '+' '-') goto error4 + # displacement: + # read integer into disp # skip whitespace # if (*word->start != ')') goto error5 # . prolog @@ -1553,7 +1553,7 @@ $parse-effective-address:simple-register: # . base = *EAX 8b/copy 0/mod/indirect 0/rm32/EAX . . . 7/r32/EDI . . # copy *EAX to EDI # return - eb/jump $parse-effective-address:end/disp8 + e9/jump $parse-effective-address:end/disp32 $parse-effective-address:compound-expression: # ++word->start to skip '(' ff 0/subop/increment 0/mod/indirect 6/rm32/ESI . . . . . . # increment *ESI @@ -1593,24 +1593,93 @@ $parse-effective-address:compound-expression: 8a/copy-byte 0/mod/indirect 0/rm32/EAX . . . 0/r32/AL . . # copy byte at *EAX to AL 81 4/subop/and 3/mod/direct 0/rm32/EAX . . . . . 0xff/imm32 # bitwise and of EAX 3d/compare-EAX-and 0x29/imm32/close-paren - 74/jump-if-equal $parse-effective-address:end/disp8 + 0f 84/jump-if-equal $parse-effective-address:end/disp32 # if (*word->start != '+') goto error2 - # ++word->start +$parse-effective-address:check-for-index: + # ++word->start to skip '+' + ff 0/subop/increment 0/mod/indirect 6/rm32/ESI . . . . . . # increment *ESI # skip whitespace + # . EAX = skip-chars-matching-whitespace-in-slice(word->start, word->end) + # . . push args + ff 6/subop/push 1/mod/*+disp8 6/rm32/ESI . . . . 4/disp8 . # push *(ESI+4) + ff 6/subop/push 0/mod/indirect 6/rm32/ESI . . . . . . # push *ESI + # . . call + e8/call skip-chars-matching-whitespace-in-slice/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP + # . word->start = EAX + 89/copy 0/mod/indirect 6/rm32/ESI . . . 0/r32/EAX . . # copy EAX to *ESI +$parse-effective-address:resolve-ambiguity: + # if next 3 characters don't make a register, goto displacement + # . spill ECX + 51/push-ECX + # . var tmp/ECX = {word->start, word->start+3} + # . . ECX = word->start + 89/copy 3/mod/direct 1/rm32/ECX . . . 0/r32/EAX . . # copy EAX to ECX + # . . EAX = word->start+3 + 05/add-to-EAX 3/imm32 + # . . push + 50/push-EAX + 51/push-ECX + # . . copy ESP to ECX + 89/copy 3/mod/direct 1/rm32/ECX . . . 4/r32/ESP . . # copy ESP to ECX + # . EAX = maybe-get-slice(Register, tmp, row-size=8) + # . . push args + 68/push 8/imm32/row-size + 51/push-ECX + 68/push Registers/imm32 + # . . call + e8/call maybe-get-slice/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + # . reclaim tmp + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP + # . restore ECX + 59/pop-to-ECX + # . if (EAX == 0) goto displacement + 3d/compare-EAX-and 0/imm32 + 0f 84/jump-if-equal $parse-effective-address:displacement/disp32 +$parse-effective-address:index: # read register into index + # . EAX = next-register(word) + # . . push args + ff 6/subop/push 1/mod/*+disp8 5/rm32/EBP . . . . 8/disp8 . # push *(EBP+8) + # . . call + e8/call next-register/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP + # . ECX = *EAX + 8b/copy 0/mod/indirect 0/rm32/EAX . . . 1/r32/ECX . . # copy *EAX to ECX # skip whitespace + # . EAX = skip-chars-matching-whitespace-in-slice(word->start, word->end) + # . . push args + ff 6/subop/push 1/mod/*+disp8 6/rm32/ESI . . . . 4/disp8 . # push *(ESI+4) + ff 6/subop/push 0/mod/indirect 6/rm32/ESI . . . . . . # push *ESI + # . . call + e8/call skip-chars-matching-whitespace-in-slice/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP + # . word->start = EAX + 89/copy 0/mod/indirect 6/rm32/ESI . . . 0/r32/EAX . . # copy EAX to *ESI # if (*word->start == ')') goto end - # if (*word->start == '<') { - # ++word->start to skip '<' - # if (*word->start != '<') goto error3 - # ++word->start to skip '<' - # skip whitespace - # read register into scale - # skip whitespace - # if (*word->start == ')') goto end - # } + 8a/copy-byte 0/mod/indirect 0/rm32/EAX . . . 0/r32/AL . . # copy byte at *EAX to AL + 81 4/subop/and 3/mod/direct 0/rm32/EAX . . . . . 0xff/imm32 # bitwise and of EAX + 3d/compare-EAX-and 0x29/imm32/close-paren + 74/jump-if-equal $parse-effective-address:end/disp8 +$parse-effective-address:check-for-scale: + # if (*word->start != '<') goto displacement + # ++word->start to skip '<' + # if (*word->start != '<') goto error3 + # ++word->start to skip '<' + # skip whitespace +$parse-effective-address:scale: + # read register into scale + # skip whitespace + # if (*word->start == ')') goto end +$parse-effective-address:check-for-displacement: # if (*word->start not in '+' '-') goto error4 - # read int into disp +$parse-effective-address:displacement: + # read integer into disp # . EAX = next-hex-int(word) # . . push args ff 6/subop/push 1/mod/*+disp8 5/rm32/EBP . . . . 8/disp8 . # push *(EBP+8) @@ -1869,8 +1938,68 @@ test-parse-effective-address-base-displacement: 5d/pop-to-EBP c3/return -#? test-parse-effective-address-base-index: -#? +test-parse-effective-address-base-index: + # . prolog + 55/push-EBP + 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP + # var slice/ECX = "*(esi+ecx)" + b8/copy-to-EAX "*(esi+ecx)"/imm32 + 8b/copy 0/mod/indirect 0/rm32/EAX . . . 1/r32/ECX . . # copy *EAX to ECX + 8d/copy-address 1/mod/*+disp8 4/rm32/sib 0/base/EAX 1/index/ECX . 1/r32/ECX 4/disp8 . # copy EAX+ECX+4 to ECX + 05/add-to-EAX 4/imm32 + # . ECX = {EAX, ECX} + 51/push-ECX + 50/push-EAX + 89/copy 3/mod/direct 1/rm32/ECX . . . 4/r32/ESP . . # copy ESP to ECX + # EAX, ECX, EDX, EBX = parse-effective-address(slice) + # . . push args + 51/push-ECX + # . . call + e8/call parse-effective-address/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP + # slice clobbered beyond this point + # check-ints-equal(EAX, 6, msg) + # . . push args + 68/push "F - test-parse-effective-address-base-index/base"/imm32 + 68/push 6/imm32/ESI + 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 + # check-ints-equal(ECX, 1, msg) + # . . push args + 68/push "F - test-parse-effective-address-base-index/index"/imm32 + 68/push 1/imm32/none + 51/push-ECX + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + # check-ints-equal(EDX, 0, msg) + # . . push args + 68/push "F - test-parse-effective-address-base-index/scale"/imm32 + 68/push 0/imm32/none + 52/push-EDX + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + # check-ints-equal(EBX, 0, msg) + # . . push args + 68/push "F - test-parse-effective-address-base-index/displacement"/imm32 + 68/push 0/imm32 + 53/push-EBX + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + # . epilog + 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP + 5d/pop-to-EBP + c3/return + #? test-parse-effective-address-base-index-scale: #? #? test-parse-effective-address-base-index-scale-displacement: @@ -2398,7 +2527,7 @@ test-skip-until-close-paren-in-slice-stops-at-end: 5d/pop-to-EBP c3/return -# assumes 'in' starts with a '+' or '-', optional whitespace, and an unsigned integer +# assumes 'in' starts with optional '+' or '-', optional whitespace, and an unsigned integer # returns the value of the integer # side-effect: modifies 'in' to skip past the integer next-hex-int: # in : (address slice) -> result/EAX @@ -2434,7 +2563,7 @@ $next-hex-int:positive: $next-hex-int:negative: # else if (*curr == '-') ++curr, negate = true 3d/compare-EAX-and 0x2d/imm32/- - 75/jump-if-not-equal $next-hex-int:abort/disp8 + 75/jump-if-not-equal $next-hex-int:skip-whitespace/disp8 # . ++curr 41/increment-ECX # . negate = true |