From 7996a9997a50d306c513ebc4079ac44f62c86a0a Mon Sep 17 00:00:00 2001 From: Virgil Dupras Date: Wed, 17 Apr 2019 14:47:42 -0400 Subject: [PATCH] zasm: add support for numerical constants --- apps/zasm/zasm.asm | 157 +++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 147 insertions(+), 10 deletions(-) diff --git a/apps/zasm/zasm.asm b/apps/zasm/zasm.asm index 1eec924..454773f 100644 --- a/apps/zasm/zasm.asm +++ b/apps/zasm/zasm.asm @@ -33,6 +33,64 @@ rlaX: djnz .loop ret +; Parse the decimal char at A and extract it's 0-9 numerical value. Put the +; result in A. +; +; On success, the carry flag is reset. On error, it is set. +parseDecimal: + ; First, let's see if we have an easy 0-9 case + cp '0' + ret c ; if < '0', we have a problem + cp '9'+1 + ; We are in the 0-9 range + sub a, '0' ; C is clear + ret + +; Parses the string at (HL) and returns the 16-bit value in IX. +; As soon as the number doesn't fit 16-bit any more, parsing stops and the +; number is invalid. If the number is valid, Z is set, otherwise, unset. +parseNumber: + push hl + push de + + ld ix, 0 +.loop: + ld a, (hl) + cp 0 + jr z, .end ; success! + call parseDecimal + jr c, .error + + ; Now, let's add A to IX. First, multiply by 10. + ld d, ixh ; we need a copy of the initial copy for later + ld e, ixl + add ix, ix ; x2 + add ix, ix ; x4 + add ix, ix ; x8 + add ix, de ; x9 + add ix, de ; x10 + add a, ixl + jr nc, .nocarry + inc ixh +.nocarry: + ld ixl, a + + ; We didn't bother checking for the C flag at each step because we + ; check for overflow afterwards. If ixh < d, we overflowed + ld a, ixh + cp d + jr c, .error ; carry is set? overflow + + inc hl + jr .loop + +.error: + call unsetZ +.end: + pop de + pop hl + ret + ; Sets Z is A is ';', CR, LF, or null. isLineEnd: cp ';' @@ -112,14 +170,24 @@ toWord: ; HL is advanced to the next word. Z is set if there's a next word. readArg: push de - ld de, tmpVal + ld de, tmpBuf call readWord push hl - ld hl, tmpVal + ld hl, tmpBuf call parseArg pop hl pop de ld (de), a + ; When A is a number, IX is set with the value of that number. Because + ; We don't use the space allocated to store those numbers in any other + ; occasion, we store IX there unconditonally, LSB first. + inc de + ld a, ixl + ld (de), a + inc de + ld a, ixh + ld (de), a + call toWord ret @@ -168,6 +236,9 @@ strlen: ; Return value 0xff holds a special meaning: arg is not empty, but doesn't match ; any argspec (A == 0 means arg is empty). A return value of 0xff means an ; error. +; +; If the parsed argument is a number constant, 'N' is returned and IX contains +; the value of that constant. parseArg: call strlen cp 0 @@ -190,8 +261,14 @@ parseArg: ld a, 5 call JUMP_ADDDE djnz .loop1 - ; exhausted? we have a problem os specifying a wrong argspec. This is - ; an internal consistency error. + + ; We exhausted the argspecs. Let's see if it's a number + call parseNumber + jr nz, .notanumber + ; Alright, we have a parsed number in IX. We're done. + ld a, 'N' + jr .end +.notanumber: ld a, 0xff jr .end .found: @@ -291,11 +368,24 @@ findInGroup: ; Compare argspec from instruction table in A with argument in (HL). ; For constant args, it's easy: if A == (HL), it's a success. +; If it's not this, then we check if it's a numerical arg. ; If A is a group ID, we do something else: we check that (HL) exists in the ; groupspec (argGrpTbl) matchArg: cp a, (hl) ret z + ; not an exact match, let's check for numerical constants. + cp 'N' + jr z, .expectsNumber + cp 'n' + jr z, .expectsNumber + jr .notNumber +.expectsNumber: + ld a, (hl) + cp 'N' ; In parsed arg, we don't have 'n', only 'N' + ret ; whether we match or not, the result of Z is the good + ; one +.notNumber: ; A bit of a delicate situation here: we want A to go in H but also ; (HL) to go in A. If not careful, we overwrite each other. EXX is ; necessary to avoid invoving other registers. @@ -336,6 +426,8 @@ matchPrimaryRow: ; Parse line at (HL) and write resulting opcode(s) in (DE). Returns the number ; of bytes written in A. +; +; Overwrites IX parseLine: call readLine ; Check whether we have errors. We don't do any parsing if we do. @@ -368,7 +460,6 @@ parseLine: ; We have our matching instruction row. We're getting pretty near our ; goal here! ; First, let's go in IX mode. It's easier to deal with offsets here. - push ix ld ixh, d ld ixl, e ; First, let's see if we're dealing with a group here @@ -409,18 +500,63 @@ parseLine: pop hl ; Success! - jr .end + jr .writeFirstOpcode .notgroup: ; not a group? easy as pie: we return the opcode directly. ld a, (ix+7) ; upcode is on 8th byte -.end: +.writeFirstOpcode: ; At the end, we have our final opcode in A! - pop ix pop de ld (de), a + + ; Good, we are probably finished here for many primary opcodes. However, + ; some primary opcodes take 8 or 16 bit constants as an argument and + ; if that's the case here, we need to write it too. + ; We still have our instruction row in IX. Let's revisit it. + push hl ; we use HL to point to the currently read arg + ld a, (ix+4) ; first argspec + ld hl, curArg1 + cp 'N' + jr z, .withWord + cp 'n' + jr z, .withByte + ld a, (ix+5) ; second argspec + ld hl, curArg2 + cp 'N' + jr z, .withWord + cp 'n' + jr z, .withByte + ; nope, no number, aright, only one opcode ld a, 1 + jr .end +.withByte: + ; verify that the MSB in argument is zero + inc hl + inc hl ; MSB is 2nd byte + ld a, (hl) + dec hl ; HL now points to LSB + cp 0 + jr nz, .numberTruncated + ; Clear to proceed. HL already points to our number + inc de + ldi + ld a, 2 + jr .end + +.withWord: + inc hl ; HL now points to LSB + ldi ; LSB written, we point to MSB now + ldi ; MSB written + ld a, 3 + jr .end +.numberTruncated: + ; problem: not zero, so value is truncated. error + xor a +.end: + pop hl ret + ; In instruction metadata below, argument types arge indicated with a single ; char mnemonic that is called "argspec". This is the table of correspondance. ; Single letters are represented by themselves, so we don't need as much @@ -523,6 +659,7 @@ instrTBlPrimary: .db "LD",0,0, 's', 'h', 0, 0x0a ; LD SP, HL .db "LD",0,0, 'l', 0xb, 0, 0b01110000 ; LD (HL), r .db "LD",0,0, 0xb, 'l', 3, 0b01000110 ; LD r, (HL) + .db "LD",0,0, 'l', 'n', 0, 0x36 ; LD (HL), n .db "NOP", 0, 0, 0, 0, 0x00 ; NOP .db "OR",0,0, 'l', 0, 0, 0xb6 ; OR (HL) .db "OR",0,0, 0xb, 0, 0, 0b10110000 ; OR r @@ -556,6 +693,6 @@ curArg2: .db 0, 0, 0 ; space for tmp stuff -tmpVal: - .db 0, 0, 0, 0, 0 +tmpBuf: + .fill 0x20