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diff 68kinst.c @ 2:5df303bf72e6

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Improve 68K instruction decoding. Add simple disassembler.
author Mike Pavone <pavone@retrodev.com>
date Sat, 03 Nov 2012 21:38:28 -0700
parents 2432d177e1ac
children a4ad0e3e3e0e
line wrap: on
line diff
--- a/68kinst.c	Sat Nov 03 21:37:38 2012 -0700
+++ b/68kinst.c	Sat Nov 03 21:38:28 2012 -0700
@@ -1,25 +1,104 @@
 #include "68kinst.h"
+#include <string.h>
+#include <stdio.h>
+
+uint32_t sign_extend16(uint32_t val)
+{
+	return (val & 0x8000) ? val | 0xFFFF0000 : val;
+}
 
-void m68k_decode_op(uint16_t op, m68k_op_info *dst)
+uint32_t sign_extend8(uint32_t val)
 {
-	uint8_t mode = (op >> 3) & 0x7;
-	uint8_t reg = op & 0x7;
+	return (val & 0x80) ? val | 0xFFFFFF00 : val;
+}
+
+uint16_t *m68k_decode_op_ex(uint16_t *cur, uint8_t mode, uint8_t reg, uint8_t size, m68k_op_info *dst)
+{
+	uint16_t ext;
 	dst->addr_mode = mode;
 	switch(mode)
 	{
 	case MODE_REG:
 	case MODE_AREG:
+	case MODE_AREG_INDIRECT:
+	case MODE_AREG_POSTINC:
+	case MODE_AREG_PREDEC:
 		dst->params.regs.pri = reg;
 		break;
-	case MODE_
+	case MODE_AREG_DISPLACE:
+		ext = *(++cur);
+		dst->params.regs.pri = reg;
+		dst->params.regs.displacement = sign_extend16(ext);
+		break;
+	case MODE_AREG_INDEX_MEM:
+		//TODO: implement me
+		break;
+	case MODE_PC_INDIRECT_ABS_IMMED:
+		switch(reg)
+		{
+		case 0:
+			dst->addr_mode = MODE_ABSOLUTE_SHORT;
+			ext = *(++cur);
+			dst->params.u32 = sign_extend16(ext);
+			break;
+		case 1:
+			dst->addr_mode = MODE_ABSOLUTE;
+			ext = *(++cur);
+			dst->params.u32 = ext << 16 | *(++cur);
+			break;
+		case 2:
+			dst->addr_mode = MODE_PC_DISPLACE;
+			ext = *(++cur);
+			dst->params.regs.displacement = sign_extend16(ext);
+			break;
+		case 4:
+			dst->addr_mode = MODE_IMMEDIATE;
+			ext = *(++cur);
+			switch (size)
+			{
+			case OPSIZE_BYTE:
+				dst->params.u8 = ext;
+				break;
+			case OPSIZE_WORD:
+				dst->params.u16 = ext;
+				break;
+			case OPSIZE_LONG:
+				dst->params.u32 = ext << 16 | *(++cur);
+				break;
+			}
+			break;
+		//TODO: implement the rest of these
+		}
+		break;
 	}
+	return cur;
+}
+
+uint16_t *m68k_decode_op(uint16_t *cur, uint8_t size, m68k_op_info *dst)
+{
+	uint8_t mode = (*cur >> 3) & 0x7;
+	uint8_t reg = *cur & 0x7;
+	return m68k_decode_op_ex(cur, mode, reg, size, dst);
+}
+
+void m68k_decode_cond(uint16_t op, m68kinst * decoded)
+{
+	decoded->extra.cond = (op >> 0x8) & 0xF;
+}
+
+uint8_t m68K_reg_quick_field(uint16_t op)
+{
+	return (op >> 9) & 0x7;
 }
 
 uint16_t * m68K_decode(uint16_t * istream, m68kinst * decoded)
 {
 	uint8_t optype = *istream >> 12;
 	uint8_t size;
-	uint8_t immed;
+	uint32_t immed;
+	decoded->op = M68K_INVALID;
+	decoded->src.addr_mode = decoded->dst.addr_mode = MODE_UNUSED;
+	decoded->variant = VAR_NORMAL;
 	switch(optype)
 	{
 	case BIT_MOVEP_IMMED:
@@ -30,63 +109,529 @@
 	case MOVE_WORD:
 		decoded->op = M68K_MOVE;
 		decoded->extra.size = optype == MOVE_BYTE ? OPSIZE_BYTE : (optype == MOVE_WORD ? OPSIZE_WORD : OPSIZE_LONG);
-		m68k_decode_op(*istream, &(decoded->src));
-		m68k_decode_op(((*istream >> 9) & 0x7) | , &(decoded->dst));
+		istream = m68k_decode_op(istream, decoded->extra.size, &(decoded->src));
+		istream = m68k_decode_op_ex(istream, (*istream >> 6) & 0x7, m68K_reg_quick_field(*istream), decoded->extra.size, &(decoded->dst));
 		break;
 	case MISC:
-		//TODO: Implement me
+		
+		if ((*istream & 0x1C0) == 0x1C0) {
+			decoded->op = M68K_LEA;
+			decoded->extra.size = OPSIZE_LONG;
+			decoded->dst.addr_mode = MODE_AREG;
+			decoded->dst.params.regs.pri = m68K_reg_quick_field(*istream);
+			istream = m68k_decode_op(istream, decoded->extra.size, &(decoded->src));
+		} else {
+			if (*istream & 0x100) {
+				decoded->op = M68K_CHK;
+				if ((*istream & 0x180) == 0x180) {
+					decoded->extra.size = OPSIZE_WORD;
+				} else {
+					//only on M68020+
+					decoded->extra.size = OPSIZE_LONG;
+				}
+				istream = m68k_decode_op(istream, decoded->extra.size, &(decoded->src));
+				decoded->dst.addr_mode = MODE_REG;
+				decoded->dst.addr_mode = m68K_reg_quick_field(*istream);
+			} else {
+				optype = (*istream >> 9) & 0x7;
+				switch(optype)
+				{
+				case 0:
+					//Move from SR or NEGX
+					break;
+				case 1:
+					//MOVE from CCR or CLR
+					break;
+				case 2:
+					//MOVE to CCR or NEG
+					break;
+				case 3:
+					//MOVE to SR or NOT
+					break;
+				case 4:
+					//EXT, EXTB, LINK.l, NBCD, SWAP, BKPT, PEA, MOVEM
+					break;
+				case 5:
+					//BGND, ILLEGAL, TAS, TST
+					optype = *istream & 0xFF;
+					if (optype == 0xFA) {
+						//BGND - CPU32 only
+					} else if (optype == 0xFC) {
+						decoded->op = M68K_ILLEGAL;
+					} else {
+						size = (*istream & 0xC0) >> 6;
+						if (size == OPSIZE_INVALID) {
+							decoded->op = M68K_TAS;
+						} else {
+							decoded->op = M68K_TST;
+							decoded->extra.size = size;
+							istream = m68k_decode_op(istream, decoded->extra.size, &(decoded->src));
+						}
+					}
+					break;	
+				case 6:
+					//MULU, MULS, DIVU, DIVUL, DIVS, DIVSL, MOVEM
+					break;
+				case 7:
+					//TRAP, LINK.w, UNLNK, MOVE USP, RESET, NOP, STOP, RTE, RTD, RTS, TRAPV, RTR, MOVEC, JSR, JMP
+					if (*istream & 0x80) {
+						//JSR, JMP
+					} else {
+						//it would appear bit 6 needs to be set for it to be a valid instruction here
+						switch((*istream >> 3) & 0x7)
+						{
+						case 0:
+						case 1:
+							//TRAP
+							break;
+						case 2:
+							//LINK.w
+							break;
+						case 3:
+							//UNLNK
+							break;
+						case 4:
+						case 5:
+							//MOVE USP
+							break;
+						case 6:
+							switch(*istream & 0x7)
+							{
+							case 0:
+								decoded->op = M68K_RESET;
+								break;
+							case 1:
+								decoded->op = M68K_NOP;
+								break;
+							case 2:
+								decoded->op = M68K_STOP;
+								decoded->extra.size = OPSIZE_WORD;
+								decoded->src.addr_mode = MODE_IMMEDIATE;
+								decoded->src.params.u16 =*(++istream);
+								break;
+							case 3:
+								decoded->op = M68K_RTE;
+								break;
+							case 4:
+#ifdef M68010
+								decoded->op = M68K_RTD;
+								decoded->extra.size = OPSIZE_WORD;
+								decoded->src.addr_mode = MODE_IMMEDIATE;
+								decoded->src.params.u16 =*(++istream);
+#endif
+								break;
+							case 5:
+								decoded->op = M68K_RTS;
+								break;
+							case 6:
+								decoded->op = M68K_TRAPV;
+								break;
+							case 7:
+								decoded->op = M68K_RTR;
+								break;
+							}
+							break;
+						case 7:
+							//MOVEC
+							break;
+						}
+					}
+					break;
+				}
+			}
+		}
 		break;
 	case QUICK_ARITH_LOOP:
 		size = (*istream >> 6) & 3;
 		if (size == 0x3) {
 			//DBcc, TRAPcc or Scc
-			decoded->extra.cond = (*istream >> 0x8) & 0xF;
+			m68k_decode_cond(*istream, decoded);
 			switch ((*istream >> 3) & 0x7)
 			{
 			case 1: //DBcc
 				decoded->op = M68K_DBCC;
+				decoded->src.addr_mode = MODE_IMMEDIATE;
+				decoded->src.params.u16 = *(++istream);
 				decoded->dst.addr_mode = MODE_REG;
-				decoded->dst.regs.pri = *istream & 0x7;
+				decoded->dst.params.regs.pri = *istream & 0x7;
 				break;
 			case 7: //TRAPcc
+#ifdef M68020
 				decoded->op = M68K_TRAPCC;
-				decoded->src.addr_mode = MODE_PC_INDIRECT_ABS_IMMED;
-				decoded->src.regs.pri = MODE_IMMEDIATE;
+				decoded->src.addr_mode = MODE_IMMEDIATE;
 				//TODO: Figure out what to do with OPMODE and optional extention words
+#endif
 				break;
 			default: //Scc
 				decoded->op = M68K_SCC;
-				M68k_decode_op(*istream, &(decoded->dst));
+				istream = m68k_decode_op(istream, OPSIZE_BYTE, &(decoded->dst));
 				break;
 			}
 		} else {
 			//ADDQ, SUBQ
 			decoded->variant = VAR_QUICK;
 			decoded->extra.size = size;
-			decoded->src.addr_mode = MODE_PC_INDIRECT_ABS_IMMED;
-			decoded->src.regs.pri = MODE_IMMEDIATE;
-			immed = (*istream >> 9) & 0x7
+			decoded->src.addr_mode = MODE_IMMEDIATE;
+			istream = m68k_decode_op(istream, size, &(decoded->dst));
+			immed = m68K_reg_quick_field(*istream);
 			if (!immed) {
 				immed = 8;
 			}
 			switch (size)
 			{
-			case OPSIZE_BYTE;
+			case OPSIZE_BYTE:
 				decoded->src.params.u8 = immed;
 				break;
 			case OPSIZE_WORD:
 				decoded->src.params.u16 = immed;
 				break;
 			case OPSIZE_LONG:
-				decoded->src.params.u38 = immed;
+				decoded->src.params.u32 = immed;
 				break;
 			}
-			if (*istream & 0x10) {
+			if (*istream & 0x100) {
 				decoded->op = M68K_SUB;
 			} else {
 				decoded->op = M68K_ADD;
 			}
 		}
 		break;
+	case BRANCH:
+		m68k_decode_cond(*istream, decoded);
+		decoded->op = decoded->extra.cond == COND_FALSE ? M68K_BSR : M68K_BCC;
+		decoded->src.addr_mode = MODE_IMMEDIATE;
+		immed = *istream & 0xFF;
+		if (immed == 0) {
+			decoded->variant = VAR_WORD;
+			immed = *(++istream);
+			immed = sign_extend16(immed);
+		} else if (immed == 0xFF) {
+			decoded->variant = VAR_LONG;
+			immed = *(++istream) << 16;
+			immed |= *(++istream);
+		} else {
+			decoded->variant = VAR_BYTE;
+			immed = sign_extend8(immed);
+		}
+		decoded->src.params.u32 = immed;
+		break;
+	case MOVEQ:
+		decoded->op = M68K_MOVE;
+		decoded->variant = VAR_QUICK;
+		decoded->src.addr_mode = MODE_IMMEDIATE;
+		decoded->src.params.u32 = sign_extend8(*istream & 0xFF);
+		decoded->dst.addr_mode = MODE_REG;
+		decoded->dst.params.regs.pri = m68K_reg_quick_field(*istream);
+		immed = *istream & 0xFF;
+		break;
+	case OR_DIV_SBCD:
+		//TODO: Implement me
+		break;
+	case SUB_SUBX:
+		size = *istream >> 6 & 0x3;
+		decoded->op = M68K_SUB;
+		if (*istream & 0x100) {
+			//<ea> destination, SUBA.l or SUBX
+			if (*istream & 0x6) {
+				if (size == OPSIZE_INVALID) {
+					//SUBA.l
+					decoded->extra.size = OPSIZE_LONG;
+					decoded->dst.addr_mode = MODE_AREG;
+					istream = m68k_decode_op(istream, OPSIZE_LONG, &(decoded->src));
+				} else {
+					decoded->extra.size = size;
+					decoded->src.addr_mode = MODE_REG;
+					istream = m68k_decode_op(istream, size, &(decoded->dst));
+				}
+			} else {
+				//SUBX
+				decoded->op = M68K_SUBX;
+				decoded->extra.size = size;
+				istream = m68k_decode_op(istream, size, &(decoded->src));
+				decoded->dst.addr_mode = decoded->src.addr_mode;
+				decoded->dst.params.regs.pri = m68K_reg_quick_field(*istream);
+			}
+		} else {
+			if (size == OPSIZE_INVALID) {
+				//SUBA.w
+				decoded->extra.size = OPSIZE_WORD;
+				decoded->dst.addr_mode = MODE_AREG;
+			} else {
+				decoded->extra.size = size;
+				decoded->dst.addr_mode = MODE_REG;
+			}
+			decoded->dst.params.regs.pri = m68K_reg_quick_field(*istream);
+			istream = m68k_decode_op(istream, decoded->extra.size, &(decoded->src));
+		}
+		break;
+	case RESERVED:
+		//TODO: implement me
+		break;
+	case CMP_XOR:
+		size = *istream >> 6 & 0x3;
+		decoded->op = M68K_CMP;
+		if (*istream & 0x100) {
+			//CMPM or EOR
+			istream = m68k_decode_op(istream, size, &(decoded->dst));
+			if (decoded->src.addr_mode == MODE_AREG) {
+				//CMPM
+				decoded->src.addr_mode = decoded->dst.addr_mode = MODE_AREG_POSTINC;
+				decoded->src.params.regs.pri = decoded->dst.params.regs.pri;
+				decoded->dst.params.regs.pri = m68K_reg_quick_field(*istream);
+			} else {
+				//EOR
+				decoded->op = M68K_EOR;
+				decoded->extra.size = size;
+				decoded->src.addr_mode = MODE_REG;
+				decoded->src.params.regs.pri = m68K_reg_quick_field(*istream);
+			}
+		} else {
+			//CMP
+			decoded->extra.size = size;
+			decoded->dst.addr_mode = MODE_REG;
+			decoded->dst.params.regs.pri = m68K_reg_quick_field(*istream);
+			istream = m68k_decode_op(istream, size, &(decoded->src));
+		}
+		break;
+	case AND_MUL_ABCD_EXG:
+		//page 575 for summary
+		//EXG opmodes:
+		//01000 -data regs
+		//01001 -addr regs
+		//10001 -one of each
+		//AND opmodes:
+		//operand order bit + 2 size bits (00 - 10)
+		//no address register direct addressing
+		//data register direct not allowed when <ea> is the source (operand order bit of 1)
+		if (*istream & 0x100) {
+			if ((*istream & 0xC0) == 0xC0) {
+				decoded->op = M68K_MULS;
+				decoded->extra.size = OPSIZE_WORD;
+				istream = m68k_decode_op(istream, OPSIZE_WORD, &(decoded->src));
+			} else if(!(*istream & 0xF0)) {
+				decoded->op = M68K_ABCD;
+			} else if(!(*istream & 0x30)) {
+				decoded->op = M68K_EXG;
+				decoded->extra.size = OPSIZE_LONG;
+				decoded->src.params.regs.pri = m68K_reg_quick_field(*istream);
+				decoded->dst.params.regs.pri = *istream & 0x7;
+				if (*istream & 0x8) {
+					if (*istream & 0x80) {
+						decoded->src.addr_mode = MODE_REG;
+						decoded->dst.addr_mode = MODE_AREG;
+					} else {
+						decoded->src.addr_mode = decoded->dst.addr_mode = MODE_AREG;
+					}
+				} else {
+					decoded->src.addr_mode = decoded->dst.addr_mode = MODE_REG;
+				}
+			} else {
+				decoded->op = M68K_AND;
+				decoded->extra.size = (*istream >> 6);
+				decoded->dst.addr_mode = MODE_REG;
+				decoded->dst.params.regs.pri = m68K_reg_quick_field(*istream);
+				istream = m68k_decode_op(istream, decoded->extra.size, &(decoded->src));
+			}
+		} else {
+			if ((*istream & 0xC0) == 0xC0) {
+				decoded->op = M68K_MULU;
+				decoded->extra.size = OPSIZE_WORD;
+				istream = m68k_decode_op(istream, OPSIZE_WORD, &(decoded->src));
+			} else {
+				decoded->op = M68K_AND;
+				decoded->extra.size = (*istream >> 6);
+				decoded->src.addr_mode = MODE_REG;
+				decoded->src.params.regs.pri = m68K_reg_quick_field(*istream);
+				istream = m68k_decode_op(istream, decoded->extra.size, &(decoded->dst));
+			}
+		}
+		break;
+	case ADD_ADDX:
+		size = *istream >> 6 & 0x3;
+		decoded->op = M68K_ADD;
+		if (*istream & 0x100) {
+			//<ea> destination, ADDA.l or ADDX
+			if (*istream & 0x6) {
+				if (size == OPSIZE_INVALID) {
+					//ADDA.l
+					decoded->extra.size = OPSIZE_LONG;
+					decoded->dst.addr_mode = MODE_AREG;
+					istream = m68k_decode_op(istream, OPSIZE_LONG, &(decoded->src));
+				} else {
+					decoded->extra.size = size;
+					decoded->src.addr_mode = MODE_REG;
+					istream = m68k_decode_op(istream, size, &(decoded->dst));
+				}
+			} else {
+				//ADDX
+				decoded->op = M68K_ADDX;
+				//FIXME: Size is not technically correct
+				decoded->extra.size = size;
+				istream = m68k_decode_op(istream, size, &(decoded->src));
+				decoded->dst.addr_mode = decoded->src.addr_mode;
+				decoded->dst.params.regs.pri = m68K_reg_quick_field(*istream);
+			}
+		} else {
+			if (size == OPSIZE_INVALID) {
+				//ADDA.w
+				decoded->extra.size = OPSIZE_WORD;
+				decoded->dst.addr_mode = MODE_AREG;
+			} else {
+				decoded->extra.size = size;
+				decoded->dst.addr_mode = MODE_REG;
+			}
+			decoded->dst.params.regs.pri = m68K_reg_quick_field(*istream);
+			istream = m68k_decode_op(istream, decoded->extra.size, &(decoded->src));
+		}
+		break;
+	case SHIFT_ROTATE:
+		//TODO: Implement me
+		break;
+	case COPROC:
+		//TODO: Implement me
+		break;
+	}
+	return istream+1;
+}
+
+char * mnemonics[] = {
+	"abcd",
+	"add",
+	"addx",
+	"and",
+	"andi_ccr",
+	"andi_sr",
+	"asl",
+	"asr",
+	"bcc",
+	"bchg",
+	"bclr",
+	"bset",
+	"bsr",
+	"btst",
+	"chk",
+	"clr",
+	"cmp",
+	"dbcc",
+	"divs",
+	"divu",
+	"eor",
+	"eori_ccr",
+	"eori_sr",
+	"exg",
+	"ext",
+	"illegal",
+	"jmp",
+	"jsr",
+	"lea",
+	"link",
+	"lsl",
+	"lsr",
+	"move",
+	"move_ccr",
+	"move_from_sr",
+	"move_sr",
+	"move_usp",
+	"movem",
+	"movep",
+	"muls",
+	"mulu",
+	"nbcd",
+	"neg",
+	"negx",
+	"nop",
+	"not",
+	"or",
+	"ori_ccr",
+	"ori_sr",
+	"pea",
+	"reset",
+	"rol",
+	"ror",
+	"roxl",
+	"roxr",
+	"rte",
+	"rtr",
+	"rts",
+	"sbcd",
+	"scc",
+	"stop",
+	"sub",
+	"subx",
+	"swap",
+	"tas",
+	"trap",
+	"trapv",
+	"tst",
+	"unlnk",
+	"invalid"
+};
+
+char * cond_mnem[] = {
+	"ra",
+	"f",
+	"hi",
+	"ls",
+	"cc",
+	"cs",
+	"ne",
+	"eq",
+	"vc",
+	"vs",
+	"pl",
+	"mi",
+	"ge",
+	"lt",
+	"gt",
+	"le"
+};
+
+int m68K_disasm_op(m68k_op_info *decoded, uint8_t size, char *dst, int need_comma)
+{
+	char * c = need_comma ? "," : "";
+	switch(decoded->addr_mode)
+	{
+	case MODE_REG:
+		return sprintf(dst, "%s d%d", c, decoded->params.regs.pri);
+	case MODE_AREG:
+		return sprintf(dst, "%s a%d", c, decoded->params.regs.pri);
+	case MODE_AREG_INDIRECT:
+		return sprintf(dst, "%s (a%d)", c, decoded->params.regs.pri);
+	case MODE_AREG_POSTINC:
+		return sprintf(dst, "%s (a%d)+", c, decoded->params.regs.pri);
+	case MODE_AREG_PREDEC:
+		return sprintf(dst, "%s -(a%d)", c, decoded->params.regs.pri);
+	case MODE_IMMEDIATE:
+		return sprintf(dst, "%s #%d", c, size == OPSIZE_LONG ? decoded->params.u32 : (size == OPSIZE_WORD ? decoded->params.u16 : decoded->params.u8));
+	default:
+		return 0;
 	}
 }
+
+int m68k_disasm(m68kinst * decoded, char * dst)
+{
+	int ret,op1len;
+	uint8_t size;
+	if (decoded->op == M68K_BCC || decoded->op == M68K_DBCC || decoded->op == M68K_SCC) {
+		ret = strlen(mnemonics[decoded->op]) - 2;
+		memcpy(dst, mnemonics[decoded->op], ret);
+		dst[ret] = 0;
+		strcat(dst, cond_mnem[decoded->extra.cond]);
+		ret = strlen(dst);
+		size = decoded->op = M68K_BCC ? OPSIZE_LONG : OPSIZE_WORD;
+	} else if (decoded->op == M68K_BSR) {
+		size = OPSIZE_LONG;
+		ret = sprintf(dst, "bsr%s", decoded->variant == VAR_BYTE ? ".s" : "");
+	} else {
+		size = decoded->extra.size;
+		ret = sprintf(dst, "%s%s.%c", 
+				mnemonics[decoded->op], 
+				decoded->variant == VAR_QUICK ? "q" : "", 
+				decoded->extra.size == OPSIZE_BYTE ? 'b' : (size == OPSIZE_WORD ? 'w' : 'l'));
+	}
+	op1len = m68K_disasm_op(&(decoded->src), size, dst + ret, 0);
+	ret += op1len;
+	ret += m68K_disasm_op(&(decoded->dst), size, dst + ret, op1len);
+	return ret;
+}
+