Merge pull request #29 from Sonic-Amiga/cpu-fixes-from-phire

Cpu fixes from phire

cpu6.c

@@ -530,7 +530,7 @@ static int block_op(int inst)
 		return 0;
 	default:
 		fprintf(stderr, "%04X: Unknown block xfer %02X\n", cpu6_pc(), op);
-		return 0;
+		exit(1);
 	}
 }
 
@@ -563,7 +563,6 @@ static int bignum_sub(int a_len, int b_len, uint64_t a_addr, uint16_t b_addr, in
 		fprintf(stderr, "unsupported SUBBIG at %04X\n", exec_pc);
 		exit(-1);
 	}
-	int a_idx = b_len - a_len; // might be negative
 
 	// For debugging
 	uint64_t result_big = 0;
@@ -1259,6 +1258,46 @@ static uint16_t rlc16(uint16_t a, uint16_t count)
 	return r;
 }
 
+static int mul16(unsigned dsta, unsigned a, unsigned b)
+{
+	uint32_t r = (uint32_t)a * (uint32_t)b;
+	unsigned expected_sign = (a ^ b) & 0x8000;
+	unsigned sign = r & 0x8000;
+
+	mmu_mem_write16(dsta, r & 0xffff);
+
+	// These flags are a total guess
+	alu_out &= ~(ALU_F | ALU_M | ALU_V);
+	if (sign)
+		alu_out |= ALU_M;
+	if ((r & 0xffff) == 0)
+		alu_out |= ALU_V;
+	if (sign != expected_sign || r > 0xffff)
+		alu_out |= ALU_F;
+
+	return 0;
+}
+
+static int div16(unsigned dsta, unsigned a, unsigned b)
+{
+	uint32_t r = (uint32_t)a / (uint32_t)b;
+	unsigned expected_sign = (a ^ b) & 0x8000;
+	unsigned sign = r & 0x8000;
+
+	mmu_mem_write16(dsta, r & 0xffff);
+
+	// These flags are a total guess
+	alu_out &= ~(ALU_F | ALU_M | ALU_V);
+	if (sign)
+		alu_out |= ALU_M;
+	if ((r & 0xffff) == 0)
+		alu_out |= ALU_V;
+	if (sign != expected_sign || r > 0xffff)
+		alu_out |= ALU_F;
+
+	return 0;
+}
+
 static int add16(unsigned dsta, unsigned a, unsigned b)
 {
 	mmu_mem_write16(dsta, a + b);
@@ -1390,6 +1429,7 @@ static uint16_t decode_address(unsigned size, unsigned mode)
 	case 7:
 		fprintf(stderr, "unknown address indexing %X at %04X\n",
 			mode, exec_pc);
+		exit(1);
 		break;
 	default:
 		/* indexed off a register */
@@ -1594,7 +1634,9 @@ static int low_op(void)
 			new_pc = regpair_read(X);
 			{
 				uint8_t byte = popbyte();
-				alu_out = byte & (ALU_L | ALU_F | ALU_M | ALU_V);
+				// JSYS might have saved the flags, but RSYS doesn't restore them
+				// Syscalls sometimes return results as flags
+
 				/* We flip MMU context after all the POP cases */
 				cpu_mmu = byte & 0x07;
 			}
@@ -1670,6 +1712,7 @@ static int dma_op(void)
 	default:
 		fprintf(stderr, "Unknown DMA operations 2F%02X at %04X\n",
 			op, exec_pc);
+		exit(1);
 		break;
 	}
 	return 0;
@@ -2106,6 +2149,7 @@ static int alu4x_op(void)
 	case 0x4F:		/* unused */
 		fprintf(stderr, "Unknown ALU4 op %02X at %04X\n", op,
 			exec_pc);
+		exit(1);
 		return 0;
 	default:
 		fprintf(stderr, "internal error alu4\n");
@@ -2182,6 +2226,7 @@ static int alu5x_op(void)
 	case 0x57:		/* unused */
 		fprintf(stderr, "Unknown ALU5 op %02X at %04X\n", op,
 			exec_pc);
+		exit(1);
 		return 0;
 	case 0x58:
 		return add16(dsta, a, b);
@@ -2206,6 +2251,51 @@ static int alu5x_op(void)
 	}
 }
 
+static int muldiv_op() {
+
+	unsigned src, dst;
+	uint16_t addr;
+	uint16_t a; // First argument isn't always dst anymore.
+	uint16_t b;
+	uint16_t dsta;
+
+	// This is the same as alu5x
+
+	dst = fetch();
+	src = dst >> 4;
+	b = regpair_read(src & 0x0E);
+	dsta = regpair_addr(dst & 0x0E);
+	a = regpair_read(dst & 0XE);
+	switch(dst & 0x11) {
+	case 0x00: // dst_reg <- src_reg
+		break;
+	case 0x01: // dst_reg <- src_reg OP (direct)
+				// mov takes (direct)
+		addr = fetch16();
+		b = mmu_mem_read16(addr);
+		break;
+	case 0x10: // dst_reg <- src_reg OP literal
+				// mov takes literal
+		b = fetch16();
+		break;
+	case 0x11: // dst_reg <- (src_reg + disp16) OP dst_reg
+				// mov takes (src_reg + disp16)
+		addr = fetch16() + b;
+		b = a;
+		a = mmu_mem_read16(addr);
+		break;
+	}
+
+	switch (op) {
+	case 0x77: // 16bit Multiply
+		return mul16(dsta, a, b);
+	case 0x78: // 16bit Divide
+		return div16(dsta, a, b);
+	}
+	fprintf(stderr, "Unknown MULDIV op %02X at %04X\n", op, exec_pc);
+	exit(1);
+}
+
 /* It's not entirely clear what these instructions are for
  * they set Level 1's AH to 0 and -1
  *
@@ -2278,9 +2368,9 @@ void cpu_deassert_irq(unsigned ipl) {
 
 unsigned cpu6_execute_one(unsigned trace)
 {
+	cpu6_interrupt(trace);
 	exec_pc = pc;
 
-	cpu6_interrupt(trace);
 	if (trace)
 		fprintf(stderr, "CPU %04X: ", pc);
 	op = fetch();
@@ -2316,6 +2406,8 @@ unsigned cpu6_execute_one(unsigned trace)
 		return block_op(0x67);
 	if (op < 0x70)
 		return x_op();
+	if (op == 0x77 || op == 0x78)
+		return muldiv_op();
 	if (op < 0x80)
 		return jump_op();
 	if (op == 0xb6 || op == 0xc6)