cpu: fix dec_16

When getting the register index, an incorrect shift was being
used. Fix the test case by correcting this.

Signed-off-by: Max Regan <mgregan2@gmail.com>

src/apps/cpu_integ_test.c

@@ -78,7 +78,6 @@ static void test_dec(const void *test_data)
 
 	g_assert_cmpint(lr35902_get_reg_16(&cpu, LR35902_REG_DE), ==, 0xffff);
 	
-	
 	free(src);
 }
 

src/cpu.c

@@ -734,10 +734,9 @@ static void ld_c_offset(struct lr35902_state *cpu, uint8_t instr)
 
 static void ld_hl_d16(struct lr35902_state *cpu, uint8_t inst)
 {
-	cpu->a = cpu->mem_read(cpu, cpu->hl++);
+	cpu->hl = _pop_stack_16(cpu);
 }
 
-
 static void inc_16(struct lr35902_state *cpu, uint8_t instr)
 {
 	uint8_t reg;
@@ -772,8 +771,11 @@ static void dec(struct lr35902_state *cpu, uint8_t instr)
 {
 	uint8_t reg = (instr >> 3) & 0x7;
 	uint8_t val = _get_reg_8(cpu, reg);
+	DEBUG_LOG("reg=%d, val=%d", reg, val);
  	val--;
+	DEBUG_LOG("val2=%d", val);
 	_set_reg_8(cpu, reg, val);
+	DEBUG_LOG("val3=%d", _get_reg_8(cpu, reg));
 
 	WRITE_BIT(cpu->f, LR35902_FLAG_BIT_Z, val == 0);
 	WRITE_BIT(cpu->f, LR35902_FLAG_BIT_N, 1);
@@ -782,7 +784,7 @@ static void dec(struct lr35902_state *cpu, uint8_t instr)
 
 static void dec_16(struct lr35902_state *cpu, uint8_t instr)
 {
-	uint8_t reg = (instr & 0xF0) >> 8;
+	uint8_t reg = (instr & 0xF0) >> 4;
 	uint16_t val;
 
 	switch (reg) {

src/cpu.h

@@ -37,7 +37,6 @@ typedef enum {
 	NUM_LR35902_REGS_8
 } lr35902_regs_8;
 
-
 typedef enum {
 	LR35902_INT_ON,
 	LR35902_INT_OFF,