Added the ability to disable the prefix byte.

Any instructions that either have a register size of
8 bits, use implied addressing, or branch can save a
byte by disabling the prefix byte.

It does this by checking if the first three bits are
all set to 1.
If true, then it will treat it as a prefix
byte, otherwise, it will treat it as an opcode.

1 files changed, 18 insertions, 4 deletions

diff --git a/opcode.c b/opcode.c
index 0bee207..4484466 100644
--- a/opcode.c
+++ b/opcode.c
@@ -12,8 +12,9 @@ void setps(struct sux *cpu, uint8_t thread) {
 void adc(struct sux *cpu, uint64_t adr, uint8_t thread, uint8_t regsize) {
 	uint64_t value;
 	value = (uint64_t)addr[adr];
-	if (regsize >= 2)
+	if (regsize >= 2) {
 		value += (uint64_t)addr[adr+1] << 8;
+	}
 	if (regsize >= 4) {
 		value += (uint64_t)addr[adr+2] << 16;
 		value += (uint64_t)addr[adr+3] << 24;
@@ -385,6 +386,7 @@ uint64_t absaddr(struct sux *cpu, uint8_t thread) {
 			| (uint64_t)addr[cpu->pc[thread]+6] << 48
 			| (uint64_t)addr[cpu->pc[thread]+7] << 56;
 	cpu->pc[thread]+=8;
+	ibcount+=8;
 	clk++;
 	return adr;
 }
@@ -395,7 +397,11 @@ uint32_t zeromtx(struct sux *cpu, uint8_t thread) {
 			| (uint32_t)addr[cpu->pc[thread]+2] << 16
 			| (uint32_t)addr[cpu->pc[thread]+3] << 24;
 	cpu->pc[thread]+=4;
-	clk++;
+	ibcount+=4;
+	if (ibcount > 8) {
+		clk++;
+		ibcount = 0;
+	}
 	return adr;
 }
 
@@ -406,7 +412,11 @@ uint32_t zeromx(struct sux *cpu, uint8_t thread) {
 			| (uint32_t)addr[cpu->pc[thread]+3] << 24;
 	adr += cpu->x[thread];
 	cpu->pc[thread]+=4;
-	clk++;
+	ibcount+=4;
+	if (ibcount > 8) {
+		clk++;
+		ibcount = 0;
+	}
 	return adr;
 }
 
@@ -417,6 +427,10 @@ uint32_t zeromy(struct sux *cpu, uint8_t thread) {
 			| (uint32_t)addr[cpu->pc[thread]+3] << 24;
 	adr += cpu->y[thread];
 	cpu->pc[thread]+=4;
-	clk++;
+	ibcount+=4;
+	if (ibcount > 8) {
+		clk++;
+		ibcount = 0;
+	}
 	return adr;
 }