From 13877785aa812501843ea8260016f292833fdc45 Mon Sep 17 00:00:00 2001
From: Nathaniel Walizer <robots.are.love@gmail.com>
Date: Sun, 22 Dec 2024 19:40:11 -0800
Subject: [PATCH] Define HCF feature (tight loop detection); debug fixup

---
 e6502.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/e6502.c b/e6502.c
index be977b8..c65451e 100644
--- a/e6502.c
+++ b/e6502.c
@@ -207,6 +207,7 @@ static inline void eor(e6502_Core *core, e6502_Address adr) {
 }
 
 static inline void asl(e6502_Core *core, e6502_Address adr) {
+    // TODO: Emulate double-read or double-write
     uint8_t val = e6502_adr_r8(core, adr);
     core->registers.P &= ~(e6502_Status_C |
                            e6502_Status_Z |
@@ -231,6 +232,7 @@ static inline void asl_a(e6502_Core *core, e6502_Address adr) {
 }
 
 static inline void lsr(e6502_Core *core, e6502_Address adr) {
+    // TODO: Emulate double-read or double-write
     uint8_t val = e6502_adr_r8(core, adr);
     core->registers.P &= ~(e6502_Status_C |
                            e6502_Status_Z |
@@ -255,6 +257,7 @@ static inline void lsr_a(e6502_Core *core, e6502_Address adr) {
 }
 
 static inline void rol(e6502_Core *core, e6502_Address adr) {
+    // TODO: Emulate double-read or double-write
     uint8_t val = e6502_adr_r8(core, adr);
     uint8_t new_c = (val & 0x80) ? e6502_Status_C : 0;
     val <<= 1;
@@ -283,6 +286,7 @@ static inline void rol_a(e6502_Core *core, e6502_Address adr) {
 }
 
 static inline void ror(e6502_Core *core, e6502_Address adr) {
+    // TODO: Emulate double-read or double-write
     uint8_t val = e6502_adr_r8(core, adr);
     uint8_t new_c = (val & e6502_Status_C);
     val >>= 1;
@@ -509,6 +513,7 @@ static inline void sbc(e6502_Core *core, e6502_Address adr) {
 }
 
 static inline void inc(e6502_Core *core, e6502_Address adr) {
+    // TODO: Emulate double-read or double-write
     uint8_t val = e6502_adr_r8(core, adr) + 1;
     core->registers.P &= ~(e6502_Status_Z | e6502_Status_N);
     core->registers.P |= (val & e6502_Status_N);
@@ -533,6 +538,7 @@ static inline void iny(e6502_Core *core, e6502_Address) {
 }
 
 static inline void dec(e6502_Core *core, e6502_Address adr) {
+    // TODO: Emulate double-read or double-write
     uint8_t val = e6502_adr_r8(core, adr) - 1;
     core->registers.P &= ~(e6502_Status_Z | e6502_Status_N);
     core->registers.P |= (val & e6502_Status_N);
@@ -892,7 +898,7 @@ int e6502_dump_instr(e6502_Core* core, e6502_Mem_Addr addr,
 */
 
 #ifdef E6502_DEBUG
-int e6502_dump_regs(e6502_Core* core, FILE* file) {
+void e6502_dump_regs(e6502_Core* core, FILE* file) {
     fprintf(file, "S:%02x A:%02x X:%02x Y:%02x P:%02x\n",
             core->registers.S, core->registers.A,
             core->registers.X, core->registers.Y,
@@ -930,18 +936,21 @@ int e6502_run(e6502_Core* core,
     int end = start + remaining;
     int last_pc = -1;
     while ((instructions ? i_count : core->cycle) < end) {
+#ifdef E6502_HCF
         if (core->registers.PC == last_pc) {
             // Trapped.
             status = -2;
             break;
         }
+#endif
         last_pc = core->registers.PC;
+        (void)last_pc;
         uint8_t opcode = e6502_r8(core, core->registers.PC);
         const e6502_Instruction* instr =
                 &e6502_instructions[opcode];
         if (!instr->operator) {
 #ifdef E6502_DEBUG
-            fprintf(stdout, "$%04x: %02x\n", last_pc, opcode);
+            fprintf(stdout, "$%04x: $%02x\n", last_pc, opcode);
 #endif
             status = -1;
             break;