From 6994d2404b8ddcb818202d84b77bdc389724fa65 Mon Sep 17 00:00:00 2001
From: notaz <notasas@gmail.com>
Date: Wed, 18 Dec 2024 01:28:49 +0200
Subject: [PATCH] drc: allow address 0 in thread mode

Otherwise the compile thread would spin endlessly.
Noticed it when another bug caused exec at address 0.
---
 libpcsxcore/new_dynarec/emu_if.c      | 32 +++++++++++++--------------
 libpcsxcore/new_dynarec/new_dynarec.h |  3 +--
 2 files changed, 17 insertions(+), 18 deletions(-)

diff --git a/libpcsxcore/new_dynarec/emu_if.c b/libpcsxcore/new_dynarec/emu_if.c
index 9ceca916..a9122c81 100644
--- a/libpcsxcore/new_dynarec/emu_if.c
+++ b/libpcsxcore/new_dynarec/emu_if.c
@@ -342,11 +342,10 @@ static void clear_local_cache(void)
 static noinline void ari64_execute_threaded_slow(struct psxRegisters *regs,
 	enum blockExecCaller block_caller)
 {
-	if (!ndrc_g.thread.busy) {
+	if (ndrc_g.thread.busy_addr == ~0u) {
 		memcpy(ndrc_smrv_regs, regs->GPR.r, sizeof(ndrc_smrv_regs));
 		slock_lock(ndrc_g.thread.lock);
-		ndrc_g.thread.addr = regs->pc;
-		ndrc_g.thread.busy = 1;
+		ndrc_g.thread.busy_addr = regs->pc;
 		slock_unlock(ndrc_g.thread.lock);
 		scond_signal(ndrc_g.thread.cond);
 	}
@@ -357,7 +356,7 @@ static noinline void ari64_execute_threaded_slow(struct psxRegisters *regs,
 	{
 		psxInt.ExecuteBlock(regs, block_caller);
 	}
-	while (!regs->stop && ndrc_g.thread.busy && block_caller == EXEC_CALLER_OTHER);
+	while (!regs->stop && ndrc_g.thread.busy_addr != ~0u && block_caller == EXEC_CALLER_OTHER);
 
 	psxInt.Notify(R3000ACPU_NOTIFY_BEFORE_SAVE, NULL);
 	//ari64_notify(R3000ACPU_NOTIFY_AFTER_LOAD, NULL);
@@ -372,8 +371,7 @@ static void ari64_execute_threaded_once(struct psxRegisters *regs,
 		*(void **)((char *)drc_local + LO_hash_table_ptr);
 	void *target;
 
-	if (likely(!ndrc_g.thread.busy)) {
-		ndrc_g.thread.addr = 0;
+	if (likely(ndrc_g.thread.busy_addr == ~0u)) {
 		target = ndrc_get_addr_ht_param(hash_table, regs->pc,
 				ndrc_cm_no_compile);
 		if (target) {
@@ -412,12 +410,12 @@ static void ari64_execute_threaded_block(struct psxRegisters *regs,
 
 static void ari64_thread_sync(void)
 {
-	if (!ndrc_g.thread.lock || !ndrc_g.thread.busy)
+	if (!ndrc_g.thread.lock || ndrc_g.thread.busy_addr == ~0u)
 		return;
 	for (;;) {
 		slock_lock(ndrc_g.thread.lock);
 		slock_unlock(ndrc_g.thread.lock);
-		if (!ndrc_g.thread.busy)
+		if (ndrc_g.thread.busy_addr == ~0)
 			break;
 		retro_sleep(0);
 	}
@@ -425,8 +423,8 @@ static void ari64_thread_sync(void)
 
 static int ari64_thread_check_range(unsigned int start, unsigned int end)
 {
-	u32 addr = ndrc_g.thread.addr;
-	if (!addr)
+	u32 addr = ndrc_g.thread.busy_addr;
+	if (addr == ~0u)
 		return 0;
 
 	addr &= 0x1fffffff;
@@ -451,16 +449,17 @@ static void ari64_compile_thread(void *unused)
 	slock_lock(ndrc_g.thread.lock);
 	while (!ndrc_g.thread.exit)
 	{
-		if (!ndrc_g.thread.busy)
+		addr = *(volatile unsigned int *)&ndrc_g.thread.busy_addr;
+		if (addr == ~0u)
 			scond_wait(ndrc_g.thread.cond, ndrc_g.thread.lock);
-		addr = ndrc_g.thread.addr;
-		if (!ndrc_g.thread.busy || !addr || ndrc_g.thread.exit)
+		addr = *(volatile unsigned int *)&ndrc_g.thread.busy_addr;
+		if (addr == ~0u || ndrc_g.thread.exit)
 			continue;
 
 		target = ndrc_get_addr_ht_param(hash_table, addr,
 				ndrc_cm_compile_in_thread);
 		//printf("c  %08x -> %p\n", addr, target);
-		ndrc_g.thread.busy = 0;
+		ndrc_g.thread.busy_addr = ~0u;
 	}
 	slock_unlock(ndrc_g.thread.lock);
 	(void)target;
@@ -490,7 +489,7 @@ static void ari64_thread_shutdown(void)
 		slock_free(ndrc_g.thread.lock);
 		ndrc_g.thread.lock = NULL;
 	}
-	ndrc_g.thread.busy = ndrc_g.thread.addr = 0;
+	ndrc_g.thread.busy_addr = ~0u;
 }
 
 static void ari64_thread_init(void)
@@ -514,7 +513,8 @@ static void ari64_thread_init(void)
 		return;
 
 	ari64_thread_shutdown();
-	ndrc_g.thread.busy = ndrc_g.thread.addr = ndrc_g.thread.exit = 0;
+	ndrc_g.thread.exit = 0;
+	ndrc_g.thread.busy_addr = ~0u;
 
 	if (enable) {
 		ndrc_g.thread.lock = slock_new();
diff --git a/libpcsxcore/new_dynarec/new_dynarec.h b/libpcsxcore/new_dynarec/new_dynarec.h
index 5d3057b7..0d3a6868 100644
--- a/libpcsxcore/new_dynarec/new_dynarec.h
+++ b/libpcsxcore/new_dynarec/new_dynarec.h
@@ -24,8 +24,7 @@ struct ndrc_globals
 		void *cond;
 		void *dirty_start;
 		void *dirty_end;
-		unsigned int addr;
-		int busy;
+		unsigned int busy_addr; // 0 is valid, ~0 == none
 		int exit;
 	} thread;
 };
-- 
2.39.5