GBA: Disable Self Modifying Code detection

When the dynamic recompiler isn't used we don't need to detect SMC.

This saves 288KB of memory, giving us room for one more block of ROM and it makes it possible to now move a few more things to internal memory.

Author: ducalex

gbsp/components/gbsp-libretro/cpu.cpp

@@ -1454,8 +1454,8 @@ u16 oam_ram[512];
 u16 palette_ram[512];
 u16 palette_ram_converted[512];
 #ifndef RETRO_GO
-u8 ewram[1024 * 256 * 2];
-u8 iwram[1024 * 32 * 2];
+u8 ewram[(1024 * 256) << SMC_DETECTION];
+u8 iwram[(1024 * 32) << SMC_DETECTION];
 u8 vram[1024 * 96];
 u8 *memory_map_read[8 * 1024];
 #endif

gbsp/components/gbsp-libretro/gba_memory.c

@@ -665,7 +665,7 @@ u32 function_cc read_eeprom(void)
                                                                               \
     case 0x03:                                                                \
       /* internal work RAM */                                                 \
-      value = readaddress##type(iwram, (address & 0x7FFF) + 0x8000);          \
+      value = readaddress##type(iwram, (address & 0x7FFF) + (0x8000 * SMC_DETECTION));\
       break;                                                                  \
                                                                               \
     case 0x04:                                                                \
@@ -1418,7 +1418,7 @@ void function_cc write_gpio(u32 address, u32 value) {
                                                                               \
     case 0x03:                                                                \
       /* internal work RAM */                                                 \
-      address##type(iwram, (address & 0x7FFF) + 0x8000) = eswap##type(value); \
+      address##type(iwram, (address & 0x7FFF) + (0x8000 * SMC_DETECTION)) = eswap##type(value); \
       break;                                                                  \
                                                                               \
     case 0x04:                                                                \
@@ -1730,7 +1730,7 @@ const dma_region_type dma_region_map[17] =
   }                                                                           \
 
 #define dma_read_iwram(type, tfsize)                                          \
-  read_value = readaddress##tfsize(iwram + 0x8000, type##_ptr & 0x7FFF)       \
+  read_value = readaddress##tfsize(iwram + (0x8000 * SMC_DETECTION), type##_ptr & 0x7FFF) \
 
 #define dma_read_vram(type, tfsize) {                                         \
   u32 rdaddr = type##_ptr & 0x1FFFF;                                          \
@@ -1763,9 +1763,9 @@ const dma_region_type dma_region_map[17] =
   read_value = read_memory##tfsize(type##_ptr)                                \
 
 #define dma_write_iwram(type, tfsize)                                         \
-  address##tfsize(iwram + 0x8000, type##_ptr & 0x7FFF) =                      \
+  address##tfsize(iwram + (0x8000 * SMC_DETECTION), type##_ptr & 0x7FFF) =    \
                                           eswap##tfsize(read_value);          \
-  if (address##tfsize(iwram, type##_ptr & 0x7FFF))                            \
+  if (SMC_DETECTION && address##tfsize(iwram, type##_ptr & 0x7FFF))           \
     alerts |= CPU_ALERT_SMC;                                                  \
 
 #define dma_write_vram(type, tfsize) {                                        \
@@ -1788,7 +1788,7 @@ const dma_region_type dma_region_map[17] =
 
 #define dma_write_ewram(type, tfsize)                                         \
   address##tfsize(ewram, type##_ptr & 0x3FFFF) = eswap##tfsize(read_value);   \
-  if (address##tfsize(ewram, (type##_ptr & 0x3FFFF) + 0x40000))               \
+  if (SMC_DETECTION && address##tfsize(ewram, (type##_ptr & 0x3FFFF) + 0x40000)) \
     alerts |= CPU_ALERT_SMC;                                                  \
 
 #define print_line()                                                          \
@@ -2261,7 +2261,7 @@ void init_memory(void)
   map_region(read, 0x0000000, 0x1000000, 1, bios_rom);
   map_null(read, 0x1000000, 0x2000000);
   map_region(read, 0x2000000, 0x3000000, 8, ewram);
-  map_region(read, 0x3000000, 0x4000000, 1, &iwram[0x8000]);
+  map_region(read, 0x3000000, 0x4000000, 1, &iwram[0x8000 * SMC_DETECTION]);
   map_region(read, 0x4000000, 0x5000000, 1, io_registers);
   map_null(read, 0x5000000, 0x6000000);
   map_null(read, 0x6000000, 0x7000000);
@@ -2381,7 +2381,7 @@ bool memory_read_savestate(const u8 *src)
     return false;
 
   if (!(
-    bson_read_bytes(memdoc, "iwram", &iwram[0x8000], 0x8000) &&
+    bson_read_bytes(memdoc, "iwram", &iwram[0x8000 * SMC_DETECTION], 0x8000) &&
     bson_read_bytes(memdoc, "ewram", ewram, 0x40000) &&
     bson_read_bytes(memdoc, "vram", vram, sizeof(vram)) &&
     bson_read_bytes(memdoc, "oamram", oam_ram, sizeof(oam_ram)) &&
@@ -2443,7 +2443,7 @@ unsigned memory_write_savestate(u8 *dst)
   u32 rtc_data_array[2] = { (u32)rtc_data, (u32)(rtc_data >> 32) };
 
   bson_start_document(dst, "memory", wbptr);
-  bson_write_bytes(dst, "iwram", &iwram[0x8000], 0x8000);
+  bson_write_bytes(dst, "iwram", &iwram[0x8000 * SMC_DETECTION], 0x8000);
   bson_write_bytes(dst, "ewram", ewram, 0x40000);
   bson_write_bytes(dst, "vram", vram, sizeof(vram));
   bson_write_bytes(dst, "oamram", oam_ram, sizeof(oam_ram));

gbsp/components/gbsp-libretro/gba_memory.h

@@ -258,15 +258,23 @@ extern u32 oam_update;
 extern u32 gbc_sound_wave_update;
 extern dma_transfer_type dma[DMA_CHAN_CNT];
 
+// If we're not using the dynamic recompiler we don't need to detect SMC (Self Modifying Code)
+// So we can save 288KB of memory by effectively disabling the SMC check.
+#ifdef HAVE_DYNAREC
+#define SMC_DETECTION 1
+#else /* RETRO_GO */
+#define SMC_DETECTION 0
+#endif
+
 extern u16 palette_ram[512];
 extern u16 oam_ram[512];
 extern u16 palette_ram_converted[512];
 extern u16 io_registers[512];
 extern u8 vram[1024 * 96];
 extern u8 bios_rom[1024 * 16];
 // Double buffer used for SMC detection
-extern u8 ewram[1024 * 256 * 2];
-extern u8 iwram[1024 * 32 * 2];
+extern u8 ewram[(1024 * 256) << SMC_DETECTION];
+extern u8 iwram[(1024 * 32) << SMC_DETECTION];
 
 extern u8 *memory_map_read[8 * 1024];
 
@@ -336,8 +344,8 @@ typedef struct
   // TODO: Evaluate what is best left in internal memory for performance reasons (for the few that could fit)
   u8 vram[1024 * 96];
   u8 bios_rom[1024 * 16];
-  u8 ewram[1024 * 256 * 2];
-  u8 iwram[1024 * 32 * 2];
+  u8 ewram[(1024 * 256) << SMC_DETECTION];
+  u8 iwram[(1024 * 32) << SMC_DETECTION];
   u8 *memory_map_read[8 * 1024];
   u8 gamepak_backup[1024 * 128];
   // There's also stuff from video.cpp to consider: