mips: Embed constants from Thumb PC-relative LDR instructions in ROM

Formerly those effective constants would be reloaded from the ROM at
every access; now, they are emitted directly in native code.

Execution-wise, this saves 13 instructions minus those needed by the
constant load; code generation-wise, this saves 4 instructions minus
those needed by the constant load.

6 files changed, 51 insertions, 5 deletions

diff --git a/source/cpu_asm.c b/source/cpu_asm.c
index f2e34d1..b9f93d5 100644
--- a/source/cpu_asm.c
+++ b/source/cpu_asm.c
@@ -262,7 +262,7 @@ typedef struct
 extern void call_bios_hle(void* func);
 
 #define check_pc_region(pc)                                                   \
-  new_pc_region = (pc >> 15);                                                 \
+  new_pc_region = (pc) >> 15;                                                 \
   if(new_pc_region != pc_region)                                              \
   {                                                                           \
     pc_region = new_pc_region;                                                \
@@ -1892,8 +1892,10 @@ static void arm_flag_status(block_data_arm_type* block_data, uint32_t opcode)
                                                                               \
     case 0x48 ... 0x4F:                                                       \
       /* LDR r0..r7, [pc + imm] */                                            \
-      thumb_access_memory(load, imm, (((opcode >> 8) & 0xFF) - 0x48), 0, 0,   \
-       pc_relative, ((pc & ~2) + (imm << 2) + 4), u32);                       \
+      thumb_ldr_from_pc(((opcode >> 8) & 0xFF) - 0x48,                        \
+        ((pc & ~2) + (imm << 2) + 4), u32);                                   \
+      /*thumb_access_memory(load, imm, (((opcode >> 8) & 0xFF) - 0x48), 0, 0, \
+       pc_relative, ((pc & ~2) + (imm << 2) + 4), u32);*/                     \
       break;                                                                  \
                                                                               \
     case 0x50 ... 0x51:                                                       \
diff --git a/source/dstwo/gui.c b/source/dstwo/gui.c
index 5cd8550..84b8f54 100644
--- a/source/dstwo/gui.c
+++ b/source/dstwo/gui.c
@@ -2938,6 +2938,7 @@ const char* TextFramesRendered = "Frames rendered";
 #ifdef PERFORMANCE_IMPACTING_STATISTICS
 const char* TextARMOpcodes = "ARM opcodes decoded";
 const char* TextThumbOpcodes = "Thumb opcodes decoded";
+const char* TextThumbROMConstants = "Thumb ROM constants";
 const char* TextWrongAddressLines = "Memory accessors patched";
 #endif
 
@@ -2962,6 +2963,10 @@ static struct Entry ExecutionStats_ThumbOpcodes = {
 	ENTRY_DISPLAY(&TextThumbOpcodes, &Stats.ThumbOpcodesDecoded, TYPE_UINT64)
 };
 
+static struct Entry ExecutionStats_ThumbROMConstants = {
+	ENTRY_DISPLAY(&TextThumbROMConstants, &Stats.ThumbROMConstants, TYPE_UINT64)
+};
+
 static struct Entry ExecutionStats_WrongAddressLines = {
 	ENTRY_DISPLAY(&TextWrongAddressLines, &Stats.WrongAddressLineCount, TYPE_UINT32)
 };
@@ -2971,7 +2976,7 @@ struct Menu ExecutionStats = {
 	.Parent = &Debugging, .Title = &TextExecutionStats,
 	.Entries = { &Back, &ExecutionStats_BufferUnderruns, &ExecutionStats_FramesEmulated, &ExecutionStats_FramesRendered,
 #ifdef PERFORMANCE_IMPACTING_STATISTICS
-		&ExecutionStats_ARMOpcodes, &ExecutionStats_ThumbOpcodes, &ExecutionStats_WrongAddressLines,
+		&ExecutionStats_ARMOpcodes, &ExecutionStats_ThumbOpcodes, &ExecutionStats_ThumbROMConstants, &ExecutionStats_WrongAddressLines,
 #endif
 		NULL }
 };
diff --git a/source/mips/emit.h b/source/mips/emit.h
index d46678b..c6d8a9b 100644
--- a/source/mips/emit.h
+++ b/source/mips/emit.h
@@ -2306,6 +2306,37 @@ uint32_t execute_store_cpsr_body(uint32_t _cpsr, uint32_t store_mask, uint32_t a
   thumb_access_memory_##access_type(mem_type, reg_rd);                        \
 }                                                                             \
 
+#ifdef PERFORMANCE_IMPACTING_STATISTICS
+
+static inline void StatsAddThumbROMConstant(void)
+{
+	Stats.ThumbROMConstants++;
+}
+
+#else
+
+static inline void StatsAddThumbROMConstant(void) {}
+
+#endif /* PERFORMANCE_IMPACTING_STATISTICS */
+
+#define thumb_ldr_from_pc(reg_rd, offset, mem_type)                           \
+{                                                                             \
+  thumb_decode_imm();                                                         \
+  if ((offset) >= 0x08000000 && (offset) < 0x0E000000)                        \
+  {                                                                           \
+    StatsAddThumbROMConstant();                                               \
+    cycle_count += 2;                                                         \
+    check_pc_region(offset);                                                  \
+    generate_load_imm(arm_to_mips_reg[reg_rd],                                \
+      ADDRESS32(memory_map_read[pc_region], (offset) & 0x7FFF));              \
+  }                                                                           \
+  else                                                                        \
+  {                                                                           \
+    thumb_access_memory_generate_address_pc_relative(offset, 0,               \
+     0);                                                                      \
+    thumb_access_memory_load(mem_type, reg_rd);                               \
+  }                                                                           \
+}                                                                             \
 
 #define thumb_block_address_preadjust_no(base_reg)                            \
   mips_emit_addu(reg_a2, arm_to_mips_reg[base_reg], reg_zero)                 \
diff --git a/source/opendingux/gui.c b/source/opendingux/gui.c
index beffcdd..d123e77 100644
--- a/source/opendingux/gui.c
+++ b/source/opendingux/gui.c
@@ -1066,6 +1066,10 @@ static struct MenuEntry ExecutionMenu_ThumbOps = {
 	ENTRY_DISPLAY("Thumb opcodes decoded", &Stats.ThumbOpcodesDecoded, TYPE_UINT64)
 };
 
+static struct MenuEntry ExecutionMenu_ThumbROMConsts = {
+	ENTRY_DISPLAY("Thumb ROM constants", &Stats.ThumbROMConstants, TYPE_UINT64)
+};
+
 static struct MenuEntry ExecutionMenu_MemAccessors = {
 	ENTRY_DISPLAY("Memory accessors patched", &Stats.WrongAddressLineCount, TYPE_UINT32)
 };
@@ -1075,7 +1079,7 @@ static struct Menu ExecutionMenu = {
 	.Parent = &DebugMenu, .Title = "Execution statistics",
 	.Entries = { &ExecutionMenu_SoundUnderruns, &ExecutionMenu_FramesEmulated, &ExecutionMenu_FramesRendered
 #ifdef PERFORMANCE_IMPACTING_STATISTICS
-	, &ExecutionMenu_ARMOps, &ExecutionMenu_ThumbOps, &ExecutionMenu_MemAccessors
+	, &ExecutionMenu_ARMOps, &ExecutionMenu_ThumbOps, &ExecutionMenu_ThumbROMConsts, &ExecutionMenu_MemAccessors
 #endif
 	, NULL }
 };
diff --git a/source/stats.c b/source/stats.c
index f3e3b68..3bd4e2d 100644
--- a/source/stats.c
+++ b/source/stats.c
@@ -65,6 +65,7 @@ void StatsInitGame(void)
 #ifdef PERFORMANCE_IMPACTING_STATISTICS
 	Stats.ARMOpcodesDecoded = 0;
 	Stats.ThumbOpcodesDecoded = 0;
+	Stats.ThumbROMConstants = 0;
 	Stats.BlockReuseCount = 0;
 	Stats.BlockRecompilationCount = 0;
 	Stats.OpcodeReuseCount = 0;
diff --git a/source/stats.h b/source/stats.h
index 6632ec4..d0018a1 100644
--- a/source/stats.h
+++ b/source/stats.h
@@ -60,6 +60,9 @@ struct ReGBA_Stats {
 	 * scratch since the current game started running? */
 	uint64_t        ARMOpcodesDecoded;
 	uint64_t        ThumbOpcodesDecoded;
+	/* How many times have we met a Thumb PC-relative LDR instruction that
+	 * loads from the ROM? */
+	uint64_t        ThumbROMConstants;
 	/* How many times have we recompiled a block anew since the current
 	 * game started running? */
 	uint64_t        BlockRecompilationCount;