M include/mgba/internal/arm/emitter-thumb.h → include/mgba/internal/arm/emitter-thumb.h

@@ -50,8 +50,8 @@ DECLARE_INSTRUCTION_WITH_HIGH_THUMB(EMITTER, CMP3), \
 	DECLARE_INSTRUCTION_WITH_HIGH_THUMB(EMITTER, MOV3), \
 	DECLARE_INSTRUCTION_THUMB(EMITTER, BX), \
 	DECLARE_INSTRUCTION_THUMB(EMITTER, BX), \
-	DECLARE_INSTRUCTION_THUMB(EMITTER, ILL), \
-	DECLARE_INSTRUCTION_THUMB(EMITTER, ILL), \
+	MIN_V(DECLARE_INSTRUCTION_THUMB(EMITTER, BLX2), DECLARE_INSTRUCTION_THUMB(EMITTER, ILL), V >= 5), \
+	MIN_V(DECLARE_INSTRUCTION_THUMB(EMITTER, BLX2), DECLARE_INSTRUCTION_THUMB(EMITTER, ILL), V >= 5), \
 	DO_8(DO_4(DECLARE_INSTRUCTION_THUMB(EMITTER, LDR3))), \
 	DO_8(DECLARE_INSTRUCTION_THUMB(EMITTER, STR2)), \
 	DO_8(DECLARE_INSTRUCTION_THUMB(EMITTER, STRH2)), \

M src/arm/decoder-thumb.c → src/arm/decoder-thumb.c

@@ -290,6 +290,12 @@ info->operandFormat = ARM_OPERAND_REGISTER_1 | ARM_OPERAND_AFFECTED_1 |
 		ARM_OPERAND_REGISTER_2 | ARM_OPERAND_IMMEDIATE_3;
 	info->branchType = ARM_BRANCH_LINKED;)
 
+DEFINE_THUMB_DECODER(BLX2, BLX,
+	info->op1.reg = (opcode >> 3) & 0xF;
+	info->op2.reg = ARM_LR;
+	info->operandFormat = ARM_OPERAND_REGISTER_1 | ARM_OPERAND_REGISTER_2 | ARM_OPERAND_AFFECTED_2;
+	info->branchType = ARM_BRANCH_INDIRECT;)
+
 DEFINE_THUMB_DECODER(BX, BX,
 	info->op1.reg = (opcode >> 3) & 0xF;
 	info->operandFormat = ARM_OPERAND_REGISTER_1;

M src/arm/decoder.c → src/arm/decoder.c

@@ -393,6 +393,13 @@ case ARM_MN_BLX:
 		if (info->operandFormat & ARM_OPERAND_IMMEDIATE_1) {
 			written = _decodePCRelative(info->op1.immediate, pc, buffer, blen);
 			ADVANCE(written);
+		} else if (info->operandFormat & ARM_OPERAND_REGISTER_1) {
+			written = _decodeRegister(info->op1.reg, buffer, blen);
+			ADVANCE(written);
+			if (info->op1.reg > ARM_PC) {
+				written = _decodePSR(info->op1.psrBits, buffer, blen);
+				ADVANCE(written);
+			}
 		}
 		break;
 	default:

M src/arm/isa-thumb.c → src/arm/isa-thumb.c

@@ -404,6 +404,21 @@ } else {
 		ARM_WRITE_PC;
 	})
 
+DEFINE_INSTRUCTION_THUMB(BLX2,
+	int rm = (opcode >> 3) & 0xF;
+	_ARMSetMode(cpu, cpu->gprs[rm] & 0x00000001);
+	int misalign = 0;
+	if (rm == ARM_PC) {
+		misalign = cpu->gprs[rm] & 0x00000002;
+	}
+	cpu->gprs[ARM_LR] = cpu->gprs[ARM_PC] - 1;
+	cpu->gprs[ARM_PC] = (cpu->gprs[rm] & 0xFFFFFFFE) - misalign;
+	if (cpu->executionMode == MODE_THUMB) {
+		THUMB_WRITE_PC;
+	} else {
+		ARM_WRITE_PC;
+	})
+
 DEFINE_INSTRUCTION_THUMB(SWI, cpu->irqh.swi16(cpu, opcode & 0xFF))
 
 const ThumbInstruction _thumbv4Table[0x400] = {