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LR35902: Support PC-relative opcode decoding

This commit is contained in:
Vicki Pfau 2019-03-04 18:28:27 -08:00
parent c3ec7311e8
commit d6ac0dc6f5
3 changed files with 14 additions and 6 deletions
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1
CHANGES
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@ -22,6 +22,7 @@ Misc:
- Qt: Don't unload ROM immediately if it crashes
- Debugger: Add breakpoint and watchpoint listing
- Qt: Add missing HEVC NVENC option (fixes mgba.io/i/1323)
- LR35902: Support PC-relative opcode decoding
0.7.1: (2019-02-24)
Bugfixes:

3
include/mgba/internal/lr35902/decoder.h
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@ -86,6 +86,7 @@ enum {
LR35902_OP_FLAG_MEMORY = 2,
LR35902_OP_FLAG_INCREMENT = 4,
LR35902_OP_FLAG_DECREMENT = 8,
LR35902_OP_FLAG_RELATIVE = 16,
};
struct LR35902Operand {
@ -104,7 +105,7 @@ struct LR35902InstructionInfo {
};
size_t LR35902Decode(uint8_t opcode, struct LR35902InstructionInfo* info);
int LR35902Disassemble(struct LR35902InstructionInfo* info, char* buffer, int blen);
int LR35902Disassemble(struct LR35902InstructionInfo* info, uint16_t pc, char* buffer, int blen);
CXX_GUARD_END

16
src/lr35902/decoder.c
View File

@ -199,6 +199,7 @@ DEFINE_DECODER_LR35902(ADDSP, info->mnemonic = LR35902_MN_ADD; \
DEFINE_DECODER_LR35902(JR ## CONDITION_NAME, \
info->mnemonic = LR35902_MN_JR; \
info->condition = CONDITION; \
info->op1.flags = LR35902_OP_FLAG_RELATIVE; \
return 1;)
#define DEFINE_CALL_INSTRUCTION_LR35902(CONDITION_NAME, CONDITION) \
@ -497,7 +498,7 @@ static const char* _lr35902MnemonicStrings[] = {
};
static int _decodeOperand(struct LR35902Operand op, char* buffer, int blen) {
static int _decodeOperand(struct LR35902Operand op, uint16_t pc, char* buffer, int blen) {
int total = 0;
if (op.flags & LR35902_OP_FLAG_IMPLICIT) {
return 0;
@ -511,7 +512,12 @@ static int _decodeOperand(struct LR35902Operand op, char* buffer, int blen) {
int written = snprintf(buffer, blen - 1, "%s", _lr35902Registers[op.reg]);
ADVANCE(written);
} else {
int written = snprintf(buffer, blen - 1, "$%02X", op.immediate);
int written;
if (op.flags & LR35902_OP_FLAG_RELATIVE) {
written = snprintf(buffer, blen - 1, "$%04X", pc + (int8_t) op.immediate);
} else {
written = snprintf(buffer, blen - 1, "$%02X", op.immediate);
}
ADVANCE(written);
if (op.reg) {
strncpy(buffer, "+", blen - 1);
@ -533,7 +539,7 @@ static int _decodeOperand(struct LR35902Operand op, char* buffer, int blen) {
return total;
}
int LR35902Disassemble(struct LR35902InstructionInfo* info, char* buffer, int blen) {
int LR35902Disassemble(struct LR35902InstructionInfo* info, uint16_t pc, char* buffer, int blen) {
const char* mnemonic = _lr35902MnemonicStrings[info->mnemonic];
int written;
int total = 0;
@ -553,7 +559,7 @@ int LR35902Disassemble(struct LR35902InstructionInfo* info, char* buffer, int bl
}
if (info->op1.reg || info->op1.immediate || info->op2.reg || info->op2.immediate) {
written = _decodeOperand(info->op1, buffer, blen);
written = _decodeOperand(info->op1, pc, buffer, blen);
ADVANCE(written);
}
@ -562,7 +568,7 @@ int LR35902Disassemble(struct LR35902InstructionInfo* info, char* buffer, int bl
strncpy(buffer, ", ", blen - 1);
ADVANCE(2);
}
written = _decodeOperand(info->op2, buffer, blen);
written = _decodeOperand(info->op2, pc, buffer, blen);
ADVANCE(written);
}