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jit: Implement arm32 instruction decoding logic

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Introduces the core Arm32 decoder, including the instruction parsing
mechanism and an initial set of defined instructions.

Signed-off-by: Ronald Caesar <github43132@proton.me>
This commit is contained in:
Ronald Caesar 2025-10-19 00:33:42 -04:00
parent 2e2b5df20c
commit a0ed4382a5
No known key found for this signature in database
GPG key ID: 04307C401999C596
5 changed files with 308 additions and 337 deletions
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79
src/jit/decoder/arm32.cpp
View file

@ -7,17 +7,16 @@
namespace pound::jit::decoder
{
/* Increase value as more instructions get implemented */
#define INSTRUCTION_ARRAY_CAPACITY 4
arm32_decoder_t g_arm32_decoder = {};
#define INSTRUCTION_ARRAY_CAPACITY 261
#define HASH_TABLE_INVALID_INDEX 0xFFFF
/*
* ============================================================================
* Foward Declarations
* ============================================================================
*/
void arm32_add_instruction(arm32_decoder_t* decoder, const char* name, const char* bitstring, arm32_handler_fn handler);
void arm32_ADD_imm_handler(arm32_decoder_t* decoder, arm32_instruction_t instruction);
void arm32_add_instruction(arm32_decoder_t* decoder, const char* name, const char* bitstring);
void arm32_parse_bitstring(const char* bitstring, uint32_t* mask, uint32_t* expected);
void arm32_grow_instructions_array(arm32_decoder_t* decoder, size_t new_capacity);
@ -38,7 +37,7 @@ void arm32_init(pound::host::memory::arena_t allocator, arm32_decoder_t* decoder
/* Setup Instructions array.*/
size_t instructions_array_size = INSTRUCTION_ARRAY_CAPACITY * sizeof(arm32_instruction_info_t);
PVM_ASSERT(instructions_array_size <= decoder->allocator.capacity);
LOG_TRACE("Growing instructions array to %d bytes", instructions_array_size);
LOG_TRACE("Allocated %d bytes to instructions array", instructions_array_size);
void* new_ptr = pound::host::memory::arena_allocate(&decoder->allocator, instructions_array_size);
PVM_ASSERT(nullptr != new_ptr);
@ -47,12 +46,32 @@ void arm32_init(pound::host::memory::arena_t allocator, arm32_decoder_t* decoder
decoder->instruction_capacity = INSTRUCTION_ARRAY_CAPACITY;
/* Add all Arm32 instructions */
#define INST(fn, name, bitstring) arm32_add_instruction(decoder, name, bitstring, &arm32_##fn##_handler);
#define INST(fn, name, bitstring) arm32_add_instruction(decoder, name, bitstring);
#include "./arm32.inc"
#undef INST
}
void arm32_add_instruction(arm32_decoder_t* decoder, const char* name, const char* bitstring, arm32_handler_fn handler)
arm32_instruction_info_t* arm32_decode(arm32_decoder_t* decoder, uint32_t instruction)
{
for (size_t i = 0; i < decoder->instruction_count; ++i)
{
arm32_instruction_info_t* info = &decoder->instructions[i];
if ((instruction & info->mask) == info->expected)
{
LOG_TRACE("Instruction found for 0x%08X: %s", instruction, info->name);
return info;
}
}
PVM_ASSERT_MSG(false, "No instruction found for 0x%08X", instruction);
}
/*
* ============================================================================
* Private Functions
* ============================================================================
*/
void arm32_add_instruction(arm32_decoder_t* decoder, const char* name, const char* bitstring)
{
PVM_ASSERT(nullptr != decoder);
PVM_ASSERT(nullptr != decoder->allocator.data);
@ -60,44 +79,22 @@ void arm32_add_instruction(arm32_decoder_t* decoder, const char* name, const cha
PVM_ASSERT(nullptr != bitstring);
PVM_ASSERT(decoder->instruction_count < decoder->instruction_capacity);
arm32_opcode_t mask = 0;
arm32_opcode_t expected = 0;
uint32_t mask = 0;
uint32_t expected = 0;
arm32_parse_bitstring(bitstring, &mask, &expected);
arm32_instruction_info_t* info = &decoder->instructions[decoder->instruction_count];
PVM_ASSERT(nullptr != info);
info->name = name;
info->mask = mask;
info->expected = expected;
info->handler = handler;
/* Calculate priority based on number of fixed bits. */
info->priority = 0;
for (int i = 0; i < 32; ++i)
{
if ((mask >> i) & 1)
{
++info->priority;
}
}
++decoder->instruction_count;
LOG_TRACE("========================================");
LOG_TRACE("Instruction Registered: %s", info->name);
LOG_TRACE("Mask: 0x%08X", info->mask);
LOG_TRACE("Expected: 0x%08X", info->expected);
LOG_TRACE("Priority: %d", info->priority);
LOG_TRACE("========================================");
/* TODO(GloriousTacoo:jit): Add instruction to lookup table. */
}
void arm32_ADD_imm_handler(arm32_decoder_t* decoder, arm32_instruction_t instruction) {}
/*
* ============================================================================
* Private Functions
* ============================================================================
*/
void arm32_parse_bitstring(const char* bitstring, uint32_t* mask, uint32_t* expected)
{
@ -109,7 +106,7 @@ void arm32_parse_bitstring(const char* bitstring, uint32_t* mask, uint32_t* expe
*mask = 0;
*expected = 0;
uint8_t instruction_size_bits = 32;
for (int i = 0; (i < instruction_size_bits) && (bitstring[i] != '\0'); ++i)
for (unsigned int i = 0; (i < instruction_size_bits) && (bitstring[i] != '\0'); ++i)
{
uint32_t bit_position = 31 - i;
switch (bitstring[i])
@ -120,19 +117,9 @@ void arm32_parse_bitstring(const char* bitstring, uint32_t* mask, uint32_t* expe
case '1':
*mask |= (1U << bit_position);
*expected |= (1U << bit_position);
break;
case 'c':
case 'n':
case 'd':
case 'r':
case 'v':
case 's':
case 'S':
break;
default:
PVM_ASSERT_MSG(false, "Invalid bitstring character: %c", bitstring[i]);
break;
}
}
}
} // namespace pound::jit::decoder