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Support just-in-time (JIT) with system simulation
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This commit introduces "satp" field to the block structure in JIT mode
to ensure the block cache is replaced correctly.

The MOP fusion and T2C are disabled temporarily. Use the following
commands to boot Linux Kernel:

$ make ENABLE_SYSTEM=1 ENABLE_MOP_FUSION=0 ENABLE_JIT=1 ENABLE_T2C=0
$ ./build/rv32emu -k <image> -i <rootfs> -b <dtb>
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@vacantron
vacantron committed Dec 18, 2024
1 parent a4d3eb1 commit 73b1ba5
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Showing 11 changed files with 918 additions and 181 deletions.
2 changes: 1 addition & 1 deletion Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -188,7 +188,7 @@ ifeq ($(call has, JIT), 1)
ifeq ("$(CHECK_LLVM_LIBS)", "0")
OBJS_EXT += t2c.o
CFLAGS += -g $(shell $(LLVM_CONFIG) --cflags)
LDFLAGS += $(shell $(LLVM_CONFIG) --libs)
LDFLAGS += $(shell $(LLVM_CONFIG) --libfiles)
else
$(error No llvm-config-18 installed. Check llvm-config-18 installation in advance, or use "ENABLE_T2C=0" to disable tier-2 LLVM compiler)
endif
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3 changes: 3 additions & 0 deletions src/decode.h
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Original file line number Diff line number Diff line change
Expand Up @@ -288,6 +288,9 @@ typedef struct {
struct rv_insn *target[HISTORY_SIZE];
#else
uint32_t times[HISTORY_SIZE];
#if RV32_HAS(SYSTEM)
uint32_t satp[HISTORY_SIZE];
#endif
#endif
} branch_history_table_t;

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71 changes: 58 additions & 13 deletions src/emulate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,9 @@ extern struct target_ops gdbstub_ops;
#define IF_imm(i, v) (i->imm == v)

#if RV32_HAS(SYSTEM)
#if !RV32_HAS(JIT)
static bool need_clear_block_map = false;
#endif
static uint32_t reloc_enable_mmu_jalr_addr;
static bool reloc_enable_mmu = false;
bool need_retranslate = false;
Expand Down Expand Up @@ -704,6 +706,7 @@ static inline void remove_next_nth_ir(const riscv_t *rv,
* Strategies are being devised to increase the number of instructions that
* match the pattern, including possible instruction reordering.
*/
#if RV32_HAS(MOP_FUSION)
static void match_pattern(riscv_t *rv, block_t *block)
{
uint32_t i;
Expand Down Expand Up @@ -795,7 +798,7 @@ static void match_pattern(riscv_t *rv, block_t *block)
}
}
}

#endif
typedef struct {
bool is_constant[N_RV_REGS];
uint32_t const_val[N_RV_REGS];
Expand Down Expand Up @@ -838,12 +841,11 @@ static block_t *block_find_or_translate(riscv_t *rv)
block_t *next_blk = block_find(map, rv->PC);
#else
/* lookup the next block in the block cache */
/*
* The function "cache_get()" gets the cached block by the given "key (PC)".
* In system simulation, the returned block might be dropped because it is
* not the one from the current process (by checking SATP CSR register).
*/
block_t *next_blk = (block_t *) cache_get(rv->block_cache, rv->PC, true);
#if RV32_HAS(SYSTEM)
if (next_blk && next_blk->satp != rv->csr_satp)
next_blk = NULL;
#endif
#endif

if (next_blk)
Expand All @@ -861,12 +863,20 @@ static block_t *block_find_or_translate(riscv_t *rv)

block_translate(rv, next_blk);

#if RV32_HAS(JIT) && RV32_HAS(SYSTEM)
/*
* may be an ifetch fault which changes satp, Do not do this
* in "block_alloc()
*/
next_blk->satp = rv->csr_satp;
#endif

optimize_constant(rv, next_blk);

#if RV32_HAS(GDBSTUB)
if (likely(!rv->debug_mode))
#endif
#if RV32_HAS(MOP_FUSION)
/* macro operation fusion */
#if RV32_HAS(GDBSTUB) || RV32_HAS(MOP_FUSION)
match_pattern(rv, next_blk);
#endif

Expand All @@ -890,8 +900,6 @@ static block_t *block_find_or_translate(riscv_t *rv)
return next_blk;
}

list_del_init(&replaced_blk->list);

if (prev == replaced_blk)
prev = NULL;

Expand All @@ -910,6 +918,32 @@ static block_t *block_find_or_translate(riscv_t *rv)
if (untaken == replaced_blk_entry) {
entry->ir_tail->branch_untaken = NULL;
}

/* upadte JALR LUT */
if (!entry->ir_tail->branch_table)
continue;

#if 0
/*
* This branch lookup updating is unused since we get the PC from it and
* use function "cache_get()" achieve the branch prediction of T1C.
* However, if the structure "branch_table_t" is going to reference the
* block directly, this updating is nacessary to avoid to use the freed
* blocks.
*/
for (int i = 0; i < HISTORY_SIZE; i++) {
if (entry->ir_tail->branch_table->PC[i] == replaced_blk->pc_start) {
IIF(RV32_HAS(SYSTEM))
(if (entry->ir_tail->branch_table->satp[i] ==
replaced_blk->satp), )
{
entry->ir_tail->branch_table->PC[i] =
entry->ir_tail->branch_table->satp[i] =
entry->ir_tail->branch_table->times[i] = 0;
}
}
}
#endif
}

/* free IRs in replaced block */
Expand All @@ -923,6 +957,7 @@ static block_t *block_find_or_translate(riscv_t *rv)
mpool_free(rv->block_ir_mp, ir);
}

list_del_init(&replaced_blk->list);
mpool_free(rv->block_mp, replaced_blk);
#if RV32_HAS(T2C)
pthread_mutex_unlock(&rv->cache_lock);
Expand All @@ -941,6 +976,10 @@ static bool runtime_profiler(riscv_t *rv, block_t *block)
* we posit that our profiler could effectively identify hotspots using
* three key indicators.
*/
#if RV32_HAS(SYSTEM)
if (block->satp != rv->csr_satp)
return false;
#endif
uint32_t freq = cache_freq(rv->block_cache, block->pc_start);
/* To profile a block after chaining, it must first be executed. */
if (unlikely(freq >= 2 && block->has_loops))
Expand Down Expand Up @@ -1022,15 +1061,21 @@ void rv_step(void *arg)
block_t *block = block_find_or_translate(rv);
/* by now, a block should be available */
assert(block);
#if RV32_HAS(JIT) && RV32_HAS(SYSTEM)
assert(block->satp == rv->csr_satp);
#endif

/* After emulating the previous block, it is determined whether the
* branch is taken or not. The IR array of the current block is then
* assigned to either the branch_taken or branch_untaken pointer of
* the previous block.
*/

#if RV32_HAS(BLOCK_CHAINING)
if (prev) {
if (prev
#if RV32_HAS(JIT) && RV32_HAS(SYSTEM)
&& prev->satp == rv->csr_satp
#endif
) {
rv_insn_t *last_ir = prev->ir_tail;
/* chain block */
if (!insn_is_unconditional_branch(last_ir->opcode)) {
Expand All @@ -1048,7 +1093,7 @@ void rv_step(void *arg)
#endif
last_pc = rv->PC;
#if RV32_HAS(JIT)
#if RV32_HAS(T2C)
#if RV32_HAS(T2C) && !RV32_HAS(SYSTEM)
/* executed through the tier-2 JIT compiler */
if (block->hot2) {
((exec_t2c_func_t) block->func)(rv);
Expand Down
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