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tcg/ppc: Revise goto_tb implementation 

Restrict the size of code_gen_buffer to 2GB on ppc64, which
lets us assert that everything is reachable with addis+addi
from tb_ret_addr.  This lets us use a max of 4 insns for goto_tb
instead of 7.

Emit the indirect branch portion of goto_tb up front, which
means we only have to update two insns to update any link.
With a 64-bit store, we can update the link atomically, which
may be required in future.

Signed-off-by: Richard Henderson <rth@twiddle.net>
stable-2.5
Richard Henderson 2015-10-02 22:25:28 +00:00
parent 70f897bdc4
commit 5bfd75a35c
2 changed files with 40 additions and 11 deletions
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49
tcg/ppc/tcg-target.c
View File

@ -1239,11 +1239,36 @@ static void tcg_out_brcond2 (TCGContext *s, const TCGArg *args,
void ppc_tb_set_jmp_target(uintptr_t jmp_addr, uintptr_t addr)
{
TCGContext s;
tcg_insn_unit i1, i2;
uint64_t pair;
intptr_t diff = addr - jmp_addr;
s.code_buf = s.code_ptr = (tcg_insn_unit *)jmp_addr;
tcg_out_b(&s, 0, (tcg_insn_unit *)addr);
flush_icache_range(jmp_addr, jmp_addr + tcg_current_code_size(&s));
if (in_range_b(diff)) {
i1 = B | (diff & 0x3fffffc);
i2 = NOP;
} else if (USE_REG_RA) {
intptr_t lo, hi;
diff = addr - (uintptr_t)tb_ret_addr;
lo = (int16_t)diff;
hi = (int32_t)(diff - lo);
assert(diff == hi + lo);
i1 = ADDIS | TAI(TCG_REG_TMP1, TCG_REG_RA, hi >> 16);
i2 = ADDI | TAI(TCG_REG_TMP1, TCG_REG_TMP1, lo);
} else {
assert(TCG_TARGET_REG_BITS == 32 || addr == (int32_t)addr);
i1 = ADDIS | TAI(TCG_REG_TMP1, 0, addr >> 16);
i2 = ORI | SAI(TCG_REG_TMP1, TCG_REG_TMP1, addr);
}
#ifdef HOST_WORDS_BIGENDIAN
pair = (uint64_t)i1 << 32 | i2;
#else
pair = (uint64_t)i2 << 32 | i1;
#endif
/* ??? __atomic_store_8, presuming there's some way to do that
for 32-bit, otherwise this is good enough for 64-bit. */
*(uint64_t *)jmp_addr = pair;
flush_icache_range(jmp_addr, jmp_addr + 8);
}
static void tcg_out_call(TCGContext *s, tcg_insn_unit *target)
@ -1869,14 +1894,16 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, const TCGArg *args,
tcg_out_b(s, 0, tb_ret_addr);
break;
case INDEX_op_goto_tb:
if (s->tb_jmp_offset) {
/* Direct jump method. */
s->tb_jmp_offset[args[0]] = tcg_current_code_size(s);
s->code_ptr += 7;
} else {
/* Indirect jump method. */
tcg_abort();
tcg_debug_assert(s->tb_jmp_offset);
/* Direct jump. Ensure the next insns are 8-byte aligned. */
if ((uintptr_t)s->code_ptr & 7) {
tcg_out32(s, NOP);
}
s->tb_jmp_offset[args[0]] = tcg_current_code_size(s);
/* To be replaced by either a branch+nop or a load into TMP1. */
s->code_ptr += 2;
tcg_out32(s, MTSPR | RS(TCG_REG_TMP1) | CTR);
tcg_out32(s, BCCTR | BO_ALWAYS);
s->tb_next_offset[args[0]] = tcg_current_code_size(s);
break;
case INDEX_op_br:

2
translate-all.c
View File

@ -468,6 +468,8 @@ static inline PageDesc *page_find(tb_page_addr_t index)
# define MAX_CODE_GEN_BUFFER_SIZE (2ul * 1024 * 1024 * 1024)
#elif defined(__sparc__)
# define MAX_CODE_GEN_BUFFER_SIZE (2ul * 1024 * 1024 * 1024)
#elif defined(__powerpc64__)
# define MAX_CODE_GEN_BUFFER_SIZE (2ul * 1024 * 1024 * 1024)
#elif defined(__aarch64__)
# define MAX_CODE_GEN_BUFFER_SIZE (128ul * 1024 * 1024)
#elif defined(__arm__)