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tcg: synchronize globals for ops with side effects

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Operations with side effects (in practice qemu_ld/st ops), only need to
synchronize globals to make sure the CPU state is consistent in case of
exception.

Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Aurelien Jarno 2012-10-09 21:53:08 +02:00
parent b202d41ee7
commit 3d5c5f876d
2 changed files with 26 additions and 11 deletions
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33
tcg/tcg.c
View File

@ -1407,9 +1407,8 @@ static void tcg_liveness_analysis(TCGContext *s)
/* if end of basic block, update */ /* if end of basic block, update */
if (def->flags & TCG_OPF_BB_END) { if (def->flags & TCG_OPF_BB_END) {
tcg_la_bb_end(s, dead_temps, mem_temps); tcg_la_bb_end(s, dead_temps, mem_temps);
} else if (def->flags & TCG_OPF_CALL_CLOBBER) { } else if (def->flags & TCG_OPF_SIDE_EFFECTS) {
/* globals should go back to memory */ /* globals should be synced to memory */
memset(dead_temps, 1, s->nb_globals);
memset(mem_temps, 1, s->nb_globals); memset(mem_temps, 1, s->nb_globals);
} }
@ -1670,6 +1669,23 @@ static void save_globals(TCGContext *s, TCGRegSet allocated_regs)
} }
} }
/* sync globals to their canonical location and assume they can be
read by the following code. 'allocated_regs' is used in case a
temporary registers needs to be allocated to store a constant. */
static void sync_globals(TCGContext *s, TCGRegSet allocated_regs)
{
int i;
for (i = 0; i < s->nb_globals; i++) {
#ifdef USE_LIVENESS_ANALYSIS
assert(s->temps[i].val_type != TEMP_VAL_REG || s->temps[i].fixed_reg ||
s->temps[i].mem_coherent);
#else
temp_sync(s, i, allocated_regs);
#endif
}
}
/* at the end of a basic block, we assume all temporaries are dead and /* at the end of a basic block, we assume all temporaries are dead and
all globals are stored at their canonical location. */ all globals are stored at their canonical location. */
static void tcg_reg_alloc_bb_end(TCGContext *s, TCGRegSet allocated_regs) static void tcg_reg_alloc_bb_end(TCGContext *s, TCGRegSet allocated_regs)
@ -1907,12 +1923,11 @@ static void tcg_reg_alloc_op(TCGContext *s,
tcg_reg_free(s, reg); tcg_reg_free(s, reg);
} }
} }
/* XXX: for load/store we could do that only for the slow path }
(i.e. when a memory callback is called) */ if (def->flags & TCG_OPF_SIDE_EFFECTS) {
/* sync globals if the op has side effects and might trigger
/* store globals and free associated registers (we assume the insn an exception. */
can modify any global. */ sync_globals(s, allocated_regs);
save_globals(s, allocated_regs);
} }
/* satisfy the output constraints */ /* satisfy the output constraints */

4
tcg/tcg.h
View File

@ -530,8 +530,8 @@ enum {
TCG_OPF_BB_END = 0x01, TCG_OPF_BB_END = 0x01,
/* Instruction clobbers call registers and potentially update globals. */ /* Instruction clobbers call registers and potentially update globals. */
TCG_OPF_CALL_CLOBBER = 0x02, TCG_OPF_CALL_CLOBBER = 0x02,
/* Instruction has side effects: it cannot be removed /* Instruction has side effects: it cannot be removed if its outputs
if its outputs are not used. */ are not used, and might trigger exceptions. */
TCG_OPF_SIDE_EFFECTS = 0x04, TCG_OPF_SIDE_EFFECTS = 0x04,
/* Instruction operands are 64-bits (otherwise 32-bits). */ /* Instruction operands are 64-bits (otherwise 32-bits). */
TCG_OPF_64BIT = 0x08, TCG_OPF_64BIT = 0x08,