From 25f49c5f1508ddf081ce89fa6bbfd87a51eea37b Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Tue, 27 Nov 2018 12:45:26 -0800 Subject: [PATCH] tcg: Record register preferences during liveness With these preferences, we can arrange for function call arguments to be computed into the proper registers instead of requiring extra moves. Reviewed-by: Emilio G. Cota Signed-off-by: Richard Henderson --- tcg/tcg.c | 197 ++++++++++++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 165 insertions(+), 32 deletions(-) diff --git a/tcg/tcg.c b/tcg/tcg.c index d40edb4f57..5f8c09b0b4 100644 --- a/tcg/tcg.c +++ b/tcg/tcg.c @@ -2365,6 +2365,21 @@ static void reachable_code_pass(TCGContext *s) #define IS_DEAD_ARG(n) (arg_life & (DEAD_ARG << (n))) #define NEED_SYNC_ARG(n) (arg_life & (SYNC_ARG << (n))) +/* For liveness_pass_1, the register preferences for a given temp. */ +static inline TCGRegSet *la_temp_pref(TCGTemp *ts) +{ + return ts->state_ptr; +} + +/* For liveness_pass_1, reset the preferences for a given temp to the + * maximal regset for its type. + */ +static inline void la_reset_pref(TCGTemp *ts) +{ + *la_temp_pref(ts) + = (ts->state == TS_DEAD ? 0 : tcg_target_available_regs[ts->type]); +} + /* liveness analysis: end of function: all temps are dead, and globals should be in memory. */ static void la_func_end(TCGContext *s, int ng, int nt) @@ -2373,9 +2388,11 @@ static void la_func_end(TCGContext *s, int ng, int nt) for (i = 0; i < ng; ++i) { s->temps[i].state = TS_DEAD | TS_MEM; + la_reset_pref(&s->temps[i]); } for (i = ng; i < nt; ++i) { s->temps[i].state = TS_DEAD; + la_reset_pref(&s->temps[i]); } } @@ -2387,11 +2404,13 @@ static void la_bb_end(TCGContext *s, int ng, int nt) for (i = 0; i < ng; ++i) { s->temps[i].state = TS_DEAD | TS_MEM; + la_reset_pref(&s->temps[i]); } for (i = ng; i < nt; ++i) { s->temps[i].state = (s->temps[i].temp_local ? TS_DEAD | TS_MEM : TS_DEAD); + la_reset_pref(&s->temps[i]); } } @@ -2401,7 +2420,12 @@ static void la_global_sync(TCGContext *s, int ng) int i; for (i = 0; i < ng; ++i) { - s->temps[i].state |= TS_MEM; + int state = s->temps[i].state; + s->temps[i].state = state | TS_MEM; + if (state == TS_DEAD) { + /* If the global was previously dead, reset prefs. */ + la_reset_pref(&s->temps[i]); + } } } @@ -2412,6 +2436,29 @@ static void la_global_kill(TCGContext *s, int ng) for (i = 0; i < ng; i++) { s->temps[i].state = TS_DEAD | TS_MEM; + la_reset_pref(&s->temps[i]); + } +} + +/* liveness analysis: note live globals crossing calls. */ +static void la_cross_call(TCGContext *s, int nt) +{ + TCGRegSet mask = ~tcg_target_call_clobber_regs; + int i; + + for (i = 0; i < nt; i++) { + TCGTemp *ts = &s->temps[i]; + if (!(ts->state & TS_DEAD)) { + TCGRegSet *pset = la_temp_pref(ts); + TCGRegSet set = *pset; + + set &= mask; + /* If the combination is not possible, restart. */ + if (set == 0) { + set = tcg_target_available_regs[ts->type] & mask; + } + *pset = set; + } } } @@ -2423,16 +2470,23 @@ static void liveness_pass_1(TCGContext *s) int nb_globals = s->nb_globals; int nb_temps = s->nb_temps; TCGOp *op, *op_prev; + TCGRegSet *prefs; + int i; + + prefs = tcg_malloc(sizeof(TCGRegSet) * nb_temps); + for (i = 0; i < nb_temps; ++i) { + s->temps[i].state_ptr = prefs + i; + } /* ??? Should be redundant with the exit_tb that ends the TB. */ la_func_end(s, nb_globals, nb_temps); QTAILQ_FOREACH_REVERSE_SAFE(op, &s->ops, TCGOpHead, link, op_prev) { - int i, nb_iargs, nb_oargs; + int nb_iargs, nb_oargs; TCGOpcode opc_new, opc_new2; bool have_opc_new2; TCGLifeData arg_life = 0; - TCGTemp *arg_ts; + TCGTemp *ts; TCGOpcode opc = op->opc; const TCGOpDef *def = &tcg_op_defs[opc]; @@ -2440,6 +2494,7 @@ static void liveness_pass_1(TCGContext *s) case INDEX_op_call: { int call_flags; + int nb_call_regs; nb_oargs = TCGOP_CALLO(op); nb_iargs = TCGOP_CALLI(op); @@ -2448,8 +2503,8 @@ static void liveness_pass_1(TCGContext *s) /* pure functions can be removed if their result is unused */ if (call_flags & TCG_CALL_NO_SIDE_EFFECTS) { for (i = 0; i < nb_oargs; i++) { - arg_ts = arg_temp(op->args[i]); - if (arg_ts->state != TS_DEAD) { + ts = arg_temp(op->args[i]); + if (ts->state != TS_DEAD) { goto do_not_remove_call; } } @@ -2457,16 +2512,20 @@ static void liveness_pass_1(TCGContext *s) } do_not_remove_call: - /* output args are dead */ + /* Output args are dead. */ for (i = 0; i < nb_oargs; i++) { - arg_ts = arg_temp(op->args[i]); - if (arg_ts->state & TS_DEAD) { + ts = arg_temp(op->args[i]); + if (ts->state & TS_DEAD) { arg_life |= DEAD_ARG << i; } - if (arg_ts->state & TS_MEM) { + if (ts->state & TS_MEM) { arg_life |= SYNC_ARG << i; } - arg_ts->state = TS_DEAD; + ts->state = TS_DEAD; + la_reset_pref(ts); + + /* Not used -- it will be tcg_target_call_oarg_regs[i]. */ + op->output_pref[i] = 0; } if (!(call_flags & (TCG_CALL_NO_WRITE_GLOBALS | @@ -2476,18 +2535,42 @@ static void liveness_pass_1(TCGContext *s) la_global_sync(s, nb_globals); } - /* record arguments that die in this helper */ + /* Record arguments that die in this helper. */ for (i = nb_oargs; i < nb_iargs + nb_oargs; i++) { - arg_ts = arg_temp(op->args[i]); - if (arg_ts && arg_ts->state & TS_DEAD) { + ts = arg_temp(op->args[i]); + if (ts && ts->state & TS_DEAD) { arg_life |= DEAD_ARG << i; } } - /* input arguments are live for preceding opcodes */ - for (i = nb_oargs; i < nb_iargs + nb_oargs; i++) { - arg_ts = arg_temp(op->args[i]); - if (arg_ts) { - arg_ts->state &= ~TS_DEAD; + + /* For all live registers, remove call-clobbered prefs. */ + la_cross_call(s, nb_temps); + + nb_call_regs = ARRAY_SIZE(tcg_target_call_iarg_regs); + + /* Input arguments are live for preceding opcodes. */ + for (i = 0; i < nb_iargs; i++) { + ts = arg_temp(op->args[i + nb_oargs]); + if (ts && ts->state & TS_DEAD) { + /* For those arguments that die, and will be allocated + * in registers, clear the register set for that arg, + * to be filled in below. For args that will be on + * the stack, reset to any available reg. + */ + *la_temp_pref(ts) + = (i < nb_call_regs ? 0 : + tcg_target_available_regs[ts->type]); + ts->state &= ~TS_DEAD; + } + } + + /* For each input argument, add its input register to prefs. + If a temp is used once, this produces a single set bit. */ + for (i = 0; i < MIN(nb_call_regs, nb_iargs); i++) { + ts = arg_temp(op->args[i + nb_oargs]); + if (ts) { + tcg_regset_set_reg(*la_temp_pref(ts), + tcg_target_call_iarg_regs[i]); } } } @@ -2496,7 +2579,9 @@ static void liveness_pass_1(TCGContext *s) break; case INDEX_op_discard: /* mark the temporary as dead */ - arg_temp(op->args[0])->state = TS_DEAD; + ts = arg_temp(op->args[0]); + ts->state = TS_DEAD; + la_reset_pref(ts); break; case INDEX_op_add2_i32: @@ -2600,43 +2685,91 @@ static void liveness_pass_1(TCGContext *s) break; do_not_remove: - /* output args are dead */ for (i = 0; i < nb_oargs; i++) { - arg_ts = arg_temp(op->args[i]); - if (arg_ts->state & TS_DEAD) { + ts = arg_temp(op->args[i]); + + /* Remember the preference of the uses that followed. */ + op->output_pref[i] = *la_temp_pref(ts); + + /* Output args are dead. */ + if (ts->state & TS_DEAD) { arg_life |= DEAD_ARG << i; } - if (arg_ts->state & TS_MEM) { + if (ts->state & TS_MEM) { arg_life |= SYNC_ARG << i; } - arg_ts->state = TS_DEAD; + ts->state = TS_DEAD; + la_reset_pref(ts); } - /* if end of basic block, update */ + /* If end of basic block, update. */ if (def->flags & TCG_OPF_BB_EXIT) { la_func_end(s, nb_globals, nb_temps); } else if (def->flags & TCG_OPF_BB_END) { la_bb_end(s, nb_globals, nb_temps); } else if (def->flags & TCG_OPF_SIDE_EFFECTS) { la_global_sync(s, nb_globals); + if (def->flags & TCG_OPF_CALL_CLOBBER) { + la_cross_call(s, nb_temps); + } } - /* record arguments that die in this opcode */ + /* Record arguments that die in this opcode. */ for (i = nb_oargs; i < nb_oargs + nb_iargs; i++) { - arg_ts = arg_temp(op->args[i]); - if (arg_ts->state & TS_DEAD) { + ts = arg_temp(op->args[i]); + if (ts->state & TS_DEAD) { arg_life |= DEAD_ARG << i; } } - /* input arguments are live for preceding opcodes */ + + /* Input arguments are live for preceding opcodes. */ for (i = nb_oargs; i < nb_oargs + nb_iargs; i++) { - arg_temp(op->args[i])->state &= ~TS_DEAD; + ts = arg_temp(op->args[i]); + if (ts->state & TS_DEAD) { + /* For operands that were dead, initially allow + all regs for the type. */ + *la_temp_pref(ts) = tcg_target_available_regs[ts->type]; + ts->state &= ~TS_DEAD; + } + } + + /* Incorporate constraints for this operand. */ + switch (opc) { + case INDEX_op_mov_i32: + case INDEX_op_mov_i64: + /* Note that these are TCG_OPF_NOT_PRESENT and do not + have proper constraints. That said, special case + moves to propagate preferences backward. */ + if (IS_DEAD_ARG(1)) { + *la_temp_pref(arg_temp(op->args[0])) + = *la_temp_pref(arg_temp(op->args[1])); + } + break; + + default: + for (i = nb_oargs; i < nb_oargs + nb_iargs; i++) { + const TCGArgConstraint *ct = &def->args_ct[i]; + TCGRegSet set, *pset; + + ts = arg_temp(op->args[i]); + pset = la_temp_pref(ts); + set = *pset; + + set &= ct->u.regs; + if (ct->ct & TCG_CT_IALIAS) { + set &= op->output_pref[ct->alias_index]; + } + /* If the combination is not possible, restart. */ + if (set == 0) { + set = ct->u.regs; + } + *pset = set; + } + break; } break; } op->life = arg_life; - op->output_pref[0] = 0; - op->output_pref[1] = 0; } } -- 2.11.4.GIT