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tcg: Improve register allocation for matching constraints 

Try harder to honor the output_pref.  When we're forced to allocate
a second register for the input, it does not need to use the input
constraint; that will be honored by the register we allocate for the
output and a move is already required.

Reviewed-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2018-11-27 20:21:31 -08:00
parent 69e3706d2b
commit d62816f2db
1 changed files with 24 additions and 12 deletions
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36
tcg/tcg.c
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@ -3213,6 +3213,8 @@ static void tcg_reg_alloc_op(TCGContext *s, const TCGOp *op)
/* satisfy input constraints */
for (k = 0; k < nb_iargs; k++) {
TCGRegSet i_preferred_regs, o_preferred_regs;
i = def->sorted_args[nb_oargs + k];
arg = op->args[i];
arg_ct = &def->args_ct[i];
@ -3223,17 +3225,18 @@ static void tcg_reg_alloc_op(TCGContext *s, const TCGOp *op)
/* constant is OK for instruction */
const_args[i] = 1;
new_args[i] = ts->val;
goto iarg_end;
continue;
}
temp_load(s, ts, arg_ct->u.regs, i_allocated_regs, 0);
i_preferred_regs = o_preferred_regs = 0;
if (arg_ct->ct & TCG_CT_IALIAS) {
o_preferred_regs = op->output_pref[arg_ct->alias_index];
if (ts->fixed_reg) {
/* if fixed register, we must allocate a new register
if the alias is not the same register */
if (arg != op->args[arg_ct->alias_index])
if (arg != op->args[arg_ct->alias_index]) {
goto allocate_in_reg;
}
} else {
/* if the input is aliased to an output and if it is
not dead after the instruction, we must allocate
@ -3241,33 +3244,42 @@ static void tcg_reg_alloc_op(TCGContext *s, const TCGOp *op)
if (!IS_DEAD_ARG(i)) {
goto allocate_in_reg;
}
/* check if the current register has already been allocated
for another input aliased to an output */
int k2, i2;
for (k2 = 0 ; k2 < k ; k2++) {
i2 = def->sorted_args[nb_oargs + k2];
if ((def->args_ct[i2].ct & TCG_CT_IALIAS) &&
(new_args[i2] == ts->reg)) {
goto allocate_in_reg;
if (ts->val_type == TEMP_VAL_REG) {
int k2, i2;
reg = ts->reg;
for (k2 = 0 ; k2 < k ; k2++) {
i2 = def->sorted_args[nb_oargs + k2];
if ((def->args_ct[i2].ct & TCG_CT_IALIAS) &&
reg == new_args[i2]) {
goto allocate_in_reg;
}
}
}
i_preferred_regs = o_preferred_regs;
}
}
temp_load(s, ts, arg_ct->u.regs, i_allocated_regs, i_preferred_regs);
reg = ts->reg;
if (tcg_regset_test_reg(arg_ct->u.regs, reg)) {
/* nothing to do : the constraint is satisfied */
} else {
allocate_in_reg:
/* allocate a new register matching the constraint
and move the temporary register into it */
temp_load(s, ts, tcg_target_available_regs[ts->type],
i_allocated_regs, 0);
reg = tcg_reg_alloc(s, arg_ct->u.regs, i_allocated_regs,
0, ts->indirect_base);
o_preferred_regs, ts->indirect_base);
tcg_out_mov(s, ts->type, reg, ts->reg);
}
new_args[i] = reg;
const_args[i] = 0;
tcg_regset_set_reg(i_allocated_regs, reg);
iarg_end: ;
}
/* mark dead temporaries and free the associated registers */