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tcg: Merge two sequential labels

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Remove the first label and redirect all uses to the second.

Tested-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2023-03-03 14:22:02 -08:00
parent f85b1fc4a0
commit 968f305e08
1 changed files with 43 additions and 1 deletions
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44
tcg/tcg.c
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@ -2628,6 +2628,31 @@ TCGOp *tcg_op_insert_after(TCGContext *s, TCGOp *old_op,
return new_op; return new_op;
} }
static void move_label_uses(TCGLabel *to, TCGLabel *from)
{
TCGLabelUse *u;
QSIMPLEQ_FOREACH(u, &from->branches, next) {
TCGOp *op = u->op;
switch (op->opc) {
case INDEX_op_br:
op->args[0] = label_arg(to);
break;
case INDEX_op_brcond_i32:
case INDEX_op_brcond_i64:
op->args[3] = label_arg(to);
break;
case INDEX_op_brcond2_i32:
op->args[5] = label_arg(to);
break;
default:
g_assert_not_reached();
}
}
QSIMPLEQ_CONCAT(&to->branches, &from->branches);
}
/* Reachable analysis : remove unreachable code. */ /* Reachable analysis : remove unreachable code. */
static void __attribute__((noinline)) static void __attribute__((noinline))
reachable_code_pass(TCGContext *s) reachable_code_pass(TCGContext *s)
@ -2643,6 +2668,24 @@ reachable_code_pass(TCGContext *s)
case INDEX_op_set_label: case INDEX_op_set_label:
label = arg_label(op->args[0]); label = arg_label(op->args[0]);
/*
* Note that the first op in the TB is always a load,
* so there is always something before a label.
*/
op_prev = QTAILQ_PREV(op, link);
/*
* If we find two sequential labels, move all branches to
* reference the second label and remove the first label.
* Do this before branch to next optimization, so that the
* middle label is out of the way.
*/
if (op_prev->opc == INDEX_op_set_label) {
move_label_uses(label, arg_label(op_prev->args[0]));
tcg_op_remove(s, op_prev);
op_prev = QTAILQ_PREV(op, link);
}
/* /*
* Optimization can fold conditional branches to unconditional. * Optimization can fold conditional branches to unconditional.
* If we find a label which is preceded by an unconditional * If we find a label which is preceded by an unconditional
@ -2650,7 +2693,6 @@ reachable_code_pass(TCGContext *s)
* processing the branch because any dead code between the branch * processing the branch because any dead code between the branch
* and label had not yet been removed. * and label had not yet been removed.
*/ */
op_prev = QTAILQ_PREV(op, link);
if (op_prev->opc == INDEX_op_br && if (op_prev->opc == INDEX_op_br &&
label == arg_label(op_prev->args[0])) { label == arg_label(op_prev->args[0])) {
tcg_op_remove(s, op_prev); tcg_op_remove(s, op_prev);