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From: Richard Henderson <richard.henderson@linaro.org>
To: qemu-devel@nongnu.org
Cc: peter.maydell@linaro.org,
Taylor Simpson <tsimpson@quicinc.com>
Subject: [PULL 03/84] tcg: Merge two sequential labels
Date: Sun, 5 Mar 2023 16:38:33 -0800
Message-Id: <20230306003954.1866998-4-richard.henderson@linaro.org>
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Content-Type: text/plain; charset="utf-8"
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>
---
tcg/tcg.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 43 insertions(+), 1 deletion(-)
diff --git a/tcg/tcg.c b/tcg/tcg.c
index 0b93359d3c..cd8f356adb 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -2628,6 +2628,31 @@ TCGOp *tcg_op_insert_after(TCGContext *s, TCGOp *old=
_op,
return new_op;
}
=20
+static void move_label_uses(TCGLabel *to, TCGLabel *from)
+{
+ TCGLabelUse *u;
+
+ QSIMPLEQ_FOREACH(u, &from->branches, next) {
+ TCGOp *op =3D u->op;
+ switch (op->opc) {
+ case INDEX_op_br:
+ op->args[0] =3D label_arg(to);
+ break;
+ case INDEX_op_brcond_i32:
+ case INDEX_op_brcond_i64:
+ op->args[3] =3D label_arg(to);
+ break;
+ case INDEX_op_brcond2_i32:
+ op->args[5] =3D label_arg(to);
+ break;
+ default:
+ g_assert_not_reached();
+ }
+ }
+
+ QSIMPLEQ_CONCAT(&to->branches, &from->branches);
+}
+
/* Reachable analysis : remove unreachable code. */
static void __attribute__((noinline))
reachable_code_pass(TCGContext *s)
@@ -2643,6 +2668,24 @@ reachable_code_pass(TCGContext *s)
case INDEX_op_set_label:
label =3D arg_label(op->args[0]);
=20
+ /*
+ * Note that the first op in the TB is always a load,
+ * so there is always something before a label.
+ */
+ op_prev =3D 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 =3D=3D INDEX_op_set_label) {
+ move_label_uses(label, arg_label(op_prev->args[0]));
+ tcg_op_remove(s, op_prev);
+ op_prev =3D QTAILQ_PREV(op, link);
+ }
+
/*
* Optimization can fold conditional branches to 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 bra=
nch
* and label had not yet been removed.
*/
- op_prev =3D QTAILQ_PREV(op, link);
if (op_prev->opc =3D=3D INDEX_op_br &&
label =3D=3D arg_label(op_prev->args[0])) {
tcg_op_remove(s, op_prev);
--=20
2.34.1