Hi!
On 2021-03-17T00:24:55+0100, I wrote:
> Now, walking each function backwards (!), [...]
> I've now got a simple 'callback_op', which for '!is_lhs' looks at
> 'get_base_address ([op])', and if that 'var' is contained in the set of
> current candidates (initialized per containg 'bind's, which we enter
> first, even if walking a 'gimple_seq' backwards), removes that 'var' as a
> candidate for such optimization. (Plus some "details", of couse.) This
> seems to work fine, as far as I can tell. :-)
Is something like the attached "[WIP] 'walk_gimple_seq' backward" OK
conceptually? (For next development stage 1 and with all the TODOs
resolved, of course.)
The 'backward' flag cannot simply be a argument to 'walk_gimple_seq'
etc.: it needs to also be passed to 'walk_gimple_seq_mod' calls triggered
from inside 'walk_gimple_stmt'. Hence, I've put it into the state
'struct walk_stmt_info'.
Grüße
Thomas
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>From 48036d65cea6bb47c7d4eca3b4fea77e058f29e3 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <tho...@codesourcery.com>
Date: Mon, 15 Mar 2021 17:31:00 +0100
Subject: [PATCH] [WIP] 'walk_gimple_seq' backward
This seems to work -- for the one case where I'm using it...
---
gcc/doc/gimple.texi | 2 ++
gcc/gimple-walk.c | 15 ++++++++++++---
gcc/gimple-walk.h | 4 ++++
3 files changed, 18 insertions(+), 3 deletions(-)
diff --git a/gcc/doc/gimple.texi b/gcc/doc/gimple.texi
index 5e0fc2e0dc5..51fe0f2d715 100644
--- a/gcc/doc/gimple.texi
+++ b/gcc/doc/gimple.texi
@@ -2778,4 +2778,6 @@ calling @code{walk_gimple_stmt} on each one. @code{WI} is as in
@code{walk_gimple_stmt}. If @code{walk_gimple_stmt} returns non-@code{NULL}, the walk
is stopped and the value returned. Otherwise, all the statements
are walked and @code{NULL_TREE} returned.
+
+TODO update for forward vs. backward.
@end deftypefn
diff --git a/gcc/gimple-walk.c b/gcc/gimple-walk.c
index 9a761f32578..dfc2f0b4dbc 100644
--- a/gcc/gimple-walk.c
+++ b/gcc/gimple-walk.c
@@ -32,6 +32,8 @@ along with GCC; see the file COPYING3. If not see
/* Walk all the statements in the sequence *PSEQ calling walk_gimple_stmt
on each one. WI is as in walk_gimple_stmt.
+ TODO update for forward vs. backward.
+
If walk_gimple_stmt returns non-NULL, the walk is stopped, and the
value is stored in WI->CALLBACK_RESULT. Also, the statement that
produced the value is returned if this statement has not been
@@ -44,9 +46,10 @@ gimple *
walk_gimple_seq_mod (gimple_seq *pseq, walk_stmt_fn callback_stmt,
walk_tree_fn callback_op, struct walk_stmt_info *wi)
{
- gimple_stmt_iterator gsi;
+ bool forward = !(wi && wi->backward);
- for (gsi = gsi_start (*pseq); !gsi_end_p (gsi); )
+ gimple_stmt_iterator gsi = forward ? gsi_start (*pseq) : gsi_last (*pseq);
+ for (; !gsi_end_p (gsi); )
{
tree ret = walk_gimple_stmt (&gsi, callback_stmt, callback_op, wi);
if (ret)
@@ -60,7 +63,13 @@ walk_gimple_seq_mod (gimple_seq *pseq, walk_stmt_fn callback_stmt,
}
if (!wi->removed_stmt)
- gsi_next (&gsi);
+ {
+ if (forward)
+ gsi_next (&gsi);
+ else //TODO Correct?
+ gsi_prev (&gsi);
+ //TODO This could do with some unit testing, to make sure all the corner cases (removing first/last, for example) work correctly.
+ }
}
if (wi)
diff --git a/gcc/gimple-walk.h b/gcc/gimple-walk.h
index bdc7351f190..9590c63ba18 100644
--- a/gcc/gimple-walk.h
+++ b/gcc/gimple-walk.h
@@ -71,6 +71,10 @@ struct walk_stmt_info
/* True if we've removed the statement that was processed. */
BOOL_BITFIELD removed_stmt : 1;
+
+ /*TODO */
+ //TODO Only applicable for 'walk_gimple_seq'.
+ BOOL_BITFIELD backward : 1;
};
/* Callback for walk_gimple_stmt. Called for every statement found
--
2.17.1
