93 lines
3.1 KiB
Diff
93 lines
3.1 KiB
Diff
From c0aaf329d9c547b249ac120a8d1995d8546a1edb Mon Sep 17 00:00:00 2001
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From: Richard Sandiford <richard.sandiford@arm.com>
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Date: Sat, 11 Nov 2023 17:28:57 +0000
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Subject: [PATCH 038/157] [Backport][SME] mode-switching: Tweak entry/exit
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handling
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Reference: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=e59ec35276599805cdc6c3979d8a167b027d286e
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An entity isn't transparent in a block that requires a specific mode.
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optimize_mode_switching took that into account for normal insns,
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but didn't for the exit block. Later patches misbehaved because
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of this.
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In contrast, an entity was correctly marked as non-transparent
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in the entry block, but the reasoning seemed a bit convoluted.
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It also referred to a function that no longer exists.
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Since KILL = ~TRANSP, the entity is by definition not transparent
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in a block that defines the entity, so I think we can make it so
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without comment.
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Finally, the exit handling was nested in the entry handling,
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but that doesn't seem necessary. A target could say that an
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entity is undefined on entry but must be defined on return,
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on a "be liberal in what you accept, be conservative in what
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you do" principle.
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gcc/
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* mode-switching.cc (optimize_mode_switching): Mark the exit
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block as nontransparent if it requires a specific mode.
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Handle the entry and exit mode as sibling rather than nested
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concepts. Remove outdated comment.
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---
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gcc/mode-switching.cc | 34 +++++++++++++++-------------------
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1 file changed, 15 insertions(+), 19 deletions(-)
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diff --git a/gcc/mode-switching.cc b/gcc/mode-switching.cc
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index 4d2b9e284..4761c2ff0 100644
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--- a/gcc/mode-switching.cc
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+++ b/gcc/mode-switching.cc
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@@ -649,34 +649,30 @@ optimize_mode_switching (void)
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}
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if (targetm.mode_switching.entry && targetm.mode_switching.exit)
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{
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- int mode = targetm.mode_switching.entry (e);
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-
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info[post_entry->index].mode_out =
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info[post_entry->index].mode_in = no_mode;
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- if (pre_exit)
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- {
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- info[pre_exit->index].mode_out =
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- info[pre_exit->index].mode_in = no_mode;
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- }
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+ int mode = targetm.mode_switching.entry (e);
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if (mode != no_mode)
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{
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- bb = post_entry;
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-
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- /* By always making this nontransparent, we save
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- an extra check in make_preds_opaque. We also
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- need this to avoid confusing pre_edge_lcm when
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- antic is cleared but transp and comp are set. */
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- bitmap_clear_bit (transp_all, bb->index);
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-
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/* Insert a fake computing definition of MODE into entry
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blocks which compute no mode. This represents the mode on
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entry. */
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- info[bb->index].computing = mode;
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+ info[post_entry->index].computing = mode;
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+ bitmap_clear_bit (transp_all, post_entry->index);
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+ }
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- if (pre_exit)
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- info[pre_exit->index].seginfo->mode =
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- targetm.mode_switching.exit (e);
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+ if (pre_exit)
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+ {
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+ info[pre_exit->index].mode_out =
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+ info[pre_exit->index].mode_in = no_mode;
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+
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+ int mode = targetm.mode_switching.exit (e);
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+ if (mode != no_mode)
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+ {
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+ info[pre_exit->index].seginfo->mode = mode;
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+ bitmap_clear_bit (transp_all, pre_exit->index);
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+ }
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}
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}
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--
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2.33.0
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