The interesting case where we encounter a basic block head is when the
check of return_copy for BB_HEAD check succeeds with return_copy being
a label;
then last_insn is a NOTE_INSN_BASIC_BLOCK, and we must not try to split
off a part of the basic block before that note.
That can be properly tested for by changing the !INSN_P (last_insn)
check into a
NOTE_INSN_BASIC_BLOCK_P (last_insn) check.
last_insn == BB_HEAD (src_bb) can't actually be true, because we don't copy
return_copy to last_insn when we've bit BB_HEAD, so I removed that test.
bootstrapped / regtested on i686-pc-linux-gnu .
AFAICT, the second block split is useless, and could be replaced with
pre_exit = src_bb;
, and then the slack space allocated for post_entry / pre_exit blocks reduced
to two. However, I didn't want to tie a bugfix with a potentialy
destabilizing
cleanup - maybe there's some target port code (in the context of
likely spilled
classes?) that relies on the MODE_EXIT switch note only before, but in
a block separate from the return value copy?
2013-07-29 Joern Rennecke <joern.renne...@embecosm.com>
PR rtl-optimization/58021
* mode-switching.c (create_pre_exit): Always split of preceding
insns if we are not at the basic block head.
Index: mode-switching.c
===================================================================
--- mode-switching.c (revision 201313)
+++ mode-switching.c (working copy)
@@ -420,7 +420,7 @@ create_pre_exit (int n_entities, int *en
|| (GET_MODE_CLASS (GET_MODE (ret_reg)) != MODE_INT
&& nregs != 1));
- if (INSN_P (last_insn))
+ if (!NOTE_INSN_BASIC_BLOCK_P (last_insn))
{
before_return_copy
= emit_note_before (NOTE_INSN_DELETED, last_insn);
@@ -428,9 +428,8 @@ create_pre_exit (int n_entities, int *en
require a different mode than MODE_EXIT, so if we might
have such instructions, keep them in a separate block
from pre_exit. */
- if (last_insn != BB_HEAD (src_bb))
- src_bb = split_block (src_bb,
- PREV_INSN (before_return_copy))->dest;
+ src_bb = split_block (src_bb,
+ PREV_INSN (before_return_copy))->dest;
}
else
before_return_copy = last_insn;
