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loop.c (check_dbra_loop): When reversing a loop... 

* loop.c (check_dbra_loop): When reversing a loop, delete all
	REG_EQUAL notes referencing the reversed biv except those which are
	for a giv based on it.

From-SVN: r28043
This commit is contained in:
Bernd Schmidt 1999-07-09 03:34:26 +00:00 committed by Bernd Schmidt
parent 4470c3998c
commit 22b452e755
2 changed files with 40 additions and 0 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
Fri Jul 9 10:48:28 1999 Bernd Schmidt <bernds@cygnus.co.uk>
* loop.c (check_dbra_loop): When reversing a loop, delete all
REG_EQUAL notes referencing the reversed biv except those which are
for a giv based on it.
Fri Jul 9 03:51:52 1999 Jeffrey A Law (law@cygnus.com)
* version.c: Drop "gcc-" prefix from version #.

34
gcc/loop.c
View File

@ -8107,6 +8107,40 @@ check_dbra_loop (loop_end, insn_count, loop_start, loop_info)
bl->nonneg = 1;
}
/* No insn may reference both the reversed and another biv or it
will fail (see comment near the top of the loop reversal
code).
Earlier on, we have verified that the biv has no use except
counting, or it is the only biv in this function.
However, the code that computes no_use_except_counting does
not verify reg notes. It's possible to have an insn that
references another biv, and has a REG_EQUAL note with an
expression based on the reversed biv. To avoid this case,
remove all REG_EQUAL notes based on the reversed biv
here. */
for (p = loop_start; p != loop_end; p = NEXT_INSN (p))
if (GET_RTX_CLASS (GET_CODE (p)) == 'i')
{
rtx *pnote;
rtx set = single_set (p);
/* If this is a set of a GIV based on the reversed biv, any
REG_EQUAL notes should still be correct. */
if (! set
|| GET_CODE (SET_DEST (set)) != REG
|| REGNO (SET_DEST (set)) >= reg_iv_type->num_elements
|| REG_IV_TYPE (REGNO (SET_DEST (set))) != GENERAL_INDUCT
|| REG_IV_INFO (REGNO (SET_DEST (set)))->src_reg != bl->biv->src_reg)
for (pnote = &REG_NOTES (p); *pnote;)
{
if (REG_NOTE_KIND (*pnote) == REG_EQUAL
&& reg_mentioned_p (regno_reg_rtx[bl->regno],
XEXP (*pnote, 0)))
*pnote = XEXP (*pnote, 1);
else
pnote = &XEXP (*pnote, 1);
}
}
/* Mark that this biv has been reversed. Each giv which depends
on this biv, and which is also live past the end of the loop
will have to be fixed up. */