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author | Jeffrey A Law <law@cygnus.com> | 1998-08-28 00:10:42 +0000 |
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committer | Jeff Law <law@gcc.gnu.org> | 1998-08-27 18:10:42 -0600 |
commit | 3aa94dc884332bb8d40441cfbb7c695708a783c0 (patch) | |
tree | 1f869e9b2d08caaad6f7fa6c36b368469ed62ad6 /gcc | |
parent | 78b87d18ae25299f9da51225378397abbdbb5349 (diff) | |
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loop.c (check_dbra_loop): The loop ending comparison value must be an invariant or we can not reverse the...
* loop.c (check_dbra_loop): The loop ending comparison value
must be an invariant or we can not reverse the loop.
From-SVN: r22045
Diffstat (limited to 'gcc')
-rw-r--r-- | gcc/ChangeLog | 3 | ||||
-rw-r--r-- | gcc/loop.c | 9 |
2 files changed, 12 insertions, 0 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 6db8cead..ae5ef3d 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,5 +1,8 @@ Thu Aug 27 20:10:46 1998 Jeffrey A Law (law@cygnus.com) + * loop.c (check_dbra_loop): The loop ending comparison value + must be an invariant or we can not reverse the loop. + * loop.c (scan_loop): Count down from max_reg_num - 1 to FIRST_PSEUDO_REGISTER to avoid calling max_reg_num each iteration of the loop. @@ -6904,6 +6904,15 @@ check_dbra_loop (loop_end, insn_count, loop_start) comparison_sign_mask = (unsigned HOST_WIDE_INT)1 << (comparison_const_width - 1); + /* If the comparison value is not a loop invariant, then we + can not reverse this loop. + + ??? If the insns which initialize the comparison value as + a whole compute an invariant result, then we could move + them out of the loop and proceed with loop reversal. */ + if (!invariant_p (comparison_val)) + return 0; + if (GET_CODE (comparison_value) == CONST_INT) comparison_val = INTVAL (comparison_value); initial_value = bl->initial_value; |