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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
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Jeffrey A Law 1998-08-28 00:10:42 +00:00 committed by Jeff Law
parent 78b87d18ae
commit 3aa94dc884
2 changed files with 12 additions and 0 deletions
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3
gcc/ChangeLog
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@ -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.

9
gcc/loop.c
View File

@ -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;