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unroll.c (unroll_loop): Do not abort for an UNROLL_MODULO or UNROLL_COMPLETELY loop that starts with a...

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        * unroll.c (unroll_loop): Do not abort for an UNROLL_MODULO
        or UNROLL_COMPLETELY loop that starts with a jump to its
        exit code.

From-SVN: r21476
This commit is contained in:
Jeff Law 1998-07-29 15:41:04 -06:00
parent 47d41103c5
commit 15fec413e7
1 changed files with 24 additions and 5 deletions
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29
gcc/unroll.c
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@ -431,15 +431,34 @@ unroll_loop (loop_end, insn_count, loop_start, end_insert_before,
if (unroll_type == UNROLL_COMPLETELY || unroll_type == UNROLL_MODULO)
{
/* Loops of these types should never start with a jump down to
the exit condition test. For now, check for this case just to
be sure. UNROLL_NAIVE loops can be of this form, this case is
handled below. */
/* Loops of these types can start with jump down to the exit condition
in rare circumstances.
Consider a pair of nested loops where the inner loop is part
of the exit code for the outer loop.
In this case jump.c will not duplicate the exit test for the outer
loop, so it will start with a jump to the exit code.
Then consider if the inner loop turns out to iterate once and
only once. We will end up deleting the jumps associated with
the inner loop. However, the loop notes are not removed from
the instruction stream.
And finally assume that we can compute the number of iterations
for the outer loop.
In this case unroll may want to unroll the outer loop even though
it starts with a jump to the outer loop's exit code.
We could try to optimize this case, but it hardly seems worth it.
Just return without unrolling the loop in such cases. */
insn = loop_start;
while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
insn = NEXT_INSN (insn);
if (GET_CODE (insn) == JUMP_INSN)
abort ();
return;
}
if (unroll_type == UNROLL_COMPLETELY)