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(unroll_loop): Add check for naive loop that ends with 

conditional branch that does not branch back to loop start.

From-SVN: r13672
This commit is contained in:
Jim Wilson 1997-02-20 13:43:33 -08:00
parent 7657bf2fbf
commit 9290558260
1 changed files with 17 additions and 0 deletions
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17
gcc/unroll.c
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@ -637,6 +637,23 @@ unroll_loop (loop_end, insn_count, loop_start, end_insert_before,
copy_end = last_loop_insn;
}
if (unroll_type == UNROLL_NAIVE
&& GET_CODE (last_loop_insn) == JUMP_INSN
&& start_label != JUMP_LABEL (last_loop_insn))
{
/* ??? The loop ends with a conditional branch that does not branch back
to the loop start label. In this case, we must emit an unconditional
branch to the loop exit after emitting the final branch.
copy_loop_body does not have support for this currently, so we
give up. It doesn't seem worthwhile to unroll anyways since
unrolling would increase the number of branch instructions
executed. */
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Unrolling failure: final conditional branch not to loop start\n");
return;
}
/* Allocate a translation table for the labels and insn numbers.
They will be filled in as we copy the insns in the loop. */