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unroll.c (loop_iterations): Return 0 if the last loop insn is not a jump insn or if...

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	* unroll.c (loop_iterations): Return 0 if the last loop insn
	is not a jump insn or if the loop has multiple back edges.

From-SVN: r24680
This commit is contained in:
Michael Hayes 1999-01-15 03:05:56 -07:00 committed by Jeff Law
parent 9f16f9324c
commit 98dcbc07f5
1 changed files with 26 additions and 5 deletions
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31
gcc/unroll.c
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@ -3480,22 +3480,43 @@ loop_iterations (loop_start, loop_end, loop_info)
loop_info->unroll_number = 1;
loop_info->vtop = 0;
/* First find the iteration variable. If the last insn is a conditional
branch, and the insn before tests a register value, make that the
iteration variable. */
/* We used to use prev_nonnote_insn here, but that fails because it might
accidentally get the branch for a contained loop if the branch for this
loop was deleted. We can only trust branches immediately before the
loop_end. */
last_loop_insn = PREV_INSN (loop_end);
/* ??? We should probably try harder to find the jump insn
at the end of the loop. The following code assumes that
the last loop insn is a jump to the top of the loop. */
if (GET_CODE (last_loop_insn) != JUMP_INSN)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: No final conditional branch found.\n");
return 0;
}
/* If there is a more than a single jump to the top of the loop
we cannot (easily) determine the iteration count. */
if (LABEL_NUSES (JUMP_LABEL (last_loop_insn)) > 1)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: Loop has multiple back edges.\n");
return 0;
}
/* Find the iteration variable. If the last insn is a conditional
branch, and the insn before tests a register value, make that the
iteration variable. */
comparison = get_condition_for_loop (last_loop_insn);
if (comparison == 0)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: No final conditional branch found.\n");
"Loop iterations: No final comparison found.\n");
return 0;
}