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Re: [PATCH] doloop_optimize miscompiles openssl
At 00:34 26.09.00, Geoff Keating wrote:
>Franz Sirl <Franz.Sirlfirstname.lastname@example.org> writes:
> > * doloop.c (doloop_modify): Prevent delete_insn() from
> > deleting too much. Prefer loop->top over loop->start as
> > target for the new JUMP insn.
> > (doloop_valid_p): Ignore loop with exit_count > 1.
>This is OK.
Hmm, already lying in bed, it occurred to me that I'm not sure about the
exact definition for loop->exit_count. I seem to remember (I can't test
right now) that it was set to 3 for the testcase, this would mean the main
loop exit isn't counted here and I have to compare for >0, not >1. But I
don't know enough about the loop detection algorithm to be 100% sure, maybe
I have to test other loop structure members too for a correct test?
In the meantime, while browsing the code, I found another suspicious code
/* Some targets (eg, C4x) need to initialize special looping
init = gen_doloop_begin (counter_reg,
GET_CODE (iterations) == CONST_INT
? iterations : const0_rtx, iterations_max,
sequence = gen_sequence ();
emit_insn_after (sequence, loop->start);
Do we need to prefer loop->top here too? The comment doesn't specify if the
initialization is needed on every loop run...
Maybe the originator of the code should comment on the patches? Michael?
>(You should say how you tested your patch; I'm assuming you did a
>bootstrap on powerpc-linux.)
Well, since I've caught a cold my mind is a bit dizzy, so I didn't want to
ask for commit before sleeping over it :-), but I passed my status to the
list to get some comments.
BTW, I will try to turn both testcases in this thread into executable