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Re: RFC: SMS problem with emit_copy_of_insn_after copying REG_NOTEs
- From: Jan Hubicka <hubicka at ucw dot cz>
- To: Vladimir Yanovsky <volodyan at gmail dot com>
- Cc: gcc at gcc dot gnu dot org, jh at suse dot cz, Vladimir Yanovsky <yanov at il dot ibm dot com>, Ayal Zaks <zaks at il dot ibm dot com>
- Date: Mon, 18 Dec 2006 21:58:23 +0100
- Subject: Re: RFC: SMS problem with emit_copy_of_insn_after copying REG_NOTEs
- References: <48ee23ef0612181248l255833bcjd529c1651aef7a28@mail.gmail.com>
> Hello all,
>
> I'm preparing and testing SMS correction/improvements patch and while
> testing it on the SPU with the vectorizer testcases I've got an ICE in
> the "gcc_assert ( MAX_RECOG_OPERANDS - i)" in function copy_insn_1 in
> emit_rtl.c. The call traces back to the loop versionioning called in
> modulo-sched.c before the SMSing actually starts. The specific
> instruction it tries to copy when it fails is
>
> (insn 32 31 33 4 (parallel [
> (set (reg:SI 162)
> (div:SI (reg:SI 164)
> (reg:SI 156)))
> (set (reg:SI 163)
> (mod:SI (reg:SI 164)
> (reg:SI 156)))
> (clobber (scratch:SI))
> (clobber (scratch:SI))
> (clobber (scratch:SI))
> (clobber (scratch:SI))
> (clobber (scratch:SI))
> (clobber (scratch:SI))
> (clobber (scratch:SI))
> (clobber (scratch:SI))
> (clobber (scratch:SI))
> (clobber (reg:SI 130 hbr))
> ]) 129 {divmodsi4} (insn_list:REG_DEP_TRUE 30
> (insn_list:REG_DEP_TRUE 31 (nil)))
> (expr_list:REG_DEAD (reg:SI 164)
> (expr_list:REG_DEAD (reg:SI 156)
> (expr_list:REG_UNUSED (reg:SI 130 hbr)
> (expr_list:REG_UNUSED (scratch:SI)
> (expr_list:REG_UNUSED (scratch:SI)
> (expr_list:REG_UNUSED (scratch:SI)
> (expr_list:REG_UNUSED (scratch:SI)
> (expr_list:REG_UNUSED (scratch:SI)
> (expr_list:REG_UNUSED (scratch:SI)
> (expr_list:REG_UNUSED (scratch:SI)
> (expr_list:REG_UNUSED
> (scratch:SI)
> (expr_list:REG_UNUSED
> (scratch:SI)
> (expr_list:REG_UNUSED (reg:SI 163)
> (nil)))))))))))))))
>
> The error happens in the first call to copy_insn_1 in the loop below
> (copied from emit_copy_of_insn_after from emit_rtl.c):
>
>
> for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
> if (REG_NOTE_KIND (link) != REG_LABEL)
> {
> if (GET_CODE (link) == EXPR_LIST)
> REG_NOTES (new)
> = copy_insn_1 (gen_rtx_EXPR_LIST (REG_NOTE_KIND (link),
> XEXP (link, 0),
> REG_NOTES (new)));
> else
> REG_NOTES (new)
> = copy_insn_1 (gen_rtx_INSN_LIST (REG_NOTE_KIND (link),
> XEXP (link, 0),
> REG_NOTES (new)));
> }
>
THanks for sending updated patch, I will try to look across it tomorrow
> Tracing the execution of copy_insn_1, it seems that it goes over the
> same REG_NOTES many times (it seems to be a quadratic time complexity
> algorithm). This causes "copy_insn_n_scratches++" to be executed more
> times than there are SCRATCH registers (and even REG_NOTES) leading to
> the failure in the assert. There are 9 SCRATCH registers used in the
> instruction and MAX_RECOG_OPERANDS is 30 for the SPU.
>
> Since copy_insn_n_scratches is initialized in copy_insn and since we
> go over regnotes over and over again, I've modified in the loop
> above the two calls to copy_insn_1 with the calls to copy_insn. This
> caused the ICEs in the testsuite to disappear.
>
> I wonder if this constitutes a legitimate fix or I'm missing something?
I believe you really want to avoid quadratic amount of work. This is
probably best done by
REG_NOTES (new)
= gen_rtx_EXPR_LIST (REG_NOTE_KIND (link),
copy_insn_1 (XEXP (link, 0)),
REG_NOTES (new)));
so copy_insn_1 don't recusively descend into already copied chain.
Honza
>
> Thanks in advance,
> Vladimir