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On 04/22/11 14:19, Easwaran Raman wrote:
> Hi,
> This patch improves RTL DSE by not assuming that calls read all
> memory locations. With this patch, calls are assumed to read any
> non-frame memory and any stack variables that can potentially escape.
> This patch partly addresses PR rtl-optimization/44194. Bootstraps and
> no test regressions. OK for trunk?
>
> Thanks,
> Easwaran
>
> 2011-04-22 Easwaran Raman <[email protected]>
>
> PR rtl-optimization/44194
> * dse.c (header files): Include tree-flow.h.
> (group_info): Add fields.
> (globals): Add a new variable kill_on_calls.
> (get_group_info): Initialize added fields.
> (dse_step0): Initialize kill_on_calls.
> (can_escape): New function.
> (record_store): Pass EXPR corresponding to MEM to
> set_usage_bits.
> (dse_step2_nospill): Set kill_on_calls based on
> group->escaped_*.
> (scan_reads_nospill): Handle call instructions.
> (find_insn_before_first_wild_read): Remove the function.
> (dse_step3_scan): Remove call to find_insn_before_first_wild_read.
> (dse_step5_nospill): Do not kill everything on call.
>
> testsuite/ChangeLog:
>
> 2011-04-22 Easwaran Raman <[email protected]>
>
> PR rtl-optimization/44194
> * gcc.dg/pr44194-1.c: New test.
On a bookkeeping note, it doesn't appear that you ever release the
bitmaps for gi->escaped_{p,n} or kill_on_calls. This should probably be
done in dse_step7.
I'm going to assume that you and Richi have agreed upon the form of
can_escape.
AFAICT, even after your patch we still have a wild read recorded for
most CALL_INSNs (see this code in scan_insn which was not modified):
else
/* Every other call, including pure functions, may read memory. */
add_wild_read (bb_info);
It appears that you effectively ignore the wild_read in
scan_reads_nospill by special casing CALL_INSNs. Correct? Is so, does
it make still sense to call add_wild_read in scan_insn?
ISTM that wild reads are still possible due to a few other constructs
such as asms, address canonicalization failure, etc, so why is the
removal of the wild read support in dse_step5_nospill correct?
Just to be clear, I generally like the change, but there's some details
that I think need to be better understood before installing.
jeff
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