On Tue, 18 Oct 2016, Kyrill Tkachov wrote:
> Hi Richard,
>
> This patch is a merge of [1] and [2] and implements the manual merging of
> bitfields
> as outlined in [1] but actually makes it work on BYTES_BIG_ENDIAN too.
> It caused me a lot of headeache because the bit offset is counted from the
> most significant bit
> in the byte, even though BITS_BIG_ENDIAN was 0 (BITS_BIG_ENDIAN looks
> irrelevant for store merging
> anyway as it's just used to described RTL extract operations).
> I've included ASCII diagrams of the steps in the merging algorithm.
Heh, thanks.
> Bootstrapped and tested on arm-none-linux-gnueabihf, aarch64-none-linux-gnu,
> x86_64-unknown-linux-gnu.
> Also tested on aarch64_be-none-elf.
>
> How does this version look now?
Mostly good. For
+bool
+pass_store_merging::terminate_all_aliasing_chains (tree dest, tree base,
+ gimple *stmt)
+{
...
+ /* Check if the assignment destination (BASE) is part of a store chain.
+ This is to catch non-constant stores to destinations that may be
part
+ of a chain. */
+ if (base)
+ {
+ chain_info = m_stores.get (base);
+ if (chain_info)
+ {
+ struct store_immediate_info *info;
+ unsigned int i;
+ FOR_EACH_VEC_ELT ((*chain_info)->m_store_info, i, info)
+ {
+ if (refs_may_alias_p (info->dest, dest))
+ {
I suppose the chain is not yet sorted in any way?
At least for 'dest' which do not have a known constant offset we
could do
if (base)
terminate_and_release_chain (base);
to speed things up? IIRC we do not terminate chains early in
this phase when we have enough stores to form a group, so
writing a testcase that triggers quadraticness would be as simple
as having
char a[1000000];
void foo ()
{
a[0] = 1;
a[1] = 2;
....
a[9999999] = 3;
}
?
so I think you probably want to limit the number of stores you
ever put onto a chain and if you reach that limit, terminate
and release it? Like just choose 16 or 64? (and experiment
with the above kind of testcases)
+ bit_off = byte_off << LOG2_BITS_PER_UNIT;
+ if (!wi::neg_p (bit_off) && wi::fits_shwi_p (bit_off))
+ {
+ bitpos += bit_off.to_shwi ();
+
I think you want bit_off += bitpos before the fits_shwi check
otherwise this add may still overflow.
+ base_addr = copy_node (base_addr);
+ TREE_OPERAND (base_addr, 1)
+ = build_zero_cst (TREE_TYPE (TREE_OPERAND (
+ base_addr, 1)));
I'd prefer
base_addr = build2 (MEM_REF, ...);
here.
Thanks,
Richard.
> Thanks,
> Kyrill
>
> [1] https://gcc.gnu.org/ml/gcc-patches/2016-10/msg00573.html
> [2] https://gcc.gnu.org/ml/gcc-patches/2016-10/msg00572.html
>
> 2016-10-18 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
>
> PR middle-end/22141
> * Makefile.in (OBJS): Add gimple-ssa-store-merging.o.
> * common.opt (fstore-merging): New Optimization option.
> * opts.c (default_options_table): Add entry for
> OPT_ftree_store_merging.
> * fold-const.h (can_native_encode_type_p): Declare prototype.
> * fold-const.c (can_native_encode_type_p): Define.
> * params.def (PARAM_STORE_MERGING_ALLOW_UNALIGNED): Define.
> * passes.def: Insert pass_tree_store_merging.
> * tree-pass.h (make_pass_store_merging): Declare extern
> prototype.
> * gimple-ssa-store-merging.c: New file.
> * doc/invoke.texi (Optimization Options): Document
> -fstore-merging.
>
> 2016-10-18 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
> Jakub Jelinek <ja...@redhat.com>
> Andrew Pinski <pins...@gmail.com>
>
> PR middle-end/22141
> PR rtl-optimization/23684
> * gcc.c-torture/execute/pr22141-1.c: New test.
> * gcc.c-torture/execute/pr22141-2.c: Likewise.
> * gcc.target/aarch64/ldp_stp_1.c: Adjust for -fstore-merging.
> * gcc.target/aarch64/ldp_stp_4.c: Likewise.
> * gcc.dg/store_merging_1.c: New test.
> * gcc.dg/store_merging_2.c: Likewise.
> * gcc.dg/store_merging_3.c: Likewise.
> * gcc.dg/store_merging_4.c: Likewise.
> * gcc.dg/store_merging_5.c: Likewise.
> * gcc.dg/store_merging_6.c: Likewise.
> * gcc.dg/store_merging_7.c: Likewise.
> * gcc.target/i386/pr22141.c: Likewise.
> * gcc.target/i386/pr34012.c: Add -fno-store-merging to dg-options.
> * g++.dg/init/new17.C: Likewise.
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
