On May 21, 2020 1:11:33 PM GMT+02:00, Jan Hubicka <hubi...@ucw.cz> wrote:
>Hi,
>this patch saves few bytes from SCC streaming. First we stream end
>markers
>that are fully ignored at stream in.
>Second I missed streaming of emtry_len in the previous change so it is
>pointlessly streamed for LTO_trees. Moreover entry_len is almost always
>1
>(always during gcc bootstrap) and thus it makes sense to avoid
>stremaing it
>in majority of cases.
It's then only one byte, no? But yes...
>
>ltobootstrapped/regtested x86_64-linux, OK?
OK.
Richard.
>gcc/ChangeLog:
>
>2020-05-21 Jan Hubicka <hubi...@ucw.cz>
>
> * lto-streamer-in.c (lto_read_tree): Do not stream end markers.
> (lto_input_scc): Optimize streaming of entry lengths.
> * lto-streamer-out.c (lto_write_tree): Do not stream end markers
> (DFS::DFS): Optimize stremaing of entry lengths
>
>gcc/lto/ChangeLog:
>
>2020-05-21 Jan Hubicka <hubi...@ucw.cz>
>
> * lto-common.c (compare_tree_sccs):
>
>diff --git a/gcc/lto-streamer-in.c b/gcc/lto-streamer-in.c
>index 85d0edf49a7..d0532c5ac51 100644
>--- a/gcc/lto-streamer-in.c
>+++ b/gcc/lto-streamer-in.c
>@@ -1417,8 +1417,6 @@ lto_read_tree (class lto_input_block *ib, class
>data_in *data_in,
>
> lto_read_tree_1 (ib, data_in, result);
>
>- /* end_marker = */ streamer_read_uchar (ib);
>-
> return result;
> }
>
>@@ -1431,12 +1429,18 @@ hashval_t
> lto_input_scc (class lto_input_block *ib, class data_in *data_in,
> unsigned *len, unsigned *entry_len, bool shared_scc)
> {
>- /* A blob of unnamed tree nodes, fill the cache from it and
>- recurse. */
> unsigned size = streamer_read_uhwi (ib);
>- hashval_t scc_hash = shared_scc ? streamer_read_uhwi (ib) : 0;
>+ hashval_t scc_hash = 0;
> unsigned scc_entry_len = 1;
>
>+ if (shared_scc)
>+ {
>+ if (size & 1)
>+ scc_entry_len = streamer_read_uhwi (ib);
>+ size /= 2;
>+ scc_hash = streamer_read_uhwi (ib);
>+ }
>+
> if (size == 1)
> {
> enum LTO_tags tag = streamer_read_record_start (ib);
>@@ -1447,8 +1451,6 @@ lto_input_scc (class lto_input_block *ib, class
>data_in *data_in,
> unsigned int first = data_in->reader_cache->nodes.length ();
> tree result;
>
>- scc_entry_len = streamer_read_uhwi (ib);
>-
> /* Materialize size trees by reading their headers. */
> for (unsigned i = 0; i < size; ++i)
> {
>@@ -1471,7 +1473,6 @@ lto_input_scc (class lto_input_block *ib, class
>data_in *data_in,
> result = streamer_tree_cache_get_tree (data_in->reader_cache,
> first + i);
> lto_read_tree_1 (ib, data_in, result);
>- /* end_marker = */ streamer_read_uchar (ib);
> }
> }
>
>diff --git a/gcc/lto-streamer-out.c b/gcc/lto-streamer-out.c
>index 0e179468043..09a2e827f8e 100644
>--- a/gcc/lto-streamer-out.c
>+++ b/gcc/lto-streamer-out.c
>@@ -473,9 +473,6 @@ lto_write_tree (struct output_block *ob, tree expr,
>bool ref_p)
> streamer_write_tree_header (ob, expr);
>
> lto_write_tree_1 (ob, expr, ref_p);
>-
>- /* Mark the end of EXPR. */
>- streamer_write_zero (ob);
> }
>
>/* Emit the physical representation of tree node EXPR to output block
>OB,
>@@ -764,7 +761,12 @@ DFS::DFS (struct output_block *ob, tree expr, bool
>ref_p, bool this_ref_p,
> {
> gcc_checking_assert (ob->section_type == LTO_section_decls);
> streamer_write_record_start (ob, LTO_tree_scc);
>- streamer_write_uhwi (ob, size);
>+ /* In wast majority of cases scc_entry_len is 1 and size is
>small
>+ integer. Use extra bit of size to stream info about
>+ exceptions. */
>+ streamer_write_uhwi (ob, size * 2 + (scc_entry_len != 1));
>+ if (scc_entry_len != 1)
>+ streamer_write_uhwi (ob, scc_entry_len);
> streamer_write_uhwi (ob, scc_hash);
> }
> /* Non-trivial SCCs must be packed to trees blocks so forward
>@@ -783,8 +785,6 @@ DFS::DFS (struct output_block *ob, tree expr, bool
>ref_p, bool this_ref_p,
> lto_output_tree_1 (ob, expr, scc_hash, ref_p, this_ref_p);
> else
> {
>- /* Write the size of the SCC entry candidates. */
>- streamer_write_uhwi (ob, scc_entry_len);
>
> /* Write all headers and populate the streamer cache. */
> for (unsigned i = 0; i < size; ++i)
>@@ -807,12 +807,7 @@ DFS::DFS (struct output_block *ob, tree expr, bool
>ref_p, bool this_ref_p,
>
> /* Write the bitpacks and tree references. */
> for (unsigned i = 0; i < size; ++i)
>- {
>- lto_write_tree_1 (ob, sccstack[first+i].t, ref_p);
>-
>- /* Mark the end of the tree. */
>- streamer_write_zero (ob);
>- }
>+ lto_write_tree_1 (ob, sccstack[first+i].t, ref_p);
> }
>
> /* Finally truncate the vector. */
