On Fri, Aug 28, 2020 at 06:25:46PM +0200, Jakub Jelinek via Gcc-patches wrote:
> You're right, thanks for spotting it, I've missed native_encode_rtx will do
> quick_push rather than safe_push.
>
> Updated patch below, it shouldn't be needed in the second loop, because
> the first loop should already grow it to the largest size.
Testing beyond a bug in i386.md revealed also that I've lost a cast to long
to avoid breaking 32-bit bootstrap.
This is the version that passed bootstrap/regtest on both x86_64-linux and
i686-linux. In both bootstraps/regtests together, it saved (from the
statistics I've gathered) 63104 .rodata bytes (before constant merging),
in 6814 hits of the data->desc->mark = ~(*slot)->desc->labelno;.
Ok for trunk?
2020-08-30 Jakub Jelinek <ja...@redhat.com>
PR middle-end/54201
* varasm.c: Include alloc-pool.h.
(output_constant_pool_contents): Emit desc->mark < 0 entries as
aliases.
(struct constant_descriptor_rtx_data): New type.
(constant_descriptor_rtx_data_cmp): New function.
(struct const_rtx_data_hasher): New type.
(const_rtx_data_hasher::hash, const_rtx_data_hasher::equal): New
methods.
(optimize_constant_pool): New function.
(output_shared_constant_pool): Call it if TARGET_SUPPORTS_ALIASES.
--- gcc/varasm.c.jj 2020-07-28 15:39:10.091755086 +0200
+++ gcc/varasm.c 2020-08-28 18:21:58.943759578 +0200
@@ -57,6 +57,7 @@ along with GCC; see the file COPYING3.
#include "asan.h"
#include "rtl-iter.h"
#include "file-prefix-map.h" /* remap_debug_filename() */
+#include "alloc-pool.h"
#ifdef XCOFF_DEBUGGING_INFO
#include "xcoffout.h" /* Needed for external data declarations. */
@@ -4198,7 +4199,27 @@ output_constant_pool_contents (struct rt
class constant_descriptor_rtx *desc;
for (desc = pool->first; desc ; desc = desc->next)
- if (desc->mark)
+ if (desc->mark < 0)
+ {
+#ifdef ASM_OUTPUT_DEF
+ const char *name = targetm.strip_name_encoding (XSTR (desc->sym, 0));
+ char label[256];
+ char buffer[256 + 32];
+ const char *p;
+
+ ASM_GENERATE_INTERNAL_LABEL (label, "LC", ~desc->mark);
+ p = targetm.strip_name_encoding (label);
+ if (desc->offset)
+ {
+ sprintf (buffer, "%s+%ld", p, (long) (desc->offset));
+ p = buffer;
+ }
+ ASM_OUTPUT_DEF (asm_out_file, name, p);
+#else
+ gcc_unreachable ();
+#endif
+ }
+ else if (desc->mark)
{
/* If the constant is part of an object_block, make sure that
the constant has been positioned within its block, but do not
@@ -4216,6 +4237,160 @@ output_constant_pool_contents (struct rt
}
}
+struct constant_descriptor_rtx_data {
+ constant_descriptor_rtx *desc;
+ target_unit *bytes;
+ unsigned short size;
+ unsigned short offset;
+ unsigned int hash;
+};
+
+/* qsort callback to sort constant_descriptor_rtx_data * vector by
+ decreasing size. */
+
+static int
+constant_descriptor_rtx_data_cmp (const void *p1, const void *p2)
+{
+ constant_descriptor_rtx_data *const data1
+ = *(constant_descriptor_rtx_data * const *) p1;
+ constant_descriptor_rtx_data *const data2
+ = *(constant_descriptor_rtx_data * const *) p2;
+ if (data1->size > data2->size)
+ return -1;
+ if (data1->size < data2->size)
+ return 1;
+ if (data1->hash < data2->hash)
+ return -1;
+ gcc_assert (data1->hash > data2->hash);
+ return 1;
+}
+
+struct const_rtx_data_hasher : nofree_ptr_hash<constant_descriptor_rtx_data>
+{
+ static hashval_t hash (constant_descriptor_rtx_data *);
+ static bool equal (constant_descriptor_rtx_data *,
+ constant_descriptor_rtx_data *);
+};
+
+/* Hash and compare functions for const_rtx_data_htab. */
+
+hashval_t
+const_rtx_data_hasher::hash (constant_descriptor_rtx_data *data)
+{
+ return data->hash;
+}
+
+bool
+const_rtx_data_hasher::equal (constant_descriptor_rtx_data *x,
+ constant_descriptor_rtx_data *y)
+{
+ if (x->hash != y->hash || x->size != y->size)
+ return 0;
+ unsigned int align1 = x->desc->align;
+ unsigned int align2 = y->desc->align;
+ unsigned int offset1 = (x->offset * BITS_PER_UNIT) & (align1 - 1);
+ unsigned int offset2 = (y->offset * BITS_PER_UNIT) & (align2 - 1);
+ if (offset1)
+ align1 = least_bit_hwi (offset1);
+ if (offset2)
+ align2 = least_bit_hwi (offset2);
+ if (align2 > align1)
+ return 0;
+ if (memcmp (x->bytes, y->bytes, x->size * sizeof (target_unit)) != 0)
+ return 0;
+ return 1;
+}
+
+/* Attempt to optimize constant pool POOL. If it contains both CONST_VECTOR
+ constants and scalar constants with the values of CONST_VECTOR elements,
+ try to alias the scalar constants with the CONST_VECTOR elements. */
+
+static void
+optimize_constant_pool (struct rtx_constant_pool *pool)
+{
+ auto_vec<target_unit, 128> buffer;
+ auto_vec<constant_descriptor_rtx_data *, 128> vec;
+ object_allocator<constant_descriptor_rtx_data>
+ data_pool ("constant_descriptor_rtx_data_pool");
+ int idx = 0;
+ size_t size = 0;
+ for (constant_descriptor_rtx *desc = pool->first; desc; desc = desc->next)
+ if (desc->mark > 0
+ && ! (SYMBOL_REF_HAS_BLOCK_INFO_P (desc->sym)
+ && SYMBOL_REF_BLOCK (desc->sym)))
+ {
+ buffer.truncate (0);
+ buffer.reserve (GET_MODE_SIZE (desc->mode));
+ if (native_encode_rtx (desc->mode, desc->constant, buffer, 0,
+ GET_MODE_SIZE (desc->mode)))
+ {
+ constant_descriptor_rtx_data *data = data_pool.allocate ();
+ data->desc = desc;
+ data->bytes = NULL;
+ data->size = GET_MODE_SIZE (desc->mode);
+ data->offset = 0;
+ data->hash = idx++;
+ size += data->size;
+ vec.safe_push (data);
+ }
+ }
+ if (idx)
+ {
+ vec.qsort (constant_descriptor_rtx_data_cmp);
+ unsigned min_size = vec.last ()->size;
+ target_unit *bytes = XNEWVEC (target_unit, size);
+ unsigned int i;
+ constant_descriptor_rtx_data *data;
+ hash_table<const_rtx_data_hasher> * htab
+ = new hash_table<const_rtx_data_hasher> (31);
+ size = 0;
+ FOR_EACH_VEC_ELT (vec, i, data)
+ {
+ buffer.truncate (0);
+ native_encode_rtx (data->desc->mode, data->desc->constant,
+ buffer, 0, data->size);
+ memcpy (bytes + size, buffer.address (), data->size);
+ data->bytes = bytes + size;
+ data->hash = iterative_hash (data->bytes,
+ data->size * sizeof (target_unit), 0);
+ size += data->size;
+ constant_descriptor_rtx_data **slot
+ = htab->find_slot_with_hash (data, data->hash, INSERT);
+ if (*slot)
+ {
+ data->desc->mark = ~(*slot)->desc->labelno;
+ data->desc->offset = (*slot)->offset;
+ }
+ else
+ {
+ unsigned int sz = 1 << floor_log2 (data->size);
+
+ *slot = data;
+ for (sz >>= 1; sz >= min_size; sz >>= 1)
+ for (unsigned off = 0; off + sz <= data->size; off += sz)
+ {
+ constant_descriptor_rtx_data tmp;
+ tmp.desc = data->desc;
+ tmp.bytes = data->bytes + off;
+ tmp.size = sz;
+ tmp.offset = off;
+ tmp.hash = iterative_hash (tmp.bytes,
+ sz * sizeof (target_unit), 0);
+ slot = htab->find_slot_with_hash (&tmp, tmp.hash, INSERT);
+ if (*slot == NULL)
+ {
+ *slot = data_pool.allocate ();
+ **slot = tmp;
+ }
+ }
+ }
+ }
+ delete htab;
+ XDELETE (bytes);
+ }
+ data_pool.release ();
+}
+
/* Mark all constants that are used in the current function, then write
out the function's private constant pool. */
@@ -4251,6 +4426,10 @@ output_constant_pool (const char *fnname
void
output_shared_constant_pool (void)
{
+ if (optimize
+ && TARGET_SUPPORTS_ALIASES)
+ optimize_constant_pool (shared_constant_pool);
+
output_constant_pool_contents (shared_constant_pool);
}
Jakub
