gas: xtensa: implement trampoline coalescing
There is a recurring pattern in assembly files generated by a compiler where a lot of jumps in a function are going to the same place. When these jumps are relaxed with trampolines the assembler generates a separate jump thread from each source. Create an index of trampoline jump targets for each segment and see if a jump being relaxed goes to a location from that index, in which case replace its target with a location of existing trampoline jump that results in the shortest path to the original target. gas/ 2017-11-27 Max Filippov <jcmvbkbc@gmail.com> * config/tc-xtensa.c (trampoline_chain_entry, trampoline_chain) (trampoline_chain_index): New structures. (trampoline_index): Add chain_index field. (xg_order_trampoline_chain_entry, xg_sort_trampoline_chain) (xg_find_chain_entry, xg_get_best_chain_entry) (xg_order_trampoline_chain, xg_get_trampoline_chain) (xg_find_best_eq_target, xg_add_location_to_chain) (xg_create_trampoline_chain, xg_get_single_symbol_slot): New functions. (xg_relax_fixups): Call xg_find_best_eq_target to adjust jump target to point to an existing jump. Call xg_create_trampoline_chain to create new jump target. Call xg_add_location_to_chain to add newly created trampoline jump to the corresponding chain. (add_jump_to_trampoline): Extract loop searching for a single slot with a symbol into a separate function, replace that code with a call to that function. (relax_frag_immed): Call xg_find_best_eq_target to adjust jump target to point to an existing jump. * testsuite/gas/xtensa/all.exp: Add trampoline-2 test. * testsuite/gas/xtensa/trampoline.d: Adjust absolute addresses as many duplicate trampoline chains are now coalesced. * testsuite/gas/xtensa/trampoline.s: Add _nop so that objdump stays in sync with instruction stream. * testsuite/gas/xtensa/trampoline-2.l: New test result file. * testsuite/gas/xtensa/trampoline-2.s: New test source file.
This commit is contained in:
Max Filippov
parent
76a493ab99
commit
148d638429
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@ -1,3 +1,32 @@
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2017-11-27 Max Filippov <jcmvbkbc@gmail.com>
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* config/tc-xtensa.c (trampoline_chain_entry, trampoline_chain)
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(trampoline_chain_index): New structures.
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(trampoline_index): Add chain_index field.
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(xg_order_trampoline_chain_entry, xg_sort_trampoline_chain)
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(xg_find_chain_entry, xg_get_best_chain_entry)
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(xg_order_trampoline_chain, xg_get_trampoline_chain)
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(xg_find_best_eq_target, xg_add_location_to_chain)
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(xg_create_trampoline_chain, xg_get_single_symbol_slot): New
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functions.
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(xg_relax_fixups): Call xg_find_best_eq_target to adjust jump
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target to point to an existing jump. Call
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xg_create_trampoline_chain to create new jump target. Call
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xg_add_location_to_chain to add newly created trampoline jump
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to the corresponding chain.
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(add_jump_to_trampoline): Extract loop searching for a single
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slot with a symbol into a separate function, replace that code
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with a call to that function.
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(relax_frag_immed): Call xg_find_best_eq_target to adjust jump
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target to point to an existing jump.
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* testsuite/gas/xtensa/all.exp: Add trampoline-2 test.
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* testsuite/gas/xtensa/trampoline.d: Adjust absolute addresses
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as many duplicate trampoline chains are now coalesced.
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* testsuite/gas/xtensa/trampoline.s: Add _nop so that objdump
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stays in sync with instruction stream.
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* testsuite/gas/xtensa/trampoline-2.l: New test result file.
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* testsuite/gas/xtensa/trampoline-2.s: New test source file.
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2017-11-27 Max Filippov <jcmvbkbc@gmail.com>
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* config/tc-xtensa.c (search_trampolines, get_best_trampoline):
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@ -7348,6 +7348,33 @@ xtensa_end (void)
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xtensa_check_frag_count ();
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}
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struct trampoline_chain_entry
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{
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symbolS *sym;
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addressT offset;
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};
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/* Trampoline chain for a given (sym, offset) pair is a sorted array
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of locations of trampoline jumps leading there. Jumps are represented
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as pairs (sym, offset): trampoline frag symbol and offset of the jump
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inside the frag. */
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struct trampoline_chain
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{
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struct trampoline_chain_entry target;
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struct trampoline_chain_entry *entry;
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size_t n_entries;
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size_t n_max;
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bfd_boolean needs_sorting;
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};
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struct trampoline_chain_index
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{
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struct trampoline_chain *entry;
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size_t n_entries;
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size_t n_max;
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bfd_boolean needs_sorting;
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};
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struct trampoline_index
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{
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fragS **entry;
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@ -7359,7 +7386,10 @@ struct trampoline_seg
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{
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struct trampoline_seg *next;
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asection *seg;
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/* Trampolines ordered by their frag fr_address */
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struct trampoline_index index;
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/* Known trampoline chains ordered by (sym, offset) pair */
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struct trampoline_chain_index chain_index;
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};
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static struct trampoline_seg trampoline_seg_list;
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@ -7520,6 +7550,187 @@ static bfd_boolean xg_is_trampoline_frag_full (const fragS *fragP)
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return fragP->fr_var < 3;
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}
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static int xg_order_trampoline_chain_entry (const void *a, const void *b)
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{
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const struct trampoline_chain_entry *pa = a;
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const struct trampoline_chain_entry *pb = b;
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if (pa->sym == pb->sym ||
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S_GET_VALUE (pa->sym) == S_GET_VALUE (pb->sym))
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if (pa->offset == pb->offset)
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return 0;
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else
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return pa->offset < pb->offset ? -1 : 1;
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else
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return S_GET_VALUE (pa->sym) < S_GET_VALUE (pb->sym) ? -1 : 1;
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}
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static void xg_sort_trampoline_chain (struct trampoline_chain *tc)
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{
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qsort (tc->entry, tc->n_entries, sizeof (*tc->entry),
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xg_order_trampoline_chain_entry);
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tc->needs_sorting = FALSE;
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}
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/* Find entry index in the given chain with maximal address <= source. */
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static size_t xg_find_chain_entry (struct trampoline_chain *tc,
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addressT source)
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{
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size_t a = 0;
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size_t b = tc->n_entries;
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if (tc->needs_sorting)
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xg_sort_trampoline_chain (tc);
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while (b - a > 1)
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{
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size_t c = (a + b) / 2;
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struct trampoline_chain_entry *e = tc->entry + c;
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if (S_GET_VALUE(e->sym) + e->offset <= source)
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a = c;
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else
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b = c;
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}
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return a;
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}
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/* Find the best jump target for the source in the given trampoline chain.
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The best jump target is the one that results in the shortest path to the
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final target, it's the location of the jump closest to the final target,
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but within the J_RANGE - J_MARGIN from the source. */
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static struct trampoline_chain_entry *
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xg_get_best_chain_entry (struct trampoline_chain *tc, addressT source)
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{
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addressT target = S_GET_VALUE(tc->target.sym) + tc->target.offset;
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size_t i = xg_find_chain_entry (tc, source);
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struct trampoline_chain_entry *e = tc->entry + i;
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int step = target < source ? -1 : 1;
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addressT chained_target;
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offsetT off;
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if (target > source &&
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S_GET_VALUE(e->sym) + e->offset <= source &&
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i + 1 < tc->n_entries)
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++i;
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while (i + step < tc->n_entries)
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{
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struct trampoline_chain_entry *next = tc->entry + i + step;
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chained_target = S_GET_VALUE(next->sym) + next->offset;
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off = source - chained_target;
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if (labs (off) >= J_RANGE - J_MARGIN)
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break;
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i += step;
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}
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e = tc->entry + i;
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chained_target = S_GET_VALUE(e->sym) + e->offset;
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off = source - chained_target;
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if (labs (off) < J_MARGIN ||
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labs (off) >= J_RANGE - J_MARGIN)
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return &tc->target;
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return tc->entry + i;
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}
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static int xg_order_trampoline_chain (const void *a, const void *b)
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{
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const struct trampoline_chain *pa = a;
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const struct trampoline_chain *pb = b;
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return xg_order_trampoline_chain_entry (&pa->target, &pb->target);
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}
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static struct trampoline_chain *
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xg_get_trampoline_chain (struct trampoline_seg *ts,
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symbolS *sym,
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addressT offset)
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{
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struct trampoline_chain_index *idx = &ts->chain_index;
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struct trampoline_chain c;
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if (idx->needs_sorting)
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{
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qsort (idx->entry, idx->n_entries, sizeof (*idx->entry),
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xg_order_trampoline_chain);
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idx->needs_sorting = FALSE;
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}
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c.target.sym = sym;
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c.target.offset = offset;
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return bsearch (&c, idx->entry, idx->n_entries,
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sizeof (struct trampoline_chain),
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xg_order_trampoline_chain);
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}
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/* Find trampoline chain in the given trampoline segment that is going
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to the *sym + *offset. If found, replace *sym and *offset with the
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best jump target in that chain. */
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static struct trampoline_chain *
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xg_find_best_eq_target (struct trampoline_seg *ts,
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addressT source, symbolS **sym,
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addressT *offset)
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{
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struct trampoline_chain *tc = xg_get_trampoline_chain (ts, *sym, *offset);
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if (tc)
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{
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struct trampoline_chain_entry *e = xg_get_best_chain_entry (tc, source);
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*sym = e->sym;
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*offset = e->offset;
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}
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return tc;
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}
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static void xg_add_location_to_chain (struct trampoline_chain *tc,
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symbolS *sym, addressT offset)
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{
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struct trampoline_chain_entry *e;
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if (tc->n_entries == tc->n_max)
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{
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tc->n_max = (tc->n_max + 1) * 2;
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tc->entry = xrealloc (tc->entry, sizeof (*tc->entry) * tc->n_max);
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}
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e = tc->entry + tc->n_entries;
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e->sym = sym;
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e->offset = offset;
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++tc->n_entries;
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tc->needs_sorting = TRUE;
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}
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static struct trampoline_chain *
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xg_create_trampoline_chain (struct trampoline_seg *ts,
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symbolS *sym, addressT offset)
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{
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struct trampoline_chain_index *idx = &ts->chain_index;
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struct trampoline_chain *tc;
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if (idx->n_entries == idx->n_max)
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{
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idx->n_max = (idx->n_max + 1) * 2;
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idx->entry = xrealloc (idx->entry,
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sizeof (*idx->entry) * idx->n_max);
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}
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tc = idx->entry + idx->n_entries;
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tc->target.sym = sym;
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tc->target.offset = offset;
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tc->entry = NULL;
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tc->n_entries = 0;
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tc->n_max = 0;
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xg_add_location_to_chain (tc, sym, offset);
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++idx->n_entries;
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idx->needs_sorting = TRUE;
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return tc;
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}
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void dump_trampolines (void);
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void
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@ -9200,9 +9411,24 @@ static void xg_relax_fixups (struct trampoline_seg *ts)
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for (fx = seginfo->fix_root; fx; fx = fx->fx_next)
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{
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fixS *fixP = fx;
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struct trampoline_chain *tc = NULL;
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if (xg_is_relaxable_fixup (fixP))
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{
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tc = xg_find_best_eq_target (ts, fixP->fx_frag->fr_address,
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&fixP->fx_addsy, &fixP->fx_offset);
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if (!tc)
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tc = xg_create_trampoline_chain (ts, fixP->fx_addsy,
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fixP->fx_offset);
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gas_assert (tc);
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}
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while (xg_is_relaxable_fixup (fixP))
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fixP = xg_relax_fixup (idx, fixP);
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{
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fixP = xg_relax_fixup (idx, fixP);
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xg_add_location_to_chain (tc, fixP->fx_frag->fr_symbol,
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fixP->fx_where);
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}
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}
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}
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@ -9889,14 +10115,14 @@ init_trampoline_frag (fragS *fp)
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return growth;
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}
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static int
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add_jump_to_trampoline (fragS *tramp, fragS *origfrag)
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xg_get_single_symbol_slot (fragS *fragP)
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{
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int i, slot = -1;
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int i;
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int slot = -1;
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for (i = 0; i < MAX_SLOTS; ++i)
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if (origfrag->tc_frag_data.slot_symbols[i])
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if (fragP->tc_frag_data.slot_symbols[i])
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{
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gas_assert (slot == -1);
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slot = i;
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@ -9904,10 +10130,19 @@ add_jump_to_trampoline (fragS *tramp, fragS *origfrag)
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gas_assert (slot >= 0 && slot < MAX_SLOTS);
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return slot;
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}
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static fixS *
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add_jump_to_trampoline (fragS *tramp, fragS *origfrag)
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{
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int slot = xg_get_single_symbol_slot (origfrag);
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fixS *fixP;
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/* Assemble a jump to the target label in the trampoline frag. */
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xg_append_jump (tramp,
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origfrag->tc_frag_data.slot_symbols[slot],
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origfrag->tc_frag_data.slot_offsets[slot]);
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fixP = xg_append_jump (tramp,
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origfrag->tc_frag_data.slot_symbols[slot],
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origfrag->tc_frag_data.slot_offsets[slot]);
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/* Modify the original j to point here. */
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origfrag->tc_frag_data.slot_symbols[slot] = tramp->fr_symbol;
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@ -9923,7 +10158,7 @@ add_jump_to_trampoline (fragS *tramp, fragS *origfrag)
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xg_remove_trampoline_from_index (&ts->index, tr);
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}
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return 3;
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return fixP;
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}
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@ -10072,15 +10307,42 @@ relax_frag_immed (segT segP,
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istack.insn[istack.ninsn - 2].opcode == xtensa_j_opcode)
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{
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TInsn *jinsn = &istack.insn[istack.ninsn - 2];
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struct trampoline_seg *ts = find_trampoline_seg (segP);
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struct trampoline_chain *tc = NULL;
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if (!xg_symbolic_immeds_fit (jinsn, segP, fragP, fragP->fr_offset, total_text_diff))
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if (ts &&
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!xg_symbolic_immeds_fit (jinsn, segP, fragP, fragP->fr_offset,
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total_text_diff))
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{
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int s = xg_get_single_symbol_slot (fragP);
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addressT offset = fragP->tc_frag_data.slot_offsets[s];
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tc = xg_find_best_eq_target (ts, fragP->fr_address,
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&fragP->tc_frag_data.slot_symbols[s],
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&offset);
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if (!tc)
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tc = xg_create_trampoline_chain (ts,
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fragP->tc_frag_data.slot_symbols[s],
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offset);
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fragP->tc_frag_data.slot_offsets[s] = offset;
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tinsn_immed_from_frag (jinsn, fragP, s);
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}
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if (!xg_symbolic_immeds_fit (jinsn, segP, fragP, fragP->fr_offset,
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total_text_diff))
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{
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fragS *tf = xg_find_best_trampoline_for_tinsn (jinsn, fragP);
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if (tf)
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{
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this_text_diff += init_trampoline_frag (tf);
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this_text_diff += add_jump_to_trampoline (tf, fragP);
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fixS *fixP;
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this_text_diff += init_trampoline_frag (tf) + 3;
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fixP = add_jump_to_trampoline (tf, fragP);
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xg_add_location_to_chain (tc, fixP->fx_frag->fr_symbol,
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fixP->fx_where);
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fragP->tc_frag_data.relax_seen = FALSE;
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}
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else
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{
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@ -99,6 +99,7 @@ if [istarget xtensa*-*-*] then {
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run_dump_test "weak-call"
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run_dump_test "jlong"
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run_dump_test "trampoline"
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run_list_test "trampoline-2"
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run_dump_test "first_frag_align"
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run_dump_test "auto-litpools"
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run_dump_test "auto-litpools-first1"
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@ -0,0 +1 @@
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# No warnings or errors expected!
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@ -0,0 +1,20 @@
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.text
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.rep 4000
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bnez a2, .L1
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.endr
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.rep 100000
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_nop
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.endr
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.L1:
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j .L1
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.rep 100000
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_nop
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.endr
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.rep 4000
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bnez a2, .L1
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.endr
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@ -5,29 +5,28 @@
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.*: +file format .*xtensa.*
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#...
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.*0:.*j.0x1194c
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.*3:.*j.0x1194f
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||||
.*6:.*j.0x11952
|
||||
.*9:.*j.0x11955
|
||||
.*3:.*j.0x1194c
|
||||
.*6:.*j.0x1194f
|
||||
.*9:.*j.0x11952
|
||||
#...
|
||||
.*11949:.*j.0x11958
|
||||
.*1194c:.*j.0x24a0b
|
||||
.*11949:.*j.0x11955
|
||||
.*1194c:.*j.0x24a08
|
||||
.*1194f:.*j.0x24a0b
|
||||
.*11952:.*j.0x24a0e
|
||||
.*11955:.*j.0x2d687
|
||||
.*11952:.*j.0x2d684
|
||||
#...
|
||||
.*24a08:.*j.0x24a08
|
||||
.*24a0b:.*j.0x24a0b
|
||||
.*24a0e:.*j.0x24a0e
|
||||
#...
|
||||
.*2d684:.*ret
|
||||
.*2d687:.*j.0x49404
|
||||
.*2d681:.*ret
|
||||
.*2d684:.*j.0x49401
|
||||
#...
|
||||
.*49404:.*j.0x49404
|
||||
.*49407:.*beqz.n.a2,.0x4940c
|
||||
.*49409:.*j.0x61aa2
|
||||
.*49401:.*j.0x49401
|
||||
.*49404:.*beqz.n.a2,.0x49409
|
||||
.*49406:.*j.0x61a9f
|
||||
#...
|
||||
.*61aa2:.*j.0x7a13b
|
||||
.*61a9f:.*j.0x7a138
|
||||
#...
|
||||
.*7a13b:.*j.0x927f5
|
||||
.*7a138:.*j.0x927f8
|
||||
#...
|
||||
.*927f5:.*j.0x927f5
|
||||
.*927f8:.*j.0x927f8
|
||||
#...
|
||||
|
|
|
|||
|
|
@ -25,6 +25,7 @@
|
|||
_ret
|
||||
.endr
|
||||
_nop
|
||||
_nop
|
||||
4:
|
||||
j 4b
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue