From: David Weatherford Date: Fri, 21 Mar 2014 11:53:42 +0000 (+0000) Subject: Add support to the Xtensa target for creating trampolines for out-of-range branches. X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=a82c7d9030b67a6a76a5403d0e1641f9e42141ac;p=binutils-gdb.git Add support to the Xtensa target for creating trampolines for out-of-range branches. * tc-xtensa.c (xtensa_check_frag_count, xtensa_create_trampoline_frag) (xtensa_maybe_create_trampoline_frag, init_trampoline_frag) (find_trampoline_seg, search_trampolines, get_best_trampoline) (check_and_update_trampolines, add_jump_to_trampoline) (dump_trampolines): New function. (md_parse_option): Add cases for --[no-]trampolines options. (md_assemble, finish_vinsn, xtensa_end): Add call to xtensa_check_frag_count. (xg_assemble_vliw_tokens): Add call to xtensa_maybe_create_trampoline_frag. (xtensa_relax_frag): Relax fragments with RELAX_TRAMPOLINE state. (relax_frag_immed): Relax jump instructions that cannot reach its target. * tc-xtensa.h (xtensa_relax_statesE::RELAX_TRAMPOLINE): New relax state. * as.texinfo: Document --[no-]trampolines command-line options. * c-xtensa.texi: Document trampolines relaxation and command line options. * frags.c (get_frag_count, clear_frag_count): New function. (frag_alloc): Increment totalfrags counter. * frags.h (get_frag_count, clear_frag_count): New function. * all.exp: Add test for trampoline relaxation. * trampoline.d: Trampoline relaxation expected dump. * trampoline.s: Trampoline relaxation test source. --- diff --git a/gas/ChangeLog b/gas/ChangeLog index 52fb7242a29..ef4b6869b3f 100644 --- a/gas/ChangeLog +++ b/gas/ChangeLog @@ -1,3 +1,29 @@ +2014-03-21 David Weatherford + Max Filippov + + * config/tc-xtensa.c (xtensa_check_frag_count) + xtensa_create_trampoline_frag, + xtensa_maybe_create_trampoline_frag, init_trampoline_frag, + find_trampoline_seg, search_trampolines, get_best_trampoline, + check_and_update_trampolines, add_jump_to_trampoline, + dump_trampolines): New functions. + (md_parse_option): Add cases for --[no-]trampolines options. + (md_assemble, finish_vinsn, xtensa_end): Add call to + xtensa_check_frag_count. + (xg_assemble_vliw_tokens): Add call to + xtensa_maybe_create_trampoline_frag. + (xtensa_relax_frag): Relax fragments with RELAX_TRAMPOLINE state. + (relax_frag_immed): Relax jump instructions that cannot reach its + target. + * config/tc-xtensa.h (xtensa_relax_statesE::RELAX_TRAMPOLINE): New + relax state. + * doc/as.texinfo: Document --[no-]trampolines command-line options. + * doc/c-xtensa.texi: Document trampolines relaxation and command + line options. + * frags.c (get_frag_count, clear_frag_count): New function. + (frag_alloc): Increment totalfrags counter. + * frags.h (get_frag_count, clear_frag_count): New function. + 2014-03-20 DJ Delorie * config/rl78-defs.h (RL78_RELAX_NONE, RL78_RELAX_BRANCH): Add. diff --git a/gas/config/tc-xtensa.c b/gas/config/tc-xtensa.c index fe8ec0fe380..ea23c965323 100644 --- a/gas/config/tc-xtensa.c +++ b/gas/config/tc-xtensa.c @@ -468,6 +468,12 @@ static void xtensa_set_frag_assembly_state (fragS *); static void finish_vinsn (vliw_insn *); static bfd_boolean emit_single_op (TInsn *); static int total_frag_text_expansion (fragS *); +static bfd_boolean use_trampolines = TRUE; +static void xtensa_check_frag_count (void); +static void xtensa_create_trampoline_frag (bfd_boolean); +static void xtensa_maybe_create_trampoline_frag (void); +struct trampoline_frag; +static int init_trampoline_frag (struct trampoline_frag *); /* Alignment Functions. */ @@ -520,6 +526,7 @@ static void tinsn_from_chars (TInsn *, char *, int); static void tinsn_immed_from_frag (TInsn *, fragS *, int); static int get_num_stack_text_bytes (IStack *); static int get_num_stack_literal_bytes (IStack *); +static bfd_boolean tinsn_to_slotbuf (xtensa_format, int, TInsn *, xtensa_insnbuf); /* vliw_insn functions. */ @@ -687,7 +694,10 @@ enum option_prefer_l32r, option_prefer_const16, - option_target_hardware + option_target_hardware, + + option_trampolines, + option_no_trampolines, }; const char *md_shortopts = ""; @@ -760,6 +770,9 @@ struct option md_longopts[] = { "target-hardware", required_argument, NULL, option_target_hardware }, + { "trampolines", no_argument, NULL, option_trampolines }, + { "no-trampolines", no_argument, NULL, option_no_trampolines }, + { NULL, no_argument, NULL, 0 } }; @@ -940,6 +953,14 @@ md_parse_option (int c, char *arg) directive_state[directive_transform] = FALSE; return 1; + case option_trampolines: + use_trampolines = TRUE; + return 1; + + case option_no_trampolines: + use_trampolines = FALSE; + return 1; + default: return 0; } @@ -963,7 +984,9 @@ Xtensa options:\n\ flix bundles\n\ --no-allow-flix neither allow hand-written nor generate\n\ flix bundles\n\ - --rename-section old=new Rename section 'old' to 'new'\n", stream); + --rename-section old=new Rename section 'old' to 'new'\n\ + --[no-]trampolines [Do not] generate trampolines (jumps to jumps)\n\ + when jumps do not reach their targets\n", stream); } @@ -5568,6 +5591,8 @@ md_assemble (char *str) /* We've just emitted a new instruction so clear the list of labels. */ xtensa_clear_insn_labels (); + + xtensa_check_frag_count (); } @@ -6372,6 +6397,8 @@ finish_vinsn (vliw_insn *vinsn) xg_assemble_vliw_tokens (vinsn); xg_clear_vinsn (vinsn); + + xtensa_check_frag_count (); } @@ -7140,6 +7167,7 @@ xg_assemble_vliw_tokens (vliw_insn *vinsn) RELAX_UNREACHABLE, frag_now->fr_symbol, frag_now->fr_offset, NULL); xtensa_set_frag_assembly_state (frag_now); + xtensa_maybe_create_trampoline_frag (); } else if (is_branch && do_align_targets ()) { @@ -7222,9 +7250,164 @@ xtensa_end (void) xtensa_sanity_check (); xtensa_add_config_info (); + + xtensa_check_frag_count (); +} + + +struct trampoline_frag +{ + struct trampoline_frag *next; + bfd_boolean needs_jump_around; + fragS *fragP; + fixS *fixP; +}; + +struct trampoline_seg +{ + struct trampoline_seg *next; + asection *seg; + struct trampoline_frag trampoline_list; +}; + +static struct trampoline_seg trampoline_seg_list; +#define J_RANGE (128 * 1024) + +static int unreachable_count = 0; + + +static void +xtensa_maybe_create_trampoline_frag (void) +{ + if (!use_trampolines) + return; + + /* We create an area for possible trampolines every 10 unreachable frags. + These are preferred over the ones not preceded by an unreachable frag, + because we don't have to jump around them. This function is called after + each RELAX_UNREACHABLE frag is created. */ + + if (++unreachable_count > 10) + { + xtensa_create_trampoline_frag (FALSE); + clear_frag_count (); + unreachable_count = 0; + } +} + +static void +xtensa_check_frag_count (void) +{ + if (!use_trampolines || frag_now->tc_frag_data.is_no_transform) + return; + + /* We create an area for possible trampolines every 8000 frags or so. This + is an estimate based on the max range of a "j" insn (+/-128K) divided + by a typical frag byte count (16), minus a few for safety. This function + is called after each source line is processed. */ + + if (get_frag_count () > 8000) + { + xtensa_create_trampoline_frag (TRUE); + clear_frag_count (); + unreachable_count = 0; + } +} + +static xtensa_insnbuf trampoline_buf = NULL; +static xtensa_insnbuf trampoline_slotbuf = NULL; + +#define TRAMPOLINE_FRAG_SIZE 3000 + +static void +xtensa_create_trampoline_frag (bfd_boolean needs_jump_around) +{ + /* Emit a frag where we can place intermediate jump instructions, + in case we need to jump farther than 128K bytes. + Each jump instruction takes three bytes. + We allocate enough for 1000 trampolines in each frag. + If that's not enough, oh well. */ + + struct trampoline_seg *ts = trampoline_seg_list.next; + struct trampoline_frag *tf; + char *varP; + fragS *fragP; + int size = TRAMPOLINE_FRAG_SIZE; + + for ( ; ts; ts = ts->next) + { + if (ts->seg == now_seg) + break; + } + + if (ts == NULL) + { + ts = (struct trampoline_seg *)xcalloc(sizeof (struct trampoline_seg), 1); + ts->next = trampoline_seg_list.next; + trampoline_seg_list.next = ts; + ts->seg = now_seg; + } + + frag_wane (frag_now); + frag_new (0); + xtensa_set_frag_assembly_state (frag_now); + varP = frag_var (rs_machine_dependent, size, size, RELAX_TRAMPOLINE, NULL, 0, NULL); + fragP = (fragS *)(varP - SIZEOF_STRUCT_FRAG); + if (trampoline_buf == NULL) + { + trampoline_buf = xtensa_insnbuf_alloc (xtensa_default_isa); + trampoline_slotbuf = xtensa_insnbuf_alloc (xtensa_default_isa); + } + tf = (struct trampoline_frag *)xmalloc(sizeof (struct trampoline_frag)); + tf->next = ts->trampoline_list.next; + ts->trampoline_list.next = tf; + tf->needs_jump_around = needs_jump_around; + tf->fragP = fragP; + tf->fixP = NULL; +} + + +static struct trampoline_seg * +find_trampoline_seg (asection *seg) +{ + struct trampoline_seg *ts = trampoline_seg_list.next; + + for ( ; ts; ts = ts->next) + { + if (ts->seg == seg) + return ts; + } + + return NULL; } +void dump_trampolines (void); + +void +dump_trampolines (void) +{ + struct trampoline_seg *ts = trampoline_seg_list.next; + + for ( ; ts; ts = ts->next) + { + asection *seg = ts->seg; + + if (seg == NULL) + continue; + fprintf(stderr, "SECTION %s\n", seg->name); + struct trampoline_frag *tf = ts->trampoline_list.next; + for ( ; tf; tf = tf->next) + { + if (tf->fragP == NULL) + continue; + fprintf(stderr, " 0x%08x: fix=%d, jump_around=%s\n", + (int)tf->fragP->fr_address, (int)tf->fragP->fr_fix, + tf->needs_jump_around ? "T" : "F"); + } + } +} + static void xtensa_cleanup_align_frags (void) { @@ -8708,6 +8891,149 @@ xtensa_relax_frag (fragS *fragP, long stretch, int *stretched_p) new_stretch += relax_frag_for_align (fragP, stretch); break; + case RELAX_TRAMPOLINE: + if (fragP->tc_frag_data.relax_seen) + { + segment_info_type *seginfo = seg_info (now_seg); + fragS *fP; /* The out-of-range jump. */ + fixS *fixP; + + /* Scan for jumps that will not reach. */ + for (fixP = seginfo->fix_root; fixP ; fixP = fixP->fx_next) + { + symbolS *s = fixP->fx_addsy; + xtensa_opcode opcode; + int target; + int addr; + int delta; + + if (fixP->fx_r_type < BFD_RELOC_XTENSA_SLOT0_OP || + fixP->fx_r_type > BFD_RELOC_XTENSA_SLOT14_OP) + continue; + xtensa_insnbuf_from_chars (isa, trampoline_buf, + (unsigned char *) fixP->fx_frag->fr_literal + fixP->fx_where, + 0); + fmt = xtensa_format_decode (isa, trampoline_buf); + gas_assert (fmt != XTENSA_UNDEFINED); + slot = fixP->tc_fix_data.slot; + xtensa_format_get_slot (isa, fmt, slot, trampoline_buf, trampoline_slotbuf); + opcode = xtensa_opcode_decode (isa, fmt, slot, trampoline_slotbuf); + if (opcode != xtensa_j_opcode) + continue; + target = S_GET_VALUE (s); + addr = fixP->fx_frag->fr_address; + delta = target - addr + stretch; + if (delta > J_RANGE || delta < -1 * J_RANGE) + { /* Found an out-of-range jump; scan the list of trampolines for the best match. */ + struct trampoline_seg *ts = find_trampoline_seg (now_seg); + struct trampoline_frag *tf = ts->trampoline_list.next; + struct trampoline_frag *prev = &ts->trampoline_list; + int lower = (target < addr) ? target : addr; + int upper = (target > addr) ? target : addr; + int midpoint = lower + (upper - lower) / 2; + + if ((upper - lower) > 2 * J_RANGE) + { + /* One trampoline won't suffice; we need multiple jumps. + Jump to the trampoline that's farthest, but still in + range relative to the original "j" instruction. */ + for ( ; tf; prev = tf, tf = tf->next ) + { + int this_addr = tf->fragP->fr_address + tf->fragP->fr_fix; + int next_addr = (tf->next) ? tf->next->fragP->fr_address + tf->next->fragP->fr_fix : 0 ; + + if (addr == lower) + { + /* Forward jump. */ + if (this_addr - addr < J_RANGE) + break; + } + else + { + /* Backward jump. */ + if (next_addr == 0 || addr - next_addr > J_RANGE) + break; + } + } + } + else + { + struct trampoline_frag *best_tf = NULL; + int best_delta = 0; + + for ( ; tf; prev = tf, tf = tf->next ) + { + int this_addr = tf->fragP->fr_address + tf->fragP->fr_fix; + int this_delta = abs (this_addr - midpoint); + + if (!best_tf || this_delta < best_delta) + { + best_tf = tf; + best_delta = this_delta; + } + } + tf = best_tf; + } + if (tf->fragP == fragP) + { + int trampaddr = fragP->fr_address + fragP->fr_fix; + + if (abs (addr - trampaddr) < J_RANGE) + { /* The trampoline is in range of original; fix it! */ + fixS *newfixP; + int offset; + TInsn insn; + symbolS *lsym; + + new_stretch += init_trampoline_frag (tf); + offset = fragP->fr_fix; /* Where to assemble the j insn. */ + lsym = fragP->fr_symbol; + fP = fixP->fx_frag; + /* Assemble a jump to the target label here. */ + tinsn_init (&insn); + insn.insn_type = ITYPE_INSN; + insn.opcode = xtensa_j_opcode; + insn.ntok = 1; + set_expr_symbol_offset (&insn.tok[0], lsym, offset); + fmt = xg_get_single_format (xtensa_j_opcode); + tinsn_to_slotbuf (fmt, 0, &insn, trampoline_slotbuf); + xtensa_format_set_slot (isa, fmt, 0, trampoline_buf, trampoline_slotbuf); + xtensa_insnbuf_to_chars (isa, trampoline_buf, (unsigned char *)fragP->fr_literal + offset, 3); + fragP->fr_fix += 3; + fragP->fr_var -= 3; + /* Add a fix-up for the original j insn. */ + newfixP = fix_new (fP, fixP->fx_where, fixP->fx_size, lsym, fragP->fr_fix - 3, TRUE, fixP->fx_r_type); + newfixP->fx_no_overflow = 1; + newfixP->tc_fix_data.X_add_symbol = lsym; + newfixP->tc_fix_data.X_add_number = offset; + newfixP->tc_fix_data.slot = slot; + /* Move the fix-up from the original j insn to this one. */ + fixP->fx_frag = fragP; + fixP->fx_where = fragP->fr_fix - 3; + fixP->tc_fix_data.slot = 0; + /* Adjust the jump around this trampoline (if present). */ + if (tf->fixP != NULL) + { + tf->fixP->fx_offset += 3; + } + new_stretch += 3; + fragP->tc_frag_data.relax_seen = FALSE; /* Need another pass. */ + /* Do we have room for more? */ + if (fragP->fr_var < 3) + { /* No, convert to fill. */ + frag_wane (fragP); + fragP->fr_subtype = 0; + /* Remove from the trampoline_list. */ + prev->next = tf->next; + break; + } + } + } + } + } + } + break; + default: as_bad (_("bad relaxation state")); } @@ -9146,6 +9472,200 @@ bytes_to_stretch (fragS *this_frag, } +static struct trampoline_frag * +search_trampolines (TInsn *tinsn, fragS *fragP, bfd_boolean unreachable_only) +{ + struct trampoline_seg *ts = find_trampoline_seg (now_seg); + struct trampoline_frag *tf = (ts) ? ts->trampoline_list.next : NULL; + struct trampoline_frag *best_tf = NULL; + int best_delta = 0; + int best_addr = 0; + symbolS *sym = tinsn->tok[0].X_add_symbol; + offsetT target = S_GET_VALUE (sym) + tinsn->tok[0].X_add_number; + offsetT addr = fragP->fr_address; + offsetT lower = (addr < target) ? addr : target; + offsetT upper = (addr > target) ? addr : target; + int delta = upper - lower; + offsetT midpoint = lower + delta / 2; + int this_delta = -1; + int this_addr = -1; + + if (delta > 2 * J_RANGE) + { + /* One trampoline won't do; we need multiple. + Choose the farthest trampoline that's still in range of the original + and let a later pass finish the job. */ + for ( ; tf; tf = tf->next) + { + int next_addr = (tf->next) ? tf->next->fragP->fr_address + tf->next->fragP->fr_fix : 0; + + this_addr = tf->fragP->fr_address + tf->fragP->fr_fix; + if (lower == addr) + { + /* Forward jump. */ + if (this_addr - addr < J_RANGE) + break; + } + else + { + /* Backward jump. */ + if (next_addr == 0 || addr - next_addr > J_RANGE) + break; + } + if (abs (addr - this_addr) < J_RANGE) + return tf; + + return NULL; + } + } + for ( ; tf; tf = tf->next) + { + this_addr = tf->fragP->fr_address + tf->fragP->fr_fix; + this_delta = abs (this_addr - midpoint); + if (unreachable_only && tf->needs_jump_around) + continue; + if (!best_tf || this_delta < best_delta) + { + best_tf = tf; + best_delta = this_delta; + best_addr = this_addr; + } + } + + if (best_tf && + best_delta < J_RANGE && + abs(best_addr - lower) < J_RANGE && + abs(best_addr - upper) < J_RANGE) + return best_tf; + + return NULL; /* No suitable trampoline found. */ +} + + +static struct trampoline_frag * +get_best_trampoline (TInsn *tinsn, fragS *fragP) +{ + struct trampoline_frag *tf = NULL; + + tf = search_trampolines (tinsn, fragP, TRUE); /* Try unreachable first. */ + + if (tf == NULL) + tf = search_trampolines (tinsn, fragP, FALSE); /* Try ones needing a jump-around, too. */ + + return tf; +} + + +static void +check_and_update_trampolines (void) +{ + struct trampoline_seg *ts = find_trampoline_seg (now_seg); + struct trampoline_frag *tf = ts->trampoline_list.next; + struct trampoline_frag *prev = &ts->trampoline_list; + + for ( ; tf; prev = tf, tf = tf->next) + { + if (tf->fragP->fr_var < 3) + { + frag_wane (tf->fragP); + prev->next = tf->next; + tf->fragP = NULL; + } + } +} + + +static int +init_trampoline_frag (struct trampoline_frag *trampP) +{ + fragS *fp = trampP->fragP; + int growth = 0; + + if (fp->fr_fix == 0) + { + symbolS *lsym; + char label[10 + 2 * sizeof(fp)]; + sprintf (label, ".L0_TR_%p", fp); + + lsym = (symbolS *)local_symbol_make (label, now_seg, 0, fp); + fp->fr_symbol = lsym; + if (trampP->needs_jump_around) + { + /* Add a jump around this block of jumps, in case + control flows into this block. */ + fixS *fixP; + TInsn insn; + xtensa_format fmt; + xtensa_isa isa = xtensa_default_isa; + + fp->tc_frag_data.is_insn = 1; + /* Assemble a jump insn. */ + tinsn_init (&insn); + insn.insn_type = ITYPE_INSN; + insn.opcode = xtensa_j_opcode; + insn.ntok = 1; + set_expr_symbol_offset (&insn.tok[0], lsym, 3); + fmt = xg_get_single_format (xtensa_j_opcode); + tinsn_to_slotbuf (fmt, 0, &insn, trampoline_slotbuf); + xtensa_format_set_slot (isa, fmt, 0, trampoline_buf, trampoline_slotbuf); + xtensa_insnbuf_to_chars (isa, trampoline_buf, (unsigned char *)fp->fr_literal, 3); + fp->fr_fix += 3; + fp->fr_var -= 3; + growth = 3; + fixP = fix_new (fp, 0, 3, lsym, 3, TRUE, BFD_RELOC_XTENSA_SLOT0_OP); + trampP->fixP = fixP; + } + } + return growth; +} + + +static int +add_jump_to_trampoline (struct trampoline_frag *trampP, fragS *origfrag) +{ + fragS *tramp = trampP->fragP; + fixS *fixP; + int offset = tramp->fr_fix; /* Where to assemble the j insn. */ + TInsn insn; + symbolS *lsym; + symbolS *tsym; + int toffset; + xtensa_format fmt; + xtensa_isa isa = xtensa_default_isa; + int growth = 0; + + lsym = tramp->fr_symbol; + /* Assemble a jump to the target label in the trampoline frag. */ + tsym = origfrag->tc_frag_data.slot_symbols[0]; + toffset = origfrag-> tc_frag_data.slot_offsets[0]; + tinsn_init (&insn); + insn.insn_type = ITYPE_INSN; + insn.opcode = xtensa_j_opcode; + insn.ntok = 1; + set_expr_symbol_offset (&insn.tok[0], tsym, toffset); + fmt = xg_get_single_format (xtensa_j_opcode); + tinsn_to_slotbuf (fmt, 0, &insn, trampoline_slotbuf); + xtensa_format_set_slot (isa, fmt, 0, trampoline_buf, trampoline_slotbuf); + xtensa_insnbuf_to_chars (isa, trampoline_buf, (unsigned char *)tramp->fr_literal + offset, 3); + tramp->fr_fix += 3; + tramp->fr_var -= 3; + growth = 3; + /* add a fix-up for the trampoline jump. */ + fixP = fix_new (tramp, tramp->fr_fix - 3, 3, tsym, toffset, TRUE, BFD_RELOC_XTENSA_SLOT0_OP); + /* Modify the jump at the start of this trampoline to point past the newly-added jump. */ + fixP = trampP->fixP; + if (fixP) + fixP->fx_offset += 3; + /* Modify the original j to point here. */ + origfrag->tc_frag_data.slot_symbols[0] = lsym; + origfrag->tc_frag_data.slot_offsets[0] = tramp->fr_fix - 3; + /* If trampoline is full, remove it from the list. */ + check_and_update_trampolines (); + + return growth; +} + + static long relax_frag_immed (segT segP, fragS *fragP, @@ -9284,6 +9804,37 @@ relax_frag_immed (segT segP, if (negatable_branch && istack.ninsn > 1) update_next_frag_state (fragP); + /* If last insn is a jump, and it cannot reach its target, try to find a trampoline. */ + if (istack.ninsn > 2 && + istack.insn[istack.ninsn - 1].insn_type == ITYPE_LABEL && + istack.insn[istack.ninsn - 2].insn_type == ITYPE_INSN && + istack.insn[istack.ninsn - 2].opcode == xtensa_j_opcode) + { + TInsn *jinsn = &istack.insn[istack.ninsn - 2]; + + if (!xg_symbolic_immeds_fit (jinsn, segP, fragP, fragP->fr_offset, total_text_diff)) + { + struct trampoline_frag *tf = get_best_trampoline (jinsn, fragP); + + if (tf) + { + this_text_diff += init_trampoline_frag (tf); + this_text_diff += add_jump_to_trampoline (tf, fragP); + } + else + { + /* If target symbol is undefined, assume it will reach once linked. */ + expressionS *exp = &istack.insn[istack.ninsn - 2].tok[0]; + + if (exp->X_op == O_symbol && S_IS_DEFINED (exp->X_add_symbol)) + { + as_bad_where (fragP->fr_file, fragP->fr_line, + _("jump target out of range; no usable trampoline found")); + } + } + } + } + return this_text_diff; } @@ -9404,6 +9955,9 @@ md_convert_frag (bfd *abfd ATTRIBUTE_UNUSED, segT sec, fragS *fragp) else as_bad (_("invalid relaxation fragment result")); break; + + case RELAX_TRAMPOLINE: + break; } fragp->fr_var = 0; diff --git a/gas/config/tc-xtensa.h b/gas/config/tc-xtensa.h index 0bf1240e464..4672bc60c42 100644 --- a/gas/config/tc-xtensa.h +++ b/gas/config/tc-xtensa.h @@ -180,6 +180,11 @@ enum xtensa_relax_statesE prevent the linker from changing the size of any frag between the section start and the org frag. */ + RELAX_TRAMPOLINE, + /* Every few thousand frags, we insert one of these, just in case we may + need some space for a trampoline (jump to a jump) because the function + has gotten too big. If not needed, it disappears. */ + RELAX_NONE }; diff --git a/gas/doc/as.texinfo b/gas/doc/as.texinfo index 5c8b000f60f..dc971754d7d 100644 --- a/gas/doc/as.texinfo +++ b/gas/doc/as.texinfo @@ -543,6 +543,7 @@ gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}. [@b{--[no-]target-align}] [@b{--[no-]longcalls}] [@b{--[no-]transform}] [@b{--rename-section} @var{oldname}=@var{newname}] + [@b{--[no-]trampolines}] @end ifset @ifset Z80 diff --git a/gas/doc/c-xtensa.texi b/gas/doc/c-xtensa.texi index 406e635f3f8..e763e368f30 100644 --- a/gas/doc/c-xtensa.texi +++ b/gas/doc/c-xtensa.texi @@ -91,6 +91,16 @@ instruction operands to be errors. @kindex --rename-section Rename the @var{oldname} section to @var{newname}. This option can be used multiple times to rename multiple sections. + +@item --trampolines | --no-trampolines +@kindex --trampolines +@kindex --no-trampolines +Enable or disable transformation of jump instructions to allow jumps +across a greater range of addresses. @xref{Xtensa Jump Relaxation, +,Jump Trampolines}. This option should be used when jump targets can +potentially be out of range. In the absence of such jumps this option +does not affect code size or performance. The default is +@samp{--trampolines}. @end table @c man end @@ -311,6 +321,7 @@ fields. @menu * Xtensa Branch Relaxation:: Relaxation of Branches. * Xtensa Call Relaxation:: Relaxation of Function Calls. +* Xtensa Jump Relaxation:: Relaxation of Jumps. * Xtensa Immediate Relaxation:: Relaxation of other Immediate Fields. @end menu @@ -398,6 +409,87 @@ and some of the calls are out of range, function call relaxation can be enabled using the @samp{--longcalls} command-line option or the @code{longcalls} directive (@pxref{Longcalls Directive, ,longcalls}). +@node Xtensa Jump Relaxation +@subsection Jump Relaxation +@cindex relaxation of jump instructions +@cindex jump instructions, relaxation + +Jump instruction may require relaxation because the Xtensa jump instruction +(@code{J}) provide a PC-relative offset of only 128 Kbytes in either +direction. One option is to use jump long (@code{J.L}) instruction, which +depending on jump distance may be assembled as jump (@code{J}) or indirect +jump (@code{JX}). However it needs a free register. When there's no spare +register it is possible to plant intermediate jump sites (trampolines) +between the jump instruction and its target. These sites may be located in +areas unreachable by normal code execution flow, in that case they only +contain intermediate jumps, or they may be inserted in the middle of code +block, in which case there's an additional jump from the beginning of the +trampoline to the instruction past its end. So, for example: + +@smallexample +@group + j 1f + ... + retw + ... + mov a10, a2 + call8 func + ... +1: + ... +@end group +@end smallexample + +might be relaxed to: + +@smallexample +@group + j .L0_TR_1 + ... + retw +.L0_TR_1: + j 1f + ... + mov a10, a2 + call8 func + ... +1: + ... +@end group +@end smallexample + +or to: + +@smallexample +@group + j .L0_TR_1 + ... + retw + ... + mov a10, a2 + j .L0_TR_0 +.L0_TR_1: + j 1f +.L0_TR_0: + call8 func + ... +1: + ... +@end group +@end smallexample + +The Xtensa assempler uses trampolines with jump around only when it cannot +find suitable unreachable trampoline. There may be multiple trampolines +between the jump instruction and its target. + +This relaxation does not apply to jumps to undefined symbols, assuming they +will reach their targets once resolved. + +Jump relaxation is enabled by default because it does not affect code size +or performance while the code itself is small. This relaxation may be +disabled completely with @samp{--no-trampolines} or @samp{--no-transform} +command-line options (@pxref{Xtensa Options, ,Command Line Options}). + @node Xtensa Immediate Relaxation @subsection Other Immediate Field Relaxation @cindex immediate fields, relaxation diff --git a/gas/frags.c b/gas/frags.c index 5f68480e512..e14099dda45 100644 --- a/gas/frags.c +++ b/gas/frags.c @@ -24,6 +24,20 @@ extern fragS zero_address_frag; extern fragS predefined_address_frag; + +static int totalfrags; + +int +get_frag_count (void) +{ + return totalfrags; +} + +void +clear_frag_count (void) +{ + totalfrags = 0; +} /* Initialization for frag routines. */ @@ -70,6 +84,7 @@ frag_alloc (struct obstack *ob) ptr = (fragS *) obstack_alloc (ob, SIZEOF_STRUCT_FRAG); obstack_alignment_mask (ob) = oalign; memset (ptr, 0, SIZEOF_STRUCT_FRAG); + totalfrags++; return ptr; } diff --git a/gas/frags.h b/gas/frags.h index 319898fbecc..2f9e1b571d2 100644 --- a/gas/frags.h +++ b/gas/frags.h @@ -155,4 +155,7 @@ char *frag_var (relax_stateT type, bfd_boolean frag_offset_fixed_p (const fragS *, const fragS *, offsetT *); +int get_frag_count (void); +void clear_frag_count (void); + #endif /* FRAGS_H */ diff --git a/gas/testsuite/ChangeLog b/gas/testsuite/ChangeLog index a7bec28ccfd..d29e949dd5c 100644 --- a/gas/testsuite/ChangeLog +++ b/gas/testsuite/ChangeLog @@ -1,3 +1,10 @@ +2014-03-21 David Weatherford + Max Filippov + + * gas/xtensa/all.exp: Add test for trampoline relaxation. + * gas/xtensa/trampoline.d: Trampoline relaxation expected dump. + * gas/xtensa/trampoline.s: Trampoline relaxation test source. + 2014-03-20 Richard Sandiford * gas/all/gas.exp: Remove XFAIL of forward.d for MIPS. diff --git a/gas/testsuite/gas/xtensa/all.exp b/gas/testsuite/gas/xtensa/all.exp index 2b2c294b8fb..3683b78f4ad 100644 --- a/gas/testsuite/gas/xtensa/all.exp +++ b/gas/testsuite/gas/xtensa/all.exp @@ -98,6 +98,7 @@ if [istarget xtensa*-*-*] then { run_dump_test "pcrel" run_dump_test "weak-call" run_dump_test "jlong" + run_dump_test "trampoline" } if [info exists errorInfo] then { diff --git a/gas/testsuite/gas/xtensa/trampoline.d b/gas/testsuite/gas/xtensa/trampoline.d new file mode 100644 index 00000000000..b4f65dc8c73 --- /dev/null +++ b/gas/testsuite/gas/xtensa/trampoline.d @@ -0,0 +1,26 @@ +#as: +#objdump: -d +#name: trampolines relaxation + +.*: +file format .*xtensa.* +#... +.*0:.*j.0x1194c +.*3:.*j.0x1194f +.*6:.*j.0x11952 +.*9:.*j.0x1d4e4 +#... +.*11949:.*j.0x11955 +.*1194c:.*j.0x24a0e +.*1194f:.*j.0x24a0e +.*11952:.*j.0x24a11 +#... +.*1d4e1:.*j.0x1d4e7 +.*1d4e4:.*j.0x33462 +#... +.*24a0e:.*j.0x24a0e +.*24a11:.*j.0x24a11 +#... +.*3345f:.*ret +.*33462:.*j.0x49407 +#... +.*49407:.*j.0x49407 diff --git a/gas/testsuite/gas/xtensa/trampoline.s b/gas/testsuite/gas/xtensa/trampoline.s new file mode 100644 index 00000000000..259a3bbedcf --- /dev/null +++ b/gas/testsuite/gas/xtensa/trampoline.s @@ -0,0 +1,21 @@ + .text + j 1f + j 1f + j 2f + j 3f + .rep 25000 +99: + and a2, a2, a3 + bne a2, a3, 99b + .endr +1: + j 1b +2: + j 2b + + .rep 25000 + and a2, a2, a3 + _ret + .endr +3: + j 3b