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gh-113603: Compiler no longer tries to maintain the no-empty-block invariant (#113636)
This commit is contained in:
Irit Katriel
GitHub
parent
0c3455a969
commit
7d01fb4808
3 changed files with 52 additions and 78 deletions
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@ -449,6 +449,15 @@ _PyCfgBuilder_Addop(cfg_builder *g, int opcode, int oparg, location loc)
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}
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static basicblock *
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next_nonempty_block(basicblock *b)
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{
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while (b && b->b_iused == 0) {
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b = b->b_next;
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}
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return b;
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}
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/***** debugging helpers *****/
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#ifndef NDEBUG
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@ -464,24 +473,16 @@ no_redundant_nops(cfg_builder *g) {
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return true;
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}
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static bool
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no_empty_basic_blocks(cfg_builder *g) {
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for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
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if (b->b_iused == 0) {
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return false;
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}
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}
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return true;
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}
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static bool
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no_redundant_jumps(cfg_builder *g) {
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for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
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cfg_instr *last = basicblock_last_instr(b);
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if (last != NULL) {
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if (IS_UNCONDITIONAL_JUMP_OPCODE(last->i_opcode)) {
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assert(last->i_target != b->b_next);
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if (last->i_target == b->b_next) {
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basicblock *next = next_nonempty_block(b->b_next);
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basicblock *jump_target = next_nonempty_block(last->i_target);
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assert(jump_target != next);
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if (jump_target == next) {
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return false;
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}
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}
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@ -961,42 +962,6 @@ mark_reachable(basicblock *entryblock) {
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return SUCCESS;
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}
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static void
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eliminate_empty_basic_blocks(cfg_builder *g) {
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/* Eliminate empty blocks */
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for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
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basicblock *next = b->b_next;
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while (next && next->b_iused == 0) {
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next = next->b_next;
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}
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b->b_next = next;
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}
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while(g->g_entryblock && g->g_entryblock->b_iused == 0) {
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g->g_entryblock = g->g_entryblock->b_next;
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}
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int next_lbl = get_max_label(g->g_entryblock) + 1;
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for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
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assert(b->b_iused > 0);
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for (int i = 0; i < b->b_iused; i++) {
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cfg_instr *instr = &b->b_instr[i];
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if (HAS_TARGET(instr->i_opcode)) {
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basicblock *target = instr->i_target;
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while (target->b_iused == 0) {
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target = target->b_next;
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}
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if (instr->i_target != target) {
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if (!IS_LABEL(target->b_label)) {
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target->b_label.id = next_lbl++;
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}
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instr->i_target = target;
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instr->i_oparg = target->b_label.id;
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}
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assert(instr->i_target && instr->i_target->b_iused > 0);
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}
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}
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}
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}
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static int
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remove_redundant_nops(basicblock *bb) {
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/* Remove NOPs when legal to do so. */
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@ -1025,10 +990,7 @@ remove_redundant_nops(basicblock *bb) {
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}
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}
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else {
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basicblock* next = bb->b_next;
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while (next && next->b_iused == 0) {
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next = next->b_next;
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}
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basicblock *next = next_nonempty_block(bb->b_next);
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/* or if last instruction in BB and next BB has same line number */
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if (next) {
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location next_loc = NO_LOCATION;
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@ -1112,25 +1074,22 @@ remove_redundant_jumps(cfg_builder *g) {
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* can be deleted.
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*/
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assert(no_empty_basic_blocks(g));
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bool remove_empty_blocks = false;
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for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
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cfg_instr *last = basicblock_last_instr(b);
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assert(last != NULL);
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if (last == NULL) {
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continue;
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}
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assert(!IS_ASSEMBLER_OPCODE(last->i_opcode));
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if (IS_UNCONDITIONAL_JUMP_OPCODE(last->i_opcode)) {
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if (last->i_target == NULL) {
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basicblock* jump_target = next_nonempty_block(last->i_target);
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if (jump_target == NULL) {
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PyErr_SetString(PyExc_SystemError, "jump with NULL target");
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return ERROR;
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}
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if (last->i_target == b->b_next) {
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assert(b->b_next->b_iused);
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basicblock *next = next_nonempty_block(b->b_next);
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if (jump_target == next) {
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if (last->i_loc.lineno == NO_LOCATION.lineno) {
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b->b_iused--;
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if (b->b_iused == 0) {
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remove_empty_blocks = true;
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}
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}
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else {
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INSTR_SET_OP0(last, NOP);
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@ -1138,10 +1097,6 @@ remove_redundant_jumps(cfg_builder *g) {
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}
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}
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}
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if (remove_empty_blocks) {
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eliminate_empty_basic_blocks(g);
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}
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assert(no_empty_basic_blocks(g));
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return SUCCESS;
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}
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@ -1749,11 +1704,9 @@ optimize_cfg(cfg_builder *g, PyObject *consts, PyObject *const_cache)
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{
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assert(PyDict_CheckExact(const_cache));
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RETURN_IF_ERROR(check_cfg(g));
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eliminate_empty_basic_blocks(g);
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for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
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RETURN_IF_ERROR(inline_small_exit_blocks(b));
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}
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assert(no_empty_basic_blocks(g));
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for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
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RETURN_IF_ERROR(optimize_basic_block(const_cache, b, consts));
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assert(b->b_predecessors == 0);
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@ -1768,14 +1721,21 @@ optimize_cfg(cfg_builder *g, PyObject *consts, PyObject *const_cache)
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for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
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if (b->b_predecessors == 0) {
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b->b_iused = 0;
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b->b_except_handler = 0;
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}
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}
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for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
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remove_redundant_nops(b);
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}
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eliminate_empty_basic_blocks(g);
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assert(no_redundant_nops(g));
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RETURN_IF_ERROR(remove_redundant_jumps(g));
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for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
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remove_redundant_nops(b);
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}
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RETURN_IF_ERROR(remove_redundant_jumps(g));
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assert(no_redundant_jumps(g));
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return SUCCESS;
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}
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@ -1825,7 +1785,6 @@ insert_superinstructions(cfg_builder *g)
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for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
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remove_redundant_nops(b);
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}
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eliminate_empty_basic_blocks(g);
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assert(no_redundant_nops(g));
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}
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@ -2299,8 +2258,6 @@ is_exit_without_lineno(basicblock *b) {
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static int
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duplicate_exits_without_lineno(cfg_builder *g)
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{
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assert(no_empty_basic_blocks(g));
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int next_lbl = get_max_label(g->g_entryblock) + 1;
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/* Copy all exit blocks without line number that are targets of a jump.
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@ -2308,9 +2265,11 @@ duplicate_exits_without_lineno(cfg_builder *g)
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basicblock *entryblock = g->g_entryblock;
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for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
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cfg_instr *last = basicblock_last_instr(b);
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assert(last != NULL);
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if (last == NULL) {
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continue;
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}
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if (is_jump(last)) {
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basicblock *target = last->i_target;
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basicblock *target = next_nonempty_block(last->i_target);
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if (is_exit_without_lineno(target) && target->b_predecessors > 1) {
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basicblock *new_target = copy_basicblock(g, target);
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if (new_target == NULL) {
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@ -2367,9 +2326,10 @@ propagate_line_numbers(basicblock *entryblock) {
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}
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}
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if (BB_HAS_FALLTHROUGH(b) && b->b_next->b_predecessors == 1) {
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assert(b->b_next->b_iused);
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if (b->b_next->b_instr[0].i_loc.lineno < 0) {
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b->b_next->b_instr[0].i_loc = prev_location;
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if (b->b_next->b_iused > 0) {
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if (b->b_next->b_instr[0].i_loc.lineno < 0) {
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b->b_next->b_instr[0].i_loc = prev_location;
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}
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}
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}
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if (is_jump(last)) {
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