diff options
Diffstat (limited to 'gcc/gimplify.c')
| -rw-r--r-- | gcc/gimplify.c | 454 |
1 files changed, 449 insertions, 5 deletions
diff --git a/gcc/gimplify.c b/gcc/gimplify.c index e378ed0..66bb8be 100644 --- a/gcc/gimplify.c +++ b/gcc/gimplify.c @@ -160,6 +160,7 @@ struct gimplify_ctx unsigned in_cleanup_point_expr : 1; unsigned keep_stack : 1; unsigned save_stack : 1; + unsigned in_switch_expr : 1; }; struct gimplify_omp_ctx @@ -1626,6 +1627,430 @@ maybe_warn_switch_unreachable (gimple_seq seq) } } + +/* A label entry that pairs label and a location. */ +struct label_entry +{ + tree label; + location_t loc; +}; + +/* Find LABEL in vector of label entries VEC. */ + +static struct label_entry * +find_label_entry (const auto_vec<struct label_entry> *vec, tree label) +{ + unsigned int i; + struct label_entry *l; + + FOR_EACH_VEC_ELT (*vec, i, l) + if (l->label == label) + return l; + return NULL; +} + +/* Return true if LABEL, a LABEL_DECL, represents a case label + in a vector of labels CASES. */ + +static bool +case_label_p (const vec<tree> *cases, tree label) +{ + unsigned int i; + tree l; + + FOR_EACH_VEC_ELT (*cases, i, l) + if (CASE_LABEL (l) == label) + return true; + return false; +} + +/* Find the last statement in a scope STMT. */ + +static gimple * +last_stmt_in_scope (gimple *stmt) +{ + if (!stmt) + return NULL; + + switch (gimple_code (stmt)) + { + case GIMPLE_BIND: + { + gbind *bind = as_a <gbind *> (stmt); + stmt = gimple_seq_last_stmt (gimple_bind_body (bind)); + return last_stmt_in_scope (stmt); + } + + case GIMPLE_TRY: + { + gtry *try_stmt = as_a <gtry *> (stmt); + stmt = gimple_seq_last_stmt (gimple_try_eval (try_stmt)); + gimple *last_eval = last_stmt_in_scope (stmt); + if (gimple_stmt_may_fallthru (last_eval) + && gimple_try_kind (try_stmt) == GIMPLE_TRY_FINALLY) + { + stmt = gimple_seq_last_stmt (gimple_try_cleanup (try_stmt)); + return last_stmt_in_scope (stmt); + } + else + return last_eval; + } + + default: + return stmt; + } +} + +/* Collect interesting labels in LABELS and return the statement preceding + another case label, or a user-defined label. */ + +static gimple * +collect_fallthrough_labels (gimple_stmt_iterator *gsi_p, + auto_vec <struct label_entry> *labels) +{ + gimple *prev = NULL; + + do + { + if (gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_BIND + || gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_TRY) + { + /* Nested scope. Only look at the last statement of + the innermost scope. */ + location_t bind_loc = gimple_location (gsi_stmt (*gsi_p)); + gimple *last = last_stmt_in_scope (gsi_stmt (*gsi_p)); + if (last) + { + prev = last; + /* It might be a label without a location. Use the + location of the scope then. */ + if (!gimple_has_location (prev)) + gimple_set_location (prev, bind_loc); + } + gsi_next (gsi_p); + continue; + } + + /* Ifs are tricky. */ + if (gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_COND) + { + gcond *cond_stmt = as_a <gcond *> (gsi_stmt (*gsi_p)); + tree false_lab = gimple_cond_false_label (cond_stmt); + location_t if_loc = gimple_location (cond_stmt); + + /* If we have e.g. + if (i > 1) goto <D.2259>; else goto D; + we can't do much with the else-branch. */ + if (!DECL_ARTIFICIAL (false_lab)) + break; + + /* Go on until the false label, then one step back. */ + for (; !gsi_end_p (*gsi_p); gsi_next (gsi_p)) + { + gimple *stmt = gsi_stmt (*gsi_p); + if (gimple_code (stmt) == GIMPLE_LABEL + && gimple_label_label (as_a <glabel *> (stmt)) == false_lab) + break; + } + + /* Not found? Oops. */ + if (gsi_end_p (*gsi_p)) + break; + + struct label_entry l = { false_lab, if_loc }; + labels->safe_push (l); + + /* Go to the last statement of the then branch. */ + gsi_prev (gsi_p); + + /* if (i != 0) goto <D.1759>; else goto <D.1760>; + <D.1759>: + <stmt>; + goto <D.1761>; + <D.1760>: + */ + if (gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_GOTO + && !gimple_has_location (gsi_stmt (*gsi_p))) + { + /* Look at the statement before, it might be + attribute fallthrough, in which case don't warn. */ + gsi_prev (gsi_p); + bool fallthru_before_dest + = gimple_call_internal_p (gsi_stmt (*gsi_p), IFN_FALLTHROUGH); + gsi_next (gsi_p); + tree goto_dest = gimple_goto_dest (gsi_stmt (*gsi_p)); + if (!fallthru_before_dest) + { + struct label_entry l = { goto_dest, if_loc }; + labels->safe_push (l); + } + } + /* And move back. */ + gsi_next (gsi_p); + } + + /* Remember the last statement. Skip labels that are of no interest + to us. */ + if (gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_LABEL) + { + tree label = gimple_label_label (as_a <glabel *> (gsi_stmt (*gsi_p))); + if (find_label_entry (labels, label)) + prev = gsi_stmt (*gsi_p); + } + else + prev = gsi_stmt (*gsi_p); + gsi_next (gsi_p); + } + while (!gsi_end_p (*gsi_p) + /* Stop if we find a case or a user-defined label. */ + && (gimple_code (gsi_stmt (*gsi_p)) != GIMPLE_LABEL + || !gimple_has_location (gsi_stmt (*gsi_p)))); + + return prev; +} + +/* Return true if the switch fallthough warning should occur. LABEL is + the label statement that we're falling through to. */ + +static bool +should_warn_for_implicit_fallthrough (gimple_stmt_iterator *gsi_p, tree label) +{ + gimple_stmt_iterator gsi = *gsi_p; + + /* Don't warn for a non-case label followed by a statement: + case 0: + foo (); + label: + bar (); + as these are likely intentional. */ + if (!case_label_p (&gimplify_ctxp->case_labels, label)) + { + gsi_next (&gsi); + if (gsi_end_p (gsi) || gimple_code (gsi_stmt (gsi)) != GIMPLE_LABEL) + return false; + } + + /* Don't warn for terminated branches, i.e. when the subsequent case labels + immediately breaks. */ + gsi = *gsi_p; + + /* Skip all immediately following labels. */ + while (!gsi_end_p (gsi) && gimple_code (gsi_stmt (gsi)) == GIMPLE_LABEL) + gsi_next (&gsi); + + /* { ... something; default:; } */ + if (gsi_end_p (gsi) + /* { ... something; default: break; } or + { ... something; default: goto L; } */ + || gimple_code (gsi_stmt (gsi)) == GIMPLE_GOTO + /* { ... something; default: return; } */ + || gimple_code (gsi_stmt (gsi)) == GIMPLE_RETURN) + return false; + + return true; +} + +/* Callback for walk_gimple_seq. */ + +static tree +warn_implicit_fallthrough_r (gimple_stmt_iterator *gsi_p, bool *handled_ops_p, + struct walk_stmt_info *) +{ + gimple *stmt = gsi_stmt (*gsi_p); + + *handled_ops_p = true; + switch (gimple_code (stmt)) + { + case GIMPLE_TRY: + case GIMPLE_BIND: + case GIMPLE_CATCH: + case GIMPLE_EH_FILTER: + case GIMPLE_TRANSACTION: + /* Walk the sub-statements. */ + *handled_ops_p = false; + break; + + /* Find a sequence of form: + + GIMPLE_LABEL + [...] + <may fallthru stmt> + GIMPLE_LABEL + + and possibly warn. */ + case GIMPLE_LABEL: + { + /* Found a label. Skip all immediately following labels. */ + while (!gsi_end_p (*gsi_p) + && gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_LABEL) + gsi_next (gsi_p); + + /* There might be no more statements. */ + if (gsi_end_p (*gsi_p)) + return integer_zero_node; + + /* Vector of labels that fall through. */ + auto_vec <struct label_entry> labels; + gimple *prev = collect_fallthrough_labels (gsi_p, &labels); + + /* There might be no more statements. */ + if (gsi_end_p (*gsi_p)) + return integer_zero_node; + + gimple *next = gsi_stmt (*gsi_p); + tree label; + /* If what follows is a label, then we may have a fallthrough. */ + if (gimple_code (next) == GIMPLE_LABEL + && gimple_has_location (next) + && (label = gimple_label_label (as_a <glabel *> (next))) + && !FALLTHROUGH_LABEL_P (label) + && prev != NULL) + { + struct label_entry *l; + bool warned_p = false; + if (!should_warn_for_implicit_fallthrough (gsi_p, label)) + /* Quiet. */; + else if (gimple_code (prev) == GIMPLE_LABEL + && (label = gimple_label_label (as_a <glabel *> (prev))) + && (l = find_label_entry (&labels, label))) + warned_p = warning_at (l->loc, OPT_Wimplicit_fallthrough, + "this statement may fall through"); + else if (!gimple_call_internal_p (prev, IFN_FALLTHROUGH) + /* Try to be clever and don't warn when the statement + can't actually fall through. */ + && gimple_stmt_may_fallthru (prev) + && gimple_has_location (prev)) + warned_p = warning_at (gimple_location (prev), + OPT_Wimplicit_fallthrough, + "this statement may fall through"); + if (warned_p) + inform (gimple_location (next), "here"); + + /* Mark this label as processed so as to prevent multiple + warnings in nested switches. */ + FALLTHROUGH_LABEL_P (label) = true; + + /* So that next warn_implicit_fallthrough_r will start looking for + a new sequence starting with this label. */ + gsi_prev (gsi_p); + } + } + break; + default: + break; + } + return NULL_TREE; +} + +/* Warn when a switch case falls through. */ + +static void +maybe_warn_implicit_fallthrough (gimple_seq seq) +{ + if (!warn_implicit_fallthrough) + return; + + /* This warning is meant for C/C++/ObjC/ObjC++ only. */ + if (!(lang_GNU_C () + || lang_GNU_CXX () + || lang_GNU_OBJC ())) + return; + + struct walk_stmt_info wi; + memset (&wi, 0, sizeof (wi)); + walk_gimple_seq (seq, warn_implicit_fallthrough_r, NULL, &wi); +} + +/* Callback for walk_gimple_seq. */ + +static tree +expand_FALLTHROUGH_r (gimple_stmt_iterator *gsi_p, bool *handled_ops_p, + struct walk_stmt_info *) +{ + gimple *stmt = gsi_stmt (*gsi_p); + + *handled_ops_p = true; + switch (gimple_code (stmt)) + { + case GIMPLE_TRY: + case GIMPLE_BIND: + case GIMPLE_CATCH: + case GIMPLE_EH_FILTER: + case GIMPLE_TRANSACTION: + /* Walk the sub-statements. */ + *handled_ops_p = false; + break; + case GIMPLE_CALL: + if (gimple_call_internal_p (stmt, IFN_FALLTHROUGH)) + { + gsi_remove (gsi_p, true); + if (gsi_end_p (*gsi_p)) + return integer_zero_node; + + bool found = false; + location_t loc = gimple_location (stmt); + + gimple_stmt_iterator gsi2 = *gsi_p; + stmt = gsi_stmt (gsi2); + if (gimple_code (stmt) == GIMPLE_GOTO && !gimple_has_location (stmt)) + { + /* Go on until the artificial label. */ + tree goto_dest = gimple_goto_dest (stmt); + for (; !gsi_end_p (gsi2); gsi_next (&gsi2)) + { + if (gimple_code (gsi_stmt (gsi2)) == GIMPLE_LABEL + && gimple_label_label (as_a <glabel *> (gsi_stmt (gsi2))) + == goto_dest) + break; + } + + /* Not found? Stop. */ + if (gsi_end_p (gsi2)) + break; + + /* Look one past it. */ + gsi_next (&gsi2); + } + + /* We're looking for a case label or default label here. */ + while (!gsi_end_p (gsi2)) + { + stmt = gsi_stmt (gsi2); + if (gimple_code (stmt) == GIMPLE_LABEL) + { + tree label = gimple_label_label (as_a <glabel *> (stmt)); + if (gimple_has_location (stmt) && DECL_ARTIFICIAL (label)) + { + found = true; + break; + } + } + else + /* Something other than a label. That's not expected. */ + break; + gsi_next (&gsi2); + } + if (!found) + warning_at (loc, 0, "attribute %<fallthrough%> not preceding " + "a case label or default label"); + } + break; + default: + break; + } + return NULL_TREE; +} + +/* Expand all FALLTHROUGH () calls in SEQ. */ + +static void +expand_FALLTHROUGH (gimple_seq *seq_p) +{ + struct walk_stmt_info wi; + memset (&wi, 0, sizeof (wi)); + walk_gimple_seq_mod (seq_p, expand_FALLTHROUGH_r, NULL, &wi); +} + /* Gimplify a SWITCH_EXPR, and collect the vector of labels it can branch to. */ @@ -1660,10 +2085,17 @@ gimplify_switch_expr (tree *expr_p, gimple_seq *pre_p) labels. Save all the things from the switch body to append after. */ saved_labels = gimplify_ctxp->case_labels; gimplify_ctxp->case_labels.create (8); + bool old_in_switch_expr = gimplify_ctxp->in_switch_expr; + gimplify_ctxp->in_switch_expr = true; gimplify_stmt (&SWITCH_BODY (switch_expr), &switch_body_seq); + gimplify_ctxp->in_switch_expr = old_in_switch_expr; maybe_warn_switch_unreachable (switch_body_seq); + maybe_warn_implicit_fallthrough (switch_body_seq); + /* Only do this for the outermost GIMPLE_SWITCH. */ + if (!gimplify_ctxp->in_switch_expr) + expand_FALLTHROUGH (&switch_body_seq); labels = gimplify_ctxp->case_labels; gimplify_ctxp->case_labels = saved_labels; @@ -1694,6 +2126,21 @@ gimplify_switch_expr (tree *expr_p, gimple_seq *pre_p) return GS_ALL_DONE; } +/* Gimplify the LABEL_EXPR pointed to by EXPR_P. */ + +static enum gimplify_status +gimplify_label_expr (tree *expr_p, gimple_seq *pre_p) +{ + gcc_assert (decl_function_context (LABEL_EXPR_LABEL (*expr_p)) + == current_function_decl); + + glabel *label_stmt = gimple_build_label (LABEL_EXPR_LABEL (*expr_p)); + gimple_set_location (label_stmt, EXPR_LOCATION (*expr_p)); + gimplify_seq_add_stmt (pre_p, label_stmt); + + return GS_ALL_DONE; +} + /* Gimplify the CASE_LABEL_EXPR pointed to by EXPR_P. */ static enum gimplify_status @@ -1711,6 +2158,7 @@ gimplify_case_label_expr (tree *expr_p, gimple_seq *pre_p) break; label_stmt = gimple_build_label (CASE_LABEL (*expr_p)); + gimple_set_location (label_stmt, EXPR_LOCATION (*expr_p)); ctxp->case_labels.safe_push (*expr_p); gimplify_seq_add_stmt (pre_p, label_stmt); @@ -10777,11 +11225,7 @@ gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p, break; case LABEL_EXPR: - ret = GS_ALL_DONE; - gcc_assert (decl_function_context (LABEL_EXPR_LABEL (*expr_p)) - == current_function_decl); - gimplify_seq_add_stmt (pre_p, - gimple_build_label (LABEL_EXPR_LABEL (*expr_p))); + ret = gimplify_label_expr (expr_p, pre_p); break; case CASE_LABEL_EXPR: |