[PATCH] Avoid some -Wunreachable-code-ctrl
Jason Merrill
jason@redhat.com
Tue Nov 30 22:16:19 GMT 2021
On 11/29/21 10:03, Richard Biener via Gcc-patches wrote:
> This cleans up unreachable code diagnosed by -Wunreachable-code-ctrl.
> It largely follows the previous series but discovers a few extra
> cases, namely dead code after break or continue or loops without
> exits.
>
> Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
>
> Richard.
>
> 2021-11-29 Richard Biener <rguenther@suse.de>
>
> gcc/c/
> * gimple-parser.c (c_parser_gimple_postfix_expression):
> avoid unreachable code after break.
>
> gcc/
> * cfgrtl.c (skip_insns_after_block): Refactor code to
> be more easily readable.
> * expr.c (op_by_pieces_d::run): Remove unreachable
> assert.
> * sched-deps.c (sched_analyze): Remove unreachable
> gcc_unreachable.
> * sel-sched-ir.c (in_same_ebb_p): Likewise.
> * tree-ssa-alias.c (nonoverlapping_refs_since_match_p):
> Remove unreachable code.
> * tree-vect-slp.c (vectorize_slp_instance_root_stmt):
> Refactor to avoid unreachable loop iteration.
> * tree.c (walk_tree_1): Remove unreachable break.
> * vec-perm-indices.c (vec_perm_indices::series_p): Remove
> unreachable return.
>
> gcc/cp/
> * parser.c (cp_parser_postfix_expression): Remove
> unreachable code.
> * pt.c (tsubst_expr): Remove unreachable breaks.
>
> gcc/fortran/
> * frontend-passes.c (gfc_expr_walker): Remove unreachable
> break.
> * scanner.c (skip_fixed_comments): Remove unreachable
> gcc_unreachable.
> * trans-expr.c (gfc_expr_is_variable): Refactor to make
> control flow more obvious.
> ---
> gcc/c/gimple-parser.c | 8 +-------
> gcc/cfgrtl.c | 10 ++--------
> gcc/cp/parser.c | 4 ----
> gcc/cp/pt.c | 2 --
> gcc/expr.c | 3 ---
> gcc/fortran/frontend-passes.c | 1 -
> gcc/fortran/scanner.c | 1 -
> gcc/fortran/trans-expr.c | 11 +++--------
> gcc/sched-deps.c | 2 --
> gcc/sel-sched-ir.c | 3 ---
> gcc/tree-ssa-alias.c | 3 ---
> gcc/tree-vect-slp.c | 22 ++++++++--------------
> gcc/tree.c | 2 --
> gcc/vec-perm-indices.c | 1 -
> 14 files changed, 14 insertions(+), 59 deletions(-)
>
> diff --git a/gcc/c/gimple-parser.c b/gcc/c/gimple-parser.c
> index 32f22dbb8a7..f594a8ccb31 100644
> --- a/gcc/c/gimple-parser.c
> +++ b/gcc/c/gimple-parser.c
> @@ -1698,13 +1698,7 @@ c_parser_gimple_postfix_expression (gimple_parser &parser)
> }
> break;
> }
> - else
> - {
> - c_parser_error (parser, "expected expression");
> - expr.set_error ();
> - break;
> - }
> - break;
> + /* Fallthru. */
> default:
> c_parser_error (parser, "expected expression");
> expr.set_error ();
> diff --git a/gcc/cfgrtl.c b/gcc/cfgrtl.c
> index 3744adcc2ba..287a3db643a 100644
> --- a/gcc/cfgrtl.c
> +++ b/gcc/cfgrtl.c
> @@ -3539,14 +3539,8 @@ skip_insns_after_block (basic_block bb)
> continue;
>
> case NOTE:
> - switch (NOTE_KIND (insn))
> - {
> - case NOTE_INSN_BLOCK_END:
> - gcc_unreachable ();
> - default:
> - continue;
> - }
> - break;
> + gcc_assert (NOTE_KIND (insn) != NOTE_INSN_BLOCK_END);
> + continue;
>
> case CODE_LABEL:
> if (NEXT_INSN (insn)
> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> index 0bd58525726..cc88a36dd39 100644
> --- a/gcc/cp/parser.c
> +++ b/gcc/cp/parser.c
> @@ -7892,10 +7892,6 @@ cp_parser_postfix_expression (cp_parser *parser, bool address_p, bool cast_p,
> return postfix_expression;
> }
> }
> -
> - /* We should never get here. */
> - gcc_unreachable ();
Hmm, I generally disagree with removing gcc_unreachable() asserts
because they are unreachable; it seems like it increases the fragility
of the code in case later changes wrongly make them reachable.
> - return error_mark_node;
> }
>
> /* Helper function for cp_parser_parenthesized_expression_list and
> diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
> index 31ed773e145..f4b9d9673fb 100644
> --- a/gcc/cp/pt.c
> +++ b/gcc/cp/pt.c
> @@ -18242,13 +18242,11 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl,
> stmt = finish_co_yield_expr (input_location,
> RECUR (TREE_OPERAND (t, 0)));
> RETURN (stmt);
> - break;
>
> case CO_AWAIT_EXPR:
> stmt = finish_co_await_expr (input_location,
> RECUR (TREE_OPERAND (t, 0)));
> RETURN (stmt);
> - break;
>
> case EXPR_STMT:
> tmp = RECUR (EXPR_STMT_EXPR (t));
> diff --git a/gcc/expr.c b/gcc/expr.c
> index 5673902b1fc..b2815257509 100644
> --- a/gcc/expr.c
> +++ b/gcc/expr.c
> @@ -1342,9 +1342,6 @@ op_by_pieces_d::run ()
> }
> }
> while (1);
> -
> - /* The code above should have handled everything. */
> - gcc_assert (!length);
> }
>
> /* Derived class from op_by_pieces_d, providing support for block move
> diff --git a/gcc/fortran/frontend-passes.c b/gcc/fortran/frontend-passes.c
> index f5ba7cecd54..16ee2afc9c0 100644
> --- a/gcc/fortran/frontend-passes.c
> +++ b/gcc/fortran/frontend-passes.c
> @@ -5229,7 +5229,6 @@ gfc_expr_walker (gfc_expr **e, walk_expr_fn_t exprfn, void *data)
> case EXPR_OP:
> WALK_SUBEXPR ((*e)->value.op.op1);
> WALK_SUBEXPR_TAIL ((*e)->value.op.op2);
> - break;
> case EXPR_FUNCTION:
> for (a = (*e)->value.function.actual; a; a = a->next)
> WALK_SUBEXPR (a->expr);
> diff --git a/gcc/fortran/scanner.c b/gcc/fortran/scanner.c
> index 69b81ab97f8..4d72ff78543 100644
> --- a/gcc/fortran/scanner.c
> +++ b/gcc/fortran/scanner.c
> @@ -1159,7 +1159,6 @@ skip_fixed_comments (void)
> skip_comment_line ();
> continue;
>
> - gcc_unreachable ();
> check_for_digits:
> {
> /* Required for OpenMP's conditional compilation sentinel. */
> diff --git a/gcc/fortran/trans-expr.c b/gcc/fortran/trans-expr.c
> index bc502c0f43c..e413b2d7a1f 100644
> --- a/gcc/fortran/trans-expr.c
> +++ b/gcc/fortran/trans-expr.c
> @@ -11079,14 +11079,9 @@ gfc_expr_is_variable (gfc_expr *expr)
> func_ifc = expr->value.function.esym;
> goto found_ifc;
> }
> - else
> - {
> - gcc_assert (expr->symtree);
> - func_ifc = expr->symtree->n.sym;
> - goto found_ifc;
> - }
> -
> - gcc_unreachable ();
> + gcc_assert (expr->symtree);
> + func_ifc = expr->symtree->n.sym;
> + goto found_ifc;
> }
>
> comp = gfc_get_proc_ptr_comp (expr);
> diff --git a/gcc/sched-deps.c b/gcc/sched-deps.c
> index 5814204c681..62aa47a73bd 100644
> --- a/gcc/sched-deps.c
> +++ b/gcc/sched-deps.c
> @@ -3816,7 +3816,6 @@ sched_analyze (class deps_desc *deps, rtx_insn *head, rtx_insn *tail)
>
> for (insn = head;; insn = NEXT_INSN (insn))
> {
> -
> if (INSN_P (insn))
> {
> /* And initialize deps_lists. */
> @@ -3836,7 +3835,6 @@ sched_analyze (class deps_desc *deps, rtx_insn *head, rtx_insn *tail)
> return;
> }
> }
> - gcc_unreachable ();
> }
>
> /* Helper for sched_free_deps ().
> diff --git a/gcc/sel-sched-ir.c b/gcc/sel-sched-ir.c
> index 48965bfb0ad..b76a48eb16e 100644
> --- a/gcc/sel-sched-ir.c
> +++ b/gcc/sel-sched-ir.c
> @@ -4918,9 +4918,6 @@ in_same_ebb_p (insn_t insn, insn_t succ)
>
> ptr = bb_next_bb (ptr);
> }
> -
> - gcc_unreachable ();
> - return false;
> }
>
> /* Recomputes the reverse topological order for the function and
> diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
> index 3c253e2843f..88fd7821c5e 100644
> --- a/gcc/tree-ssa-alias.c
> +++ b/gcc/tree-ssa-alias.c
> @@ -1800,9 +1800,6 @@ nonoverlapping_refs_since_match_p (tree match1, tree ref1,
> return 1;
> }
> }
> -
> - ++alias_stats.nonoverlapping_refs_since_match_p_must_overlap;
> - return 0;
> }
>
> /* Return TYPE_UID which can be used to match record types we consider
> diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
> index 94c75497495..cfea0c80be3 100644
> --- a/gcc/tree-vect-slp.c
> +++ b/gcc/tree-vect-slp.c
> @@ -7311,20 +7311,14 @@ vectorize_slp_instance_root_stmt (slp_tree node, slp_instance instance)
> {
> if (SLP_TREE_NUMBER_OF_VEC_STMTS (node) == 1)
> {
> - gimple *child_stmt;
> - int j;
> -
> - FOR_EACH_VEC_ELT (SLP_TREE_VEC_STMTS (node), j, child_stmt)
> - {
> - tree vect_lhs = gimple_get_lhs (child_stmt);
> - tree root_lhs = gimple_get_lhs (instance->root_stmts[0]->stmt);
> - if (!useless_type_conversion_p (TREE_TYPE (root_lhs),
> - TREE_TYPE (vect_lhs)))
> - vect_lhs = build1 (VIEW_CONVERT_EXPR, TREE_TYPE (root_lhs),
> - vect_lhs);
> - rstmt = gimple_build_assign (root_lhs, vect_lhs);
> - break;
> - }
> + gimple *child_stmt = SLP_TREE_VEC_STMTS (node)[0];
> + tree vect_lhs = gimple_get_lhs (child_stmt);
> + tree root_lhs = gimple_get_lhs (instance->root_stmts[0]->stmt);
> + if (!useless_type_conversion_p (TREE_TYPE (root_lhs),
> + TREE_TYPE (vect_lhs)))
> + vect_lhs = build1 (VIEW_CONVERT_EXPR, TREE_TYPE (root_lhs),
> + vect_lhs);
> + rstmt = gimple_build_assign (root_lhs, vect_lhs);
> }
> else if (SLP_TREE_NUMBER_OF_VEC_STMTS (node) > 1)
> {
> diff --git a/gcc/tree.c b/gcc/tree.c
> index 910fb06d6f5..4d91fdea758 100644
> --- a/gcc/tree.c
> +++ b/gcc/tree.c
> @@ -11127,7 +11127,6 @@ walk_tree_1 (tree *tp, walk_tree_fn func, void *data,
> case TREE_LIST:
> WALK_SUBTREE (TREE_VALUE (*tp));
> WALK_SUBTREE_TAIL (TREE_CHAIN (*tp));
> - break;
>
> case TREE_VEC:
> {
> @@ -11206,7 +11205,6 @@ walk_tree_1 (tree *tp, walk_tree_fn func, void *data,
> WALK_SUBTREE (OMP_CLAUSE_OPERAND (*tp, i));
> WALK_SUBTREE_TAIL (OMP_CLAUSE_CHAIN (*tp));
> }
> - break;
>
> case TARGET_EXPR:
> {
> diff --git a/gcc/vec-perm-indices.c b/gcc/vec-perm-indices.c
> index 31b32ea0589..9e6b5af327c 100644
> --- a/gcc/vec-perm-indices.c
> +++ b/gcc/vec-perm-indices.c
> @@ -228,7 +228,6 @@ vec_perm_indices::series_p (unsigned int out_base, unsigned int out_step,
>
> out_base += out_step;
> }
> - return true;
> }
>
> /* Return true if all elements of the permutation vector are in the range
>
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