Add CLOBBER_EOL to mark storage end-of-life clobbers

This adds a flag to CONSTRUCTOR nodes indicating that for
clobbers this marks the end-of-life of storage as opposed to
just ending the lifetime of the object that occupied it.
The dangling pointer diagnostics uses CLOBBERs but is confused
by those emitted by the C++ frontend for example which emits
them for the second purpose at the start of CTORs.  The issue
is also appearant for aarch64 in PR104092.

Distinguishing the two cases is also necessary for the PR90348 fix.

Since I'm going to add another flag I added an enum clobber_flags
and a defaulted argument to build_clobber plus a convenient way to
query the enum from the CTOR tree and specify it for gimple_clobber_p.
Since 'CLOBBER' is already taken and I needed a name for the unspecified
clobber we have now I used 'CLOBBER_UNDEF'.

2022-02-03  Richard Biener  <rguenther@suse.de>

	PR middle-end/90348
	PR middle-end/104092
gcc/
	* tree-core.h (clobber_kind): New enum.
	(tree_base::u::bits::address_space): Document use in CONSTRUCTORs.
	* tree.h (CLOBBER_KIND): Add.
	(build_clobber): Add clobber kind argument, defaulted to
	CLOBBER_UNDEF.
	* tree.cc (build_clobber): Likewise.
	* gimple.h (gimple_clobber_p): New overload with specified kind.
	* tree-streamer-in.cc (streamer_read_tree_bitfields): Stream
	CLOBBER_KIND.
	* tree-streamer-out.cc (streamer_write_tree_bitfields):
	Likewise.
	* tree-pretty-print.cc (dump_generic_node): Mark EOL CLOBBERs.
	* gimplify.cc (gimplify_bind_expr): Build storage end-of-life clobbers
	with CLOBBER_EOL.
	(gimplify_target_expr): Likewise.
	* tree-inline.cc (expand_call_inline): Likewise.
	* tree-ssa-ccp.cc (insert_clobber_before_stack_restore): Likewise.
	* gimple-ssa-warn-access.cc (pass_waccess::check_stmt): Only treat
	CLOBBER_EOL clobbers as ending lifetime of storage.

gcc/lto/
	* lto-common.cc (compare_tree_sccs_1): Compare CLOBBER_KIND.

gcc/testsuite/
	* gcc.dg/pr87052.c: Adjust.

diff --git a/gcc/gimple-ssa-warn-access.cc b/gcc/gimple-ssa-warn-access.cc
index 4b3d2c0..80d41ea 100644 (file)
--- a/gcc/gimple-ssa-warn-access.cc
+++ b/gcc/gimple-ssa-warn-access.cc
@@ -4328,7 +4328,8 @@ is_auto_decl (tree x)
 void
 pass_waccess::check_stmt (gimple *stmt)
 {
-  if (m_check_dangling_p && gimple_clobber_p (stmt))
+  if (m_check_dangling_p
+      && gimple_clobber_p (stmt, CLOBBER_EOL))
     {
       /* Ignore clobber statemts in blocks with exceptional edges.  */
       basic_block bb = gimple_bb (stmt);

diff --git a/gcc/gimple.h b/gcc/gimple.h
index 441d29a..77a5a07 100644 (file)
--- a/gcc/gimple.h
+++ b/gcc/gimple.h
@@ -2939,6 +2939,15 @@ gimple_clobber_p (const gimple *s)
          && TREE_CLOBBER_P (gimple_assign_rhs1 (s));
 }
 
+/* Return true if S is a clobber statement.  */
+
+static inline bool
+gimple_clobber_p (const gimple *s, enum clobber_kind kind)
+{
+  return gimple_clobber_p (s)
+        && CLOBBER_KIND (gimple_assign_rhs1 (s)) == kind;
+}
+
 /* Return true if GS is a GIMPLE_CALL.  */
 
 static inline bool

diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index cd4b613..875b115 100644 (file)
--- a/gcc/gimplify.cc
+++ b/gcc/gimplify.cc
@@ -1475,7 +1475,7 @@ gimplify_bind_expr (tree *expr_p, gimple_seq *pre_p)
              && !is_gimple_reg (t)
              && flag_stack_reuse != SR_NONE)
            {
-             tree clobber = build_clobber (TREE_TYPE (t));
+             tree clobber = build_clobber (TREE_TYPE (t), CLOBBER_EOL);
              gimple *clobber_stmt;
              clobber_stmt = gimple_build_assign (t, clobber);
              gimple_set_location (clobber_stmt, end_locus);
@@ -6981,7 +6981,7 @@ gimplify_target_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)
        {
          if (flag_stack_reuse == SR_ALL)
            {
-             tree clobber = build_clobber (TREE_TYPE (temp));
+             tree clobber = build_clobber (TREE_TYPE (temp), CLOBBER_EOL);
              clobber = build2 (MODIFY_EXPR, TREE_TYPE (temp), temp, clobber);
              gimple_push_cleanup (temp, clobber, false, pre_p, true);
            }

diff --git a/gcc/lto/lto-common.cc b/gcc/lto/lto-common.cc
index 11fde67..ca28586 100644 (file)
--- a/gcc/lto/lto-common.cc
+++ b/gcc/lto/lto-common.cc
@@ -1309,7 +1309,10 @@ compare_tree_sccs_1 (tree t1, tree t2, tree **map)
       return false;
 
   if (CODE_CONTAINS_STRUCT (code, TS_CONSTRUCTOR))
-    compare_values (CONSTRUCTOR_NELTS);
+    {
+      compare_values (CLOBBER_KIND);
+      compare_values (CONSTRUCTOR_NELTS);
+    }
 
   if (CODE_CONTAINS_STRUCT (code, TS_IDENTIFIER))
     if (IDENTIFIER_LENGTH (t1) != IDENTIFIER_LENGTH (t2)

diff --git a/gcc/testsuite/gcc.dg/pr87052.c b/gcc/testsuite/gcc.dg/pr87052.c
index 2affc48..18e092c 100644 (file)
--- a/gcc/testsuite/gcc.dg/pr87052.c
+++ b/gcc/testsuite/gcc.dg/pr87052.c
@@ -38,4 +38,4 @@ void test (void)
    { dg-final { scan-tree-dump-times "c = \"\";"  1 "gimple" } }
    { dg-final { scan-tree-dump-times "d = { *};"  1 "gimple" } }
    { dg-final { scan-tree-dump-times "e = "  1 "gimple" } }
-   { dg-final { scan-tree-dump-times "e = {CLOBBER}"  1 "gimple" } }  */
+   { dg-final { scan-tree-dump-times "e = {CLOBBER\\(eol\\)}"  1 "gimple" } }  */

diff --git a/gcc/tree-core.h b/gcc/tree-core.h
index e83669f..bf2efa6 100644 (file)
--- a/gcc/tree-core.h
+++ b/gcc/tree-core.h
@@ -963,6 +963,15 @@ enum annot_expr_kind {
   annot_expr_kind_last
 };
 
+/* The kind of a TREE_CLOBBER_P CONSTRUCTOR node.  */
+enum clobber_kind {
+  /* Unspecified, this clobber acts as a store of an undefined value.  */
+  CLOBBER_UNDEF,
+  /* This clobber ends the lifetime of the storage.  */
+  CLOBBER_EOL,
+  CLOBBER_LAST
+};
+
 /*---------------------------------------------------------------------------
                                 Type definitions
 ---------------------------------------------------------------------------*/
@@ -1055,7 +1064,8 @@ struct GTY(()) tree_base {
 
       /* This field is only used with TREE_TYPE nodes; the only reason it is
         present in tree_base instead of tree_type is to save space.  The size
-        of the field must be large enough to hold addr_space_t values.  */
+        of the field must be large enough to hold addr_space_t values.
+        For CONSTRUCTOR nodes this holds the clobber_kind enum.  */
       unsigned address_space : 8;
     } bits;
 

diff --git a/gcc/tree-inline.cc b/gcc/tree-inline.cc
index 497aa66..ca66a82 100644 (file)
--- a/gcc/tree-inline.cc
+++ b/gcc/tree-inline.cc
@@ -5138,7 +5138,7 @@ expand_call_inline (basic_block bb, gimple *stmt, copy_body_data *id,
              && !is_gimple_reg (*varp)
              && !(id->debug_map && id->debug_map->get (p)))
            {
-             tree clobber = build_clobber (TREE_TYPE (*varp));
+             tree clobber = build_clobber (TREE_TYPE (*varp), CLOBBER_EOL);
              gimple *clobber_stmt;
              clobber_stmt = gimple_build_assign (*varp, clobber);
              gimple_set_location (clobber_stmt, gimple_location (stmt));
@@ -5207,7 +5207,7 @@ expand_call_inline (basic_block bb, gimple *stmt, copy_body_data *id,
          && !is_gimple_reg (id->retvar)
          && !stmt_ends_bb_p (stmt))
        {
-         tree clobber = build_clobber (TREE_TYPE (id->retvar));
+         tree clobber = build_clobber (TREE_TYPE (id->retvar), CLOBBER_EOL);
          gimple *clobber_stmt;
          clobber_stmt = gimple_build_assign (id->retvar, clobber);
          gimple_set_location (clobber_stmt, gimple_location (old_stmt));

diff --git a/gcc/tree-pretty-print.cc b/gcc/tree-pretty-print.cc
index 6130c30..666b7a7 100644 (file)
--- a/gcc/tree-pretty-print.cc
+++ b/gcc/tree-pretty-print.cc
@@ -2500,7 +2500,11 @@ dump_generic_node (pretty_printer *pp, tree node, int spc, dump_flags_t flags,
          }
        pp_left_brace (pp);
        if (TREE_CLOBBER_P (node))
-         pp_string (pp, "CLOBBER");
+         {
+           pp_string (pp, "CLOBBER");
+           if (CLOBBER_KIND (node) == CLOBBER_EOL)
+             pp_string (pp, "(eol)");
+         }
        else if (TREE_CODE (TREE_TYPE (node)) == RECORD_TYPE
                 || TREE_CODE (TREE_TYPE (node)) == UNION_TYPE)
          is_struct_init = true;

diff --git a/gcc/tree-ssa-ccp.cc b/gcc/tree-ssa-ccp.cc
index 48683f0..9164efe 100644 (file)
--- a/gcc/tree-ssa-ccp.cc
+++ b/gcc/tree-ssa-ccp.cc
@@ -2505,7 +2505,7 @@ insert_clobber_before_stack_restore (tree saved_val, tree var,
   FOR_EACH_IMM_USE_STMT (stmt, iter, saved_val)
     if (gimple_call_builtin_p (stmt, BUILT_IN_STACK_RESTORE))
       {
-       clobber = build_clobber (TREE_TYPE (var));
+       clobber = build_clobber (TREE_TYPE (var), CLOBBER_EOL);
        clobber_stmt = gimple_build_assign (var, clobber);
 
        i = gsi_for_stmt (stmt);

diff --git a/gcc/tree-streamer-in.cc b/gcc/tree-streamer-in.cc
index 65cdf12..a35a810 100644 (file)
--- a/gcc/tree-streamer-in.cc
+++ b/gcc/tree-streamer-in.cc
@@ -559,6 +559,8 @@ streamer_read_tree_bitfields (class lto_input_block *ib,
 
   if (CODE_CONTAINS_STRUCT (code, TS_CONSTRUCTOR))
     {
+      CLOBBER_KIND (expr)
+       = bp_unpack_enum (&bp, clobber_kind, CLOBBER_LAST);
       unsigned HOST_WIDE_INT length = bp_unpack_var_len_unsigned (&bp);
       if (length > 0)
        vec_safe_grow (CONSTRUCTOR_ELTS (expr), length, true);

diff --git a/gcc/tree-streamer-out.cc b/gcc/tree-streamer-out.cc
index 783b94d..d39dc15 100644 (file)
--- a/gcc/tree-streamer-out.cc
+++ b/gcc/tree-streamer-out.cc
@@ -504,7 +504,10 @@ streamer_write_tree_bitfields (struct output_block *ob, tree expr)
     cl_optimization_stream_out (ob, &bp, TREE_OPTIMIZATION (expr));
 
   if (CODE_CONTAINS_STRUCT (code, TS_CONSTRUCTOR))
-    bp_pack_var_len_unsigned (&bp, CONSTRUCTOR_NELTS (expr));
+    {
+      bp_pack_enum (&bp, clobber_kind, CLOBBER_LAST, CLOBBER_KIND (expr));
+      bp_pack_var_len_unsigned (&bp, CONSTRUCTOR_NELTS (expr));
+    }
 
   if (CODE_CONTAINS_STRUCT (code, TS_TARGET_OPTION)
       /* Don't stream these when passing things to a different target.  */

diff --git a/gcc/tree.cc b/gcc/tree.cc
index 7ce4f24..dfcdf68 100644 (file)
--- a/gcc/tree.cc
+++ b/gcc/tree.cc
@@ -2311,10 +2311,11 @@ build_constructor_va (tree type, int nelts, ...)
 /* Return a node of type TYPE for which TREE_CLOBBER_P is true.  */
 
 tree
-build_clobber (tree type)
+build_clobber (tree type, enum clobber_kind kind)
 {
   tree clobber = build_constructor (type, NULL);
   TREE_THIS_VOLATILE (clobber) = true;
+  CLOBBER_KIND (clobber) = kind;
   return clobber;
 }
 

diff --git a/gcc/tree.h b/gcc/tree.h
index e2157d6..95334b0 100644 (file)
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -1155,6 +1155,10 @@ extern void omp_clause_range_check_failed (const_tree, const char *, int,
 #define TREE_CLOBBER_P(NODE) \
   (TREE_CODE (NODE) == CONSTRUCTOR && TREE_THIS_VOLATILE (NODE))
 
+/* Return the clobber_kind of a CLOBBER CONSTRUCTOR.  */
+#define CLOBBER_KIND(NODE) \
+  (CONSTRUCTOR_CHECK (NODE)->base.u.bits.address_space)
+
 /* Define fields and accessors for some nodes that represent expressions.  */
 
 /* Nonzero if NODE is an empty statement (NOP_EXPR <0>).  */
@@ -4559,7 +4563,7 @@ extern tree build_constructor_single (tree, tree, tree);
 extern tree build_constructor_from_list (tree, tree);
 extern tree build_constructor_from_vec (tree, const vec<tree, va_gc> *);
 extern tree build_constructor_va (tree, int, ...);
-extern tree build_clobber (tree);
+extern tree build_clobber (tree, enum clobber_kind = CLOBBER_UNDEF);
 extern tree build_real_from_int_cst (tree, const_tree);
 extern tree build_real_from_wide (tree, const wide_int_ref &, signop);
 extern tree build_complex (tree, tree, tree);