re PR tree-optimization/80032 (C++ excessive stack usage (no stack reuse))

2017-03-21  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/80032
	* gimplify.c (gimple_push_cleanup): Add force_uncond parameter,
	if set force the cleanup to happen unconditionally.
	(gimplify_target_expr): Push inserted clobbers with force_uncond
	to avoid them being removed by control-dependent DCE.

	* g++.dg/opt/pr80032.C: New testcase.

From-SVN: r246314

gcc/ChangeLog

 2017-03-21  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/80032
+	* gimplify.c (gimple_push_cleanup): Add force_uncond parameter,
+	if set force the cleanup to happen unconditionally.
+	(gimplify_target_expr): Push inserted clobbers with force_uncond
+	to avoid them being removed by control-dependent DCE.
+
+2017-03-21  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/80122
 	* tree-inline.c (copy_bb): Do not expans va-arg packs or
 	va_arg_pack_len when the inlined call stmt requires pack

gcc/gimplify.c

@@ -6288,10 +6288,13 @@ gimplify_cleanup_point_expr (tree *expr_p, gimple_seq *pre_p)
 
 /* Insert a cleanup marker for gimplify_cleanup_point_expr.  CLEANUP
    is the cleanup action required.  EH_ONLY is true if the cleanup should
-   only be executed if an exception is thrown, not on normal exit.  */
+   only be executed if an exception is thrown, not on normal exit.
+   If FORCE_UNCOND is true perform the cleanup unconditionally;  this is
+   only valid for clobbers.  */
 
 static void
-gimple_push_cleanup (tree var, tree cleanup, bool eh_only, gimple_seq *pre_p)
+gimple_push_cleanup (tree var, tree cleanup, bool eh_only, gimple_seq *pre_p,
+		     bool force_uncond = false)
 {
   gimple *wce;
   gimple_seq cleanup_stmts = NULL;
@@ -6301,7 +6304,7 @@ gimple_push_cleanup (tree var, tree cleanup, bool eh_only, gimple_seq *pre_p)
   if (seen_error ())
     return;
 
-  if (gimple_conditional_context ())
+  if (gimple_conditional_context () && ! force_uncond)
     {
       /* If we're in a conditional context, this is more complex.  We only
 	 want to run the cleanup if we actually ran the initialization that
@@ -6426,11 +6429,7 @@ gimplify_target_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)
 						NULL);
 	      TREE_THIS_VOLATILE (clobber) = true;
 	      clobber = build2 (MODIFY_EXPR, TREE_TYPE (temp), temp, clobber);
-	      if (cleanup)
-		cleanup = build2 (COMPOUND_EXPR, void_type_node, cleanup,
-				  clobber);
-	      else
-		cleanup = clobber;
+	      gimple_push_cleanup (temp, clobber, false, pre_p, true);
 	    }
 	  if (asan_poisoned_variables && dbg_cnt (asan_use_after_scope))
 	    {

gcc/testsuite/ChangeLog

 2017-03-21  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/80032
+	* g++.dg/opt/pr80032.C: New testcase.
+
+2017-03-21  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/80122
 	* gcc.dg/torture/pr80122.c: New testcase.
 

gcc/testsuite/g++.dg/opt/pr80032.C

+// PR tree-optimization/80032
+// { dg-do compile { target c++11 } }
+// { dg-options "-O2" }
+// If DCE removes too many CLOBBERs then stack usage goes through the
+// roof as stack slots can no longer be shared.
+// { dg-additional-options "-Wstack-usage=200" { target x86_64-*-* i?86-*-* } }
+
+typedef unsigned a;
+namespace test {
+    enum b { c };
+    class ADataContainer;
+    class BitMask;
+    namespace api {
+	enum DataStore { candidate };
+    }
+    using d = api::DataStore;
+    namespace db {
+	class e;
+	class f;
+	class g;
+	class ManagedObjectConst {
+	public:
+	    ManagedObjectConst(const ManagedObjectConst &);
+	    bool isFieldDefault(a, d) const;
+	    ADataContainer &getFieldDefault(a, d) const;
+	    g *h;
+	    e *i;
+	    f *j;
+	};
+	struct FieldInfo {
+	    FieldInfo(ManagedObjectConst, a, d);
+	    ManagedObjectConst k;
+	};
+	b compare(const FieldInfo &, const ADataContainer &);
+	class ManagedObject : public ManagedObjectConst {};
+    }
+    using namespace db;
+    void FN(ManagedObject &k, const BitMask &) {
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+	if (!k.isFieldDefault(8, d::candidate) &&
+	    !compare(FieldInfo(k, 11, d::candidate),
+		     k.getFieldDefault(11, d::candidate)) == c)
+	  return;
+    }
+}