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

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f48f6d39aac127a5098e438c201919c75b94a3c4..d679a5c014e2672b0bcc741359de958b26bb92cb 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+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

diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index fbf136fbce4a0242839a1171d046656728afdc6c..06f984cec01eebd8c469baf593ad91df03ee8dc2 100644 (file)
--- a/gcc/gimplify.c
+++ b/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))
            {

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 68705a7de064ce2ec4a796d6a307446a043976a2..08fcb72ca55a488d13b590a09ee1beb826f12837 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+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

diff --git a/gcc/testsuite/g++.dg/opt/pr80032.C b/gcc/testsuite/g++.dg/opt/pr80032.C
new file mode 100644 (file)
index 0000000..9cdad68
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/pr80032.C
@@ -0,0 +1,120 @@
+// 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;
+    }
+}