Attachment 36622 Details for Bug 68083 – Patch I'm testing to fix the problem

[patch] Patch I'm testing to fix the problem

PR68083-dont-ifcombine-uninitialized.patch (text/plain), 3.26 KB, created by Alexandre Oliva on 2015-10-30 13:15:57 UTC

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Creator: Alexandre Oliva

Created: 2015-10-30 13:15:57 UTC

Size: 3.26 KB

patch

obsolete

>[PR68083] don't introduce undefined behavior in ifcombine
>
>From: Alexandre Oliva <aoliva@redhat.com>
>
>The ifcombine pass may move a conditional access to an uninitialized
>value before the condition that ensures it is always well-defined,
>thus introducing undefined behavior.  Stop it from doing so.
>
>for  gcc/ChangeLog
>
>	PR tree-optimization/68083
>	* tree-ssa-ifcombine.c: Include tree-ssa.h.
>	(bb_no_side_effects_p): Test for undefined uses too.
>	* tree-ssa.c (gimple_uses_undefined_value_p): New.
>	* tree-ssa.h (gimple_uses_undefined_value_p): Declare.
>
>for  gcc/testsuite/ChangeLog
>
>	PR tree-optimization/68083
>	* gcc.dg/torture/pr68083.c: New.  From Zhendong Su.
>---
> gcc/testsuite/gcc.dg/torture/pr68083.c |   35 ++++++++++++++++++++++++++++++++
> gcc/tree-ssa-ifcombine.c               |    2 ++
> gcc/tree-ssa.c                         |   18 ++++++++++++++++
> gcc/tree-ssa.h                         |    1 +
> 4 files changed, 56 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/torture/pr68083.c
>
>diff --git a/gcc/testsuite/gcc.dg/torture/pr68083.c b/gcc/testsuite/gcc.dg/torture/pr68083.c
>new file mode 100644
>index 0000000..ae24781
>--- /dev/null
>+++ b/gcc/testsuite/gcc.dg/torture/pr68083.c
>@@ -0,0 +1,35 @@
>+/* { dg-do run } */
>+
>+int a = 2, b = 1, c = 1;
>+
>+int
>+fn1 ()
>+{
>+  int d;
>+  for (; a; a--)
>+    {
>+      for (d = 0; d < 4; d++)
>+	{
>+	  int k;
>+	  if (c < 1)
>+	    if (k)
>+	      c = 0;
>+	  if (b)
>+	    continue;
>+	  return 0;
>+	}
>+      b = !1;
>+    }
>+  return 0;
>+}
>+
>+int
>+main ()
>+{
>+  fn1 ();
>+
>+  if (a != 1)
>+    __builtin_abort ();
>+
>+  return 0;
>+}
>diff --git a/gcc/tree-ssa-ifcombine.c b/gcc/tree-ssa-ifcombine.c
>index ca55b57..622dc6b 100644
>--- a/gcc/tree-ssa-ifcombine.c
>+++ b/gcc/tree-ssa-ifcombine.c
>@@ -41,6 +41,7 @@ along with GCC; see the file COPYING3.  If not see
> #include "gimple-iterator.h"
> #include "gimplify-me.h"
> #include "tree-cfg.h"
>+#include "tree-ssa.h"
> 
> #ifndef LOGICAL_OP_NON_SHORT_CIRCUIT
> #define LOGICAL_OP_NON_SHORT_CIRCUIT \
>@@ -125,6 +126,7 @@ bb_no_side_effects_p (basic_block bb)
> 	continue;
> 
>       if (gimple_has_side_effects (stmt)
>+	  || gimple_uses_undefined_value_p (stmt)
> 	  || gimple_could_trap_p (stmt)
> 	  || gimple_vuse (stmt))
> 	return false;
>diff --git a/gcc/tree-ssa.c b/gcc/tree-ssa.c
>index c7be442..8dc2d61 100644
>--- a/gcc/tree-ssa.c
>+++ b/gcc/tree-ssa.c
>@@ -1210,6 +1210,24 @@ ssa_undefined_value_p (tree t, bool partial)
> }
> 
> 
>+/* Return TRUE iff STMT, a gimple statement, references an undefined
>+   SSA name.  */
>+
>+bool
>+gimple_uses_undefined_value_p (gimple *stmt)
>+{
>+  ssa_op_iter iter;
>+  tree op;
>+
>+  FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
>+    if (ssa_undefined_value_p (op))
>+      return true;
>+
>+  return false;
>+}
>+
>+
>+
> /* If necessary, rewrite the base of the reference tree *TP from
>    a MEM_REF to a plain or converted symbol.  */
> 
>diff --git a/gcc/tree-ssa.h b/gcc/tree-ssa.h
>index 5a409e5..3b5bd70 100644
>--- a/gcc/tree-ssa.h
>+++ b/gcc/tree-ssa.h
>@@ -51,6 +51,7 @@ extern bool tree_ssa_useless_type_conversion (tree);
> extern tree tree_ssa_strip_useless_type_conversions (tree);
> 
> extern bool ssa_undefined_value_p (tree, bool = true);
>+extern bool gimple_uses_undefined_value_p (gimple *);
> extern void execute_update_addresses_taken (void);
> 
> /* Given an edge_var_map V, return the PHI arg definition.  */

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