tree-ssa-uninit.c (is_pred_expr_subset_of): Correctly handle cases where cond2 is NE_EXPR.

	* tree-ssa-uninit.c (is_pred_expr_subset_of): Correctly handle cases
	where cond2 is NE_EXPR.
	(is_value_included_in): Update comment.

        * gcc.dg/uninit-25-gimple.c: New test.
        * gcc.dg/uninit-25.c: New test.
        * gcc.dg/uninit-26.c: New test.
        * gcc.dg/uninit-27-gimple.c: New test.

From-SVN: r270660

7 files changed, 149 insertions, 3 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d6adeda090d..8bb8dcfee1e 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2019-04-29  Vladislav Ivanishin  <vlad@ispras.ru>
+
+	* tree-ssa-uninit.c (is_pred_expr_subset_of): Correctly handle cases
+	where cond2 is NE_EXPR.
+	(is_value_included_in): Update comment.
+
 2019-04-29  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/90278
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 4089febb09c..d64281548b4 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2019-04-29  Vladislav Ivanishin  <vlad@ispras.ru>
+
+        * gcc.dg/uninit-25-gimple.c: New test.
+        * gcc.dg/uninit-25.c: New test.
+        * gcc.dg/uninit-26.c: New test.
+        * gcc.dg/uninit-27-gimple.c: New test.
+
 2019-04-29  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/90278
diff --git a/gcc/testsuite/gcc.dg/uninit-25-gimple.c b/gcc/testsuite/gcc.dg/uninit-25-gimple.c
new file mode 100644
index 00000000000..0c0acd6b83e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-25-gimple.c
@@ -0,0 +1,41 @@
+/* { dg-do compile } */
+/* { dg-options "-fgimple -O -Wmaybe-uninitialized" } */
+
+unsigned int __GIMPLE (ssa,startwith("uninit1"))
+foo (unsigned int v)
+{
+  unsigned int undef;        /* { dg-warning "may be used uninitialized" } */
+  unsigned int _2;
+  unsigned int _9;
+  unsigned int _10;
+
+  __BB(2):
+  if (v_4(D) != 1u)
+    goto __BB3;
+  else
+    goto __BB4;
+
+  __BB(3):
+  undef_8 = 8u; // 'undef' is defined conditionally (under 'v != 1' predicate)
+  goto __BB4;
+
+  __BB(4):
+  // An undef value flows into a phi.
+  undef_1 = __PHI (__BB2: undef_5(D), __BB3: undef_8);
+  if (v_4(D) != 2u) // This condition is neither a superset nor a subset of 'v != 1'.
+    goto __BB5;
+  else
+    goto __BB6;
+
+  __BB(5):
+  _9 = undef_1; // The phi value is used here (under 'v != 2' predicate).
+  goto __BB7;
+
+  __BB(6):
+  _10 = v_4(D);
+  goto __BB7;
+
+  __BB(7):
+  _2 = __PHI (__BB5: _9, __BB6: _10);
+  return _2;
+}
diff --git a/gcc/testsuite/gcc.dg/uninit-25.c b/gcc/testsuite/gcc.dg/uninit-25.c
new file mode 100644
index 00000000000..ffffce3f91c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-25.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-O -Wmaybe-uninitialized" } */
+
+extern unsigned bar (void);
+extern void quux (void);
+
+unsigned foo (unsigned v)
+{
+  unsigned u;
+  if (v != 1)
+    u = bar ();
+
+  // Prevent the "dom" pass from changing the CFG layout based on the inference
+  // 'if (v != 1) is false then (v != 2) is true'.  (Now it would have to
+  // duplicate the loop in order to do so, which is deemed expensive.)
+  for (int i = 0; i < 10; i++)
+    quux ();
+
+  if (v != 2)
+    return u;       /* { dg-warning "may be used uninitialized" } */
+
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/uninit-26.c b/gcc/testsuite/gcc.dg/uninit-26.c
new file mode 100644
index 00000000000..60ac48cdc50
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-26.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-O -Wmaybe-uninitialized" } */
+
+extern unsigned bar (void);
+extern void quux (void);
+
+unsigned foo (unsigned v)
+{
+  unsigned u;
+  if (v != 100)
+    u = bar ();
+
+  // Prevent the "dom" pass from changing the CFG layout based on the inference
+  // 'if (v != 100) is false then (v < 105) is true'.  (Now it would have to
+  // duplicate the loop in order to do so, which is deemed expensive.)
+  for (int i = 0; i < 10; i++)
+    quux ();
+
+  if (v < 105) /* v == 100 falls into this range.  */
+    return u;       /* { dg-warning "may be used uninitialized" }  */
+
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/uninit-27-gimple.c b/gcc/testsuite/gcc.dg/uninit-27-gimple.c
new file mode 100644
index 00000000000..f75469d8ef8
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-27-gimple.c
@@ -0,0 +1,41 @@
+/* { dg-do compile } */
+/* { dg-options "-fgimple -O -Wmaybe-uninitialized" } */
+
+unsigned int __GIMPLE (ssa,startwith("uninit1"))
+foo (unsigned int v)
+{
+  unsigned int undef;        /* { dg-bogus "may be used uninitialized" } */
+  unsigned int _2;
+  unsigned int _9;
+  unsigned int _10;
+
+  __BB(2):
+  if (v_4(D) != 100u)
+    goto __BB3;
+  else
+    goto __BB4;
+
+  __BB(3):
+  undef_8 = 8u; // 'undef' is defined conditionally (under 'v != 100' predicate)
+  goto __BB4;
+
+  __BB(4):
+  // An undef value flows into a phi.
+  undef_1 = __PHI (__BB2: undef_5(D), __BB3: undef_8);
+  if (v_4(D) < 100u)
+    goto __BB5;
+  else
+    goto __BB6;
+
+  __BB(5):
+  _9 = undef_1; // The phi value is used here (under 'v < 100' predicate).
+  goto __BB7;
+
+  __BB(6):
+  _10 = v_4(D);
+  goto __BB7;
+
+  __BB(7):
+  _2 = __PHI (__BB5: _9, __BB6: _10);
+  return _2;
+}
diff --git a/gcc/tree-ssa-uninit.c b/gcc/tree-ssa-uninit.c
index 55a55a05c96..831587854c6 100644
--- a/gcc/tree-ssa-uninit.c
+++ b/gcc/tree-ssa-uninit.c
@@ -1011,8 +1011,7 @@ get_cmp_code (enum tree_code orig_cmp_code, bool swap_cond, bool invert)
   return tc;
 }
 
-/* Returns true if VAL falls in the range defined by BOUNDARY and CMPC, i.e.
-   all values in the range satisfies (x CMPC BOUNDARY) == true.  */
+/* Returns whether VAL CMPC BOUNDARY is true.  */
 
 static bool
 is_value_included_in (tree val, tree boundary, enum tree_code cmpc)
@@ -1488,11 +1487,17 @@ is_pred_expr_subset_of (pred_info expr1, pred_info expr2)
   if (expr2.invert)
     code2 = invert_tree_comparison (code2, false);
 
+  if (code2 == NE_EXPR && code1 == NE_EXPR)
+    return false;
+
+  if (code2 == NE_EXPR)
+    return !is_value_included_in (expr2.pred_rhs, expr1.pred_rhs, code1);
+
   if ((code1 == EQ_EXPR || code1 == BIT_AND_EXPR) && code2 == BIT_AND_EXPR)
     return (wi::to_wide (expr1.pred_rhs)
 	    == (wi::to_wide (expr1.pred_rhs) & wi::to_wide (expr2.pred_rhs)));
 
-  if (code1 != code2 && code2 != NE_EXPR)
+  if (code1 != code2)
     return false;
 
   if (is_value_included_in (expr1.pred_rhs, expr2.pred_rhs, code2))