tree-ssa-uninit: suppress more spurious warnings

	* tree-ssa-uninit.c (value_sat_pred_p): This new function is a wrapper
        around is_value_included_in that knows how to handle BIT_AND_EXPR.
        (is_pred_expr_subset_of): Use the new function.  Handle more cases where
        code1 == EQ_EXPR and where code1 == BIT_AND_EXPR and thus fix some false
        positives.

testsuite/
        * gcc.dg/uninit-28-gimple.c: New test.
        * gcc.dg/uninit-29-gimple.c: New test.
        * gcc.dg/uninit-30-gimple.c: New test.
        * gcc.dg/uninit-31-gimple.c: New test.

From-SVN: r271460

7 files changed, 225 insertions, 10 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 17b4b10aa82..d341a64440c 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2019-05-21  Vladislav Ivanishin  <vlad@ispras.ru>
+
+	* tree-ssa-uninit.c (value_sat_pred_p): This new function is a wrapper
+	around is_value_included_in that knows how to handle BIT_AND_EXPR.
+	(is_pred_expr_subset_of): Use the new function.  Handle more cases where
+	code1 == EQ_EXPR and where code1 == BIT_AND_EXPR and thus fix some false
+	positives.
+
 2019-05-21  Martin Liska  <mliska@suse.cz>
 
 	* config/rs6000/driver-rs6000.c (elf_platform): Do not use
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index f65b6f427b6..f2bff8a0b42 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2019-05-21  Vladislav Ivanishin  <vlad@ispras.ru>
+
+	* gcc.dg/uninit-28-gimple.c: New test.
+	* gcc.dg/uninit-29-gimple.c: New test.
+	* gcc.dg/uninit-30-gimple.c: New test.
+	* gcc.dg/uninit-31-gimple.c: New test.
+
 2019-05-21  Martin Liska  <mliska@suse.cz>
 
 	* gcc.dg/pr90263.c: Add -O2.
diff --git a/gcc/testsuite/gcc.dg/uninit-28-gimple.c b/gcc/testsuite/gcc.dg/uninit-28-gimple.c
new file mode 100644
index 00000000000..0648b8a4aa7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-28-gimple.c
@@ -0,0 +1,47 @@
+/* { dg-do compile } */
+/* { dg-options "-fgimple -O -Wmaybe-uninitialized" } */
+
+unsigned int __GIMPLE (ssa,startwith("uninit1"))
+foo (unsigned int v)
+{
+  /* Uninit warning here would be bogus, because (16 & 3) == 0 and therefore
+     if v == 16, the uninit value is not used (the use is properly guarded).  */
+  unsigned int undef;        /* { dg-bogus "may be used uninitialized" } */
+  unsigned int _2;
+  unsigned int _9;
+  unsigned int _10;
+  unsigned pred;
+
+  __BB(2):
+  if (v_4(D) != 16u)
+    goto __BB3;
+  else
+    goto __BB4;
+
+  /* 'undef' is defined conditionally (under 'v != 16' predicate)  */
+  __BB(3):
+  undef_8 = 8u;
+  goto __BB4;
+
+  /* An undef value flows into a phi.  */
+  __BB(4):
+  undef_1 = __PHI (__BB2: undef_5(D), __BB3: undef_8);
+  pred = v_4(D) & 3u;
+  if (pred != 0u)
+    goto __BB5;
+  else
+    goto __BB6;
+
+  /* The phi value is used here (under 'v & 3' predicate).  */
+  __BB(5):
+  _9 = undef_1;
+  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-29-gimple.c b/gcc/testsuite/gcc.dg/uninit-29-gimple.c
new file mode 100644
index 00000000000..cb5bc97164e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-29-gimple.c
@@ -0,0 +1,45 @@
+/* { 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;
+  unsigned pred;
+
+  __BB(2):
+  pred = v_4(D) & 3u;
+  if (pred != 0u)
+    goto __BB3;
+  else
+    goto __BB4;
+
+  /* 'undef' is defined conditionally (under 'v & 3' predicate)  */
+  __BB(3):
+  undef_8 = 8u;
+  goto __BB4;
+
+  /* An undef value flows into a phi.  */
+  __BB(4):
+  undef_1 = __PHI (__BB2: undef_5(D), __BB3: undef_8);
+  if (v_4(D) != 16u)
+    goto __BB5;
+  else
+    goto __BB6;
+
+  /* The phi value is used here (under 'v != 16' predicate).  */
+  __BB(5):
+  _9 = undef_1;
+  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-30-gimple.c b/gcc/testsuite/gcc.dg/uninit-30-gimple.c
new file mode 100644
index 00000000000..8c91f79d509
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-30-gimple.c
@@ -0,0 +1,43 @@
+/* { 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;
+
+  /* 'undef' is defined conditionally (under 'v < 100' predicate).  */
+  __BB(3):
+  undef_8 = 8u;
+  goto __BB4;
+
+  /* An undef value flows into a phi.  */
+  __BB(4):
+  undef_1 = __PHI (__BB2: undef_5(D), __BB3: undef_8);
+  if (v_4(D) == 42u)
+    goto __BB5;
+  else
+    goto __BB6;
+
+  /* The phi value is used here (under 'v == 42' predicate).  */
+  __BB(5):
+  _9 = undef_1;
+  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-31-gimple.c b/gcc/testsuite/gcc.dg/uninit-31-gimple.c
new file mode 100644
index 00000000000..01118ef9823
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-31-gimple.c
@@ -0,0 +1,48 @@
+/* { dg-do compile } */
+/* { dg-options "-fgimple -O -Wmaybe-uninitialized" } */
+
+unsigned int __GIMPLE (ssa,startwith("uninit1"))
+foo (unsigned int v)
+{
+  /* If v == 2, then undef is used w/o being initialized.  */
+  unsigned int undef;        /* { dg-warning "may be used uninitialized" } */
+  unsigned int _2;
+  unsigned int _9;
+  unsigned int _10;
+  unsigned int pred2;
+  unsigned int pred1;
+
+  __BB(2):
+  pred2 = v_4(D) & 5u;
+  if (pred2 != 0u)
+    goto __BB3;
+  else
+    goto __BB4;
+
+  /* 'undef' is defined conditionally (under 'v & 5' predicate).  */
+  __BB(3):
+  undef_8 = 8u;
+  goto __BB4;
+
+  /* An undef value flows into a phi.  */
+  __BB(4):
+  undef_1 = __PHI (__BB2: undef_5(D), __BB3: undef_8);
+  pred1 = v_4(D) & 3u;
+  if (pred1 != 0u)
+    goto __BB5;
+  else
+    goto __BB6;
+
+  /* The phi value is used here (under 'v & 3' predicate).  */
+  __BB(5):
+  _9 = undef_1;
+  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 b89da4017e8..bc07afe32c8 100644
--- a/gcc/tree-ssa-uninit.c
+++ b/gcc/tree-ssa-uninit.c
@@ -1045,6 +1045,26 @@ is_value_included_in (tree val, tree boundary, enum tree_code cmpc)
   return result;
 }
 
+/* Returns whether VAL satisfies (x CMPC BOUNDARY) predicate.  CMPC can be
+   either one of the range comparison codes ({GE,LT,EQ,NE}_EXPR and the like),
+   or BIT_AND_EXPR.  EXACT_P is only meaningful for the latter.  It modifies the
+   question from whether VAL & BOUNDARY != 0 to whether VAL & BOUNDARY == VAL.
+   For other values of CMPC, EXACT_P is ignored.  */
+
+static bool
+value_sat_pred_p (tree val, tree boundary, enum tree_code cmpc,
+		  bool exact_p = false)
+{
+  if (cmpc != BIT_AND_EXPR)
+    return is_value_included_in (val, boundary, cmpc);
+
+  wi::tree_to_wide_ref andw = wi::to_wide (val) & wi::to_wide (boundary);
+  if (exact_p)
+    return andw == wi::to_wide (val);
+  else
+    return andw.to_uhwi ();
+}
+
 /* Returns true if PRED is common among all the predicate
    chains (PREDS) (and therefore can be factored out).
    NUM_PRED_CHAIN is the size of array PREDS.  */
@@ -1471,18 +1491,15 @@ is_pred_expr_subset_of (pred_info expr1, pred_info expr2)
   if (code2 == NE_EXPR && code1 == NE_EXPR)
     return false;
 
-  if (code2 == NE_EXPR && code1 != BIT_AND_EXPR)
-    return !is_value_included_in (expr2.pred_rhs, expr1.pred_rhs, code1);
+  if (code2 == NE_EXPR)
+    return !value_sat_pred_p (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 == EQ_EXPR)
+    return value_sat_pred_p (expr1.pred_rhs, expr2.pred_rhs, code2);
 
-  if (code1 != code2)
-    return false;
-
-  if (is_value_included_in (expr1.pred_rhs, expr2.pred_rhs, code2))
-    return true;
+  if (code1 == code2)
+    return value_sat_pred_p (expr1.pred_rhs, expr2.pred_rhs, code2,
+			     code1 == BIT_AND_EXPR);
 
   return false;
 }