From 1e27e7a582a9b86bcf86f5c103cd947672746e97 Mon Sep 17 00:00:00 2001
From: Andrew MacLeod <amacleod@redhat.com>
Date: Tue, 17 Nov 2020 14:47:58 -0500
Subject: [PATCH] recognize implied ranges for modulo.

implement op1_range for modulo with implied positive and negative ranges.

	gcc/
	PR tree-optimization/91029
	* range-op.cc (operator_trunc_mod::op1_range): New.
	gcc/testsuite/
	* gcc.dg/pr91029.c: New.
---
 gcc/range-op.cc                | 28 ++++++++++++++++++++
 gcc/testsuite/gcc.dg/pr91029.c | 47 ++++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/pr91029.c

diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index d0adc95527a..f37796cac70 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -2634,6 +2634,9 @@ public:
 		        const wide_int &lh_ub,
 		        const wide_int &rh_lb,
 		        const wide_int &rh_ub) const;
+  virtual bool op1_range (irange &r, tree type,
+			  const irange &lhs,
+			  const irange &op2) const;
 } op_trunc_mod;
 
 void
@@ -2680,6 +2683,31 @@ operator_trunc_mod::wi_fold (irange &r, tree type,
   value_range_with_overflow (r, type, new_lb, new_ub);
 }
 
+bool
+operator_trunc_mod::op1_range (irange &r, tree type,
+			       const irange &lhs,
+			       const irange &op2) const
+{
+  // PR 91029.  Check for signed truncation with op2 >= 0.
+  if (TYPE_SIGN (type) == SIGNED && wi::ge_p (op2.lower_bound (), 0, SIGNED))
+    {
+      unsigned prec = TYPE_PRECISION (type);
+      // if a & b >=0 , then a >= 0.
+      if (wi::ge_p (lhs.lower_bound (), 0, SIGNED))
+	{
+	  r = value_range (type, wi::zero (prec), wi::max_value (prec, SIGNED));
+	  return true;
+	}
+      // if a & b < 0 , then a <= 0.
+      if (wi::lt_p (lhs.upper_bound (), 0, SIGNED))
+	{
+	  r = value_range (type, wi::min_value (prec, SIGNED), wi::zero (prec));
+	  return true;
+	}
+    }
+  return false;
+}
+
 
 class operator_logical_not : public range_operator
 {
diff --git a/gcc/testsuite/gcc.dg/pr91029.c b/gcc/testsuite/gcc.dg/pr91029.c
new file mode 100644
index 00000000000..8a4134c5d96
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr91029.c
@@ -0,0 +1,47 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-evrp" } */
+
+void kill (void);
+int xx;
+
+void f1 (int i)
+{
+  if ((i % 7) == 3)
+    {
+      xx = (i < 0);
+      if (xx)
+        kill ();
+    }
+}
+
+void f2 (int i)
+{
+  if ((i % 7) >= 0)
+    {
+      xx = (i < 0);
+      if (xx)
+        kill ();
+    }
+}
+
+void f3 (int i)
+{
+  if ((i % 7) == -3)
+    {
+      xx = (i > 0);
+      if (xx)
+        kill ();
+    }
+}
+
+void f4 (int i)
+{
+  if ((i % 7) < 0)
+    {
+      xx = (i > 0);
+      if (xx)
+        kill ();
+    }
+}
+
+/* { dg-final { scan-tree-dump-not "kill" "evrp" } }  */
-- 
2.30.2