[PATCH] IOR with nonzero, range cannot contain 0.

[PATCH] IOR with nonzero, range cannot contain 0.

[Andrew MacLeod]

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PR 83072 mentions that we have lost the ability to recognize that when 
we see
   c |= 1;
c cannot be zero.   We can at least put it back for multi-ranges. Added 
a new testcase to make sure EVRP is tracking it.

bootstrapped on x86_64-pc-linux-gnu, no regressions.  pushed.

Andrew


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commit a5f9c27bfc4417224e332392bb81a2d733b2b5bf
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Tue Nov 17 10:04:38 2020 -0500

    IOR with nonzero, range cannot contain 0.
    
    Remove zero from IOR ranges with non-zero masks.
    
            gcc/
            PR tree-optimization/83072
            * range-op.cc (wi_optimize_and_or): Remove zero from IOR range when
            mask is non-zero.
            gcc/testsuite/
            * gcc.dg/pr83072.c: New.

diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index b746aadb603..d0adc95527a 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -2163,6 +2163,14 @@ wi_optimize_and_or (irange &r,
   else
     gcc_unreachable ();
   value_range_with_overflow (r, type, res_lb, res_ub);
+
+  // Furthermore, if the mask is non-zero, an IOR cannot contain zero.
+  if (code == BIT_IOR_EXPR && wi::ne_p (mask, 0))
+    {
+      int_range<2> tmp;
+      tmp.set_nonzero (type);
+      r.intersect (tmp);
+    }
   return true;
 }
 
diff --git a/gcc/testsuite/gcc.dg/pr83072.c b/gcc/testsuite/gcc.dg/pr83072.c
new file mode 100644
index 00000000000..3bed8d89013
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr83072.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-evrp -fno-tree-ccp -fno-tree-forwprop -fno-tree-fre" } */
+
+void kill (void);
+
+int f(int c){
+  c |= 1;
+  if (c == 0)
+    kill ();
+
+  return c;
+}
+
+/* { dg-final { scan-tree-dump-not "kill" "evrp" } }  */