Set nonzero bits for multiplication and divisions by a power of 2.

We're missing a lot of TLC in keeping track of nonzero bits across
range-ops.  It isn't an oversight, but just limited amount of hours to
implement stuff.

This patch keeps better track of the nonzero mask (really
maybe_nonzero bits as discussed) across multiplication and division
when the RHS is a power of 2.

It fixes PR107342 and also touches on PR55157.  In the latter, the
nonzero mask is being set quite late (CCP2) but could be set by evrp
time if we enhanced range-ops.  I have added tests from both PRs.

Tested

	PR tree-optimization/107342

gcc/ChangeLog:

	* range-op.cc (operator_mult::fold_range): New.
	(operator_div::fold_range): New.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/vrp122.c: New test.
	* gcc.dg/tree-ssa/vrp123.c: New test.

diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 49ee7be..25c004d 100644 (file)
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -1742,9 +1742,13 @@ cross_product_operator::wi_cross_product (irange &r, tree type,
 
 class operator_mult : public cross_product_operator
 {
+  using range_operator::fold_range;
   using range_operator::op1_range;
   using range_operator::op2_range;
 public:
+  virtual bool fold_range (irange &r, tree type,
+                          const irange &lh, const irange &rh,
+                          relation_trio = TRIO_VARYING) const final override;
   virtual void wi_fold (irange &r, tree type,
                        const wide_int &lh_lb,
                        const wide_int &lh_ub,
@@ -1763,6 +1767,32 @@ public:
 } op_mult;
 
 bool
+operator_mult::fold_range (irange &r, tree type,
+                          const irange &lh, const irange &rh,
+                          relation_trio trio) const
+{
+  if (!cross_product_operator::fold_range (r, type, lh, rh, trio))
+    return false;
+
+  if (lh.undefined_p ())
+    return true;
+
+  tree t;
+  if (rh.singleton_p (&t))
+    {
+      wide_int w = wi::to_wide (t);
+      int shift = wi::exact_log2 (w);
+      if (shift != -1)
+       {
+         wide_int nz = lh.get_nonzero_bits ();
+         nz = wi::lshift (nz, shift);
+         r.set_nonzero_bits (nz);
+       }
+    }
+  return true;
+}
+
+bool
 operator_mult::op1_range (irange &r, tree type,
                          const irange &lhs, const irange &op2,
                          relation_trio) const
@@ -1902,11 +1932,40 @@ public:
                        const wide_int &rh_ub) const;
   virtual bool wi_op_overflows (wide_int &res, tree type,
                                const wide_int &, const wide_int &) const;
+  virtual bool fold_range (irange &r, tree type,
+                          const irange &lh, const irange &rh,
+                          relation_trio trio) const final override;
 private:
   enum tree_code code;
 };
 
 bool
+operator_div::fold_range (irange &r, tree type,
+                         const irange &lh, const irange &rh,
+                         relation_trio trio) const
+{
+  if (!cross_product_operator::fold_range (r, type, lh, rh, trio))
+    return false;
+
+  if (lh.undefined_p ())
+    return true;
+
+  tree t;
+  if (rh.singleton_p (&t))
+    {
+      wide_int wi = wi::to_wide (t);
+      int shift = wi::exact_log2 (wi);
+      if (shift != -1)
+       {
+         wide_int nz = lh.get_nonzero_bits ();
+         nz = wi::rshift (nz, shift, TYPE_SIGN (type));
+         r.set_nonzero_bits (nz);
+       }
+    }
+  return true;
+}
+
+bool
 operator_div::wi_op_overflows (wide_int &res, tree type,
                               const wide_int &w0, const wide_int &w1) const
 {

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/vrp122.c b/gcc/testsuite/gcc.dg/tree-ssa/vrp122.c
new file mode 100644 (file)
index 0000000..b2ddcda
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/vrp122.c
@@ -0,0 +1,19 @@
+// { dg-do compile }
+// { dg-options "-O2 -fdump-tree-evrp-details" }
+
+void gg(void);
+int f(unsigned t)
+{
+  unsigned g = t*16;
+  if (g==0)  return 1;
+  gg();
+  gg();
+  gg();
+  gg();
+  gg();
+  gg();
+  if (g<=4)  return 1;
+  return 0;
+}
+
+// { dg-final { scan-tree-dump "Global Exported: g_.* NONZERO 0x.*fff0" "evrp" } }

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/vrp123.c b/gcc/testsuite/gcc.dg/tree-ssa/vrp123.c
new file mode 100644 (file)
index 0000000..1ad3caa
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/vrp123.c
@@ -0,0 +1,18 @@
+// { dg-options "-O1 -fdump-tree-dom3-raw" }
+
+extern int
+__attribute__((const))
+foo4b (int);
+
+int f4b (unsigned int r)
+{
+  if (foo4b (r))
+    r *= 8U;
+
+  if ((r / 2U) & 2U)
+    r += foo4b (r);
+
+  return r;
+}
+
+// { dg-final { scan-tree-dump-times {gimple_call <foo4b,} 1 dom3 } }