[PATCH] Teach VRP about ABSU_EXPR (PR tree-optimization/89143)

[Jakub Jelinek]

Hi!

As mentioned in the PR, with the introduction of ABSU_EXPR where we were
previously using ABS_EXPR we've regressed various cases where VRP used to be
able to determine ranges for ABS_EXPR, but as ABSU_EXPR is unknown, we
always defer to VARYING.  ABSU_EXPR is actually much easier to handle than
ABS_EXPR.  Bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2019-01-31  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/89143
	* wide-int-range.h (wide_int_range_absu): Declare.
	* wide-int-range.cc (wide_int_range_absu): New function.
	* tree-vrp.c (extract_range_from_unary_expr): Handle ABSU_EXPR.

	* gcc.dg/tree-ssa/vrp121.c: New test.

--- gcc/wide-int-range.h.jj	2019-01-01 12:37:19.272940249 +0100
+++ gcc/wide-int-range.h	2019-01-31 21:09:24.045463875 +0100
@@ -107,6 +107,10 @@ extern bool wide_int_range_abs (wide_int
 				const wide_int &vr0_min,
 				const wide_int &vr0_max,
 				bool overflow_undefined);
+extern void wide_int_range_absu (wide_int &min, wide_int &max,
+				 unsigned prec,
+				 const wide_int &vr0_min,
+				 const wide_int &vr0_max);
 extern bool wide_int_range_convert (wide_int &min, wide_int &max,
 				    signop inner_sign,
 				    unsigned inner_prec,
--- gcc/wide-int-range.cc.jj	2019-01-01 12:37:15.627000071 +0100
+++ gcc/wide-int-range.cc	2019-01-31 21:23:09.122900358 +0100
@@ -735,6 +735,37 @@ wide_int_range_abs (wide_int &min, wide_
   return true;
 }
 
+/* Calculate ABSU_EXPR on a range and store the result in [MIN, MAX].  */
+
+void
+wide_int_range_absu (wide_int &min, wide_int &max,
+		     unsigned prec, const wide_int &vr0_min,
+		     const wide_int &vr0_max)
+{
+  /* Pass through VR0 the easy cases.  */
+  if (wi::ges_p (vr0_min, 0))
+    {
+      min = vr0_min;
+      max = vr0_max;
+      return;
+    }
+
+  min = wi::abs (vr0_min);
+  max = wi::abs (vr0_max);
+
+  /* If the range contains zero then we know that the minimum value in the
+     range will be zero.  */
+  if (wi::ges_p (vr0_max, 0))
+    {
+      if (wi::gtu_p (min, max))
+	max = min;
+      min = wi::zero (prec);
+    }
+  else
+    /* Otherwise, swap MIN and MAX.  */
+    std::swap (min, max);
+}
+
 /* Convert range in [VR0_MIN, VR0_MAX] with INNER_SIGN and INNER_PREC,
    to a range in [MIN, MAX] with OUTER_SIGN and OUTER_PREC.
 
--- gcc/tree-vrp.c.jj	2019-01-01 12:37:15.886995805 +0100
+++ gcc/tree-vrp.c	2019-01-31 21:26:42.326334608 +0100
@@ -2196,6 +2196,16 @@ extract_range_from_unary_expr (value_ran
 	vr->set_varying ();
       return;
     }
+  else if (code == ABSU_EXPR)
+    {
+      wide_int wmin, wmax;
+      wide_int vr0_min, vr0_max;
+      extract_range_into_wide_ints (&vr0, SIGNED, prec, vr0_min, vr0_max);
+      wide_int_range_absu (wmin, wmax, prec, vr0_min, vr0_max);
+      vr->set (VR_RANGE, wide_int_to_tree (type, wmin),
+	       wide_int_to_tree (type, wmax));
+      return;
+    }
 
   /* For unhandled operations fall back to varying.  */
   vr->set_varying ();
--- gcc/testsuite/gcc.dg/tree-ssa/vrp121.c.jj	2019-01-31 22:05:49.575733486 +0100
+++ gcc/testsuite/gcc.dg/tree-ssa/vrp121.c	2019-01-31 22:05:15.813288163 +0100
@@ -0,0 +1,67 @@
+/* PR tree-optimization/89143 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-not "link_error \\\(" "optimized" } } */
+
+void link_error (void);
+
+void
+f1 (signed char i)
+{
+  if (__builtin_abs (i) < 0 || __builtin_abs (i) > __SCHAR_MAX__ + 1)
+    link_error ();
+}
+
+void
+f2 (signed char i)
+{
+  if (i < 0 || i > 15)
+    __builtin_unreachable ();
+  if (__builtin_abs (i) < 0 || __builtin_abs (i) > 15)
+    link_error ();
+}
+
+void
+f3 (signed char i)
+{
+  if (i < 19 || i > 25)
+    __builtin_unreachable ();
+  if (__builtin_abs (i) < 19 || __builtin_abs (i) > 25)
+    link_error ();
+}
+
+void
+f4 (signed char i)
+{
+  if (i > -60)
+    __builtin_unreachable ();
+  if (__builtin_abs (i) < 60 || __builtin_abs (i) > __SCHAR_MAX__ + 1)
+    link_error ();
+}
+
+void
+f5 (signed char i)
+{
+  if (i < -__SCHAR_MAX__ || i > -30)
+    __builtin_unreachable ();
+  if (__builtin_abs (i) < 30 || __builtin_abs (i) > __SCHAR_MAX__)
+    link_error ();
+}
+
+void
+f6 (signed char i)
+{
+  if (i < -__SCHAR_MAX__ || i > 30)
+    __builtin_unreachable ();
+  if (__builtin_abs (i) < 0 || __builtin_abs (i) > __SCHAR_MAX__)
+    link_error ();
+}
+
+void
+f7 (signed char i)
+{
+  if (i < -31 || i > 30)
+    __builtin_unreachable ();
+  if (__builtin_abs (i) < 0 || __builtin_abs (i) > 31)
+    link_error ();
+}

	Jakub