gimple-range-op: Handle sqrt (basic bounds only)

The following patch adds sqrt support (but similarly to sincos, only
dumb basic ranges only).

Will improve this incrementally and sin/cos as well.

2023-04-28  Jakub Jelinek  <jakub@redhat.com>

	* gimple-range-op.cc (class cfn_sqrt): New type.
	(op_cfn_sqrt): New variable.
	(gimple_range_op_handler::maybe_builtin_call): Handle
	CASE_CFN_SQRT{,_FN}.

	* gcc.dg/tree-ssa/range-sqrt.c: New test.
	* gfortran.dg/ieee/ieee_6.f90: Make x volatile to avoid
	ranger optimizing sqrt (-1) call away because it is only used in
	test for whether it returns NaN.

3 files changed, 126 insertions, 1 deletions

diff --git a/gcc/gimple-range-op.cc b/gcc/gimple-range-op.cc
index b66a4a0..6fa26f5 100644
--- a/gcc/gimple-range-op.cc
+++ b/gcc/gimple-range-op.cc
@@ -401,6 +401,83 @@ public:
   }
 } op_cfn_copysign;
 
+class cfn_sqrt : public range_operator_float
+{
+public:
+  using range_operator_float::fold_range;
+  using range_operator_float::op1_range;
+  virtual bool fold_range (frange &r, tree type,
+			   const frange &lh, const frange &,
+			   relation_trio) const final override
+  {
+    if (lh.undefined_p ())
+      return false;
+    if (lh.known_isnan () || real_less (&lh.upper_bound (), &dconstm0))
+      {
+	r.set_nan (type);
+	return true;
+      }
+    unsigned bulps
+      = targetm.libm_function_max_error (CFN_SQRT, TYPE_MODE (type), true);
+    if (bulps == ~0U)
+      r.set_varying (type);
+    else if (bulps == 0)
+      r.set (type, dconstm0, dconstinf);
+    else
+      {
+	REAL_VALUE_TYPE boundmin = dconstm0;
+	while (bulps--)
+	  frange_nextafter (TYPE_MODE (type), boundmin, dconstninf);
+	r.set (type, boundmin, dconstinf);
+      }
+    if (!lh.maybe_isnan () && !real_less (&lh.lower_bound (), &dconst0))
+      r.clear_nan ();
+    return true;
+  }
+  virtual bool op1_range (frange &r, tree type,
+			  const frange &lhs, const frange &,
+			  relation_trio) const final override
+  {
+    if (lhs.undefined_p ())
+      return false;
+
+    // A known NAN means the input is [-INF,-0.) U +-NAN.
+    if (lhs.known_isnan ())
+      {
+      known_nan:
+	REAL_VALUE_TYPE ub = dconstm0;
+	frange_nextafter (TYPE_MODE (type), ub, dconstninf);
+	r.set (type, dconstninf, ub);
+	// No r.flush_denormals_to_zero (); here - it is a reverse op.
+	return true;
+      }
+
+    // Results outside of [-0.0, +Inf] are impossible.
+    const REAL_VALUE_TYPE &ub = lhs.upper_bound ();
+    if (real_less (&ub, &dconstm0))
+      {
+	if (!lhs.maybe_isnan ())
+	  r.set_undefined ();
+	else
+	  // If lhs could be NAN and finite result is impossible,
+	  // the range is like lhs.known_isnan () above.
+	  goto known_nan;
+	return true;
+      }
+
+    if (!lhs.maybe_isnan ())
+      {
+	// If NAN is not valid result, the input cannot include either
+	// a NAN nor values smaller than -0.
+	r.set (type, dconstm0, dconstinf, nan_state (false, false));
+	return true;
+      }
+
+    r.set_varying (type);
+    return true;
+  }
+} op_cfn_sqrt;
+
 class cfn_sincos : public range_operator_float
 {
 public:
@@ -962,6 +1039,13 @@ gimple_range_op_handler::maybe_builtin_call ()
       m_valid = true;
       break;
 
+    CASE_CFN_SQRT:
+    CASE_CFN_SQRT_FN:
+      m_op1 = gimple_call_arg (call, 0);
+      m_float = &op_cfn_sqrt;
+      m_valid = true;
+      break;
+
     CASE_CFN_SIN:
     CASE_CFN_SIN_FN:
       m_op1 = gimple_call_arg (call, 0);
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/range-sqrt.c b/gcc/testsuite/gcc.dg/tree-ssa/range-sqrt.c
new file mode 100644
index 0000000..d2a2626
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/range-sqrt.c
@@ -0,0 +1,41 @@
+// { dg-do compile }
+// { dg-options "-O2 -fdump-tree-evrp -fno-thread-jumps" }
+
+#include <math.h>
+
+void use (double);
+void link_error ();
+
+void
+foo (double x)
+{
+  if (__builtin_isnan (x))
+    __builtin_unreachable ();
+  x = sqrt (x);
+  if (x < -0.0)
+    link_error ();
+  use (x);
+}
+
+void
+bar (double x)
+{
+  if (!__builtin_isnan (sqrt (x)))
+    {
+      if (__builtin_isnan (x))
+	link_error ();
+      if (x < -0.0)
+	link_error ();
+    }
+}
+
+void
+stool (double x)
+{
+  double res1 = sqrt (x);
+  double res2 = __builtin_sqrt (x);
+  if (res1 < -0.0 || res2 < -0.0)
+    link_error ();
+}
+
+// { dg-final { scan-tree-dump-not "link_error" "evrp" { target { { *-*-linux* } && { glibc } } } } }
diff --git a/gcc/testsuite/gfortran.dg/ieee/ieee_6.f90 b/gcc/testsuite/gfortran.dg/ieee/ieee_6.f90
index 1af7ed3..fd637eb 100644
--- a/gcc/testsuite/gfortran.dg/ieee/ieee_6.f90
+++ b/gcc/testsuite/gfortran.dg/ieee/ieee_6.f90
@@ -12,7 +12,7 @@
   type(ieee_status_type) :: s1, s2
   logical :: flags(5), halt(5), haltworks
   type(ieee_round_type) :: mode
-  real :: x
+  real, volatile :: x
 
   ! Test IEEE_GET_STATUS and IEEE_SET_STATUS