Re: [PATCH] range-op-float: Further comparison fixes

[Jakub Jelinek <jakub@redhat.com>]

On Fri, Mar 31, 2023 at 01:28:35PM +0200, Aldy Hernandez wrote:
> > Ok for trunk if this passes bootstrap/regtest?
> 
> LGTM

Unfortunately I ran into 4 tests where we run into the known bug
where if ranger finds out a range of some floating point operation
it folds it and throws away the trapping side-effects with it.
In particular, e.g. VARYING > __builtin_inf () is now folded to false
because no finite or infinite value is larger than +inf, and if
NAN is compared against it, the result is false as well.

Given that it is a known problem we need to find some solution for
in GCC 14, I've just changed those testcases to disable dom and vrp
passes which were optimizing it.  Another workaround would be
to hide the infinity from the optimizers, but given that the test was
added exactly to verify match.pd doesn't optimize this for -ftrapping-math,
I think disabling dom/vrp is better.

So, here is what I've committed (the other patch committed unchanged):

2023-04-01  Jakub Jelinek  <jakub@redhat.com>

	* range-op-float.cc (foperator_equal::fold_range): Perform the
	non-singleton handling regardless of maybe_isnan (op1, op2).
	(foperator_not_equal::fold_range): Likewise.
	(foperator_lt::fold_range, foperator_le::fold_range,
	foperator_gt::fold_range, foperator_ge::fold_range): Perform the
	real_* comparison check which results in range_false (type)
	even if maybe_isnan (op1, op2).  Simplify.
	(foperator_ltgt): New class.
	(fop_ltgt): New variable.
	(floating_op_table::floating_op_table): Handle LTGT_EXPR using
	fop_ltgt.

	* gcc.dg/torture/inf-compare-1.c: Add dg-additional-options
	-fno-tree-dominator-opts -fno-tree-vrp.
	* gcc.dg/torture/inf-compare-1-float.c: Likewise.
	* gcc.dg/torture/inf-compare-2.c: Likewise.
	* gcc.dg/torture/inf-compare-2-float.c: Likewise.

--- gcc/range-op-float.cc.jj	2023-03-31 09:30:11.245296618 +0200
+++ gcc/range-op-float.cc	2023-03-31 11:23:04.817876083 +0200
@@ -616,7 +616,7 @@ foperator_equal::fold_range (irange &r,
       else
 	r = range_false (type);
     }
-  else if (!maybe_isnan (op1, op2))
+  else
     {
       // If ranges do not intersect, we know the range is not equal,
       // otherwise we don't know anything for sure.
@@ -638,8 +638,6 @@ foperator_equal::fold_range (irange &r,
       else
 	r = range_true_and_false (type);
     }
-  else
-    r = range_true_and_false (type);
   return true;
 }
 
@@ -734,7 +732,7 @@ foperator_not_equal::fold_range (irange
       else
 	r = range_true (type);
     }
-  else if (!maybe_isnan (op1, op2))
+  else
     {
       // If ranges do not intersect, we know the range is not equal,
       // otherwise we don't know anything for sure.
@@ -756,8 +754,6 @@ foperator_not_equal::fold_range (irange
       else
 	r = range_true_and_false (type);
     }
-  else
-    r = range_true_and_false (type);
   return true;
 }
 
@@ -839,17 +835,13 @@ foperator_lt::fold_range (irange &r, tre
   if (frelop_early_resolve (r, type, op1, op2, rel, VREL_LT))
     return true;
 
-  if (op1.known_isnan () || op2.known_isnan ())
+  if (op1.known_isnan ()
+      || op2.known_isnan ()
+      || !real_less (&op1.lower_bound (), &op2.upper_bound ()))
     r = range_false (type);
-  else if (!maybe_isnan (op1, op2))
-    {
-      if (real_less (&op1.upper_bound (), &op2.lower_bound ()))
-	r = range_true (type);
-      else if (!real_less (&op1.lower_bound (), &op2.upper_bound ()))
-	r = range_false (type);
-      else
-	r = range_true_and_false (type);
-    }
+  else if (!maybe_isnan (op1, op2)
+	   && real_less (&op1.upper_bound (), &op2.lower_bound ()))
+    r = range_true (type);
   else
     r = range_true_and_false (type);
   return true;
@@ -959,17 +951,13 @@ foperator_le::fold_range (irange &r, tre
   if (frelop_early_resolve (r, type, op1, op2, rel, VREL_LE))
     return true;
 
-  if (op1.known_isnan () || op2.known_isnan ())
+  if (op1.known_isnan ()
+      || op2.known_isnan ()
+      || !real_compare (LE_EXPR, &op1.lower_bound (), &op2.upper_bound ()))
     r = range_false (type);
-  else if (!maybe_isnan (op1, op2))
-    {
-      if (real_compare (LE_EXPR, &op1.upper_bound (), &op2.lower_bound ()))
-	r = range_true (type);
-      else if (!real_compare (LE_EXPR, &op1.lower_bound (), &op2.upper_bound ()))
-	r = range_false (type);
-      else
-	r = range_true_and_false (type);
-    }
+  else if (!maybe_isnan (op1, op2)
+	   && real_compare (LE_EXPR, &op1.upper_bound (), &op2.lower_bound ()))
+    r = range_true (type);
   else
     r = range_true_and_false (type);
   return true;
@@ -1073,17 +1061,13 @@ foperator_gt::fold_range (irange &r, tre
   if (frelop_early_resolve (r, type, op1, op2, rel, VREL_GT))
     return true;
 
-  if (op1.known_isnan () || op2.known_isnan ())
+  if (op1.known_isnan ()
+      || op2.known_isnan ()
+      || !real_compare (GT_EXPR, &op1.upper_bound (), &op2.lower_bound ()))
     r = range_false (type);
-  else if (!maybe_isnan (op1, op2))
-    {
-      if (real_compare (GT_EXPR, &op1.lower_bound (), &op2.upper_bound ()))
-	r = range_true (type);
-      else if (!real_compare (GT_EXPR, &op1.upper_bound (), &op2.lower_bound ()))
-	r = range_false (type);
-      else
-	r = range_true_and_false (type);
-    }
+  else if (!maybe_isnan (op1, op2)
+	   && real_compare (GT_EXPR, &op1.lower_bound (), &op2.upper_bound ()))
+    r = range_true (type);
   else
     r = range_true_and_false (type);
   return true;
@@ -1197,17 +1181,13 @@ foperator_ge::fold_range (irange &r, tre
   if (frelop_early_resolve (r, type, op1, op2, rel, VREL_GE))
     return true;
 
-  if (op1.known_isnan () || op2.known_isnan ())
+  if (op1.known_isnan ()
+      || op2.known_isnan ()
+      || !real_compare (GE_EXPR, &op1.upper_bound (), &op2.lower_bound ()))
     r = range_false (type);
-  else if (!maybe_isnan (op1, op2))
-    {
-      if (real_compare (GE_EXPR, &op1.lower_bound (), &op2.upper_bound ()))
-	r = range_true (type);
-      else if (!real_compare (GE_EXPR, &op1.upper_bound (), &op2.lower_bound ()))
-	r = range_false (type);
-      else
-	r = range_true_and_false (type);
-    }
+  else if (!maybe_isnan (op1, op2)
+	   && real_compare (GE_EXPR, &op1.lower_bound (), &op2.upper_bound ()))
+    r = range_true (type);
   else
     r = range_true_and_false (type);
   return true;
@@ -2092,6 +2072,87 @@ foperator_unordered_equal::op1_range (fr
   return true;
 }
 
+class foperator_ltgt : public range_operator_float
+{
+  using range_operator_float::fold_range;
+  using range_operator_float::op1_range;
+  using range_operator_float::op2_range;
+public:
+  bool fold_range (irange &r, tree type,
+		   const frange &op1, const frange &op2,
+		   relation_trio rel = TRIO_VARYING) const final override
+  {
+    if (op1.known_isnan () || op2.known_isnan ())
+      {
+	r = range_false (type);
+	return true;
+      }
+    frange op1_no_nan = op1;
+    frange op2_no_nan = op2;
+    if (op1.maybe_isnan ())
+      op1_no_nan.clear_nan ();
+    if (op2.maybe_isnan ())
+      op2_no_nan.clear_nan ();
+    if (!fop_not_equal.fold_range (r, type, op1_no_nan, op2_no_nan, rel))
+      return false;
+    // The result is the same as the ordered version when the
+    // comparison is true or when the operands cannot be NANs.
+    if (!maybe_isnan (op1, op2) || r == range_false (type))
+      return true;
+    else
+      {
+	r = range_true_and_false (type);
+	return true;
+      }
+  }
+  bool op1_range (frange &r, tree type,
+		  const irange &lhs, const frange &op2,
+		  relation_trio = TRIO_VARYING) const final override;
+  bool op2_range (frange &r, tree type,
+		  const irange &lhs, const frange &op1,
+		  relation_trio rel = TRIO_VARYING) const final override
+  {
+    return op1_range (r, type, lhs, op1, rel.swap_op1_op2 ());
+  }
+} fop_ltgt;
+
+bool
+foperator_ltgt::op1_range (frange &r, tree type,
+			   const irange &lhs,
+			   const frange &op2,
+			   relation_trio) const
+{
+  switch (get_bool_state (r, lhs, type))
+    {
+    case BRS_TRUE:
+      // A true LTGT means both operands are !NAN, so it's
+      // impossible for op2 to be a NAN.
+      if (op2.known_isnan ())
+	r.set_undefined ();
+      else
+	{
+	  // The true side indicates !NAN and not equal.  We can at least
+	  // represent !NAN.
+	  r.set_varying (type);
+	  r.clear_nan ();
+	}
+      break;
+
+    case BRS_FALSE:
+      // If it's false, the result is the same as OP2 plus a NAN.
+      r = op2;
+      // Add both zeros if there's the possibility of zero equality.
+      frange_add_zeros (r, type);
+      // Add the possibility of a NAN.
+      r.update_nan ();
+      break;
+
+    default:
+      break;
+    }
+  return true;
+}
+
 // Final tweaks for float binary op op1_range/op2_range.
 // Return TRUE if the operation is performed and a valid range is available.
 
@@ -2767,6 +2828,7 @@ floating_op_table::floating_op_table ()
   set (UNEQ_EXPR, fop_unordered_equal);
   set (ORDERED_EXPR, fop_ordered);
   set (UNORDERED_EXPR, fop_unordered);
+  set (LTGT_EXPR, fop_ltgt);
 
   set (ABS_EXPR, fop_abs);
   set (NEGATE_EXPR, fop_negate);
--- gcc/testsuite/gcc.dg/torture/inf-compare-1.c.jj	2022-10-21 08:56:19.330180242 +0200
+++ gcc/testsuite/gcc.dg/torture/inf-compare-1.c	2023-04-01 09:26:24.385274181 +0200
@@ -3,6 +3,7 @@
 /* { dg-add-options ieee } */
 /* { dg-require-effective-target fenv_exceptions_double } */
 /* { dg-skip-if "fenv" { powerpc-ibm-aix* } } */
+/* { dg-additional-options "-fno-tree-dominator-opts -fno-tree-vrp" } */
 
 #include <fenv.h>
 
--- gcc/testsuite/gcc.dg/torture/inf-compare-1-float.c.jj	2022-10-21 08:56:19.330180242 +0200
+++ gcc/testsuite/gcc.dg/torture/inf-compare-1-float.c	2023-04-01 09:26:15.380403321 +0200
@@ -3,6 +3,7 @@
 /* { dg-add-options ieee } */
 /* { dg-require-effective-target fenv_exceptions } */
 /* { dg-skip-if "fenv" { powerpc-ibm-aix* } } */
+/* { dg-additional-options "-fno-tree-dominator-opts -fno-tree-vrp" } */
 
 #include <fenv.h>
 
--- gcc/testsuite/gcc.dg/torture/inf-compare-2.c.jj	2022-10-21 08:56:19.330180242 +0200
+++ gcc/testsuite/gcc.dg/torture/inf-compare-2.c	2023-04-01 09:26:43.555999258 +0200
@@ -3,6 +3,7 @@
 /* { dg-add-options ieee } */
 /* { dg-require-effective-target fenv_exceptions_double } */
 /* { dg-skip-if "fenv" { powerpc-ibm-aix* } } */
+/* { dg-additional-options "-fno-tree-dominator-opts -fno-tree-vrp" } */
 
 #include <fenv.h>
 
--- gcc/testsuite/gcc.dg/torture/inf-compare-2-float.c.jj	2022-10-21 08:56:19.330180242 +0200
+++ gcc/testsuite/gcc.dg/torture/inf-compare-2-float.c	2023-04-01 09:26:32.682155200 +0200
@@ -3,6 +3,7 @@
 /* { dg-add-options ieee } */
 /* { dg-require-effective-target fenv_exceptions } */
 /* { dg-skip-if "fenv" { powerpc-ibm-aix* } } */
+/* { dg-additional-options "-fno-tree-dominator-opts -fno-tree-vrp" } */
 
 #include <fenv.h>
 


	Jakub