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[COMMITTED,PR,106819] NANs can never be a singleton

Message ID 20220903153608.3043385-1-aldyh@redhat.com
State New
Headers show
Series [COMMITTED,PR,106819] NANs can never be a singleton | expand

Commit Message

Aldy Hernandez Sept. 3, 2022, 3:36 p.m. UTC 
Possible NANs can never be a singleton, so they will never be
propagated.  This was the intent, and then the signed zero code crept
in, and was mistakenly checked before the NAN.

	PR 106819

gcc/ChangeLog:

	* value-range.cc (frange::singleton_p): Move NAN check to the top.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/pr106819.c: New test.
---
 gcc/testsuite/gcc.dg/tree-ssa/pr106819.c | 24 ++++++++++++++++++++++++
 gcc/value-range.cc                       |  9 ++++-----
 2 files changed, 28 insertions(+), 5 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr106819.c
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Patch

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr106819.c b/gcc/testsuite/gcc.dg/tree-ssa/pr106819.c
new file mode 100644
index 00000000000..1272d4b5805
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr106819.c
@@ -0,0 +1,24 @@ 
+// { dg-do compile }
+// { dg-options "-O2 -fdump-tree-evrp-details" }
+
+static int isNaN(double x)
+{
+    return x != x;
+}
+
+static double opCmpProper(int lhs, double rhs)
+{
+  return lhs < rhs ? -1.0
+       : lhs > rhs ? 1.0
+       : lhs == rhs ? 0.0
+       : __builtin_nan("");
+}
+
+int main()
+{
+    if (!isNaN(opCmpProper(41, __builtin_nan(""))))
+      __builtin_abort();
+    return 0;
+}
+
+// { dg-final {scan-tree-dump-not "Folds to: 0.0" "evrp" } }
diff --git a/gcc/value-range.cc b/gcc/value-range.cc
index 6fd6e3b745c..a1c29f7bd0b 100644
--- a/gcc/value-range.cc
+++ b/gcc/value-range.cc
@@ -632,6 +632,10 @@  frange::singleton_p (tree *result) const
 {
   if (m_kind == VR_RANGE && real_identical (&m_min, &m_max))
     {
+      // Return false for any singleton that may be a NAN.
+      if (HONOR_NANS (m_type) && !get_nan ().no_p ())
+	return false;
+
       // Return the appropriate zero if known.
       if (HONOR_SIGNED_ZEROS (m_type) && zero_p ())
 	{
@@ -649,11 +653,6 @@  frange::singleton_p (tree *result) const
 	    }
 	  return false;
 	}
-
-      // Return false for any singleton that may be a NAN.
-      if (HONOR_NANS (m_type) && !get_nan ().no_p ())
-	return false;
-
       if (result)
 	*result = build_real (m_type, m_min);
       return true;