PR 23941

        * real.c (exact_real_truncate): Return false if the format cannot
        represent the number as a normal.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@104424 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 118b6b6..2a56ded 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2005-09-19  Richard Henderson  <rth@redhat.com>
+
+       PR 23941
+       * real.c (exact_real_truncate): Return false if the format cannot
+       represent the number as a normal.
+
 2005-09-19  Dorit Nuzman  <dorit@il.ibm.com>
 
        * tree-ssa-operands.c (swap_tree_operands): Export.

diff --git a/gcc/real.c b/gcc/real.c
index 2d26185..9b165ec 100644 (file)
--- a/gcc/real.c
+++ b/gcc/real.c
@@ -2399,7 +2399,19 @@ real_value_truncate (enum machine_mode mode, REAL_VALUE_TYPE a)
 bool
 exact_real_truncate (enum machine_mode mode, const REAL_VALUE_TYPE *a)
 {
+  const struct real_format *fmt;
   REAL_VALUE_TYPE t;
+  int emin2m1;
+
+  fmt = REAL_MODE_FORMAT (mode);
+  gcc_assert (fmt);
+
+  /* Don't allow conversion to denormals.  */
+  emin2m1 = (fmt->emin - 1) * fmt->log2_b;
+  if (REAL_EXP (a) <= emin2m1)
+    return false;
+
+  /* After conversion to the new mode, the value must be identical.  */
   real_convert (&t, mode, a);
   return real_identical (&t, a);
 }

diff --git a/gcc/testsuite/gcc.c-torture/execute/pr23941.c b/gcc/testsuite/gcc.c-torture/execute/pr23941.c
new file mode 100644 (file)
index 0000000..4dfd645
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr23941.c
@@ -0,0 +1,9 @@
+extern void abort (void);
+double d = __FLT_MIN__ / 2.0;
+int main()
+{
+  double x = __FLT_MIN__ / 2.0;
+  if (x != d)
+    abort ();
+  return 0;
+}