From: Richard Sandiford <rsandifo@redhat.com>
Date: Fri, 10 Sep 2004 12:00:33 +0000 (+0000)
Subject: tree-tailcall.c (process_assignment): Only do accumulator transforms for floating... 
X-Git-Tag: releases/gcc-4.0.0~5068
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=85d625202998b5153d40cf1fbc36a400e8e013dd;p=thirdparty%2Fgcc.git

tree-tailcall.c (process_assignment): Only do accumulator transforms for floating-point types if...

	* tree-tailcall.c (process_assignment): Only do accumulator transforms
	for floating-point types if flag_unsafe_math_optimizations.

From-SVN: r87297
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 71223aa95412..e44ffc55ad99 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2004-09-10  Richard Sandiford  <rsandifo@redhat.com>
+
+	* tree-tailcall.c (process_assignment): Only do accumulator transforms
+	for floating-point types if flag_unsafe_math_optimizations.
+
 2004-09-10  Kazu Hirata  <kazu@cs.umass.edu>
 
 	* config/darwin.c, config/alpha/alpha.h, config/arm/arm.c,
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c33d260b5b3c..80dd8b05c5d0 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2004-09-10  Richard Sandiford  <rsandifo@redhat.com>
+
+	* gcc.c-torture/execute/ieee/acc1.c: New test.
+	* gcc.c-torture/execute/ieee/acc2.c: New test.
+	* gcc.c-torture/execute/ieee/mzero6.c: New test.
+
 2004-09-10  Joseph S. Myers  <jsm@polyomino.org.uk>
 
 	* gcc.dg/deprecated-2.c: New test.
diff --git a/gcc/testsuite/gcc.c-torture/execute/ieee/acc1.c b/gcc/testsuite/gcc.c-torture/execute/ieee/acc1.c
new file mode 100644
index 000000000000..e0d969b9ddc9
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/ieee/acc1.c
@@ -0,0 +1,18 @@
+/* Tail call optimizations would reverse the order of additions in func().  */
+
+double func (const double *array)
+{
+  double d = *array;
+  if (d == 0.0)
+    return d;
+  else
+    return d + func (array + 1);
+}
+
+int main ()
+{
+  double values[] = { 0.1e-100, 1.0, -1.0, 0.0 };
+  if (func (values) != 0.1e-100)
+    abort ();
+  exit (0);
+}
diff --git a/gcc/testsuite/gcc.c-torture/execute/ieee/acc2.c b/gcc/testsuite/gcc.c-torture/execute/ieee/acc2.c
new file mode 100644
index 000000000000..2a44c8a01a86
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/ieee/acc2.c
@@ -0,0 +1,19 @@
+/* Tail call optimizations would reverse the order of multiplications
+   in func().  */
+
+double func (const double *array)
+{
+  double d = *array;
+  if (d == 1.0)
+    return d;
+  else
+    return d * func (array + 1);
+}
+
+int main ()
+{
+  double values[] = { __DBL_MAX__, 2.0, 0.5, 1.0 };
+  if (func (values) != __DBL_MAX__)
+    abort ();
+  exit (0);
+}
diff --git a/gcc/testsuite/gcc.c-torture/execute/ieee/mzero6.c b/gcc/testsuite/gcc.c-torture/execute/ieee/mzero6.c
new file mode 100644
index 000000000000..59ba6fee15ad
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/ieee/mzero6.c
@@ -0,0 +1,24 @@
+/* Tail call optimizations would convert func() into the moral equivalent of:
+
+       double acc = 0.0;
+       for (int i = 0; i <= n; i++)
+	 acc += d;
+       return acc;
+
+   which mishandles the case where 'd' is -0.  They also initialised 'acc'
+   to a zero int rather than a zero double.  */
+
+double func (double d, int n)
+{
+  if (n == 0)
+    return d;
+  else
+    return d + func (d, n - 1);
+}
+
+int main ()
+{
+  if (__builtin_copysign (1.0, func (0.0 / -5.0, 10)) != -1.0)
+    abort ();
+  exit (0);
+}
diff --git a/gcc/tree-tailcall.c b/gcc/tree-tailcall.c
index e3f491e2be1c..d6cfe4c49ed3 100644
--- a/gcc/tree-tailcall.c
+++ b/gcc/tree-tailcall.c
@@ -282,6 +282,13 @@ process_assignment (tree ass, tree stmt, block_stmt_iterator call, tree *m,
   if (TREE_CODE_CLASS (code) != '2')
     return false;
 
+  /* Accumulator optimizations will reverse the order of operations.
+     We can only do that for floating-point types if we're assuming
+     that addition and multiplication are associative.  */
+  if (!flag_unsafe_math_optimizations)
+    if (FLOAT_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl))))
+      return false;
+
   /* We only handle the code like
 
      x = call ();