Cache reals for 1/4, 1/6 and 1/9

We have a global 1/2 and a cached 1/3, but recalculate 1/4, 1/6 and 1/9
each time we need them.  That seems a bit arbitrary and makes the folding
code more noisy (especially once it's moved to match.pd).

This patch caches the other three constants too.  Bootstrapped &
regression-tested on x86_64-linux-gnu.

gcc/
	* real.h (dconst_quarter, dconst_sixth, dconst_ninth): New macros.
	(dconst_quarter_ptr, dconst_sixth_ptr, dconst_ninth_ptr): Declare.
	* real.c (CACHED_FRACTION): New helper macro.
	(dconst_third_ptr): Use it.
	(dconst_quarter_ptr, dconst_sixth_ptr, dconst_ninth_ptr): New.
	* builtins.c (fold_builtin_sqrt): Use dconst_quarter and
	dconst_sixth.
	(fold_builtin_cbrt): Use dconst_sixth and dconst_ninth.

From-SVN: r228561

1 files changed, 20 insertions, 15 deletions

diff --git a/gcc/real.c b/gcc/real.c
index 49d6739..f633ffd 100644
--- a/gcc/real.c
+++ b/gcc/real.c
@@ -2395,21 +2395,26 @@ dconst_e_ptr (void)
   return &value;
 }
 
-/* Returns the special REAL_VALUE_TYPE corresponding to 1/3.  */
-
-const REAL_VALUE_TYPE *
-dconst_third_ptr (void)
-{
-  static REAL_VALUE_TYPE value;
-
-  /* Initialize mathematical constants for constant folding builtins.
-     These constants need to be given to at least 160 bits precision.  */
-  if (value.cl == rvc_zero)
-    {
-      real_arithmetic (&value, RDIV_EXPR, &dconst1, real_digit (3));
-    }
-  return &value;
-}
+/* Returns a cached REAL_VALUE_TYPE corresponding to 1/n, for various n.  */
+
+#define CACHED_FRACTION(NAME, N)					\
+  const REAL_VALUE_TYPE *						\
+  NAME (void)								\
+  {									\
+    static REAL_VALUE_TYPE value;					\
+									\
+    /* Initialize mathematical constants for constant folding builtins.	\
+       These constants need to be given to at least 160 bits		\
+       precision.  */							\
+    if (value.cl == rvc_zero)						\
+      real_arithmetic (&value, RDIV_EXPR, &dconst1, real_digit (N));	\
+    return &value;							\
+  }
+
+CACHED_FRACTION (dconst_third_ptr, 3)
+CACHED_FRACTION (dconst_quarter_ptr, 4)
+CACHED_FRACTION (dconst_sixth_ptr, 6)
+CACHED_FRACTION (dconst_ninth_ptr, 9)
 
 /* Returns the special REAL_VALUE_TYPE corresponding to sqrt(2).  */