[PATCH, rs6000] Use new __builtin_pack_longdouble within libgcc's ibm-ldouble.c

[Peter Bergner <bergner at vnet dot ibm dot com>]

..after cleaning up the conflicting long double builtins and fixing a
few bugs in the test cases, I'd like to resubmit the following:

Currently, the IBM long double routines in libgcc use a union to construct
a long double from two double values.  This causes horrific code generation
that copies the two double from the FP registers over to GPRs and back
again, giving us two loads and two stores, which leads to two load-hit-store
hazzards.  The following patch makes use of the new __builtin_pack_longdouble
builtin to construct the long double giving us at worse, one or two fmrs.

This passed bootstrap and regtesting on powerpc64-linux.  Ok for trunk?

Peter


libgcc/
	* config/rs6000/ibm-ldouble.c (typedef union longDblUnion): Delete.
	(pack_ldouble): New function.
	(__gcc_qadd): Use it.
	(__gcc_qmul): Likewise.
	(__gcc_qdiv): Likewise.
	(__gcc_qneg): Likewise.
	(__gcc_stoq): Likewise.
	(__gcc_dtoq): Likewise.

Index: libgcc/config/rs6000/ibm-ldouble.c
===================================================================
--- libgcc/config/rs6000/ibm-ldouble.c	(revision 213141)
+++ libgcc/config/rs6000/ibm-ldouble.c	(working copy)
@@ -87,18 +87,30 @@ __asm__ (".symver __gcc_qadd,_xlqadd@GCC
 	 ".symver .__gcc_qdiv,._xlqdiv@GCC_3.4");
 #endif
 
-typedef union
-{
-  long double ldval;
-  double dval[2];
-} longDblUnion;
+/* Combine two 'double' values into one 'long double' and return the result.  */
+static inline long double
+pack_ldouble (double dh, double dl)
+{
+#if defined (__LONG_DOUBLE_128__) \
+    && !(defined (_SOFT_FLOAT) || defined (__NO_FPRS__))
+  return __builtin_pack_longdouble (dh, dl);
+#else
+  union
+  {
+    long double ldval;
+    double dval[2];
+  } x;
+  x.dval[0] = dh;
+  x.dval[1] = dl;
+  return x.ldval;
+#endif
+}
 
 /* Add two 'long double' values and return the result.	*/
 long double
 __gcc_qadd (double a, double aa, double c, double cc)
 {
-  longDblUnion x;
-  double z, q, zz, xh;
+  double xh, xl, z, q, zz;
 
   z = a + c;
 
@@ -109,12 +121,12 @@ __gcc_qadd (double a, double aa, double
       z = cc + aa + c + a;
       if (nonfinite (z))
 	return z;
-      x.dval[0] = z;  /* Will always be DBL_MAX.  */
+      xh = z;  /* Will always be DBL_MAX.  */
       zz = aa + cc;
       if (fabs(a) > fabs(c))
-	x.dval[1] = a - z + c + zz;
+	xl = a - z + c + zz;
       else
-	x.dval[1] = c - z + a + zz;
+	xl = c - z + a + zz;
     }
   else
     {
@@ -129,10 +141,9 @@ __gcc_qadd (double a, double aa, double
       if (nonfinite (xh))
 	return xh;
 
-      x.dval[0] = xh;
-      x.dval[1] = z - xh + zz;
+      xl = z - xh + zz;
     }
-  return x.ldval;
+  return pack_ldouble (xh, xl);
 }
 
 long double
@@ -148,8 +159,7 @@ static double fmsub (double, double, dou
 long double
 __gcc_qmul (double a, double b, double c, double d)
 {
-  longDblUnion z;
-  double t, tau, u, v, w;
+  double xh, xl, t, tau, u, v, w;
   
   t = a * c;			/* Highest order double term.  */
 
@@ -173,16 +183,15 @@ __gcc_qmul (double a, double b, double c
   /* Construct long double result.  */
   if (nonfinite (u))
     return u;
-  z.dval[0] = u;
-  z.dval[1] = (t - u) + tau;
-  return z.ldval;
+  xh = u;
+  xl = (t - u) + tau;
+  return pack_ldouble (xh, xl);
 }
 
 long double
 __gcc_qdiv (double a, double b, double c, double d)
 {
-  longDblUnion z;
-  double s, sigma, t, tau, u, v, w;
+  double xh, xl, s, sigma, t, tau, u, v, w;
   
   t = a / c;                    /* highest order double term */
   
@@ -219,9 +228,9 @@ __gcc_qdiv (double a, double b, double c
   /* Construct long double result.  */
   if (nonfinite (u))
     return u;
-  z.dval[0] = u;
-  z.dval[1] = (t - u) + tau;
-  return z.ldval;
+  xh = u;
+  xl = (t - u) + tau;
+  return pack_ldouble (xh, xl);
 }
 
 #if defined (_SOFT_DOUBLE) && defined (__LONG_DOUBLE_128__)
@@ -248,11 +257,7 @@ extern int __gedf2 (double, double);
 long double
 __gcc_qneg (double a, double aa)
 {
-  longDblUnion x;
-
-  x.dval[0] = -a;
-  x.dval[1] = -aa;
-  return x.ldval;
+  return pack_ldouble (-a, -aa);
 }
 
 /* Compare two 'long double' values for equality.  */
@@ -292,24 +297,14 @@ strong_alias (__gcc_qge, __gcc_qgt);
 long double
 __gcc_stoq (float a)
 {
-  longDblUnion x;
-
-  x.dval[0] = (double) a;
-  x.dval[1] = 0.0;
-
-  return x.ldval;
+  return pack_ldouble ((double) a, 0.0);
 }
 
 /* Convert double to long double.  */
 long double
 __gcc_dtoq (double a)
 {
-  longDblUnion x;
-
-  x.dval[0] = a;
-  x.dval[1] = 0.0;
-
-  return x.ldval;
+  return pack_ldouble (a, 0.0);
 }
 
 /* Convert long double to single.  */