[PATCH], Define __FP_FAST_FMAF128 on PowerPC ISA 3.0

[Michael Meissner]

The glibc team has requested we define the standard macro (__FP_FAST_FMAF128)
for PowerPC code when we have the IEEE 128-bit floating point hardware
instructions enabled.

This patch does this in the PowerPC backend.  As I look at the whole issue, at
some point we should do this more in the machine independent portion of the
compiler.  I have some initial patches to do this in the c-family files, but at
the present time, the patches are not complete, and I need to think about it
more.

So, I would like to check in this patch now, and if we come up with a machine
independent version, we can back out this particular patch.  I have done a full
bootstrap and regression test, there were no regressions, and the new test case
does run correctly.  Can I check this into the trunk?

[gcc]
2017-09-27  Michael Meissner  <meiss...@linux.vnet.ibm.com>

        * config/rs6000/rs6000-c.c (rs6000_target_modify_macros): Define
        __FP_FAST_FMAF128 on ISA 3.0.

[gcc/testsuite]
2017-09-27  Michael Meissner  <meiss...@linux.vnet.ibm.com>

        * gcc.target/powerpc/float128-fma3.c: New test.

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meiss...@linux.vnet.ibm.com, phone: +1 (978) 899-4797

Index: gcc/config/rs6000/rs6000-c.c
===================================================================
--- gcc/config/rs6000/rs6000-c.c        (revision 253236)
+++ gcc/config/rs6000/rs6000-c.c        (working copy)
@@ -585,7 +585,10 @@ rs6000_target_modify_macros (bool define
   /* OPTION_MASK_FLOAT128_HARDWARE can be turned on if -mcpu=power9 is used or
      via the target attribute/pragma.  */
   if ((flags & OPTION_MASK_FLOAT128_HW) != 0)
-    rs6000_define_or_undefine_macro (define_p, "__FLOAT128_HARDWARE__");
+    {
+      rs6000_define_or_undefine_macro (define_p, "__FLOAT128_HARDWARE__");
+      rs6000_define_or_undefine_macro (define_p, "__FP_FAST_FMAF128");
+    }
 
   /* options from the builtin masks.  */
   /* Note that RS6000_BTM_PAIRED is enabled only if
Index: gcc/testsuite/gcc.target/powerpc/float128-fma3.c
===================================================================
--- gcc/testsuite/gcc.target/powerpc/float128-fma3.c    (nonexistent)
+++ gcc/testsuite/gcc.target/powerpc/float128-fma3.c    (working copy)
@@ -0,0 +1,33 @@
+/* { dg-do compile { target { powerpc*-*-* && lp64 } } } */
+/* { dg-require-effective-target powerpc_p9vector_ok } */
+/* { dg-options "-mpower9-vector -O2" } */
+
+/* Make sure the appropriate FMA fast macros are defined.  */
+
+#ifdef __FP_FAST_FMAF
+float
+do_fmaf (float a, float b, float c)
+{
+  return __builtin_fmaf (a, b, c);
+}
+#endif
+
+#ifdef __FP_FAST_FMA
+double
+do_fma (double a, double b, double c)
+{
+  return __builtin_fma (a, b, c);
+}
+#endif
+
+#ifdef __FP_FAST_FMAF128
+_Float128
+do_fmaf128 (_Float128 a, _Float128 b, _Float128 c)
+{
+  return __builtin_fmaf128 (a, b, c);
+}
+#endif
+
+/* { dg-final { scan-assembler {\mfmadds\M|\mxsmadd.sp\M}  } } */
+/* { dg-final { scan-assembler {\mfmadd\M|\mxsmadd.dp\M}   } } */
+/* { dg-final { scan-assembler {\mxsmaddqp\M}              } } */