[PATCH][AArch64] Use target builtin instead of __builtin_sqrt for vsqrt_f64

[Kyrill Tkachov <kyrylo dot tkachov at arm dot com>]

Hi all,

As raised in https://gcc.gnu.org/ml/gcc-patches/2014-12/msg01237.html 
and discussed in that thread, using __builtin_sqrt for vsqrt_f64 may end 
up in a call to the library sqrt at -O0. To avoid that this patch uses a 
target builtin for sqrt on DF mode and uses that to implement the intrinsic.

With this patch I don't see sqrt calls being created at -O0 on a large 
arm_neon.h testcase where they were generated before.
aarch64-none-elf testing and the intrinsics testsuite in particular are 
clean.
Ok for trunk?

Thanks,
Kyrill

2015-01-12  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

    * config/aarch64/aarch64-simd-builtins.def (sqrt): Use BUILTIN_VDQF_DF.
    * config/aarch64/arm_neon.h (vsqrt_f64): Use __builtin_aarch64_sqrtdf
    instead of __builtin_sqrt.

commit 865be1cc8365886904d571e244746815e2317162
Author: Kyrylo Tkachov <kyrylo.tkachov@arm.com>
Date:   Fri Jan 9 12:18:59 2015 +0000

    [AArch64] Use target builtin for vsqrt_f64

diff --git a/gcc/config/aarch64/aarch64-simd-builtins.def b/gcc/config/aarch64/aarch64-simd-builtins.def
index b41d9f6..60cd1d7 100644
--- a/gcc/config/aarch64/aarch64-simd-builtins.def
+++ b/gcc/config/aarch64/aarch64-simd-builtins.def
@@ -41,7 +41,7 @@
 
   BUILTIN_VDC (COMBINE, combine, 0)
   BUILTIN_VB (BINOP, pmul, 0)
-  BUILTIN_VDQF (UNOP, sqrt, 2)
+  BUILTIN_VDQF_DF (UNOP, sqrt, 2)
   BUILTIN_VD_BHSI (BINOP, addp, 0)
   VAR1 (UNOP, addp, 0, di)
   BUILTIN_VDQ_BHSI (UNOP, clrsb, 2)
diff --git a/gcc/config/aarch64/arm_neon.h b/gcc/config/aarch64/arm_neon.h
index c679802..3b151a2 100644
--- a/gcc/config/aarch64/arm_neon.h
+++ b/gcc/config/aarch64/arm_neon.h
@@ -22194,7 +22194,7 @@ vsqrtq_f32 (float32x4_t a)
 __extension__ static __inline float64x1_t __attribute__ ((__always_inline__))
 vsqrt_f64 (float64x1_t a)
 {
-  return (float64x1_t) { __builtin_sqrt (a[0]) };
+  return (float64x1_t) { __builtin_aarch64_sqrtdf (a[0]) };
 }
 
 __extension__ static __inline float64x2_t __attribute__ ((__always_inline__))