[gcc r12-1787] libstdc++: Ensure unrolled loops inline the lambda

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:8888795ad16fc5ebf112b5bac091dc1ebb6c45d1

commit r12-1787-g8888795ad16fc5ebf112b5bac091dc1ebb6c45d1
Author: Matthias Kretz <m.kretz@gsi.de>
Date:   Thu Jun 24 14:20:15 2021 +0100

    libstdc++: Ensure unrolled loops inline the lambda
    
    Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
    
    libstdc++-v3/ChangeLog:
    
            * include/experimental/bits/simd.h (__execute_on_index_sequence)
            (__execute_on_index_sequence_with_return)
            (__call_with_n_evaluations, __call_with_subscripts): Add flatten
            attribute.

Diff:
---
 libstdc++-v3/include/experimental/bits/simd.h | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/include/experimental/bits/simd.h b/libstdc++-v3/include/experimental/bits/simd.h
index 163f1b574e2..c396ebd3ee3 100644
--- a/libstdc++-v3/include/experimental/bits/simd.h
+++ b/libstdc++-v3/include/experimental/bits/simd.h
@@ -234,7 +234,8 @@ namespace __detail
 // unrolled/pack execution helpers
 // __execute_n_times{{{
 template <typename _Fp, size_t... _I>
-  _GLIBCXX_SIMD_INTRINSIC constexpr void
+  [[__gnu__::__flatten__]] _GLIBCXX_SIMD_INTRINSIC constexpr
+  void
   __execute_on_index_sequence(_Fp&& __f, index_sequence<_I...>)
   { ((void)__f(_SizeConstant<_I>()), ...); }
 
@@ -254,7 +255,8 @@ template <size_t _Np, typename _Fp>
 // }}}
 // __generate_from_n_evaluations{{{
 template <typename _R, typename _Fp, size_t... _I>
-  _GLIBCXX_SIMD_INTRINSIC constexpr _R
+  [[__gnu__::__flatten__]] _GLIBCXX_SIMD_INTRINSIC constexpr
+  _R
   __execute_on_index_sequence_with_return(_Fp&& __f, index_sequence<_I...>)
   { return _R{__f(_SizeConstant<_I>())...}; }
 
@@ -269,7 +271,8 @@ template <size_t _Np, typename _R, typename _Fp>
 // }}}
 // __call_with_n_evaluations{{{
 template <size_t... _I, typename _F0, typename _FArgs>
-  _GLIBCXX_SIMD_INTRINSIC constexpr auto
+  [[__gnu__::__flatten__]] _GLIBCXX_SIMD_INTRINSIC constexpr
+  auto
   __call_with_n_evaluations(index_sequence<_I...>, _F0&& __f0, _FArgs&& __fargs)
   { return __f0(__fargs(_SizeConstant<_I>())...); }
 
@@ -285,7 +288,8 @@ template <size_t _Np, typename _F0, typename _FArgs>
 // }}}
 // __call_with_subscripts{{{
 template <size_t _First = 0, size_t... _It, typename _Tp, typename _Fp>
-  _GLIBCXX_SIMD_INTRINSIC constexpr auto
+  [[__gnu__::__flatten__]] _GLIBCXX_SIMD_INTRINSIC constexpr
+  auto
   __call_with_subscripts(_Tp&& __x, index_sequence<_It...>, _Fp&& __fun)
   { return __fun(__x[_First + _It]...); }