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C++ PATCH to add __integer_pack built-in for std::make_integer_sequence (c++/80396)

From: Jason Merrill <jason at redhat dot com>
To: gcc-patches List <gcc-patches at gcc dot gnu dot org>
Date: Tue, 23 May 2017 16:13:49 -0400
Subject: C++ PATCH to add __integer_pack built-in for std::make_integer_sequence (c++/80396)
Authentication-results: sourceware.org; auth=none

make_integer_sequence currently uses template metaprogramming to
generate a sequence of integers, which is fairly expensive at compile
time: PR 80396 asked for some built-in to speed it up.  This patch
introduces __integer_pack as a magic function taking a single integer
argument; a call to this function as the pattern of a pack expansion
produces a list of integers which can be used as arguments to a
template (or a function, but that's not the goal).

Rather than introduce a new keyword, I decided to use a FUNCTION_DECL,
which works fine.

Tested x86_64-pc-linux-gnu, applying to trunk.

Attachment: integer-pack4.diff
Description: Text document

Follow-Ups:
- Re: C++ PATCH to add __integer_pack built-in for std::make_integer_sequence (c++/80396)
  - From: Andreas Schwab

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