[ARM] Refactor Neon Builtins infrastructure

[James Greenhalgh <james dot greenhalgh at arm dot com>]

Hi,

I was taking a look at fixing the issues in the ARM back-end exposed
by Marc Glisse's patch in [1], and hoped to fix them by adapting the
patch recently commited by Tejas ([2]).

As I looked, I realised that the ARM target and the AArch64 target
now differ drastically in how their Advanced SIMD builtin
initialisation and expansion logic works. This is a growing
maintenance burden. This patch series is an attempt to start fixing
the problem.

From a high level, I see five problems with the ARM Neon builtin code.

First is the "magic number" interface, which gives builtins with signed
and unsigned, or saturating and non-saturating, variants an extra
parameter used to control which instruction is ultimately emitted. This
is problematic as it enforces that these intrinsics be implemented with
an UNSPEC pattern, we would like the flexibility to try to do a better job
of modeling these patterns.

Second, is that all the code lives in arm.c. This file is huge and
frightening. The least we could do is start to split it up!

Third, is the complicated builtin initialisation code. If we collect
common cases together from the large switch in the initialisation function,
it is clear we can eliminate much of the existing code. In fact, we have
already solved the same problem in AArch64 ([3]), and we don't gain
anything from having these interfaces separate.

Fourth, is that we don't have infrastructure to strongly type the functions
in arm_neon.h -  instead casting around between signed and unsigned vector
arguments as required. We need this to avoid special casing some builtins
we may want to vectorize (bswap and friends). Again we've solved this
in AArch64 ([4]).

Finally, there are the issues with type mangling Marc has seen.

This patch-set tries to fix those issues in order, and progresses as so:

First the magic words:

  [Refactor Builtins: 1/8] Remove arm_neon.h's "Magic Words"

Then moving code out to arm-builtins.c:

  [Patch ARM Refactor Builtins 2/8] Move Processor flags to arm-protos.h
  [Patch ARM Refactor Builtins 3/8] Pull builtins code to its own file

And then making the ARM backend look like the AArch64 backend and fixing
Marc's issue.

  [Patch ARM Refactor Builtins 4/8]  Refactor "VAR<n>" Macros
  [Patch ARM Refactor Builtins 5/8] Start keeping track of qualifiers in
    ARM.
  [Patch ARM Refactor Builtins 6/8] Add some tests for "poly" mangling
  [Patch ARM Refactor Builtins 7/8] Use qualifiers arrays when
    initialising builtins and fix type mangling
  [Patch ARM Refactor Builtins 8/8] Neaten up the ARM Neon builtin
    infrastructure

Clearly there is more we could do to start sharing code between the two
targets rather than duplicating it. For now, the benefit did not seem worth
the substantial churn that this would cause both back-ends.

I've bootstrapped each patch in this series in turn for both arm and
thumb on arm-none-linux-gnueabihf.

OK for trunk?

Thanks,
James

---
[1]: [c++] typeinfo for target types
     https://gcc.gnu.org/ml/gcc-patches/2014-04/msg00618.html
[2]: [AArch64, Patch] Restructure arm_neon.h vector types's implementation
     https://gcc.gnu.org/ml/gcc-patches/2014-11/msg00264.html
[3]: [AArch64] Refactor Advanced SIMD builtin initialisation.
     https://gcc.gnu.org/ml/gcc-patches/2012-10/msg00532.html
[4]: [AArch64] AArch64 SIMD Builtins Better Type Correctness.
     https://gcc.gnu.org/ml/gcc-patches/2013-11/msg02005.html

---
 gcc/config.gcc                               |    3 +-
 gcc/config/arm/arm-builtins.c                | 2925 ++++++++++++++++++++++++
 gcc/config/arm/arm-protos.h                  |  173 +-
 gcc/config/arm/arm-simd-builtin-types.def    |   48 +
 gcc/config/arm/arm.c                         | 3149 +-------------------------
 gcc/config/arm/arm_neon.h                    | 1743 +++++++-------
 gcc/config/arm/arm_neon_builtins.def         |  435 ++--
 gcc/config/arm/iterators.md                  |  167 ++
 gcc/config/arm/neon.md                       |  893 ++++----
 gcc/config/arm/t-arm                         |   11 +
 gcc/config/arm/unspecs.md                    |  109 +-
 gcc/testsuite/g++.dg/abi/mangle-arm-crypto.C |   16 +
 gcc/testsuite/g++.dg/abi/mangle-neon.C       |    5 +
 gcc/testsuite/gcc.target/arm/pr51968.c       |    2 +-
 create mode 100644 gcc/config/arm/arm-builtins.c
 create mode 100644 gcc/config/arm/arm-simd-builtin-types.def
 create mode 100644 gcc/testsuite/g++.dg/abi/mangle-arm-crypto.C
 14 files changed, 4992 insertions(+), 4687 deletions(-)