Add "fast" conversions from arrays to bitmaps

This patch adds a bitmap_view<X> class that creates a read-only,
on-stack bitmap representation of an array-like object X.  The main
use case is to allow HARD_REG_SETs to be used in REG_SET (i.e. bitmap)
operations.

For now it only handles constant-sized arrays, but I've tried to
define the types in a way that could handle variable-sized arrays
in future (although less efficiently).  E.g. this might be useful
for combining bitmaps and sbitmaps.

For the read-only view to work as intended, I needed to make
bitmap_bit_p take a const_bitmap instead of a bitmap.  Logically
the bitmap really is read-only, but we update the "current" and
"indx" fields of the bitmap_head after doing a search.

2019-09-09  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* array-traits.h: New file.
	* coretypes.h (array_traits, bitmap_view): New types.
	* bitmap.h: Include "array-traits.h"
	(bitmap_bit_p): Take a const_bitmap instead of a bitmap.
	(base_bitmap_view, bitmap_view): New classes.
	* bitmap.c (bitmap_bit_p): Take a const_bitmap instead of a bitmap.
	* hard-reg-set.h: Include array-traits.h.
	(array_traits<HARD_REG_SET>): New struct.
	* regset.h (IOR_REG_SET_HRS): New macro.
	* loop-iv.c (simplify_using_initial_values): Use IOR_REG_SET_HRS
	rather than iterating over each hard register.
	* sched-deps.c (sched_analyze_insn): Likewise.
	* sel-sched-ir.c (setup_id_implicit_regs): Likewise.

From-SVN: r275536

1 files changed, 48 insertions, 0 deletions

diff --git a/gcc/array-traits.h b/gcc/array-traits.h
new file mode 100644
index 0000000..eb65ede
--- /dev/null
+++ b/gcc/array-traits.h
@@ -0,0 +1,48 @@
+/* Descriptions of array-like objects.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_ARRAY_TRAITS_H
+#define GCC_ARRAY_TRAITS_H
+
+/* Implementation for single integers (and similar types).  */
+template<typename T, T zero = T (0)>
+struct scalar_array_traits
+{
+  typedef T element_type;
+  static const bool has_constant_size = true;
+  static const size_t constant_size = 1;
+  static const T *base (const T &x) { return &x; }
+  static size_t size (const T &) { return 1; }
+};
+
+template<typename T>
+struct array_traits : scalar_array_traits<T> {};
+
+/* Implementation for arrays with a static size.  */
+template<typename T, size_t N>
+struct array_traits<T[N]>
+{
+  typedef T element_type;
+  static const bool has_constant_size = true;
+  static const size_t constant_size = N;
+  static const T *base (const T (&x)[N]) { return x; }
+  static size_t size (const T (&x)[N]) { return N; }
+};
+
+#endif