Replace gen-as-const.awk by gen-as-const.py.

This patch replaces gen-as-const.awk, and some fragments of the
Makefile code that used it, by a Python script.  The point is not such
much that awk is problematic for this particular script, as that I'd
like to build up a general Python infrastructure for extracting
information from C headers, for use in writing tests of such headers.
Thus, although this patch does not set up such infrastructure, the
compute_c_consts function in gen-as-const.py might be moved to a
separate Python module in a subsequent patch as a starting point for
such infrastructure.

The general idea of the code is the same as in the awk version, but no
attempt is made to make the output files textually identical.  When
generating a header, a dict of constant names and values is generated
internally then defines are printed in sorted order (rather than the
order in the .sym file, which would have been used before).  When
generating a test that the values computed match those from a normal
header inclusion, the test code is made into a compilation test using
_Static_assert, where previously the comparisons were done only when
the test was executed.  One fragment of test generation (converting
the previously generated header to use asconst_* prefixes on its macro
names) is still in awk code in the makefiles; only the .sym processing
and subsequent execution of the compiler to extract constants have
moved to the Python script.

Tested for x86_64, and with build-many-glibcs.py.

	* scripts/gen-as-const.py: New file.
	* scripts/gen-as-const.awk: Remove.
	* Makerules ($(common-objpfx)%.h $(common-objpfx)%.h.d): Use
	gen-as-const.py.
	($(objpfx)test-as-const-%.c): Likewise.

1 files changed, 159 insertions, 0 deletions

diff --git a/scripts/gen-as-const.py b/scripts/gen-as-const.py
new file mode 100644
index 0000000..b7a5744
--- /dev/null
+++ b/scripts/gen-as-const.py
@@ -0,0 +1,159 @@
+#!/usr/bin/python3
+# Produce headers of assembly constants from C expressions.
+# Copyright (C) 2018 Free Software Foundation, Inc.
+# This file is part of the GNU C Library.
+#
+# The GNU C Library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# The GNU C Library 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with the GNU C Library; if not, see
+# <http://www.gnu.org/licenses/>.
+
+# The input to this script looks like:
+#       #cpp-directive ...
+#       NAME1
+#       NAME2 expression ...
+# A line giving just a name implies an expression consisting of just that name.
+
+import argparse
+import os.path
+import re
+import subprocess
+import tempfile
+
+
+def compute_c_consts(sym_data, cc):
+    """Compute the values of some C constants.
+
+    The first argument is a list whose elements are either strings
+    (preprocessor directives) or pairs of strings (a name and a C
+    expression for the corresponding value).  Preprocessor directives
+    in the middle of the list may be used to select which constants
+    end up being evaluated using which expressions.
+
+    """
+    out_lines = []
+    started = False
+    for arg in sym_data:
+        if isinstance(arg, str):
+            out_lines.append(arg)
+            continue
+        name = arg[0]
+        value = arg[1]
+        if not started:
+            out_lines.append('void\ndummy (void)\n{')
+            started = True
+        out_lines.append('asm ("@@@name@@@%s@@@value@@@%%0@@@end@@@" '
+                         ': : \"i\" ((long int) (%s)));'
+                         % (name, value))
+    if started:
+        out_lines.append('}')
+    out_lines.append('')
+    out_text = '\n'.join(out_lines)
+    with tempfile.TemporaryDirectory() as temp_dir:
+        c_file_name = os.path.join(temp_dir, 'test.c')
+        s_file_name = os.path.join(temp_dir, 'test.s')
+        with open(c_file_name, 'w') as c_file:
+            c_file.write(out_text)
+        # Compilation has to be from stdin to avoid the temporary file
+        # name being written into the generated dependencies.
+        cmd = ('%s -S -o %s -x c - < %s' % (cc, s_file_name, c_file_name))
+        subprocess.check_call(cmd, shell=True)
+        consts = {}
+        with open(s_file_name, 'r') as s_file:
+            for line in s_file:
+                match = re.search('@@@name@@@([^@]*)'
+                                  '@@@value@@@[^0-9Xxa-fA-F-]*'
+                                  '([0-9Xxa-fA-F-]+).*@@@end@@@', line)
+                if match:
+                    if (match.group(1) in consts
+                        and match.group(2) != consts[match.group(1)]):
+                        raise ValueError('duplicate constant %s'
+                                         % match.group(1))
+                    consts[match.group(1)] = match.group(2)
+        return consts
+
+
+def gen_test(sym_data):
+    """Generate a test for the values of some C constants.
+
+    The first argument is as for compute_c_consts.
+
+    """
+    out_lines = []
+    started = False
+    for arg in sym_data:
+        if isinstance(arg, str):
+            out_lines.append(arg)
+            continue
+        name = arg[0]
+        value = arg[1]
+        if not started:
+            out_lines.append('#include <stdint.h>\n'
+                             '#include <stdio.h>\n'
+                             '#include <bits/wordsize.h>\n'
+                             '#if __WORDSIZE == 64\n'
+                             'typedef uint64_t c_t;\n'
+                             '# define U(n) UINT64_C (n)\n'
+                             '#else\n'
+                             'typedef uint32_t c_t;\n'
+                             '# define U(n) UINT32_C (n)\n'
+                             '#endif\n'
+                             'static int\n'
+                             'do_test (void)\n'
+                             '{\n'
+                             # Compilation test only, using static assertions.
+                             '  return 0;\n'
+                             '}\n'
+                             '#include <support/test-driver.c>')
+            started = True
+        out_lines.append('_Static_assert (U (asconst_%s) == (c_t) (%s), '
+                         '"value of %s");'
+                         % (name, value, name))
+    return '\n'.join(out_lines)
+
+
+def main():
+    """The main entry point."""
+    parser = argparse.ArgumentParser(
+        description='Produce headers of assembly constants.')
+    parser.add_argument('--cc', metavar='CC',
+                        help='C compiler (including options) to use')
+    parser.add_argument('--test', action='store_true',
+                        help='Generate test case instead of header')
+    parser.add_argument('sym_file',
+                        help='.sym file to process')
+    args = parser.parse_args()
+    sym_data = []
+    with open(args.sym_file, 'r') as sym_file:
+        for line in sym_file:
+            line = line.strip()
+            if line == '':
+                continue
+            # Pass preprocessor directives through.
+            if line.startswith('#'):
+                sym_data.append(line)
+                continue
+            words = line.split(maxsplit=1)
+            # Separator.
+            if words[0] == '--':
+                continue
+            name = words[0]
+            value = words[1] if len(words) > 1 else words[0]
+            sym_data.append((name, value))
+    if args.test:
+        print(gen_test(sym_data))
+    else:
+        consts = compute_c_consts(sym_data, args.cc)
+        print('\n'.join('#define %s %s' % c for c in sorted(consts.items())))
+
+if __name__ == '__main__':
+    main()