gen-double-encoder-table.py (1181B)
1 #!/usr/bin/env python 2 # This Source Code Form is subject to the terms of the Mozilla Public 3 # License, v. 2.0. If a copy of the MPL was not distributed with this 4 # file, You can obtain one at http://mozilla.org/MPL/2.0/. 5 """Generate tables of immediately-encodable VFP doubles. 6 7 DOES NOT get automatically run during the build process. If you need to 8 modify this file (which is unlikely), you must re-run this script: 9 10 python gen-double-encode-table.py > $(topsrcdir)/path/to/DoubleEntryTable.tbl 11 """ 12 13 import operator 14 15 16 def rep(bit, count): 17 return reduce(operator.ior, [bit << c for c in range(count)]) 18 19 20 def encodeDouble(value): 21 """Generate an ARM ARM 'VFP modified immediate constant' with format: 22 aBbbbbbb bbcdefgh 000... 23 24 We will return the top 32 bits of the double; the rest are 0.""" 25 assert 0 <= value <= 255 26 a = value >> 7 27 b = (value >> 6) & 1 28 B = int(b == 0) 29 cdefgh = value & 0x3F 30 return (a << 31) | (B << 30) | (rep(b, 8) << 22) | cdefgh << 16 31 32 33 print("/* THIS FILE IS AUTOMATICALLY GENERATED BY gen-double-encode-table.py. */") 34 for i in range(256): 35 print(" { 0x%08x, { %d, %d, 0 } }," % (encodeDouble(i), i & 0xF, i >> 4))