src/soc/decoder/helpers.py

   1 import unittest
   2 from soc.decoder.selectable_int import SelectableInt
   3
   4
   5 def exts(value, bits):
   6     sign = 1 << (bits - 1)
   7     return (value & (sign - 1)) - (value & sign)
   8
   9
  10 def EXTS(value):
  11     """ extends sign bit out from current MSB to all 256 bits
  12     """
  13     assert isinstance(value, SelectableInt)
  14     return exts(value.value, value.bits)
  15
  16 def EXTS64(value):
  17     """ extends sign bit out from current MSB to 64 bits
  18     """
  19     assert isinstance(value, SelectableInt)
  20     return SelectableInt(exts(value.value, value.bits) & ((1 << 64)-1), 64)
  21
  22
  23 # XXX should this explicitly extend from 32 to 64?
  24 def EXTZ64(value):
  25     if isinstance(value, SelectableInt):
  26         value = value.value
  27     return SelectableInt(value & ((1<<32)-1), 64)
  28
  29
  30 def rotl(value, bits, wordlen):
  31     mask = (1 << wordlen) - 1
  32     bits = bits & (wordlen - 1)
  33     return ((value << bits) | (value >> (wordlen-bits))) & mask
  34
  35
  36 def ROTL64(value, bits):
  37     return rotl(value, bits, 64)
  38
  39
  40 def ROTL32(value, bits):
  41     return rotl(value, bits, 32)
  42
  43
  44 def MASK(x, y):
  45     if x < y:
  46         x = 64-x
  47         y = 63-y
  48         mask_a = ((1 << x) - 1) & ((1 << 64) - 1)
  49         mask_b = ((1 << y) - 1) & ((1 << 64) - 1)
  50     else:
  51         x = 64-x
  52         y = 63-y
  53         mask_a = ((1 << x) - 1) & ((1 << 64) - 1)
  54         mask_b = (~((1 << y) - 1)) & ((1 << 64) - 1)
  55     return mask_a ^ mask_b
  56
  57
  58 # For these tests I tried to find power instructions that would let me
  59 # isolate each of these helper operations. So for instance, when I was
  60 # testing the MASK() function, I chose rlwinm and rldicl because if I
  61 # set the shift equal to 0 and passed in a value of all ones, the
  62 # result I got would be exactly the same as the output of MASK()
  63
  64 class HelperTests(unittest.TestCase):
  65     def test_MASK(self):
  66         # Verified using rlwinm, rldicl, rldicr in qemu
  67         # li 1, -1
  68         # rlwinm reg, 1, 0, 5, 15
  69         self.assertHex(MASK(5+32, 15+32), 0x7ff0000)
  70         # rlwinm reg, 1, 0, 15, 5
  71         self.assertHex(MASK(15+32, 5+32), 0xfffffffffc01ffff)
  72         self.assertHex(MASK(30+32, 2+32), 0xffffffffe0000003)
  73         # rldicl reg, 1, 0, 37
  74         self.assertHex(MASK(37, 63), 0x7ffffff)
  75         self.assertHex(MASK(10, 63), 0x3fffffffffffff)
  76         self.assertHex(MASK(58, 63), 0x3f)
  77         # rldicr reg, 1, 0, 37
  78         self.assertHex(MASK(0, 37), 0xfffffffffc000000)
  79         self.assertHex(MASK(0, 10), 0xffe0000000000000)
  80         self.assertHex(MASK(0, 58), 0xffffffffffffffe0)
  81
  82     def test_ROTL64(self):
  83         # r1 = 0xdeadbeef12345678
  84         value = 0xdeadbeef12345678
  85
  86         # rldicl reg, 1, 10, 0
  87         self.assertHex(ROTL64(value, 10), 0xb6fbbc48d159e37a)
  88         # rldicl reg, 1, 35, 0
  89         self.assertHex(ROTL64(value, 35), 0x91a2b3c6f56df778)
  90         self.assertHex(ROTL64(value, 58), 0xe37ab6fbbc48d159)
  91         self.assertHex(ROTL64(value, 22), 0xbbc48d159e37ab6f)
  92
  93     def test_ROTL32(self):
  94         # r1 = 0xdeadbeef
  95         value = 0xdeadbeef
  96
  97         # rlwinm reg, 1, 10, 0, 31
  98         self.assertHex(ROTL32(value, 10), 0xb6fbbf7a)
  99         # rlwinm reg, 1, 17, 0, 31
 100         self.assertHex(ROTL32(value, 17), 0x7ddfbd5b)
 101         self.assertHex(ROTL32(value, 25), 0xdfbd5b7d)
 102         self.assertHex(ROTL32(value, 30), 0xf7ab6fbb)
 103
 104     def test_EXTS64(self):
 105         value_a = 0xdeadbeef  # r1
 106         value_b = 0x73123456  # r2
 107         value_c = 0x80000000  # r3
 108
 109         # extswsli reg, 1, 0
 110         self.assertHex(EXTS64(value_a), 0xffffffffdeadbeef)
 111         # extswsli reg, 2, 0
 112         self.assertHex(EXTS64(value_b), value_b)
 113         # extswsli reg, 3, 0
 114         self.assertHex(EXTS64(value_c), 0xffffffff80000000)
 115
 116     def assertHex(self, a, b):
 117         msg = "{:x} != {:x}".format(a, b)
 118         return self.assertEqual(a, b, msg)
 119
 120
 121 if __name__ == '__main__':
 122     unittest.main()