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