From 512cd83627c9827b6af1e8788d9451316c778836 Mon Sep 17 00:00:00 2001
From: Michael Nolan <mtnolan2640@gmail.com>
Date: Mon, 30 Mar 2020 19:15:03 -0400
Subject: [PATCH] Begin adding helper functions for PPC pseudocode compiler

---
 src/soc/decoder/helpers.py | 49 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 src/soc/decoder/helpers.py

diff --git a/src/soc/decoder/helpers.py b/src/soc/decoder/helpers.py
new file mode 100644
index 00000000..a3fbd1db
--- /dev/null
+++ b/src/soc/decoder/helpers.py
@@ -0,0 +1,49 @@
+import unittest
+def exts(value, bits):
+    sign = 1 << (bits - 1)
+    return (value * (sign - 1)) - (value * sign)
+
+def EXTS64(value):
+    return exts(value, 64) & ((1<<64)-1)
+
+def ROTL64(value, bits):
+    mask = (1 << 64) - 1
+    bits = bits & 63
+    return ((value << bits) | (value >> (64-bits))) & mask
+
+def mask(x, y):
+    if x < y:
+        x = 64-x
+        y = 63-y
+        mask_a = ((1<<x) - 1) & ((1<<64) - 1)
+        mask_b = ((1<<y) - 1) & ((1<<64) - 1)
+    else:
+        x = 64-x
+        y = 63-y
+        mask_a = ((1<<x) - 1) & ((1<<64) - 1)
+        mask_b = (~((1<<y) - 1)) & ((1<<64) - 1)
+    return mask_a ^ mask_b
+
+
+class HelperTests(unittest.TestCase):
+    def test_mask(self):
+        # Verified using rlwinm, rldicl, rldicr in qemu
+        # rlwinm reg, 0, 5, 15
+        self.assertHex(mask(5+32, 15+32), 0x7ff0000)
+        # rlwinm reg, 0, 15, 5
+        self.assertHex(mask(15+32, 5+32), 0xfffffffffc01ffff)
+        self.assertHex(mask(30+32, 2+32), 0xffffffffe0000003)
+        # rldicl reg, 0, 37
+        self.assertHex(mask(37, 63), 0x7ffffff)
+        self.assertHex(mask(10, 63), 0x3fffffffffffff)
+        self.assertHex(mask(58, 63), 0x3f)
+        # rldicr reg, 0, 37
+        self.assertHex(mask(0, 37), 0xfffffffffc000000)
+        self.assertHex(mask(0, 10), 0xffe0000000000000)
+        self.assertHex(mask(0, 58), 0xffffffffffffffe0)
+    def assertHex(self, a, b):
+        msg = "{:x} != {:x}".format(a, b)
+        return self.assertEqual(a, b, msg)
+
+if __name__ == '__main__':
+    unittest.main()
-- 
2.30.2