From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Tue, 19 Feb 2019 06:41:50 +0000 (+0000)
Subject: add shift up multi function
X-Git-Tag: ls180-24jan2020~1874
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=223916b7bb72d4dc241c8fa275b6e1db173c01fe;p=ieee754fpu.git

add shift up multi function
---

diff --git a/src/add/fpbase.py b/src/add/fpbase.py
index 48bfb822..977a00db 100644
--- a/src/add/fpbase.py
+++ b/src/add/fpbase.py
@@ -161,6 +161,17 @@ class FPNum:
                 self.m.eq(Cat(stickybits, rs))
                ]
 
+    def shift_up_multi(self, diff):
+        """ shifts a mantissa up. exponent is decreased to compensate
+        """
+        sm = MultiShift(self.width)
+        mw = Const(self.m_width, len(diff))
+        maxslen = Mux(diff > mw, mw, diff)
+
+        return [self.e.eq(self.e - diff),
+                self.m.eq(sm.lshift(self.m, maxslen))
+               ]
+
     def nan(self, s):
         return self.create(s, self.P128, 1<<(self.e_start-1))
 
@@ -264,7 +275,7 @@ class FPBase:
                   the extra mantissa bits coming from tot[0..2]
         """
         with m.If((z.m[-1] == 0) & (z.e > z.N126)):
-            m.d.sync +=[
+            m.d.sync += [
                 z.e.eq(z.e - 1),  # DECREASE exponent
                 z.m.eq(z.m << 1), # shift mantissa UP
                 z.m[0].eq(of.guard),       # steal guard bit (was tot[2])