From: Jacob Lifshay <programmerjake@gmail.com>
Date: Wed, 7 Oct 2020 02:36:11 +0000 (-0700)
Subject: add overflow detection to DIVS
X-Git-Tag: 24jan2021_ls180~11
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=9e5f483bedd63f79c647dd43d809621c4c9b99cf;p=nmutil.git

add overflow detection to DIVS

overflow shouldn't occur when calling DIVS since it should have been
detected in the code calling DIVS to properly handle edge cases.
---

diff --git a/src/nmutil/divmod.py b/src/nmutil/divmod.py
index af5d214..357fdcb 100644
--- a/src/nmutil/divmod.py
+++ b/src/nmutil/divmod.py
@@ -17,6 +17,9 @@ def trunc_divs(n, d):
     res = copy(n)
     if (sign_n == sign_d):
         res.value = abs_q
+        if res.value & (1 << (res.bits - 1)) != 0:
+            # result should be positive but is negative
+            raise OverflowError()
         return res
     mask = (1 << res.bits) - 1
     res.value = (-abs_q) & mask