From: trevor_hansen <trevor_hansen@e59a4935-1847-0410-ae03-e826735625c1>
Date: Fri, 1 Oct 2010 14:35:44 +0000 (+0000)
Subject: Bugfix. Unsigned modulus of zero returned 1, it should return 0.
X-Git-Url: https://git.unchartedbackwaters.co.uk/w/?a=commitdiff_plain;h=72bbf50e504c721df5260adcc080c639ddb0b0c0;p=francis%2Fstp.git

Bugfix. Unsigned modulus of zero returned 1, it should return 0.


git-svn-id: https://stp-fast-prover.svn.sourceforge.net/svnroot/stp-fast-prover/trunk/stp@1023 e59a4935-1847-0410-ae03-e826735625c1
---

diff --git a/src/simplifier/consteval.cpp b/src/simplifier/consteval.cpp
index d0ddeab..a5d8b66 100644
--- a/src/simplifier/consteval.cpp
+++ b/src/simplifier/consteval.cpp
@@ -450,8 +450,14 @@ namespace BEEV
           if (_bm->UserFlags.division_by_zero_returns_one_flag 
               && CONSTANTBV::BitVector_is_empty(tmp1))
             {
-              // Expecting a division by zero. Just return one.
-              OutputNode = _bm->CreateOneConst(outputwidth);
+              // a = bq + r, where b!=0 implies r < b. q is quotient, r remainder. i.e. a/b = q.
+              // It doesn't matter what q is when b=0, but r needs to be 0.
+              if (k == BVMOD)
+                OutputNode = _bm->CreateZeroConst(outputwidth);
+              else
+                OutputNode = _bm->CreateOneConst(outputwidth);
+                // Expecting a division by zero. Just return one.
+
             }
           else
             {