From 24ffde94c89ef67eed4df30ba49ccf48ca46c9a9 Mon Sep 17 00:00:00 2001
From: Adam Izraelevitz
Date: Thu, 22 Sep 2016 13:08:32 -0700
Subject: Fixed width inference for add, sub (#312)

Fixes #308 
Fixes #193 ---
 src/main/scala/firrtl/PrimOps.scala | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

(limited to 'src/main')

diff --git a/src/main/scala/firrtl/PrimOps.scala b/src/main/scala/firrtl/PrimOps.scala
index 8d677104..cf2cb74e 100644
--- a/src/main/scala/firrtl/PrimOps.scala
+++ b/src/main/scala/firrtl/PrimOps.scala
@@ -142,15 +142,15 @@ object PrimOps extends LazyLogging {
     e copy (tpe = (e.op match {
       case Add => (t1, t2) match {
         case (_: UIntType, _: UIntType) => UIntType(PLUS(MAX(w1, w2), IntWidth(1)))
-        case (_: UIntType, _: SIntType) => SIntType(PLUS(MAX(w1, w2), IntWidth(1)))
-        case (_: SIntType, _: UIntType) => SIntType(PLUS(MAX(w1, w2), IntWidth(1)))
+        case (_: UIntType, _: SIntType) => SIntType(PLUS(MAX(w1, MINUS(w2, IntWidth(1))), IntWidth(2)))
+        case (_: SIntType, _: UIntType) => SIntType(PLUS(MAX(w2, MINUS(w1, IntWidth(1))), IntWidth(2)))
         case (_: SIntType, _: SIntType) => SIntType(PLUS(MAX(w1, w2), IntWidth(1)))
         case _ => UnknownType
       }
       case Sub => (t1, t2) match {
         case (_: UIntType, _: UIntType) => SIntType(PLUS(MAX(w1, w2), IntWidth(1)))
-        case (_: UIntType, _: SIntType) => SIntType(PLUS(MAX(w1, w2), IntWidth(1)))
-        case (_: SIntType, _: UIntType) => SIntType(PLUS(MAX(w1, w2), IntWidth(1)))
+        case (_: UIntType, _: SIntType) => SIntType(MAX(PLUS(w2, IntWidth(1)), PLUS(w1, IntWidth(2))))
+        case (_: SIntType, _: UIntType) => SIntType(MAX(PLUS(w1, IntWidth(1)), PLUS(w2, IntWidth(2))))
         case (_: SIntType, _: SIntType) => SIntType(PLUS(MAX(w1, w2), IntWidth(1)))
         case _ => UnknownType
       }
-- 
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