Merge pull request #626 from freechipsproject/fix-swap-bug

Fix ConstProp bug where multiple names would swap with one

1 files changed, 4 insertions, 2 deletions

diff --git a/src/main/scala/firrtl/transforms/ConstantPropagation.scala b/src/main/scala/firrtl/transforms/ConstantPropagation.scala
index bf8b1a55..d5a4b7e1 100644
--- a/src/main/scala/firrtl/transforms/ConstantPropagation.scala
+++ b/src/main/scala/firrtl/transforms/ConstantPropagation.scala
@@ -304,7 +304,9 @@ class ConstantPropagation extends Transform {
     // When propagating a reference, check if we want to keep the name that would be deleted
     def propagateRef(lname: String, value: Expression): Unit = {
       value match {
-        case WRef(rname,_,_,_) if betterName(lname, rname) =>
+        case WRef(rname,_,_,_) if betterName(lname, rname) && !swapMap.contains(rname) =>
+          assert(!swapMap.contains(lname)) // <- Shouldn't be possible because lname is either a
+          // node declaration or the single connection to a wire or register
           swapMap += (lname -> rname, rname -> lname)
         case _ =>
       }
@@ -315,7 +317,7 @@ class ConstantPropagation extends Transform {
       val stmtx = s map constPropStmt map constPropExpression
       stmtx match {
         case x: DefNode if !dontTouches.contains(x.name) => propagateRef(x.name, x.value)
-        case Connect(_, WRef(wname, wtpe, WireKind, _), expr) if !dontTouches.contains(wname) =>
+        case Connect(_, WRef(wname, wtpe, WireKind, _), expr: Literal) if !dontTouches.contains(wname) =>
           val exprx = constPropExpression(pad(expr, wtpe))
           propagateRef(wname, exprx)
         // Const prop registers that are fed only a constant or a mux between and constant and the