From bb2783994ad3aaf0dd396fd236eb8c58c94a5418 Mon Sep 17 00:00:00 2001
From: Edward Wang <edward.c.wang@compdigitec.com>
Date: Fri, 21 Jul 2017 10:33:29 -0700
Subject: [PATCH] Only use powers of two masks, for now

---
 tapeout/src/main/scala/transforms/macros/MacroCompiler.scala | 3 +++
 tapeout/src/main/scala/transforms/macros/Utils.scala         | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/tapeout/src/main/scala/transforms/macros/MacroCompiler.scala b/tapeout/src/main/scala/transforms/macros/MacroCompiler.scala
index 46ac353c..54c35cc9 100644
--- a/tapeout/src/main/scala/transforms/macros/MacroCompiler.scala
+++ b/tapeout/src/main/scala/transforms/macros/MacroCompiler.scala
@@ -178,6 +178,9 @@ class MacroCompilerPass(mems: Option[Seq[Macro]],
               } else {
                 require(libPort.src.effectiveMaskGran == 1, "only single-bit mask supported for now")
 
+                require(isPowerOfTwo(memPort.src.effectiveMaskGran), "only powers of two masks supported for now")
+                require(isPowerOfTwo(libPort.src.effectiveMaskGran), "only powers of two masks supported for now")
+
                 cat(((low to high) map (i => bits(WRef(mem), i / memPort.src.effectiveMaskGran))).reverse)
               }
             case None =>
diff --git a/tapeout/src/main/scala/transforms/macros/Utils.scala b/tapeout/src/main/scala/transforms/macros/Utils.scala
index 275943e8..72b9c631 100644
--- a/tapeout/src/main/scala/transforms/macros/Utils.scala
+++ b/tapeout/src/main/scala/transforms/macros/Utils.scala
@@ -93,4 +93,7 @@ object Utils {
       case Some(ActiveLow) | Some(NegativeEdge) => not(exp)
       case _ => exp
     }
+
+  // Check if a number is a power of two
+  def isPowerOfTwo(x: Int): Boolean = (x & (x - 1)) == 0
 }