diff options
| -rw-r--r-- | src/main/scala/firrtl/transforms/ConstantPropagation.scala | 5 | ||||
| -rw-r--r-- | src/test/scala/firrtlTests/ConstantPropagationTests.scala | 18 |
2 files changed, 22 insertions, 1 deletions
diff --git a/src/main/scala/firrtl/transforms/ConstantPropagation.scala b/src/main/scala/firrtl/transforms/ConstantPropagation.scala index da7f1a46..ed4ecd96 100644 --- a/src/main/scala/firrtl/transforms/ConstantPropagation.scala +++ b/src/main/scala/firrtl/transforms/ConstantPropagation.scala @@ -277,6 +277,7 @@ class ConstantPropagation extends Transform with ResolvedAnnotationPaths { def optimize(e: Expression): Expression = constPropExpression(new NodeMap(), Map.empty[String, String], Map.empty[String, Map[String, Literal]])(e) def optimize(e: Expression, nodeMap: NodeMap): Expression = constPropExpression(nodeMap, Map.empty[String, String], Map.empty[String, Map[String, Literal]])(e) + private def constPropExpression(nodeMap: NodeMap, instMap: Map[String, String], constSubOutputs: Map[String, Map[String, Literal]])(e: Expression): Expression = { val old = e map constPropExpression(nodeMap, instMap, constSubOutputs) val propagated = old match { @@ -290,7 +291,9 @@ class ConstantPropagation extends Transform with ResolvedAnnotationPaths { constSubOutputs.get(module).flatMap(_.get(pname)).getOrElse(ref) case x => x } - propagated + // We're done when the Expression no longer changes + if (propagated eq old) propagated + else constPropExpression(nodeMap, instMap, constSubOutputs)(propagated) } /** Constant propagate a Module diff --git a/src/test/scala/firrtlTests/ConstantPropagationTests.scala b/src/test/scala/firrtlTests/ConstantPropagationTests.scala index 603ddc25..a6df1a3b 100644 --- a/src/test/scala/firrtlTests/ConstantPropagationTests.scala +++ b/src/test/scala/firrtlTests/ConstantPropagationTests.scala @@ -734,6 +734,24 @@ class ConstantPropagationSingleModule extends ConstantPropagationSpec { """.stripMargin (parse(exec(input))) should be(parse(check)) } + + // Optimizing this mux gives: z <= pad(UInt<2>(0), 4) + // Thus this checks that we then optimize that pad + "ConstProp" should "optimize nested Expressions" in { + val input = + """circuit Top : + | module Top : + | output z : UInt<4> + | z <= mux(UInt(1), UInt<2>(0), UInt<4>(0)) + """.stripMargin + val check = + """circuit Top : + | module Top : + | output z : UInt<4> + | z <= UInt<4>("h0") + """.stripMargin + (parse(exec(input))) should be(parse(check)) + } } // More sophisticated tests of the full compiler |