Deprecate InlineCasts, add InlineAcrossCasts (#2146)

To maintain binary compatibility, InlineAcrossCasts is just aliases to
the now deprecated InlineCasts. We can make the binary incompatible
change of renaming the class and object for 1.5.

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

11 files changed, 25 insertions, 15 deletions

diff --git a/src/main/scala/firrtl/AddDescriptionNodes.scala b/src/main/scala/firrtl/AddDescriptionNodes.scala
index 9424d4a7..123ae6e3 100644
--- a/src/main/scala/firrtl/AddDescriptionNodes.scala
+++ b/src/main/scala/firrtl/AddDescriptionNodes.scala
@@ -136,7 +136,7 @@ class AddDescriptionNodes extends Transform with DependencyAPIMigration {
       Dependency[firrtl.transforms.ReplaceTruncatingArithmetic],
       Dependency[firrtl.transforms.InlineBitExtractionsTransform],
       Dependency[firrtl.transforms.PropagatePresetAnnotations],
-      Dependency[firrtl.transforms.InlineCastsTransform],
+      Dependency[firrtl.transforms.InlineAcrossCastsTransform],
       Dependency[firrtl.transforms.LegalizeClocksTransform],
       Dependency[firrtl.transforms.FlattenRegUpdate],
       Dependency(passes.VerilogModulusCleanup),
diff --git a/src/main/scala/firrtl/passes/VerilogModulusCleanup.scala b/src/main/scala/firrtl/passes/VerilogModulusCleanup.scala
index baad2f4f..03dcf0a3 100644
--- a/src/main/scala/firrtl/passes/VerilogModulusCleanup.scala
+++ b/src/main/scala/firrtl/passes/VerilogModulusCleanup.scala
@@ -32,7 +32,7 @@ object VerilogModulusCleanup extends Pass {
       Dependency[firrtl.transforms.FixAddingNegativeLiterals],
       Dependency[firrtl.transforms.ReplaceTruncatingArithmetic],
       Dependency[firrtl.transforms.InlineBitExtractionsTransform],
-      Dependency[firrtl.transforms.InlineCastsTransform],
+      Dependency[firrtl.transforms.InlineAcrossCastsTransform],
       Dependency[firrtl.transforms.LegalizeClocksTransform],
       Dependency[firrtl.transforms.FlattenRegUpdate]
     )
diff --git a/src/main/scala/firrtl/passes/VerilogPrep.scala b/src/main/scala/firrtl/passes/VerilogPrep.scala
index ed5db92e..9499889a 100644
--- a/src/main/scala/firrtl/passes/VerilogPrep.scala
+++ b/src/main/scala/firrtl/passes/VerilogPrep.scala
@@ -28,7 +28,7 @@ object VerilogPrep extends Pass {
       Dependency[firrtl.transforms.FixAddingNegativeLiterals],
       Dependency[firrtl.transforms.ReplaceTruncatingArithmetic],
       Dependency[firrtl.transforms.InlineBitExtractionsTransform],
-      Dependency[firrtl.transforms.InlineCastsTransform],
+      Dependency[firrtl.transforms.InlineAcrossCastsTransform],
       Dependency[firrtl.transforms.LegalizeClocksTransform],
       Dependency[firrtl.transforms.FlattenRegUpdate],
       Dependency(passes.VerilogModulusCleanup),
diff --git a/src/main/scala/firrtl/stage/Forms.scala b/src/main/scala/firrtl/stage/Forms.scala
index ab082151..4132f758 100644
--- a/src/main/scala/firrtl/stage/Forms.scala
+++ b/src/main/scala/firrtl/stage/Forms.scala
@@ -101,7 +101,7 @@ object Forms {
       Dependency[firrtl.transforms.FixAddingNegativeLiterals],
       Dependency[firrtl.transforms.ReplaceTruncatingArithmetic],
       Dependency[firrtl.transforms.InlineBitExtractionsTransform],
-      Dependency[firrtl.transforms.InlineCastsTransform],
+      Dependency[firrtl.transforms.InlineAcrossCastsTransform],
       Dependency[firrtl.transforms.LegalizeClocksTransform],
       Dependency[firrtl.transforms.FlattenRegUpdate],
       Dependency(passes.VerilogModulusCleanup),
diff --git a/src/main/scala/firrtl/transforms/FlattenRegUpdate.scala b/src/main/scala/firrtl/transforms/FlattenRegUpdate.scala
index 664ce1e6..3f497c91 100644
--- a/src/main/scala/firrtl/transforms/FlattenRegUpdate.scala
+++ b/src/main/scala/firrtl/transforms/FlattenRegUpdate.scala
@@ -170,7 +170,7 @@ class FlattenRegUpdate extends Transform with DependencyAPIMigration {
       Dependency[FixAddingNegativeLiterals],
       Dependency[ReplaceTruncatingArithmetic],
       Dependency[InlineBitExtractionsTransform],
-      Dependency[InlineCastsTransform],
+      Dependency[InlineAcrossCastsTransform],
       Dependency[LegalizeClocksTransform]
     )
 
diff --git a/src/main/scala/firrtl/transforms/InlineCasts.scala b/src/main/scala/firrtl/transforms/InlineCasts.scala
index 761252c1..de54a326 100644
--- a/src/main/scala/firrtl/transforms/InlineCasts.scala
+++ b/src/main/scala/firrtl/transforms/InlineCasts.scala
@@ -10,6 +10,7 @@ import firrtl.options.Dependency
 
 import firrtl.Utils.{isBitExtract, isCast, NodeMap}
 
+@deprecated("Replaced by InlineAcrossCastsTransform", "FIRRTL 1.4.3")
 object InlineCastsTransform {
 
   // Checks if an Expression is made up of only casts terminated by a Literal or Reference
@@ -54,7 +55,7 @@ object InlineCastsTransform {
     rec(false)(expr)
   }
 
-  /** Inline casts in a Statement
+  /** Inline across casts in a statement
     *
     * @param netlist a '''mutable''' HashMap mapping references to [[firrtl.ir.DefNode DefNode]]s to their connected
     * [[firrtl.ir.Expression Expression]]s. This function '''will''' mutate
@@ -71,11 +72,17 @@ object InlineCastsTransform {
       case other => other
     }
 
-  /** Replaces truncating arithmetic in a Module */
+  /** Inline across casts in a module */
   def onMod(mod: DefModule): DefModule = mod.map(onStmt(new NodeMap))
 }
 
-/** Inline nodes that are simple casts */
+/** Inline expressions into casts and inline casts into other expressions
+  *
+  * Because casts are no-ops in the emitted Verilog, this transform eliminates statements that
+  * simply contain a cast. It does so by greedily building larger expression trees that contain at
+  * most one expression that is neither a cast nor reference-like node.
+  */
+@deprecated("Replaced by InlineAcrossCastsTransform", "FIRRTL 1.4.3")
 class InlineCastsTransform extends Transform with DependencyAPIMigration {
 
   override def prerequisites = firrtl.stage.Forms.LowFormMinimumOptimized ++
diff --git a/src/main/scala/firrtl/transforms/LegalizeClocksAndAsyncResets.scala b/src/main/scala/firrtl/transforms/LegalizeClocksAndAsyncResets.scala
index 5e3d276d..0765a2b1 100644
--- a/src/main/scala/firrtl/transforms/LegalizeClocksAndAsyncResets.scala
+++ b/src/main/scala/firrtl/transforms/LegalizeClocksAndAsyncResets.scala
@@ -91,7 +91,7 @@ class LegalizeClocksAndAsyncResetsTransform extends Transform with DependencyAPI
       Dependency[FixAddingNegativeLiterals],
       Dependency[ReplaceTruncatingArithmetic],
       Dependency[InlineBitExtractionsTransform],
-      Dependency[InlineCastsTransform]
+      Dependency[InlineAcrossCastsTransform]
     )
 
   override def optionalPrerequisites = firrtl.stage.Forms.LowFormOptimized
diff --git a/src/main/scala/firrtl/transforms/RemoveKeywordCollisions.scala b/src/main/scala/firrtl/transforms/RemoveKeywordCollisions.scala
index 0bf6419f..69d4aa8d 100644
--- a/src/main/scala/firrtl/transforms/RemoveKeywordCollisions.scala
+++ b/src/main/scala/firrtl/transforms/RemoveKeywordCollisions.scala
@@ -37,7 +37,7 @@ class VerilogRename extends RemoveKeywordCollisions(v_keywords) {
       Dependency[FixAddingNegativeLiterals],
       Dependency[ReplaceTruncatingArithmetic],
       Dependency[InlineBitExtractionsTransform],
-      Dependency[InlineCastsTransform],
+      Dependency[InlineAcrossCastsTransform],
       Dependency[LegalizeClocksTransform],
       Dependency[FlattenRegUpdate],
       Dependency(passes.VerilogModulusCleanup)
diff --git a/src/main/scala/firrtl/transforms/package.scala b/src/main/scala/firrtl/transforms/package.scala
index d758fa0a..5455690e 100644
--- a/src/main/scala/firrtl/transforms/package.scala
+++ b/src/main/scala/firrtl/transforms/package.scala
@@ -3,6 +3,9 @@
 package firrtl
 
 package object transforms {
+  type InlineAcrossCastsTransform = InlineCastsTransform
+  val InlineAcrossCastsTransform = InlineCastsTransform
+
   @deprecated("Replaced by LegalizeClocksAndAsyncResetsTransform", "FIRRTL 1.4.0")
   type LegalizeClocksTransform = LegalizeClocksAndAsyncResetsTransform
   @deprecated("Replaced by LegalizeClocksAndAsyncResetsTransform", "FIRRTL 1.4.0")
diff --git a/src/test/scala/firrtlTests/InlineCastsSpec.scala b/src/test/scala/firrtlTests/InlineAcrossCastsSpec.scala
index 7a248def..669ae077 100644
--- a/src/test/scala/firrtlTests/InlineCastsSpec.scala
+++ b/src/test/scala/firrtlTests/InlineAcrossCastsSpec.scala
@@ -2,11 +2,11 @@
 
 package firrtlTests
 
-import firrtl.transforms.InlineCastsTransform
+import firrtl.transforms.InlineAcrossCastsTransform
 import firrtl.testutils.FirrtlFlatSpec
 import firrtl.testutils.FirrtlCheckers._
 
-class InlineCastsEquivalenceSpec extends FirrtlFlatSpec {
+class InlineAcrossCastsEquivalenceSpec extends FirrtlFlatSpec {
   /*
    * Note: InlineCasts is still part of mverilog, so this test must both:
    * - Test that the InlineCasts fix is effective given the current mverilog
@@ -25,7 +25,7 @@ class InlineCastsEquivalenceSpec extends FirrtlFlatSpec {
          |    output o: SInt<8>
          |    o <= pad(asSInt(UInt<2>("h1")), 8)
          |""".stripMargin
-    firrtlEquivalenceTest(input, Seq(new InlineCastsTransform))
+    firrtlEquivalenceTest(input, Seq(new InlineAcrossCastsTransform))
   }
 
   it should "not inline complex expressions into other complex expressions" in {
diff --git a/src/test/scala/firrtlTests/LoweringCompilersSpec.scala b/src/test/scala/firrtlTests/LoweringCompilersSpec.scala
index bdc72e7b..d56ca657 100644
--- a/src/test/scala/firrtlTests/LoweringCompilersSpec.scala
+++ b/src/test/scala/firrtlTests/LoweringCompilersSpec.scala
@@ -247,7 +247,7 @@ class LoweringCompilersSpec extends AnyFlatSpec with Matchers {
       new firrtl.transforms.ReplaceTruncatingArithmetic,
       new firrtl.transforms.InlineBitExtractionsTransform,
       new firrtl.transforms.PropagatePresetAnnotations,
-      new firrtl.transforms.InlineCastsTransform,
+      new firrtl.transforms.InlineAcrossCastsTransform,
       new firrtl.transforms.LegalizeClocksTransform,
       new firrtl.transforms.FlattenRegUpdate,
       firrtl.passes.VerilogModulusCleanup,
@@ -271,7 +271,7 @@ class LoweringCompilersSpec extends AnyFlatSpec with Matchers {
       new firrtl.transforms.ReplaceTruncatingArithmetic,
       new firrtl.transforms.InlineBitExtractionsTransform,
       new firrtl.transforms.PropagatePresetAnnotations,
-      new firrtl.transforms.InlineCastsTransform,
+      new firrtl.transforms.InlineAcrossCastsTransform,
       new firrtl.transforms.LegalizeClocksTransform,
       new firrtl.transforms.FlattenRegUpdate,
       new firrtl.transforms.DeadCodeElimination,