[LLHD] Add TemporalCodeMotionPass

include/circt/Dialect/LLHD/Transforms/Passes.h

@@ -33,6 +33,8 @@ createMemoryToBlockArgumentPass();
 
 std::unique_ptr<OperationPass<hw::HWModuleOp>> createEarlyCodeMotionPass();
 
+std::unique_ptr<OperationPass<hw::HWModuleOp>> createTemporalCodeMotionPass();
+
 /// Register the LLHD Transformation passes.
 void initLLHDTransformationPasses();
 

include/circt/Dialect/LLHD/Transforms/Passes.td

@@ -109,4 +109,21 @@ def EarlyCodeMotion : Pass<"llhd-early-code-motion", "hw::HWModuleOp"> {
   let constructor = "circt::llhd::createEarlyCodeMotionPass()";
 }
 
+def TemporalCodeMotion : Pass<"llhd-temporal-code-motion", "hw::HWModuleOp"> {
+  let summary = "move drive operations to the exit basic block in processes";
+  let description = [{
+    This pass uses the temporal region analysis to transform the IR such that
+    every temporal region has a unique exit block and moves all 'llhd.drv'
+    operations in a temporal region into its exit block by adjusting the
+    enable operand.
+    Furthermore, it combines 'llhd.drv' operations driving the same signal with
+    with the same delay by multiplexing the driven value according to their
+    enable operands.
+    This pass assumes that the early code motion pass has been run beforehand.
+    Otherwise, dominance errors are to be expected.
+  }];
+
+  let constructor = "circt::llhd::createTemporalCodeMotionPass()";
+}
+
 #endif // CIRCT_DIALECT_LLHD_TRANSFORMS_PASSES

lib/Dialect/LLHD/Transforms/CMakeLists.txt

@@ -5,11 +5,13 @@ add_circt_dialect_library(CIRCTLLHDTransforms
   FunctionEliminationPass.cpp
   MemoryToBlockArgumentPass.cpp
   EarlyCodeMotionPass.cpp
+  TemporalCodeMotionPass.cpp
 
   DEPENDS
   CIRCTLLHDTransformsIncGen
 
   LINK_LIBS PUBLIC
+  CIRCTComb
   CIRCTHW
   CIRCTLLHD
   MLIRIR