chore: drop extern symbol in favor of optional parameter

External symbols in the binary will cause problems for static library
builds. Switch to using an additional parameter to pass the parameter
if it exists.

Signed-off-by: Tianrui Wei <[email protected]>

Author: tianrui-wei

include/circt/Reduce/GenericReductions.h

@@ -10,13 +10,20 @@
 #define CIRCT_REDUCE_GENERICREDUCTIONS_H
 
 #include "circt/Reduce/Reduction.h"
+#include <optional>
 
 namespace circt {
 
 /// Populate reduction patterns that are not specific to certain operations or
-/// dialects
+/// dialects.
+///
+/// The optional `maxNumRewrites` parameter allows callers to override the
+/// greedy rewrite budget used by reductions that rely on the canonicalizer
+/// pass.
 void populateGenericReducePatterns(MLIRContext *context,
-                                   ReducePatternSet &patterns);
+                                   ReducePatternSet &patterns,
+                                   std::optional<int64_t> maxNumRewrites =
+                                       std::nullopt);
 
 } // namespace circt
 

lib/Reduce/GenericReductions.cpp

@@ -11,13 +11,10 @@
 #include "mlir/IR/SymbolTable.h"
 #include "mlir/Transforms/GreedyPatternRewriteDriver.h"
 #include "mlir/Transforms/Passes.h"
-#include "llvm/Support/CommandLine.h"
 
 using namespace mlir;
 using namespace circt;
 
-extern llvm::cl::opt<int64_t> maxGreedyRewrites;
-
 //===----------------------------------------------------------------------===//
 // Reduction Patterns
 //===----------------------------------------------------------------------===//
@@ -99,20 +96,23 @@ struct MakeSymbolsPrivate : public Reduction {
 // Reduction Registration
 //===----------------------------------------------------------------------===//
 
-static std::unique_ptr<Pass> createSimpleCanonicalizerPass() {
+static std::unique_ptr<Pass>
+createSimpleCanonicalizerPass(std::optional<int64_t> maxNumRewrites) {
   GreedyRewriteConfig config;
   config.setUseTopDownTraversal(true);
   config.setRegionSimplificationLevel(
       mlir::GreedySimplifyRegionLevel::Disabled);
-  if (maxGreedyRewrites >= 0)
-    config.setMaxNumRewrites(maxGreedyRewrites);
+  if (maxNumRewrites)
+    config.setMaxNumRewrites(*maxNumRewrites);
   return createCanonicalizerPass(config);
 }
 
 void circt::populateGenericReducePatterns(MLIRContext *context,
-                                          ReducePatternSet &patterns) {
+                                          ReducePatternSet &patterns,
+                                          std::optional<int64_t> maxNumRewrites) {
   patterns.add<PassReduction, 103>(context, createSymbolDCEPass());
-  patterns.add<PassReduction, 102>(context, createSimpleCanonicalizerPass());
+  patterns.add<PassReduction, 102>(context,
+                                   createSimpleCanonicalizerPass(maxNumRewrites));
   patterns.add<PassReduction, 101>(context, createCSEPass());
   patterns.add<MakeSymbolsPrivate, 100>();
   patterns.add<UnusedSymbolPruner, 99>();

tools/circt-reduce/circt-reduce.cpp

@@ -199,7 +199,10 @@ static LogicalResult execute(MLIRContext &context) {
 
   // Gather a list of reduction patterns that we should try.
   ReducePatternSet patterns;
-  populateGenericReducePatterns(&context, patterns);
+  std::optional<int64_t> maxNumRewritesOpt;
+  if (maxGreedyRewrites >= 0)
+    maxNumRewritesOpt = maxGreedyRewrites;
+  populateGenericReducePatterns(&context, patterns, maxNumRewritesOpt);
   ReducePatternInterfaceCollection reducePatternCollection(&context);
   reducePatternCollection.populateReducePatterns(patterns);
   auto reductionFilter = [&](const Reduction &reduction) {