Expose populateStablehloToLinalgConversionPatterns function (#2695)

This function declaration has existed since the code was forked from
IREE in #1817, but the
implementation was kept private (static function within an anonymous
namespace).

I'm now trying to switch IREE from having its own implementation to
using the upstream implementation from this project in
iree-org/iree#19792, and I would like to access
these patterns directly, instead of through the
`StablehloLegalizeToLinalgPass`. With the patterns I can run conversion
including my own sets of additional patterns, while a pass runs in
isolation.

I'm also deleting the `populateLegalizeChloPatterns`,
`populateLegalizeControlFlowPatterns`, and
`populateLegalizeShapeComputationPatterns` declarations, which were not
migrated from IREE and are also dangling without implementations.

stablehlo/conversions/linalg/transforms/Rewriters.h

@@ -22,28 +22,15 @@ limitations under the License.
 namespace mlir::stablehlo {
 
 //===----------------------------------------------------------------------===//
-// General StableHLO/CHLO lowering patterns.
+// General StableHLO lowering patterns.
 //===----------------------------------------------------------------------===//
 
 /// Populates the patterns that convert from StableHLO to Linalg on tensors.
 void populateStablehloToLinalgConversionPatterns(MLIRContext *context,
                                                  TypeConverter &typeConverter,
                                                  RewritePatternSet *patterns,
-                                                 bool enablePrimitiveOps);
-
-/// Collection of rewrite patterns for lowering of CHLO ops to StableHLO and
-/// Shape ops.
-void populateLegalizeChloPatterns(MLIRContext *context,
-                                  RewritePatternSet *patterns);
-
-/// Collection of rewrite patterns for lowering of StableHLO ops to SCF control
-/// flow ops.
-void populateLegalizeControlFlowPatterns(MLIRContext *context,
-                                         RewritePatternSet *patterns);
-
-/// Collection of rewrite patterns for lowering of StableHLO dim operations.
-void populateLegalizeShapeComputationPatterns(MLIRContext *context,
-                                              RewritePatternSet *patterns);
+                                                 bool enablePrimitiveOps,
+                                                 bool enableSparseOps);
 
 //===----------------------------------------------------------------------===//
 // Fine-grained patterns used by the implementation.

stablehlo/conversions/linalg/transforms/StablehloLegalizeToLinalg.cpp

@@ -2600,11 +2600,45 @@ struct SetDimensionSizeConverter final
   }
 };
 
-static void populateConversionPatterns(MLIRContext *context,
-                                       TypeConverter &typeConverter,
-                                       RewritePatternSet *patterns,
-                                       bool enablePrimitiveOps,
-                                       bool enableSparseOps) {
+struct StablehloLegalizeToLinalgPass
+    : impl::StablehloLegalizeToLinalgPassBase<StablehloLegalizeToLinalgPass> {
+  using StablehloLegalizeToLinalgPassBase::StablehloLegalizeToLinalgPassBase;
+
+  LogicalResult initialize(MLIRContext *context) override {
+    target = std::make_shared<ConversionTarget>(*context);
+    target->addLegalDialect<
+        bufferization::BufferizationDialect, arith::ArithDialect,
+        complex::ComplexDialect, linalg::LinalgDialect, math::MathDialect,
+        tensor::TensorDialect, sparse_tensor::SparseTensorDialect,
+        scf::SCFDialect, shape::ShapeDialect>();
+    target->addLegalOp<UnrealizedConversionCastOp>();
+
+    RewritePatternSet patterns_(context);
+    populateStablehloToLinalgConversionPatterns(
+        context, converter, &patterns_, enablePrimitiveOps, enableSparseOps);
+    patterns = std::move(patterns_);
+
+    return success();
+  }
+
+  void runOnOperation() override {
+    if (failed(applyPartialConversion(getOperation(), *target, patterns))) {
+      return signalPassFailure();
+    }
+  }
+
+ private:
+  std::shared_ptr<ConversionTarget> target;
+  FrozenRewritePatternSet patterns;
+  LinalgTypeConverter converter;
+};
+}  // namespace
+
+void populateStablehloToLinalgConversionPatterns(MLIRContext *context,
+                                                 TypeConverter &typeConverter,
+                                                 RewritePatternSet *patterns,
+                                                 bool enablePrimitiveOps,
+                                                 bool enableSparseOps) {
   // clang-format off
   patterns->add<ConcatenateConverter>(typeConverter, context,
                                       enablePrimitiveOps);
@@ -2670,37 +2704,4 @@ static void populateConversionPatterns(MLIRContext *context,
   linalg::populateEraseUnusedOperandsAndResultsPatterns(*patterns);
 }
 
-struct StablehloLegalizeToLinalgPass
-    : impl::StablehloLegalizeToLinalgPassBase<StablehloLegalizeToLinalgPass> {
-  using StablehloLegalizeToLinalgPassBase::StablehloLegalizeToLinalgPassBase;
-
-  LogicalResult initialize(MLIRContext *context) override {
-    target = std::make_shared<ConversionTarget>(*context);
-    target->addLegalDialect<
-        bufferization::BufferizationDialect, arith::ArithDialect,
-        complex::ComplexDialect, linalg::LinalgDialect, math::MathDialect,
-        tensor::TensorDialect, sparse_tensor::SparseTensorDialect,
-        scf::SCFDialect, shape::ShapeDialect>();
-    target->addLegalOp<UnrealizedConversionCastOp>();
-
-    RewritePatternSet patterns_(context);
-    populateConversionPatterns(context, converter, &patterns_,
-                               enablePrimitiveOps, enableSparseOps);
-    patterns = std::move(patterns_);
-
-    return success();
-  }
-
-  void runOnOperation() override {
-    if (failed(applyPartialConversion(getOperation(), *target, patterns))) {
-      return signalPassFailure();
-    }
-  }
-
- private:
-  std::shared_ptr<ConversionTarget> target;
-  FrozenRewritePatternSet patterns;
-  LinalgTypeConverter converter;
-};
-}  // namespace
 }  // namespace mlir::stablehlo