[MLIR] Expose approximation patterns for tanh/erf. (#82750)

These patterns can already be used via
populateMathPolynomialApproximationPatterns, but that includes a number
of other patterns that may not be needed.

There are already similar functions for expansion.

For now only adding tanh and erf since I have a concrete use case for
these two.

2 files changed, 13 insertions, 0 deletions

diff --git a/mlir/include/mlir/Dialect/Math/Transforms/Passes.h b/mlir/include/mlir/Dialect/Math/Transforms/Passes.h
index 010dde5ea738..11b2c7a7afa2 100644
--- a/mlir/include/mlir/Dialect/Math/Transforms/Passes.h
+++ b/mlir/include/mlir/Dialect/Math/Transforms/Passes.h
@@ -45,6 +45,9 @@ struct MathPolynomialApproximationOptions {
   bool enableAvx2 = false;
 };
 
+void populatePolynomialApproximateTanhPattern(RewritePatternSet &patterns);
+void populatePolynomialApproximateErfPattern(RewritePatternSet &patterns);
+
 void populateMathPolynomialApproximationPatterns(
     RewritePatternSet &patterns,
     const MathPolynomialApproximationOptions &options = {});
diff --git a/mlir/lib/Dialect/Math/Transforms/PolynomialApproximation.cpp b/mlir/lib/Dialect/Math/Transforms/PolynomialApproximation.cpp
index 71e4e13103f5..962cb28b7c2a 100644
--- a/mlir/lib/Dialect/Math/Transforms/PolynomialApproximation.cpp
+++ b/mlir/lib/Dialect/Math/Transforms/PolynomialApproximation.cpp
@@ -1471,6 +1471,16 @@ RsqrtApproximation::matchAndRewrite(math::RsqrtOp op,
 
 //----------------------------------------------------------------------------//
 
+void mlir::populatePolynomialApproximateTanhPattern(
+    RewritePatternSet &patterns) {
+  patterns.add<TanhApproximation>(patterns.getContext());
+}
+
+void mlir::populatePolynomialApproximateErfPattern(
+    RewritePatternSet &patterns) {
+  patterns.add<ErfPolynomialApproximation>(patterns.getContext());
+}
+
 void mlir::populateMathPolynomialApproximationPatterns(
     RewritePatternSet &patterns,
     const MathPolynomialApproximationOptions &options) {