[mlir] Add arith-int-range-narrowing pass

mlir/include/mlir/Dialect/Arith/Transforms/Passes.h

@@ -77,9 +77,10 @@ void populateUnsignedWhenEquivalentPatterns(RewritePatternSet &patterns,
 /// Create a pass which do optimizations based on integer range analysis.
 std::unique_ptr<Pass> createIntRangeOptimizationsPass();
 
-/// Add patterns for integer bitwidth narrowing.
-void populateArithIntNarrowingPatterns(RewritePatternSet &patterns,
-                                       const ArithIntNarrowingOptions &options);
+/// Add patterns for int range based narrowing.
+void populateIntRangeNarrowingPatterns(RewritePatternSet &patterns,
+                                       DataFlowSolver &solver,
+                                       ArrayRef<unsigned> bitwidthsSupported);
 
 //===----------------------------------------------------------------------===//
 // Registration

mlir/include/mlir/Dialect/Arith/Transforms/Passes.td

@@ -50,6 +50,28 @@ def ArithIntRangeOpts : Pass<"int-range-optimizations"> {
   ];
 }
 
+def ArithIntRangeNarrowing : Pass<"arith-int-range-narrowing"> {
+  let summary = "Reduce integer operations bitwidth based on integer range analysis";
+  let description = [{
+    This pass runs integer range analysis and tries to narrow arith ops to the
+    specified bitwidth based on its results.
+
+    `bitwidthsSupported` assumed to be not wider than `index` type.
+    TODO: get index width from DLTI.
+  }];
+
+  let options = [
+    ListOption<"bitwidthsSupported", "int-bitwidths-supported", "unsigned",
+               "Integer bitwidths supported">,
+  ];
+
+  // Explicitly depend on "arith" because this pass could create operations in
+  // `arith` out of thin air in some cases.
+  let dependentDialects = [
+    "::mlir::arith::ArithDialect"
+  ];
+}
+
 def ArithEmulateUnsupportedFloats : Pass<"arith-emulate-unsupported-floats"> {
   let summary = "Emulate operations on unsupported floats with extf/truncf";
   let description = [{
@@ -92,18 +114,4 @@ def ArithEmulateWideInt : Pass<"arith-emulate-wide-int"> {
   let dependentDialects = ["vector::VectorDialect"];
 }
 
-def ArithIntNarrowing : Pass<"arith-int-narrowing"> {
-  let summary = "Reduce integer operation bitwidth";
-  let description = [{
-    Reduce bitwidths of integer types used in arith operations. This pass
-    prefers the narrowest available integer bitwidths that are guaranteed to
-    produce the same results.
-  }];
-  let dependentDialects = ["vector::VectorDialect"];
-  let options = [
-    ListOption<"bitwidthsSupported", "int-bitwidths-supported", "unsigned",
-               "Integer bitwidths supported">,
-  ];
- }
-
 #endif // MLIR_DIALECT_ARITH_TRANSFORMS_PASSES

mlir/lib/Dialect/Arith/Transforms/CMakeLists.txt

@@ -6,7 +6,6 @@ add_mlir_dialect_library(MLIRArithTransforms
   EmulateWideInt.cpp
   EmulateNarrowType.cpp
   ExpandOps.cpp
-  IntNarrowing.cpp
   IntRangeOptimizations.cpp
   ReifyValueBounds.cpp
   UnsignedWhenEquivalent.cpp