[mlir][complex] Canonicalization for consecutive complex.add and sub

[Lewuathe]

Summary

Add basic canonicalization for consecutive complex.add and sub operations.

mlir/include/mlir/Dialect/Complex/IR/ComplexOps.td

let description = [{
     The `add` operation takes two complex numbers and returns their sum.
 
     Example:
 
     ```mlir
     %a = complex.add %b, %c : complex<f32>
     ```
   }];
+
+  let hasFolder = 1;
 }
 
 //===----------------------------------------------------------------------===//
 // Atan2
 //===----------------------------------------------------------------------===//
 
 def Atan2Op : ComplexArithmeticOp<"atan2"> {
   let summary = "complex 2-argument arctangent";

mlir/lib/Dialect/Complex/IR/ComplexOps.cpp

 //===- ComplexOps.cpp - MLIR Complex Operations ---------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "mlir/Dialect/Complex/IR/Complex.h"
 #include "mlir/IR/Builders.h"
+#include "mlir/IR/Matchers.h"
 
 using namespace mlir;
 using namespace mlir::complex;
 
 //===----------------------------------------------------------------------===//
 // ConstantOp
 //===----------------------------------------------------------------------===//
 
OpFoldResult ReOp::fold(ArrayRef<Attribute> operands) {
   if (arrayAttr && arrayAttr.size() == 2)
     return arrayAttr[0];
   if (auto createOp = getOperand().getDefiningOp<CreateOp>())
     return createOp.getOperand(0);
   return {};
 }
 
 //===----------------------------------------------------------------------===//
+// AddOp
+//===----------------------------------------------------------------------===//
+
+OpFoldResult AddOp::fold(ArrayRef<Attribute> operands) {
+  assert(operands.size() == 2 && "binary op takes 2 operands");
+
+  // complex.add(complex.sub(a, b), b) -> a
+  if (auto sub = getLhs().getDefiningOp<SubOp>())
+    if (getRhs() == sub.getRhs())
+      return sub.getLhs();
+
+  // complex.add(b, complex.sub(a, b)) -> a
+  if (auto sub = getRhs().getDefiningOp<SubOp>())
+    if (getLhs() == sub.getRhs())
+      return sub.getLhs();
+
+  return {};
+}
+
+//===----------------------------------------------------------------------===//
 // TableGen'd op method definitions
 //===----------------------------------------------------------------------===//
 
 #define GET_OP_CLASSES
 #include "mlir/Dialect/Complex/IR/ComplexOps.cpp.inc"

mlir/test/Dialect/Complex/canonicalize.mlir

func.func @imag_of_create_op() -> f32 {
   // CHECK: %[[CST:.*]] = arith.constant 0.000000e+00 : f32
   // CHECK-NEXT: return %[[CST]] : f32
   %real = arith.constant 1.0 : f32
   %imag = arith.constant 0.0 : f32
   %complex = complex.create %real, %imag : complex<f32>
   %1 = complex.im %complex : complex<f32>
   return %1 : f32
 }
+
+// CHECK-LABEL: func @complex_add_sub_lhs
+func.func @complex_add_sub_lhs() -> complex<f32> {
+  %complex1 = complex.constant [1.0 : f32, 0.0 : f32] : complex<f32>
+  %complex2 = complex.constant [0.0 : f32, 2.0 : f32] : complex<f32>
+  // CHECK: %[[CPLX:.*]] = complex.constant [1.000000e+00 : f32, 0.000000e+00 : f32] : complex<f32>
+  // CHECK-NEXT: return %[[CPLX:.*]] : complex<f32>
+  %sub = complex.sub %complex1, %complex2 : complex<f32>
+  %add = complex.add %sub, %complex2 : complex<f32>
+  return %add : complex<f32>
+}
+
+// CHECK-LABEL: func @complex_add_sub_rhs
+func.func @complex_add_sub_rhs() -> complex<f32> {
+  %complex1 = complex.constant [1.0 : f32, 0.0 : f32] : complex<f32>
+  %complex2 = complex.constant [0.0 : f32, 2.0 : f32] : complex<f32>
+  // CHECK: %[[CPLX:.*]] = complex.constant [1.000000e+00 : f32, 0.000000e+00 : f32] : complex<f32>
+  // CHECK-NEXT: return %[[CPLX:.*]] : complex<f32>
+  %sub = complex.sub %complex1, %complex2 : complex<f32>
+  %add = complex.add %complex2, %sub : complex<f32>
+  return %add : complex<f32>
+}
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