[mlir][complex] Inverse canonicalization between exp and log

[Lewuathe]

Summary

We can canonicalize consecutive complex.exp and complex.log which are inverse functions each other.

[bixia]

Nice!

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

let description = [{
     Example:
 
     ```mlir
     %a = complex.exp %b : complex<f32>
     ```
   }];
 
   let results = (outs Complex<AnyFloat>:$result);
+
+  let hasFolder = 1;
 }
 
 //===----------------------------------------------------------------------===//
 // Expm1Op
 //===----------------------------------------------------------------------===//
 
 def Expm1Op : ComplexUnaryOp<"expm1", [SameOperandsAndResultType]> {
   let summary = "computes exponential of a complex number minus 1";
let description = [{
     Example:
 
     ```mlir
     %a = complex.log %b : complex<f32>
     ```
   }];
 
   let results = (outs Complex<AnyFloat>:$result);
+
+  let hasFolder = 1;
 }
 
 //===----------------------------------------------------------------------===//
 // Log1pOp
 //===----------------------------------------------------------------------===//
 
 def Log1pOp : ComplexUnaryOp<"log1p", [SameOperandsAndResultType]> {
   let summary = "computes natural logarithm of a complex number";

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

OpFoldResult NegOp::fold(ArrayRef<Attribute> operands) {
   // complex.neg(complex.neg(a)) -> a
   if (auto negOp = getOperand().getDefiningOp<NegOp>())
     return negOp.getOperand();
 
   return {};
 }
 
 //===----------------------------------------------------------------------===//
+// LogOp
+//===----------------------------------------------------------------------===//
+
+OpFoldResult LogOp::fold(ArrayRef<Attribute> operands) {
+  assert(operands.size() == 1 && "unary op takes 1 operand");
+
+  // complex.log(complex.exp(a)) -> a
+  if (auto expOp = getOperand().getDefiningOp<ExpOp>())
+    return expOp.getOperand();
+
+  return {};
+}
+
+//===----------------------------------------------------------------------===//
+// ExpOp
+//===----------------------------------------------------------------------===//
+
+OpFoldResult ExpOp::fold(ArrayRef<Attribute> operands) {
+  assert(operands.size() == 1 && "unary op takes 1 operand");
+
+  // complex.exp(complex.log(a)) -> a
+  if (auto logOp = getOperand().getDefiningOp<LogOp>())
+    return logOp.getOperand();
+
+  return {};
+}
+
+//===----------------------------------------------------------------------===//
 // TableGen'd op method definitions
 //===----------------------------------------------------------------------===//
 
 #define GET_OP_CLASSES
 #include "mlir/Dialect/Complex/IR/ComplexOps.cpp.inc"

mlir/test/Dialect/Complex/canonicalize.mlir

 // CHECK-LABEL: func @complex_neg_neg
 func.func @complex_neg_neg() -> complex<f32> {
   %complex1 = complex.constant [1.0 : f32, 0.0 : f32] : complex<f32>
   // CHECK: %[[CPLX:.*]] = complex.constant [1.000000e+00 : f32, 0.000000e+00 : f32] : complex<f32>
   // CHECK-NEXT: return %[[CPLX:.*]] : complex<f32>
   %neg1 = complex.neg %complex1 : complex<f32>
   %neg2 = complex.neg %neg1 : complex<f32>
   return %neg2 : complex<f32>
+}
+
+// CHECK-LABEL: func @complex_log_exp
+func.func @complex_log_exp() -> complex<f32> {
+  %complex1 = complex.constant [1.0 : f32, 0.0 : f32] : complex<f32>
+  // CHECK: %[[CPLX:.*]] = complex.constant [1.000000e+00 : f32, 0.000000e+00 : f32] : complex<f32>
+  // CHECK-NEXT: return %[[CPLX:.*]] : complex<f32>
+  %exp = complex.exp %complex1 : complex<f32>
+  %log = complex.log %exp : complex<f32>
+  return %log : complex<f32>
+}
+
+// CHECK-LABEL: func @complex_exp_log
+func.func @complex_exp_log() -> complex<f32> {
+  %complex1 = complex.constant [1.0 : f32, 0.0 : f32] : complex<f32>
+  // CHECK: %[[CPLX:.*]] = complex.constant [1.000000e+00 : f32, 0.000000e+00 : f32] : complex<f32>
+  // CHECK-NEXT: return %[[CPLX:.*]] : complex<f32>
+  %log = complex.log %complex1 : complex<f32>
+  %exp = complex.exp %log : complex<f32>
+  return %exp : complex<f32>
 }
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