[mlir][Arithmetic] fold overlapping negf.

This patch folds negf(negf(x)) to x. Differential Revision: https://reviews.llvm.org/D125955
devitocodes · May 20, 2022 · 0e02bf6 · 0e02bf6
1 parent 6e00a34
commit 0e02bf6
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diff --git a/mlir/lib/Dialect/Arithmetic/IR/ArithmeticOps.cpp b/mlir/lib/Dialect/Arithmetic/IR/ArithmeticOps.cpp
@@ -549,6 +549,9 @@ void arith::XOrIOp::getCanonicalizationPatterns(
 //===----------------------------------------------------------------------===//
 
 OpFoldResult arith::NegFOp::fold(ArrayRef<Attribute> operands) {
+  /// negf(negf(x)) -> x
+  if (auto op = this->getOperand().getDefiningOp<arith::NegFOp>())
+    return op.getOperand();
   return constFoldUnaryOp<FloatAttr>(operands,
                                      [](const APFloat &a) { return -a; });
 }

diff --git a/mlir/test/Dialect/Arithmetic/canonicalize.mlir b/mlir/test/Dialect/Arithmetic/canonicalize.mlir
@@ -1320,6 +1320,15 @@ func.func @test_negf() -> (f32) {
   return %0: f32
 }
 
+// CHECK-LABEL: @test_negf1(
+// CHECK-SAME: %[[arg0:.+]]:
+// CHECK: return %[[arg0]]
+func.func @test_negf1(%f : f32) -> (f32) {
+  %0 = arith.negf %f : f32
+  %1 = arith.negf %0 : f32
+  return %1: f32
+}
+
 // -----
 
 // CHECK-LABEL: @test_remui(