[Mlir-commits] [mlir] [mlir][complex] Add fold for 0+a -> a (PR #212199)

[llvmlistbot at llvm.org]

https://github.com/Brythzz created https://github.com/llvm/llvm-project/pull/212199

The complex Add operator folder currently supports the `a+0 -> 0` pattern. This PR adds the missing `0+a -> a` pattern.

>From fbabd064289db2e19b565420106daa1133e98a13 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Matt=C3=A9o=20Rizza=20Murgier?=
 <matteo.rizza-murgier at sipearl.com>
Date: Mon, 20 Jul 2026 12:49:36 +0200
Subject: [PATCH] [mlir][complex] Add fold for 0+a -> a

---
 mlir/lib/Dialect/Complex/IR/ComplexOps.cpp  |  9 +++++++++
 mlir/test/Dialect/Complex/canonicalize.mlir | 14 ++++++++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/mlir/lib/Dialect/Complex/IR/ComplexOps.cpp b/mlir/lib/Dialect/Complex/IR/ComplexOps.cpp
index b5323597b7ca4..d52f7fc316d09 100644
--- a/mlir/lib/Dialect/Complex/IR/ComplexOps.cpp
+++ b/mlir/lib/Dialect/Complex/IR/ComplexOps.cpp
@@ -270,6 +270,15 @@ OpFoldResult AddOp::fold(FoldAdaptor adaptor) {
     }
   }
 
+  // complex.add(complex.constant<0.0, 0.0>, a) -> a
+  if (auto constantOp = getLhs().getDefiningOp<ConstantOp>()) {
+    auto arrayAttr = constantOp.getValue();
+    if (llvm::cast<FloatAttr>(arrayAttr[0]).getValue().isZero() &&
+        llvm::cast<FloatAttr>(arrayAttr[1]).getValue().isZero()) {
+      return getRhs();
+    }
+  }
+
   return {};
 }
 
diff --git a/mlir/test/Dialect/Complex/canonicalize.mlir b/mlir/test/Dialect/Complex/canonicalize.mlir
index 1c5216c82e5c3..8ee4c62b216a2 100644
--- a/mlir/test/Dialect/Complex/canonicalize.mlir
+++ b/mlir/test/Dialect/Complex/canonicalize.mlir
@@ -125,8 +125,8 @@ func.func @complex_conj_conj() -> complex<f32> {
   return %conj2 : complex<f32>
 }
 
-// CHECK-LABEL: func @complex_add_zero
-func.func @complex_add_zero() -> complex<f32> {
+// CHECK-LABEL: func @complex_add_zero_rhs
+func.func @complex_add_zero_rhs() -> complex<f32> {
   %complex1 = complex.constant [1.0 : f32, 0.0 : f32] : complex<f32>
   %complex2 = complex.constant [0.0 : f32, 0.0 : f32] : complex<f32>
   // CHECK: %[[CPLX:.*]] = complex.constant [1.000000e+00 : f32, 0.000000e+00 : f32] : complex<f32>
@@ -135,6 +135,16 @@ func.func @complex_add_zero() -> complex<f32> {
   return %add : complex<f32>
 }
 
+// CHECK-LABEL: func @complex_add_zero_lhs
+func.func @complex_add_zero_lhs() -> complex<f32> {
+  %complex1 = complex.constant [0.0 : f32, 0.0 : f32] : complex<f32>
+  %complex2 = 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>
+  %add = complex.add %complex1, %complex2 : complex<f32>
+  return %add : complex<f32>
+}
+
 // CHECK-LABEL: func @complex_sub_add_lhs
 func.func @complex_sub_add_lhs() -> complex<f32> {
   %complex1 = complex.constant [1.0 : f32, 0.0 : f32] : complex<f32>