[Mlir-commits] [mlir] [mlir][emitc] Only mark operator with fundamental type have no side effect (PR #144990)

[Jianjian Guan]

https://github.com/jacquesguan created https://github.com/llvm/llvm-project/pull/144990

None

>From e27317b2b48d86fa9a622a46d857a4699673e4ea Mon Sep 17 00:00:00 2001
From: Jianjian GUAN <jacquesguan at me.com>
Date: Fri, 20 Jun 2025 15:23:33 +0800
Subject: [PATCH] [mlir][emitc] Only mark operator with fundamental type have
 no side effect

---
 mlir/include/mlir/Dialect/EmitC/IR/EmitC.h  |  3 +++
 mlir/include/mlir/Dialect/EmitC/IR/EmitC.td | 19 +++++++++++++++++--
 mlir/lib/Dialect/EmitC/IR/EmitC.cpp         |  5 +++++
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/mlir/include/mlir/Dialect/EmitC/IR/EmitC.h b/mlir/include/mlir/Dialect/EmitC/IR/EmitC.h
index 1984ed8a7f068..eb7ddeb3bfc54 100644
--- a/mlir/include/mlir/Dialect/EmitC/IR/EmitC.h
+++ b/mlir/include/mlir/Dialect/EmitC/IR/EmitC.h
@@ -53,6 +53,9 @@ bool isPointerWideType(mlir::Type type);
 struct Placeholder {};
 using ReplacementItem = std::variant<StringRef, Placeholder>;
 
+/// Determines whether \p type is a valid fundamental C++ type in EmitC.
+bool isFundamentalType(mlir::Type type);
+
 } // namespace emitc
 } // namespace mlir
 
diff --git a/mlir/include/mlir/Dialect/EmitC/IR/EmitC.td b/mlir/include/mlir/Dialect/EmitC/IR/EmitC.td
index 9ecdb74f4d82e..c66c3824bcacd 100644
--- a/mlir/include/mlir/Dialect/EmitC/IR/EmitC.td
+++ b/mlir/include/mlir/Dialect/EmitC/IR/EmitC.td
@@ -43,7 +43,11 @@ class EmitC_UnaryOp<string mnemonic, list<Trait> traits = []> :
 
   let extraClassDeclaration = [{
     bool hasSideEffects() {
-      return false;
+      // If operand is fundamental type, the operation is pure.
+      if (isFundamentalType(getOperand().getType())) {
+        return false;
+      }
+      return true;
     }
   }];
 }
@@ -57,7 +61,18 @@ class EmitC_BinaryOp<string mnemonic, list<Trait> traits = []> :
 
   let extraClassDeclaration = [{
     bool hasSideEffects() {
-      return false;
+      // If both operands are fundamental types, the operation is pure.
+      if (isFundamentalType(getOperand(0).getType()) 
+          && isFundamentalType(getOperand(1).getType())) {
+        return false;
+      }
+      // Pointer arithmetic operations is pure.
+      if (isa<emitc::PointerType>(getOperand(0).getType()) 
+          && (isFundamentalType(getOperand(1).getType()) ||
+              isa<emitc::PointerType>(getOperand(1).getType()))) {
+        return false;
+      }
+      return true;
     }
   }];
 }
diff --git a/mlir/lib/Dialect/EmitC/IR/EmitC.cpp b/mlir/lib/Dialect/EmitC/IR/EmitC.cpp
index e602210c2dc6c..bb176d5fad808 100644
--- a/mlir/lib/Dialect/EmitC/IR/EmitC.cpp
+++ b/mlir/lib/Dialect/EmitC/IR/EmitC.cpp
@@ -137,6 +137,11 @@ bool mlir::emitc::isPointerWideType(Type type) {
       type);
 }
 
+bool mlir::emitc::isFundamentalType(Type type) {
+  return llvm::isa<IndexType>(type) || isPointerWideType(type) ||
+         isSupportedIntegerType(type) || isSupportedFloatType(type);
+}
+
 /// Check that the type of the initial value is compatible with the operations
 /// result type.
 static LogicalResult verifyInitializationAttribute(Operation *op,