[Mlir-commits] [mlir] [mlir] mark ChangeResult as nodiscard (PR #76147)

[llvmlistbot at llvm.org]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-mlir

Author: Oleksandr "Alex" Zinenko (ftynse)

<details>
<summary>Changes</summary>

This enum is used by dataflow analyses to indicate whether further propagation is necessary to reach the fix point. Accidentally discarding such a value will likely lead to propagation stopping early, leading to incomplete or incorrect results. The most egregious example is the duality between `join` on the analysis class, which triggers propagation internally, and `join` on the lattice class that does not and expects the caller to trigger it depending on the returned `ChangeResult`.

---
Full diff: https://github.com/llvm/llvm-project/pull/76147.diff


3 Files Affected:

- (modified) mlir/include/mlir/Analysis/DataFlowFramework.h (+2-2) 
- (modified) mlir/lib/Analysis/DataFlow/LivenessAnalysis.cpp (+1-1) 
- (modified) mlir/test/lib/Analysis/TestDataFlowFramework.cpp (+1-1) 


``````````diff
diff --git a/mlir/include/mlir/Analysis/DataFlowFramework.h b/mlir/include/mlir/Analysis/DataFlowFramework.h
index 541cdb1e237c1b..c76cfac07fc77a 100644
--- a/mlir/include/mlir/Analysis/DataFlowFramework.h
+++ b/mlir/include/mlir/Analysis/DataFlowFramework.h
@@ -30,8 +30,8 @@ namespace mlir {
 //===----------------------------------------------------------------------===//
 
 /// A result type used to indicate if a change happened. Boolean operations on
-/// ChangeResult behave as though `Change` is truthy.
-enum class ChangeResult {
+/// ChangeResult behave as though `Change` is truth.
+enum class [[nodiscard]] ChangeResult {
   NoChange,
   Change,
 };
diff --git a/mlir/lib/Analysis/DataFlow/LivenessAnalysis.cpp b/mlir/lib/Analysis/DataFlow/LivenessAnalysis.cpp
index 2820d27b65f7a2..7875fa9d43d9e2 100644
--- a/mlir/lib/Analysis/DataFlow/LivenessAnalysis.cpp
+++ b/mlir/lib/Analysis/DataFlow/LivenessAnalysis.cpp
@@ -191,7 +191,7 @@ void LivenessAnalysis::visitCallOperand(OpOperand &operand) {
 
 void LivenessAnalysis::setToExitState(Liveness *lattice) {
   // This marks values of type (2) liveness as "live".
-  lattice->markLive();
+  (void)lattice->markLive();
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/mlir/test/lib/Analysis/TestDataFlowFramework.cpp b/mlir/test/lib/Analysis/TestDataFlowFramework.cpp
index ed361b5a0e270e..b6b33182440cf4 100644
--- a/mlir/test/lib/Analysis/TestDataFlowFramework.cpp
+++ b/mlir/test/lib/Analysis/TestDataFlowFramework.cpp
@@ -100,7 +100,7 @@ LogicalResult FooAnalysis::initialize(Operation *top) {
     return top->emitError("expected at least one block in the region");
 
   // Initialize the top-level state.
-  getOrCreate<FooState>(&top->getRegion(0).front())->join(0);
+  (void)getOrCreate<FooState>(&top->getRegion(0).front())->join(0);
 
   // Visit all nested blocks and operations.
   for (Block &block : top->getRegion(0)) {

``````````

</details>


https://github.com/llvm/llvm-project/pull/76147