[Mlir-commits] [mlir] [MLIR][Target/Cpp] Fix variable naming conflict for function declarations (PR #147927)

[llvmlistbot at llvm.org]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-mlir

Author: Niklas Degener (ndegener-amd)

<details>
<summary>Changes</summary>

This is a fix for https://github.com/llvm/llvm-project/pull/136102. It missed scoping for DeclareFuncOps.
In scenarios with multiple function declarations, the valueMapper wasn't updated and later uses of values in other functions still used the assigned names in prior functions.

This is visible in the reproducer here https://github.com/iree-org/iree/issues/21303: Although the counter for variable enumeration was reset, as it is visible for the local vars, the function arguments were mapped to old names. Due to this mapping, the counter was never increased, and the local variables conflicted with the arguments.

This fix adds proper scoping for declarations and a test-case to cover the scenario with multiple DeclareFuncOps.

---
Full diff: https://github.com/llvm/llvm-project/pull/147927.diff


2 Files Affected:

- (modified) mlir/lib/Target/Cpp/TranslateToCpp.cpp (+1) 
- (modified) mlir/test/Target/Cpp/declare_func.mlir (+17) 


``````````diff
diff --git a/mlir/lib/Target/Cpp/TranslateToCpp.cpp b/mlir/lib/Target/Cpp/TranslateToCpp.cpp
index 06977e07fda5b..a393d88ba4a08 100644
--- a/mlir/lib/Target/Cpp/TranslateToCpp.cpp
+++ b/mlir/lib/Target/Cpp/TranslateToCpp.cpp
@@ -1258,6 +1258,7 @@ static LogicalResult printOperation(CppEmitter &emitter,
                                     DeclareFuncOp declareFuncOp) {
   raw_indented_ostream &os = emitter.ostream();
 
+  CppEmitter::FunctionScope scope(emitter);
   auto functionOp = SymbolTable::lookupNearestSymbolFrom<emitc::FuncOp>(
       declareFuncOp, declareFuncOp.getSymNameAttr());
 
diff --git a/mlir/test/Target/Cpp/declare_func.mlir b/mlir/test/Target/Cpp/declare_func.mlir
index 6901e135df389..0208b92b30860 100644
--- a/mlir/test/Target/Cpp/declare_func.mlir
+++ b/mlir/test/Target/Cpp/declare_func.mlir
@@ -24,3 +24,20 @@ emitc.declare_func @array_arg
 emitc.func @array_arg(%arg0: !emitc.array<3xi32>) {
     emitc.return
 }
+
+// CHECK: int32_t foo1(int32_t [[V1:[^ ]*]]);
+emitc.declare_func @foo1
+// CHECK: int32_t foo2(int32_t [[V1]]);
+emitc.declare_func @foo2
+// CHECK: int32_t foo1(int32_t [[V1]]) {
+emitc.func @foo1(%arg0: i32) -> i32 {
+    // CHECK-NOT: int32_t [[V1]] = 0;
+    %0 = "emitc.constant"() <{value = 0 : i32}> : () -> i32
+    // CHECK: return [[V1]];
+    emitc.return %arg0 : i32
+}
+// CHECK: int32_t foo2(int32_t [[V1]]) {
+emitc.func @foo2(%arg0: i32) -> i32 {
+    // CHECK: return [[V1]];
+    emitc.return %arg0 : i32
+}
\ No newline at end of file

``````````

</details>


https://github.com/llvm/llvm-project/pull/147927