[Mlir-commits] [mlir] [MLIR][EmitC][cf] Bugfix: correctly inline emitc.expression op in the emitted if condition of a cf.cond_br (PR #128958)

[llvmlistbot at llvm.org]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-mlir

Author: None (gdehame)

<details>
<summary>Changes</summary>

[MLIR][EmitC][cf] Bugfix: correctly inline emitc.expression op in the emitted if condition of a cf.cond_br
    
    Running `mlir-translate -mlir-to-cpp -declare-variables-at-top input.mlir` with `input.mlir` as
    ```
    module {
      emitc.func @<!-- -->f(%0 : i32, %1 : i32) {
        %2 = expression : i1 {
          %3 = cmp lt, %0, %1 : (i32, i32) -> i1
          yield %3 : i1
        }
        cf.cond_br %2, ^bb1, ^bb1
      ^bb1:  // 2 preds: ^bb0, ^bb0
        return
      }
    }
    ```
    doesn't inline the expression %2 and generates a use of an undeclared variable in the generated if:
    ```
    void f(int32_t v1, int32_t v2) {
      if (v3) {
        goto label2;
      } else {
        goto label2;
      }
    label2:
      return;
    }
    ```

---
Full diff: https://github.com/llvm/llvm-project/pull/128958.diff


2 Files Affected:

- (modified) mlir/lib/Target/Cpp/TranslateToCpp.cpp (+4-2) 
- (modified) mlir/test/Target/Cpp/control_flow.mlir (+19) 


``````````diff
diff --git a/mlir/lib/Target/Cpp/TranslateToCpp.cpp b/mlir/lib/Target/Cpp/TranslateToCpp.cpp
index abff252575eb0..b00820ffc542b 100644
--- a/mlir/lib/Target/Cpp/TranslateToCpp.cpp
+++ b/mlir/lib/Target/Cpp/TranslateToCpp.cpp
@@ -613,8 +613,10 @@ static LogicalResult printOperation(CppEmitter &emitter,
   Block &trueSuccessor = *condBranchOp.getTrueDest();
   Block &falseSuccessor = *condBranchOp.getFalseDest();
 
-  os << "if (" << emitter.getOrCreateName(condBranchOp.getCondition())
-     << ") {\n";
+  os << "if (";
+  if (failed(emitter.emitOperand(condBranchOp.getCondition())))
+    return failure();
+  os << ") {\n";
 
   os.indent();
 
diff --git a/mlir/test/Target/Cpp/control_flow.mlir b/mlir/test/Target/Cpp/control_flow.mlir
index 436543f7ace95..101b30c2521c9 100644
--- a/mlir/test/Target/Cpp/control_flow.mlir
+++ b/mlir/test/Target/Cpp/control_flow.mlir
@@ -68,3 +68,22 @@ func.func @block_labels1() {
   // CPP-DECLTOP-NEXT: label2:
   // CPP-DECLTOP-NEXT: return;
   // CPP-DECLTOP-NEXT: }
+
+emitc.func @expression_inlining(%0 : i32, %1 : i32) {
+  %2 = expression : i1 {
+    %3 = cmp lt, %0, %1 : (i32, i32) -> i1
+    yield %3 : i1
+  }
+  cf.cond_br %2, ^bb1, ^bb1
+  ^bb1:  // 2 preds: ^bb0, ^bb0
+    return
+}
+// CPP-DECLTOP: void expression_inlining(int32_t [[v1:v.*]], int32_t [[v2:v.*]]) {
+// CPP-DECLTOP-NEXT:   if ([[v1]] < [[v2]]) {
+// CPP-DECLTOP-NEXT:     goto label2;
+// CPP-DECLTOP-NEXT:   } else {
+// CPP-DECLTOP-NEXT:     goto label2;
+// CPP-DECLTOP-NEXT:   }
+// CPP-DECLTOP-NEXT: label2:
+// CPP-DECLTOP-NEXT:   return;
+// CPP-DECLTOP-NEXT: }

``````````

</details>


https://github.com/llvm/llvm-project/pull/128958