[flang-commits] [flang] [Flang] External subprograms should be allowed as proc_target in procedure pointers. (PR #183268)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-flang-semantics

Author: None (ShashwathiNavada)

<details>
<summary>Changes</summary>

Fixes https://github.com/llvm/llvm-project/issues/177505.

This patch updates an existing external procedure symbol with the correct function signature and argument attributes, so it can be safely used as a proc_target without signature conflicts.

---
Full diff: https://github.com/llvm/llvm-project/pull/183268.diff


2 Files Affected:

- (modified) flang/lib/Lower/CallInterface.cpp (+15) 
- (added) flang/test/Semantics/extrn_subp.f90 (+20) 


``````````diff
diff --git a/flang/lib/Lower/CallInterface.cpp b/flang/lib/Lower/CallInterface.cpp
index f5ae2de5cad8b..65cac0466d5ea 100644
--- a/flang/lib/Lower/CallInterface.cpp
+++ b/flang/lib/Lower/CallInterface.cpp
@@ -695,6 +695,21 @@ void Fortran::lower::CallInterface<T>::declare() {
     mlir::ModuleOp module = converter.getModuleOp();
     mlir::SymbolTable *symbolTable = converter.getMLIRSymbolTable();
     func = fir::FirOpBuilder::getNamedFunction(module, symbolTable, name);
+    if (func) {
+      if constexpr (std::is_same_v<T, Fortran::lower::CalleeInterface>) {
+        mlir::FunctionType ty = genFunctionType();
+        if (!func.getBlocks().empty())
+          fir::emitFatalError(
+              func.getLoc(),
+              "conflicting procedure definition with mismatched signature");
+        if (func.getFunctionType() != ty) {
+          func.setType(ty);
+          for (const auto &placeHolder : llvm::enumerate(inputs))
+            func.setArgAttrs(placeHolder.index(),
+                             placeHolder.value().attributes);
+        }
+      }
+    }
     if (!func) {
       mlir::Location loc = side().getCalleeLocation();
       mlir::MLIRContext &mlirContext = converter.getMLIRContext();
diff --git a/flang/test/Semantics/extrn_subp.f90 b/flang/test/Semantics/extrn_subp.f90
new file mode 100644
index 0000000000000..67b3b02a85363
--- /dev/null
+++ b/flang/test/Semantics/extrn_subp.f90
@@ -0,0 +1,20 @@
+! RUN: flang %s
+
+Module m1
+  external::sub
+  type ty
+    procedure(),pointer,nopass :: ptr5=>sub
+  end type
+  procedure(),pointer:: ptr6=>sub
+end module
+ 
+use m1
+  integer::jj =4
+  call ptr6(10)
+  print*,"Pass"
+end
+ 
+subroutine sub(a)
+  integer::a
+  print*,"sub"
+end subroutine
\ No newline at end of file

``````````

</details>


https://github.com/llvm/llvm-project/pull/183268