[llvm-branch-commits] [clang] [flang] [mlir] [Flang][OpenMP] Improve implicit declare_target propagation (PR #214184)

[Sergio Afonso via llvm-branch-commits]

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@@ -1433,16 +1433,38 @@ static void getDeclareTargetInfo(
   } else {
     List<Clause> clauses = makeClauses(construct.v.Clauses(), semaCtx);
     if (clauses.empty()) {
+      // Case: implicit capture of the enclosing function/subroutine.
       Fortran::lower::pft::FunctionLikeUnit *owningProc =
           eval.getOwningProcedure();
-      // Main programs are never device routines. Skip them so that a bare
-      // '!$omp declare target' inside an interface body that lives in a named
-      // main program does not incorrectly mark _QQmain as a device function.
-      if (owningProc && !owningProc->isMainProgram()) {
-        // Case: declare target, implicit capture of enclosing
-        // function/subroutine.
+      bool owningProcNotMainProgram =
+          owningProc && !owningProc->isMainProgram();
+
+      const semantics::Symbol *owningSym =
+          owningProcNotMainProgram
+              ? &owningProc->getSubprogramSymbol()
+              : (owningProc ? owningProc->getMainProgramSymbol() : nullptr);
+
+      // A bare '!$omp declare target' may appear in the specification part of
+      // an interface body. In that case the PFT records the directive as an
+      // evaluation of the enclosing program unit rather than of the interface
+      // body's subprogram, so eval.getOwningProcedure() points at the main
+      // program. Detect this by comparing the program unit lexically containing
+      // the directive with the procedure currently being lowered; when they
+      // differ, the directive belongs to the interface-body subprogram, which
+      // is the symbol we must capture.
+      const semantics::Scope &progUnitScope =
+          semantics::GetProgramUnitContaining(
+              semaCtx.FindScope(construct.v.source));
+      const semantics::Symbol *lexicalSym = progUnitScope.symbol();
+
+      if (lexicalSym && lexicalSym != owningSym) {
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skatrak wrote:

Good catch, fixed it and added a test. I haven't tested it, but I suspect we currently have a similar bug in `declare simd`, which is what I based these changes on.

https://github.com/llvm/llvm-project/pull/214184