[flang-commits] [flang] [flang] Lowering fortran structured do-while loops to `scf.while` (PR #177476)

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@@ -1060,7 +1163,11 @@ class PFTBuilder {
                 eval.isUnstructured = true; // real-valued loop control
             } else if (std::get_if<parser::ScalarLogicalExpr>(
                            &loopControl->u)) {
-              eval.isUnstructured = true; // while loop
+              // DO WHILE structured/unstructured classification is handled by
+              // branch analysis plus the classifyDoWhiles() post-pass below
+              // when -lower-do-while-to-scf-while is enabled.
+              if (!Fortran::lower::lowerDoWhileToSCFWhile)
+                eval.isUnstructured = true; // while loop
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jeanPerier wrote:

I do not understand why all the other changes to this file are needed. The visitor is already suposed to be doing some classification/analysis of the branches.

Aside from the loopControl, DO WHILE are structurally similar to DO LOOP and I was expecting the analysis that is already here would do everything already. Why did you need a custom handling for DO WHILE with classifyDoWhiles?

https://github.com/llvm/llvm-project/pull/177476