[flang-commits] [flang] [flang] Implement !DIR$ VECTOR ALWAYS (PR #93830)

[David Truby via flang-commits]

================
@@ -2508,8 +2531,30 @@ class FirConverter : public Fortran::lower::AbstractConverter {
     }
   }
 
-  void genFIR(const Fortran::parser::CompilerDirective &) {
-    // TODO
+  void attachLoopDirective(const Fortran::parser::CompilerDirective &dir,
+                           Fortran::lower::pft::Evaluation *e) {
+    while (e->isDirective()) {
+      e = e->lexicalSuccessor;
+    }
+
+    if (e->isA<Fortran::parser::NonLabelDoStmt>()) {
+      e->dirs.push_back(&dir);
+    } else {
+      fir::emitFatalError(toLocation(),
+                          "loop directive must appear before a loop");
----------------
DavidTruby wrote:

I'm concerned about allowing this in the presence of OpenACC/OpenMP loops as I think that opens a whole can of worms for implementation. For what it's worth, clang doesn't allow the equivalent clang pragma in the presence of OpenMP directives:
```
❯ cat test.cpp
void foo(int* x, int n) {
#pragma clang loop vectorize(enable)
#pragma omp parallel for
        for (int i = 0; i < n; ++i)
                x[i] = i+i;

}
❯ clang++ -fopenmp test.cpp
test.cpp:3:1: error: expected a for, while, or do-while loop to follow '#pragma clang loop'
    3 | #pragma omp parallel for
      | ^
1 error generated.
```

https://github.com/llvm/llvm-project/pull/93830