[flang-commits] [flang] [Flang][MLIR] - Access the LEN for a `fir.boxchar<k>` and use it to set the bounds `omp.map.info` ops. (PR #134967)

[via flang-commits]

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@@ -268,8 +274,54 @@ static void bindEntryBlockArgs(lower::AbstractConverter &converter,
                                             cloneBounds(v.getLBounds())));
           },
           [&](const fir::CharBoxValue &v) {
-            converter.bindSymbol(
-                sym, fir::CharBoxValue(arg, cloneBound(v.getLen())));
+            // In some cases, v.len could reference the input to the
+            // hlfir.declare which is the corresponding v.addr. While this isn't
+            // a big problem by itself, it is desirable to extract this out of
+            // v.addr itself since it's first result will be of type
+            // fir.boxchar<>. For example, consider the following
+            //
+            // func.func private @_QFPrealtest(%arg0: !fir.boxchar<1>)
+            //  %2 = fir.dummy_scope : !fir.dscope
+            //  %3:2 = fir.unboxchar %arg0 : (!fir.boxchar<1>) ->
+            //         (!fir.ref<!fir.char<1,?>>, index)
+            //  %4:2 = hlfir.declare (%3#0, %3#1, %2):(!fir.ref<!fir.char<1,?>>,
+            //                        index,!fir.dscope) ->
+            //                       (!fir.boxchar<1>, !fir.ref<!fir.char<1,?>>)
+
+            // In the case above,
+            // v.addr is
+            //  %4:2 = hlfir.declare (%3#0, %3#1, %2):(!fir.ref<!fir.char<1,?>>,
+            //                        index,!fir.dscope) ->
+            //                       (!fir.boxchar<1>, !fir.ref<!fir.char<1,?>>)
+            // v.len is
+            //  %3:2 = fir.unboxchar %arg0 : (!fir.boxchar<1>) ->
+            //         (!fir.ref<!fir.char<1,?>>, index)
+
+            // Mapping this to the target will create a use of %arg0 on the
+            // target. Since omp.target is IsolatedFromAbove, %arg0 will have to
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agozillon wrote:

https://github.com/llvm/llvm-project/blob/main/flang/lib/Lower/OpenMP/OpenMP.cpp#L1371 this is the segment I believe, we map or clone across dependencies on the bounds

https://github.com/llvm/llvm-project/pull/134967