[flang-commits] [flang] [flang][hlfir] Reset lower bounds to one when bufferizing hlfir.as_expr move (PR #202406)

[via flang-commits]

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@@ -156,8 +156,24 @@ struct AsExprOpConversion : public mlir::OpConversionPattern<hlfir::AsExprOp> {
     fir::FirOpBuilder builder(rewriter, module);
     if (asExpr.isMove()) {
       // Move variable storage for the hlfir.expr buffer.
-      mlir::Value bufferizedExpr = packageBufferizedExpr(
-          loc, builder, hlfir::Entity{adaptor.getVar()}, adaptor.getMustFree());
+      hlfir::Entity storage{adaptor.getVar()};
+      // An hlfir.expr has lower bounds of one. When the moved storage is a
+      // descriptor that may carry non-default lower bounds (e.g. an allocatable
+      // or pointer function result used in a structure constructor), rebox it
+      // to lower bounds of one so they are not propagated to the users of the
+      // expression. This does not copy the data.
+      if (storage.isArray() && mlir::isa<fir::BaseBoxType>(storage.getType()) &&
+          storage.mayHaveNonDefaultLowerBounds()) {
+        mlir::Value one =
+            builder.createIntegerConstant(loc, builder.getIndexType(), 1);
+        llvm::SmallVector<mlir::Value> ones(storage.getRank(), one);
+        mlir::Value shift = builder.genShift(loc, ones);
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jeanPerier wrote:

No need to add the shift. No shift is equivalent to a shift with all ones and less IR/compiler code.

https://github.com/llvm/llvm-project/pull/202406