Fix bug with arguments passed in reverse. ch6egs1, 615t621, e12

Author: schweitzpgi

flang/include/flang/Optimizer/Dialect/FIROps.td

@@ -1343,6 +1343,16 @@ def fir_ArrayLoadOp : fir_Op<"array_load", [AttrSizedOperandSegments]> {
   let summary = "Load an array as a value.";
 
   let description = [{
+    This operation taken with array_merge_store captures Fortran's
+    copy-in/copy-out semantics. One way to think of this is that array_load
+    creates a snapshot copy of the entire array. This copy can then be used
+    as the "original value" of the array while the array's new value is
+    computed. The array_merge_store operation is the copy-out semantics, which
+    merge the updates with the original array value to produce the final array
+    result. This abstracts the copy operations as opposed to always creating
+    copies or requiring dependence analysis be performed on the syntax trees
+    and before lowering to the IR.
+
     Load an entire array as a single SSA value.
 
     ```fortran

flang/lib/Lower/ConvertExpr.cpp

@@ -2520,9 +2520,9 @@ createCharArrayAmend(mlir::Location loc, fir::FirOpBuilder &builder,
   fir::factory::CharacterExprHelper helper{builder, loc};
   if (!bounds.empty()) {
     dstChar = helper.createSubstring(dstChar, bounds);
-    fir::factory::genCharacterCopy(dstChar.getAddr(), dstChar.getLen(),
-                                   fir::getBase(srcExv), fir::getLen(srcExv),
-                                   builder, loc);
+    fir::factory::genCharacterCopy(fir::getBase(srcExv), fir::getLen(srcExv),
+                                   dstChar.getAddr(), dstChar.getLen(), builder,
+                                   loc);
     // Update the LEN to the substring's LEN.
     dstLen = dstChar.getLen();
   }