[flang] Handle Hollerith in data statement initialization in big endian (#103451)

Update to read the Hollerith literal in reverse order for big endian
environment.

Author: kkwli

flang/lib/Evaluate/tools.cpp

@@ -1300,12 +1300,12 @@ std::optional<Expr<SomeType>> HollerithToBOZ(FoldingContext &context,
     const Expr<SomeType> &expr, const DynamicType &type) {
   if (std::optional<std::string> chValue{GetScalarConstantValue<Ascii>(expr)}) {
     // Pad on the right with spaces when short, truncate the right if long.
-    // TODO: big-endian targets
     auto bytes{static_cast<std::size_t>(
         ToInt64(type.MeasureSizeInBytes(context, false)).value())};
     BOZLiteralConstant bits{0};
     for (std::size_t j{0}; j < bytes; ++j) {
-      char ch{j >= chValue->size() ? ' ' : chValue->at(j)};
+      auto idx{isHostLittleEndian ? j : bytes - j - 1};
+      char ch{idx >= chValue->size() ? ' ' : chValue->at(idx)};
       BOZLiteralConstant chBOZ{static_cast<unsigned char>(ch)};
       bits = bits.IOR(chBOZ.SHIFTL(8 * j));
     }

flang/test/Semantics/data08.f90

@@ -1,12 +1,19 @@
-! RUN: %flang_fc1 -fdebug-dump-symbols -pedantic %s 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -fdebug-dump-symbols -pedantic %s 2>&1 | FileCheck %s \
+! RUN:   --check-prefixes=%if system-aix %{"CHECK","BE"%} \
+! RUN:                    %else %{"CHECK","LE"%}
+
 ! CHECK: DATA statement value initializes 'jx' of type 'INTEGER(4)' with CHARACTER
 ! CHECK: DATA statement value initializes 'jy' of type 'INTEGER(4)' with CHARACTER
 ! CHECK: DATA statement value initializes 'jz' of type 'INTEGER(4)' with CHARACTER
 ! CHECK: DATA statement value initializes 'kx' of type 'INTEGER(8)' with CHARACTER
-! CHECK: jx (InDataStmt) size=4 offset=0: ObjectEntity type: INTEGER(4) init:1684234849_4
-! CHECK: jy (InDataStmt) size=4 offset=4: ObjectEntity type: INTEGER(4) init:543384161_4
-! CHECK: jz (InDataStmt) size=4 offset=8: ObjectEntity type: INTEGER(4) init:1684234849_4
-! CHECK: kx (InDataStmt) size=8 offset=16: ObjectEntity type: INTEGER(8) init:7523094288207667809_8
+! LE: jx (InDataStmt) size=4 offset=0: ObjectEntity type: INTEGER(4) init:1684234849_4
+! BE: jx (InDataStmt) size=4 offset=0: ObjectEntity type: INTEGER(4) init:1633837924_4
+! LE: jy (InDataStmt) size=4 offset=4: ObjectEntity type: INTEGER(4) init:543384161_4
+! BE: jy (InDataStmt) size=4 offset=4: ObjectEntity type: INTEGER(4) init:1633837856_4
+! LE: jz (InDataStmt) size=4 offset=8: ObjectEntity type: INTEGER(4) init:1684234849_4
+! BE: jz (InDataStmt) size=4 offset=8: ObjectEntity type: INTEGER(4) init:1633837924_4
+! LE: kx (InDataStmt) size=8 offset=16: ObjectEntity type: INTEGER(8) init:7523094288207667809_8
+! BE: kx (InDataStmt) size=8 offset=16: ObjectEntity type: INTEGER(8) init:7017280452245743464_8
 
 integer :: jx, jy, jz
 integer(8) :: kx