XFAIL external resources test cases on big-endian systems

[uweigand]

Summary

Since https://reviews.llvm.org/D126446 was merged, the builder on s390x is red, as parsing external resources does not work correctly on big-endian machines. To make the CI green again, this patch:

• Always reads and writes the "alignment" tag in little-endian byte order (this fixes failing assertions)
• XFAIL the test case that is still failing after that fix

[mehdi_amini]

Can you split the unrelated change in a separate commit?

Feel free to XFAIL for your bit without a review.

[rriddle]

In D129483#3643044, @mehdi_amini wrote:

Can you split the unrelated change in a separate commit?

Feel free to XFAIL for your bit without a review.

+1, LGTM otherwise

[uweigand]

I've now committed both changes in separate commits. Thanks!

[uweigand]

SystemZ mlir builder is now back to green. Of course, the underlying issue still needs to be fixed to we can remove the XFAIL again.

mlir/lib/IR/AsmPrinter.cpp

public:
     void buildString(StringRef key, StringRef data) final {
       printFn(key, [&](raw_ostream &os) { p.printEscapedString(data); });
     }
 
     void buildBlob(StringRef key, ArrayRef<char> data,
                    uint32_t dataAlignment) final {
       printFn(key, [&](raw_ostream &os) {
         // Store the blob in a hex string containing the alignment and the data.
+        llvm::support::ulittle32_t dataAlignmentLE(dataAlignment);
         os << "\"0x"
-           << llvm::toHex(StringRef(reinterpret_cast<char *>(&dataAlignment),
+           << llvm::toHex(StringRef(reinterpret_cast<char *>(&dataAlignmentLE),
                                     sizeof(dataAlignment)))
            << llvm::toHex(StringRef(data.data(), data.size())) << "\"";
       });
     }
 
   private:
     OperationPrinter &p;
     PrintFn printFn;

mlir/lib/Parser/Parser.cpp

 #include "mlir/IR/Verifier.h"
 #include "mlir/Parser/AsmParserState.h"
 #include "mlir/Parser/CodeComplete.h"
 #include "mlir/Parser/Parser.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/ADT/bit.h"
+#include "llvm/Support/Endian.h"
 #include "llvm/Support/PrettyStackTrace.h"
 #include "llvm/Support/SourceMgr.h"
 #include <algorithm>
 
 using namespace mlir;
 using namespace mlir::detail;
 using llvm::MemoryBuffer;
 using llvm::SourceMgr;
parseAsBlob(BlobAllocatorFn allocator) const final {
 
     // Extract the alignment of the blob data, which gets stored at the
     // beginning of the string.
     if (blobData->size() < sizeof(uint32_t)) {
       return p.emitError(value.getLoc(),
                          "expected hex string blob for key '" + key +
                              "' to encode alignment in first 4 bytes");
     }
-    uint32_t align = 0;
+    llvm::support::ulittle32_t align;
     memcpy(&align, blobData->data(), sizeof(uint32_t));
 
     // Get the data portion of the blob.
     StringRef data = StringRef(*blobData).drop_front(sizeof(uint32_t));
     if (data.empty())
       return AsmResourceBlob();
 
     // Allocate memory for the blob using the provided allocator and copy the