[JITLink][PowerPC] Fix relocations in stubs for ppc64 big-endian target

[lkail]

Summary

Offset and addend are fixed for big-endian stubs.

[lhames]

LGTM. Thanks @lkail!

llvm/include/llvm/ExecutionEngine/JITLink/ppc64.h

 inline PLTCallStubInfo pickStub(PLTCallStubKind StubKind) {
   constexpr bool isLE = Endianness == support::endianness::little;
   switch (StubKind) {
   case LongBranch: {
     ArrayRef<char> Content =
         isLE ? PointerJumpStubContent_little : PointerJumpStubContent_big;
     // Skip save r2.
     Content = Content.slice(4);
+    size_t Offset = isLE ? 0 : 2;
     return PLTCallStubInfo{
         Content,
-        {{TOCDelta16HA, 0, 0}, {TOCDelta16LO, 4, 0}},
+        {{TOCDelta16HA, Offset, 0}, {TOCDelta16LO, Offset + 4, 0}},
     };
   }
   case LongBranchSaveR2: {
     ArrayRef<char> Content =
         isLE ? PointerJumpStubContent_little : PointerJumpStubContent_big;
+    size_t Offset = isLE ? 4 : 6;
     return PLTCallStubInfo{
         Content,
-        {{TOCDelta16HA, 4, 0}, {TOCDelta16LO, 8, 0}},
+        {{TOCDelta16HA, Offset, 0}, {TOCDelta16LO, Offset + 4, 0}},
     };
   }
   case LongBranchNoTOC: {
     ArrayRef<char> Content = isLE ? PointerJumpStubNoTOCContent_little
                                   : PointerJumpStubNoTOCContent_big;
+    size_t Offset = isLE ? 16 : 18;
+    Edge::AddendT Addend = isLE ? 8 : 10;
     return PLTCallStubInfo{
         Content,
-        {{Delta16HA, 16, 8}, {Delta16LO, 20, 12}},
+        {{Delta16HA, Offset, Addend}, {Delta16LO, Offset + 4, Addend + 4}},
     };
   }
   }
   llvm_unreachable("Unknown PLTCallStubKind enum");
 }
 
 inline Symbol &createAnonymousPointer(LinkGraph &G, Section &PointerSection,
                                       Symbol *InitialTarget = nullptr,

llvm/test/ExecutionEngine/JITLink/ppc64/ELF_ppc64_relocations.s

 # RUN: rm -rf %t && mkdir -p %t
 # RUN: llvm-mc --triple=powerpc64le-unknown-linux-gnu --filetype=obj -o \
 # RUN:   %t/elf_reloc.o %s
 # RUN: llvm-jitlink --noexec \
 # RUN:              --abs external_data=0xdeadbeef \
 # RUN:              --abs external_func=0xcafef00d \
 # RUN:              --abs external_func_notoc=0x88880000 \
 # RUN:              --check %s %t/elf_reloc.o
 # RUN: llvm-mc --triple=powerpc64-unknown-linux-gnu --filetype=obj -o \
 # RUN:   %t/elf_reloc.o %s
-# RUN: not llvm-jitlink --noexec \
+# RUN: llvm-jitlink --noexec \
 # RUN:              --abs external_data=0xdeadbeef \
 # RUN:              --abs external_func=0xcafef00d \
 # RUN:              --abs external_func_notoc=0x88880000 \
 # RUN:              --check %s %t/elf_reloc.o
 
 # jitlink-check: section_addr(elf_reloc.o, $__GOT) + 0x8000 = __TOC__
   .text
   .abiversion 2