[JITLink] Add support for MachO/x86-64 UNSIGNED relocs with length=2.

MachO/x86-64 UNSIGNED relocs are almost always 64-bit (length=3), but UNSIGNED
relocs of length=2 are allowed if the target resides in the low 32-bits. This
patch adds support for such relocations in JITLink (previously they would have
triggered an unsupported relocation error).

llvm-svn: 367764

1 files changed, 22 insertions, 2 deletions

diff --git a/llvm/lib/ExecutionEngine/JITLink/MachO_x86_64.cpp b/llvm/lib/ExecutionEngine/JITLink/MachO_x86_64.cpp
index 6b2b39248a0..52481f8436e 100644
--- a/llvm/lib/ExecutionEngine/JITLink/MachO_x86_64.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/MachO_x86_64.cpp
@@ -40,8 +40,12 @@ private:
   getRelocationKind(const MachO::relocation_info &RI) {
     switch (RI.r_type) {
     case MachO::X86_64_RELOC_UNSIGNED:
-      if (!RI.r_pcrel && RI.r_length == 3)
-        return RI.r_extern ? Pointer64 : Pointer64Anon;
+      if (!RI.r_pcrel) {
+        if (RI.r_length == 3)
+          return RI.r_extern ? Pointer64 : Pointer64Anon;
+        else if (RI.r_extern && RI.r_length == 2)
+          return Pointer32;
+      }
       break;
     case MachO::X86_64_RELOC_SIGNED:
       if (RI.r_pcrel && RI.r_length == 2)
@@ -260,6 +264,13 @@ private:
             return TargetAtomOrErr.takeError();
           Addend = *(const ulittle32_t *)FixupContent;
           break;
+        case Pointer32:
+          if (auto TargetAtomOrErr = findAtomBySymbolIndex(RI))
+            TargetAtom = &*TargetAtomOrErr;
+          else
+            return TargetAtomOrErr.takeError();
+          Addend = *(const ulittle32_t *)FixupContent;
+          break;
         case Pointer64:
           if (auto TargetAtomOrErr = findAtomBySymbolIndex(RI))
             TargetAtom = &*TargetAtomOrErr;
@@ -526,6 +537,13 @@ private:
         *(little64_t *)FixupPtr = Value;
       break;
     }
+    case Pointer32: {
+      uint64_t Value = E.getTarget().getAddress() + E.getAddend();
+      if (Value > std::numeric_limits<uint32_t>::max())
+        return targetOutOfRangeError(A, E);
+      *(ulittle32_t *)FixupPtr = Value;
+      break;
+    }
     default:
       llvm_unreachable("Unrecognized edge kind");
     }
@@ -565,6 +583,8 @@ StringRef getMachOX86RelocationKindName(Edge::Kind R) {
   switch (R) {
   case Branch32:
     return "Branch32";
+  case Pointer32:
+    return "Pointer32";
   case Pointer64:
     return "Pointer64";
   case Pointer64Anon: