[SystemZ] Add MCJIT support

Another step towards reinstating the SystemZ backend.  I'll commit
the configure changes separately (TARGET_HAS_JIT etc.), then commit
a patch to enable the MCJIT tests on SystemZ.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181015 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
index 7b32db7..14c0cd8 100644
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
@@ -234,6 +234,12 @@
   Check(Section.isReadOnlyData(IsReadOnly));
   Check(Section.getSize(DataSize));
   Check(Section.getName(Name));
+  if (StubSize > 0) {
+    unsigned StubAlignment = getStubAlignment();
+    unsigned EndAlignment = (DataSize | Alignment) & -(DataSize | Alignment);
+    if (StubAlignment > EndAlignment)
+      StubBufSize += StubAlignment - EndAlignment;
+  }
 
   unsigned Allocate;
   unsigned SectionID = Sections.size();
@@ -371,6 +377,13 @@
     writeInt32BE(Addr+40, 0x4E800420); // bctr
 
     return Addr;
+  } else if (Arch == Triple::systemz) {
+    writeInt16BE(Addr,    0xC418);     // lgrl %r1,.+8
+    writeInt16BE(Addr+2,  0x0000);
+    writeInt16BE(Addr+4,  0x0004);
+    writeInt16BE(Addr+6,  0x07F1);     // brc 15,%r1
+    // 8-byte address stored at Addr + 8
+    return Addr;
   }
   return Addr;
 }