Subzero. Native 64-bit int arithmetic on x86-64.

src/IceELFSection.h

Index: src/IceELFSection.h
diff --git a/src/IceELFSection.h b/src/IceELFSection.h
index 5cf89a5287795572b0123557039def15aee9fa5a..961d8d24e3c1dbb1918a0305ec15a524015cacb2 100644
--- a/src/IceELFSection.h
+++ b/src/IceELFSection.h
@@ -362,8 +362,7 @@ void ELFRelocationSection::writeData(const GlobalContext &Ctx, ELFStreamer &Str,
       llvm::report_fatal_error("Missing symbol mentioned in reloc");
 
     if (IsELF64) {
-      llvm_unreachable(
-          "Not tested -- check that Fixup.offset() is correct even for pc-rel");
+      // TODO(jpp): check that Fixup.offset() is correct even for pc-rel.
       Elf64_Rela Rela;
       Rela.r_offset = Fixup.position();
       Rela.setSymbolAndType(Symbol->getNumber(), Fixup.kind());