Subzero. X8664. Enables RIP-based addressing mode.

src/IceInstX8664.cpp

Index: src/IceInstX8664.cpp
diff --git a/src/IceInstX8664.cpp b/src/IceInstX8664.cpp
index a7236a3f67cd6f9de5992f8692927db97e7b81e3..6746b695730f7db1fc5a2af265fb90a9931f3c80 100644
--- a/src/IceInstX8664.cpp
+++ b/src/IceInstX8664.cpp
@@ -135,7 +135,14 @@ void TargetX8664Traits::X86OperandMem::emit(const Cfg *Func) const {
     // TODO(sehr): ConstantRelocatable still needs updating for
     // rematerializable base/index and Disp.
     assert(Disp == 0);
+    if (Base == nullptr && Index == nullptr && NeedSandboxing) {
+      llvm::report_fatal_error(
+          "llvm-mc encodes rip-relative instructions incorrectly. Why?");
+      // Native code should be fine. The relocatable will be emitted with a
+      // regular, absolute relocation.
+    }
     const bool UseNonsfi = Func->getContext()->getFlags().getUseNonsfi();
+    assert(!UseNonsfi);
     CR->emitWithoutPrefix(Func->getTarget(), UseNonsfi ? "@GOTOFF" : "");
   } else {
     llvm_unreachable("Invalid offset type for x86 mem operand");
@@ -256,10 +263,12 @@ TargetX8664Traits::Address TargetX8664Traits::X86OperandMem::toAsmAddress(
   if (getOffset() != nullptr) {
     if (const auto *CI = llvm::dyn_cast<ConstantInteger32>(getOffset())) {
       Disp += static_cast<int32_t>(CI->getValue());
-    } else if (const auto CR =
+    } else if (const auto *CR =
                    llvm::dyn_cast<ConstantRelocatable>(getOffset())) {
-      Disp = CR->getOffset();
-      Fixup = Asm->createFixup(FK_Abs, CR);
+      const auto FixupKind =
+          (getBase() != nullptr || getIndex() != nullptr) ? FK_Abs : FK_PcRel;
+      Disp = CR->getOffset() - (FixupKind == FK_PcRel ? 4 : 0);
+      Fixup = Asm->createFixup(FixupKind, CR);
     } else {
       llvm_unreachable("Unexpected offset type");
     }
@@ -290,7 +299,7 @@ TargetX8664Traits::Address TargetX8664Traits::X86OperandMem::toAsmAddress(
                                   Fixup);
   }
 
-  return X8664::Traits::Address(Disp, Fixup);
+  return X8664::Traits::Address::RipRelative(Disp, Fixup);
 }
 
 TargetX8664Traits::Address