Backport https://reviews.llvm.org/D27481

See rust-lang/rust#37508

Author: aidanhs

lib/Target/X86/X86InstrBuilder.h

@@ -128,6 +128,11 @@ addOffset(const MachineInstrBuilder &MIB, int Offset) {
   return MIB.addImm(1).addReg(0).addImm(Offset).addReg(0);
 }
 
+static inline const MachineInstrBuilder &
+addOffset(const MachineInstrBuilder &MIB, const MachineOperand& Offset) {
+  return MIB.addImm(1).addReg(0).addOperand(Offset).addReg(0);
+}
+
 /// addRegOffset - This function is used to add a memory reference of the form
 /// [Reg + Offset], i.e., one with no scale or index, but with a
 /// displacement. An example is: DWORD PTR [EAX + 4].

lib/Target/X86/X86InstrInfo.cpp

@@ -3084,7 +3084,7 @@ X86InstrInfo::convertToThreeAddress(MachineFunction::iterator &MFI,
     NewMI = addOffset(BuildMI(MF, MI.getDebugLoc(), get(X86::LEA64r))
                           .addOperand(Dest)
                           .addOperand(Src),
-                      MI.getOperand(2).getImm());
+                      MI.getOperand(2));
     break;
   case X86::ADD32ri:
   case X86::ADD32ri8:
@@ -3107,7 +3107,7 @@ X86InstrInfo::convertToThreeAddress(MachineFunction::iterator &MFI,
     if (ImplicitOp.getReg() != 0)
       MIB.addOperand(ImplicitOp);
 
-    NewMI = addOffset(MIB, MI.getOperand(2).getImm());
+    NewMI = addOffset(MIB, MI.getOperand(2));
     break;
   }
   case X86::ADD16ri:
@@ -3121,7 +3121,7 @@ X86InstrInfo::convertToThreeAddress(MachineFunction::iterator &MFI,
     NewMI = addOffset(BuildMI(MF, MI.getDebugLoc(), get(X86::LEA16r))
                           .addOperand(Dest)
                           .addOperand(Src),
-                      MI.getOperand(2).getImm());
+                      MI.getOperand(2));
     break;
   }