Index: llvm/trunk/lib/Target/X86/AsmParser/X86AsmParser.cpp
===================================================================
--- llvm/trunk/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ llvm/trunk/lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -840,6 +840,11 @@
   // If we have both a base register and an index register make sure they are
   // both 64-bit or 32-bit registers.
   // To support VSIB, IndexReg can be 128-bit or 256-bit registers.
+
+  if ((BaseReg == X86::RIP && IndexReg != 0) || (IndexReg == X86::RIP)) {
+    ErrMsg = "invalid base+index expression";
+    return true;
+  }
   if (BaseReg != 0 && IndexReg != 0) {
     if (X86MCRegisterClasses[X86::GR64RegClassID].contains(BaseReg) &&
         (X86MCRegisterClasses[X86::GR16RegClassID].contains(IndexReg) ||
@@ -1781,10 +1786,12 @@
       !ParseRegister(RegNo, Start, End)) {
     // If this is a segment register followed by a ':', then this is the start
     // of a segment override, otherwise this is a normal register reference.
-    // In case it is a normal register and there is ptr in the operand this 
+    // In case it is a normal register and there is ptr in the operand this
     // is an error
-    if (getLexer().isNot(AsmToken::Colon)){
-      if (PtrInOperand){
+    if (RegNo == X86::RIP)
+      return ErrorOperand(Start, "rip can only be used as a base register");
+    if (getLexer().isNot(AsmToken::Colon)) {
+      if (PtrInOperand) {
         return ErrorOperand(Start, "expected memory operand after "
                                    "'ptr', found register operand instead");
       }
@@ -1865,6 +1872,11 @@
             SMRange(Start, End));
       return nullptr;
     }
+    if (RegNo == X86::RIP) {
+      Error(Start, "%rip can only be used as a base register",
+            SMRange(Start, End));
+      return nullptr;
+    }
 
     // If this is a segment register followed by a ':', then this is the start
     // of a memory reference, otherwise this is a normal register reference.
@@ -2044,7 +2056,16 @@
     // like "1(%eax,,1)", the assembler doesn't. Use "eiz" or "riz" for this.
     if (getLexer().is(AsmToken::Percent)) {
       SMLoc L;
-      if (ParseRegister(IndexReg, L, L)) return nullptr;
+      if (ParseRegister(IndexReg, L, L))
+        return nullptr;
+      if (BaseReg == X86::RIP) {
+        Error(IndexLoc, "%rip as base register can not have an index register");
+        return nullptr;
+      }
+      if (IndexReg == X86::RIP) {
+        Error(IndexLoc, "%rip is not allowed as an index register");
+        return nullptr;
+      }
 
       if (getLexer().isNot(AsmToken::RParen)) {
         // Parse the scale amount:
Index: llvm/trunk/lib/Target/X86/X86RegisterInfo.td
===================================================================
--- llvm/trunk/lib/Target/X86/X86RegisterInfo.td
+++ llvm/trunk/lib/Target/X86/X86RegisterInfo.td
@@ -345,6 +345,8 @@
 // GR64 - 64-bit GPRs. This oddly includes RIP, which isn't accurate, since
 // RIP isn't really a register and it can't be used anywhere except in an
 // address, but it doesn't cause trouble.
+// FIXME: it *does* cause trouble - CheckBaseRegAndIndexReg() has extra
+// tests because of the inclusion of RIP in this register class.
 def GR64 : RegisterClass<"X86", [i64], 64,
                          (add RAX, RCX, RDX, RSI, RDI, R8, R9, R10, R11,
                               RBX, R14, R15, R12, R13, RBP, RSP, RIP)>;
Index: llvm/trunk/test/MC/X86/intel-syntax-error.s
===================================================================
--- llvm/trunk/test/MC/X86/intel-syntax-error.s
+++ llvm/trunk/test/MC/X86/intel-syntax-error.s
@@ -24,3 +24,8 @@
 mov eax, DWORD PTR arr[esi*4]
 //CHECK: error: cannot use more than one symbol in memory operand
 mov eax, DWORD PTR arr[i]
+//CHECK: error: rip can only be used as a base register
+.code64
+mov rax, rip
+//CHECK: error: invalid base+index expression
+mov rbx, [rax+rip]
Index: llvm/trunk/test/MC/X86/x86_errors.s
===================================================================
--- llvm/trunk/test/MC/X86/x86_errors.s
+++ llvm/trunk/test/MC/X86/x86_errors.s
@@ -74,3 +74,11 @@
 
 // 32: error: register %dr8 is only available in 64-bit mode
 movl %edx, %dr8
+
+// 32: error: register %rip is only available in 64-bit mode
+// 64: error: %rip can only be used as a base register
+mov %rip, %rax
+
+// 32: error: register %rax is only available in 64-bit mode
+// 64: error: %rip is not allowed as an index register
+mov (%rax,%rip), %rbx