[X86] Don't randomly encode %rip where illegal

Differential Revision: https://reviews.llvm.org/D25112

llvm-svn: 283326
diff --git a/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp b/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
index 87364b2..170f55c 100644
--- a/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ b/llvm/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: