trivial fix for PR20314

Make sure that the AddrInst is an Instruction.

llvm-svn: 213197

llvm/lib/CodeGen/CodeGenPrepare.cpp

@@ -2130,8 +2130,11 @@ bool AddressingModeMatcher::MatchOperationAddr(User *AddrInst, unsigned Opcode,
     return true;
   }
   case Instruction::SExt: {
+    // Make sure this isn't a ConstantExpr (PR20314).
+    Instruction *SExt = dyn_cast<Instruction>(AddrInst);
+    if (!SExt) return false;
+
     // Try to move this sext out of the way of the addressing mode.
-    Instruction *SExt = cast<Instruction>(AddrInst);
     // Ask for a method for doing so.
     TypePromotionHelper::Action TPH = TypePromotionHelper::getAction(
         SExt, InsertedTruncs, TLI, PromotedInsts);

llvm/test/CodeGen/X86/pr20314.ll

@@ -0,0 +1,14 @@
+; RUN: llc < %s -mtriple=x86_64-pc-linux
+
+; No check as PR20314 is a crashing bug.
+
+@c = common global [2 x i32] zeroinitializer, align 4
+@a = common global i32 0, align 4
+@b = internal unnamed_addr constant [2 x i8] c"\01\00", align 1
+
+define i32 @main() {
+entry:
+  %foo = load i8* getelementptr ([2 x i8]* @b, i64 0, i64 sext (i8 or (i8 zext (i1 icmp eq (i32* getelementptr inbounds ([2 x i32]* @c, i64 0, i64 1), i32* @a) to i8), i8 1) to i64)), align 1
+  ret i32 0
+}
+