Index: lib/Transforms/IPO/MergeFunctions.cpp
===================================================================
--- lib/Transforms/IPO/MergeFunctions.cpp
+++ lib/Transforms/IPO/MergeFunctions.cpp
@@ -464,6 +464,8 @@
     if (C1->isNullValue() && C2->isNullValue() &&
         isEquivalentType(C1->getType(), C2->getType()))
       return true;
+    if (const Function *F = dyn_cast<Function>(C2))
+      if (F->isIntrinsic()) return false;
     // Try bitcasting C2 to C1's type. If the bitcast is legal and returns C1
     // then they must have equal bit patterns.
     return C1->getType()->canLosslesslyBitCastTo(C2->getType()) &&
Index: test/Transforms/MergeFunc/intrinsics.ll
===================================================================
--- /dev/null
+++ test/Transforms/MergeFunc/intrinsics.ll
@@ -0,0 +1,22 @@
+; RUN: opt -mergefunc -disable-output < %s
+; This used to crash because mergefunc created a bitcast of an intrinsic.
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare i64 @llvm.bswap.i64(i64) unnamed_addr nounwind readnone
+declare i8* @breaker(i8*) unnamed_addr
+
+; Function Attrs: inlinehint uwtable
+define void @bswap_caller(i64) unnamed_addr {
+entry-block:
+  call i64 @llvm.bswap.i64(i64 %0)
+  ret void
+}
+
+; Function Attrs: inlinehint uwtable
+define internal void @collider(i8*) unnamed_addr {
+entry-block:
+  call i8* @breaker(i8* %0)
+  ret void
+}