[PATCH] Fix a mergefunc crash caused by bitcasting intrinsics

[Björn Steinbrink]

  Generally skip the bitcast when dealing with function constants

  Bitcasting function constants is rather pointless here, as bitcasting one will
  not result in the other. So we can return early whenever one of the constants
  is a function, instead of having a special case for intrinsics.

http://reviews.llvm.org/D3437

CHANGE SINCE LAST DIFF
  http://reviews.llvm.org/D3437?vs=8691&id=8715#toc

Files:
  lib/Transforms/IPO/MergeFunctions.cpp
  test/Transforms/MergeFunc/intrinsics.ll

Index: lib/Transforms/IPO/MergeFunctions.cpp
===================================================================
--- lib/Transforms/IPO/MergeFunctions.cpp
+++ lib/Transforms/IPO/MergeFunctions.cpp
@@ -465,6 +465,8 @@
     if (C1->isNullValue() && C2->isNullValue() &&
         isEquivalentType(C1->getType(), C2->getType()))
       return true;
+    if (isa<Function>(V1) || isa<Function>(V2))
+      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
+}
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