CodeGen: Don't follow aliases when extracting type info.

This fixes a crash in the case where the type info object is an alias
pointing to a non-zero offset within a global or is otherwise unanalyzable
by the stripPointerCasts() function. Looking through the alias is not the
right thing to do anyway for similar reasons as D65118.

Differential Revision: https://reviews.llvm.org/D65314

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@367696 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/Analysis.cpp

@@ -156,7 +156,7 @@ void llvm::computeValueLLTs(const DataLayout &DL, Type &Ty,
 
 /// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V.
 GlobalValue *llvm::ExtractTypeInfo(Value *V) {
-  V = V->stripPointerCasts();
+  V = V->stripPointerCastsNoFollowAliases();
   GlobalValue *GV = dyn_cast<GlobalValue>(V);
   GlobalVariable *Var = dyn_cast<GlobalVariable>(V);
 

test/CodeGen/X86/typeid-alias.ll

@@ -0,0 +1,18 @@
+; Test that we don't crash in the case where the type info object is an
+; alias pointing to a non-zero offset within a global.
+
+; RUN: llc < %s | FileCheck %s
+
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.exception = type { i8, i8, i32, i8*, i8*, i32, i8* }
+@g = global %struct.exception zeroinitializer
+@a = alias %struct.exception, %struct.exception* inttoptr (i64 add (i64 ptrtoint (%struct.exception* @g to i64), i64 1297036692682702848) to %struct.exception*)
+
+define i32 @typeid() {
+  ; CHECK: movl $1, %eax
+  %eh_typeid = tail call i32 @llvm.eh.typeid.for( i8* getelementptr (%struct.exception, %struct.exception* @a, i32 0, i32 0))
+  ret i32 %eh_typeid
+}
+
+declare i32 @llvm.eh.typeid.for(i8*)