Revert "[CodeGenCXX] Treat 'this' as noalias in constructors"

This reverts commit https://reviews.llvm.org/rL344150 which causes
MachineOutliner related failures on the ppc64le multistage buildbot.

llvm-svn: 344526
diff --git a/clang/test/CodeGenCXX/float16-declarations.cpp b/clang/test/CodeGenCXX/float16-declarations.cpp
index 61933de..e82c05e 100644
--- a/clang/test/CodeGenCXX/float16-declarations.cpp
+++ b/clang/test/CodeGenCXX/float16-declarations.cpp
@@ -103,7 +103,7 @@
 
   C1 c1(f1l);
 // CHECK-DAG:  [[F1L:%[a-z0-9]+]] = load half, half* %{{.*}}, align 2
-// CHECK-DAG:  call void @_ZN2C1C2EDF16_(%class.C1* noalias %{{.*}}, half %{{.*}})
+// CHECK-DAG:  call void @_ZN2C1C2EDF16_(%class.C1* %{{.*}}, half %{{.*}})
 
   S1<_Float16> s1 = { 132.f16 };
 // CHECK-DAG: @_ZZ4mainE2s1 = private unnamed_addr constant %struct.S1 { half 0xH5820 }, align 2