fix PR5179 and correctly fix PR5831 to not miscompile.

The X86-64 ABI code didn't handle the case when a struct
would get classified and turn up as "NoClass INTEGER" for
example.  This is perfectly possible when the first slot
is all padding (e.g. due to empty base classes).  In this
situation, the first 8-byte doesn't take a register at all,
only the second 8-byte does.

This fixes this by enhancing the x86-64 abi stuff to allow
and handle this case, reverts the broken fix for PR5831,
and enhances the target independent stuff to be able to 
handle an argument value in registers being accessed at an
offset from the memory value.

This is the last x86-64 calling convention related miscompile
that I'm aware of.

llvm-svn: 109848

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/test/CodeGenCXX/mangle-exprs.cpp b/clang/test/CodeGenCXX/mangle-exprs.cpp
index d68425f5a57..7322171856d 100644
--- a/clang/test/CodeGenCXX/mangle-exprs.cpp
+++ b/clang/test/CodeGenCXX/mangle-exprs.cpp
@@ -39,6 +39,6 @@ namespace Casts {
   // CHECK: define weak_odr void @_ZN5Casts7static_ILj4EEEvPN9enable_ifIXleT_cvjLi4EEvE4typeE
   template void static_<4>(void*);
 
-  // CHECK: define weak_odr i8 @_ZN5Casts1fILi6EEENS_1TIXT_EEEv
+  // CHECK: define weak_odr void @_ZN5Casts1fILi6EEENS_1TIXT_EEEv
   template T<6> f<6>();
 }