Revert "Allow FDE references outside the +/-2GB range supported by PC relative offsets for code models other than small/medium. For JIT application, memory layout is less controlled and can result in truncations otherwise."

This reverts commit r222538.

It's causing test failures for CFI, at least on Darwin:

http://lab.llvm.org:8080/green/job/clang-stage1-cmake-RA-incremental/1189/
http://lab.llvm.org:8080/green/job/clang-stage1-configure-RA_check/1391/

Note that the previous incremental build was on r222537, and the CFI
tests weren't failing:
http://lab.llvm.org:8080/green/job/clang-stage1-cmake-RA-incremental/1188/

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222542 91177308-0d34-0410-b5e6-96231b3b80d8
Add a feature flag for slow 32-byte unaligned memory accesses [x86].

This patch adds a feature flag to avoid unaligned 32-byte load/store AVX codegen
for Sandy Bridge and Ivy Bridge. There is no functionality change intended for 
those chips. Previously, the absence of AVX2 was being used as a proxy to detect
this feature. But that hindered codegen for AVX-enabled AMD chips such as btver2
that do not have the 32-byte unaligned access slowdown.

Performance measurements are included in PR21541 ( http://llvm.org/bugs/show_bug.cgi?id=21541 ).

Differential Revision: http://reviews.llvm.org/D6355



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222544 91177308-0d34-0410-b5e6-96231b3b80d8