[PATCH] [COFF] Add support for .secref and .offset directives

[Rafael Ávila de Espíndola]

================
Comment at: lib/MC/MCAssembler.cpp:947
@@ -939,1 +946,3 @@
 
+bool MCAssembler::relaxCoffStaticOffsetFragment(
+    MCAsmLayout &Layout, MCCoffStaticOffsetFragment &LDF) {
----------------
Since the size is fixed, this shouldn't need to be part of the relaxation.

Relaxation exits for things that can change size depending on where other stuff is. For example, a short branch can become a long one and a uleb might need another byte if things more far apart.

What prevents this from being just a data fragment with a relocation to get the correct value?

Follow how llvm-mc implements:

--------------
foo:
    .zero 4
    .zero 4
bar:
zed = bar - foo
-------------------


http://llvm-reviews.chandlerc.com/D2445