Use function attribute "stackrealign" to decide whether stack
realignment should be forced.

With this commit, we can now force stack realignment when doing LTO and
do so on a per-function basis. Also, add a new cl::opt option
"stackrealign" to CommandFlags.h which is used to force stack
realignment via llc's command line.

Out-of-tree projects currently using -force-align-stack to force stack
realignment should make changes to attach the attribute to the functions
in the IR.

Differential Revision: http://reviews.llvm.org/D11814

llvm-svn: 247450
diff --git a/llvm/test/CodeGen/Generic/ForceStackAlign.ll b/llvm/test/CodeGen/Generic/ForceStackAlign.ll
index f798fca..57ccb2c 100644
--- a/llvm/test/CodeGen/Generic/ForceStackAlign.ll
+++ b/llvm/test/CodeGen/Generic/ForceStackAlign.ll
@@ -1,7 +1,7 @@
 ; Check that stack alignment can be forced. Individual targets should test their
 ; specific implementation details.
 
-; RUN: llc < %s -force-align-stack -stack-alignment=32 | FileCheck %s
+; RUN: llc < %s -stackrealign -stack-alignment=32 | FileCheck %s
 ; CHECK-LABEL: @f
 ; CHECK-LABEL: @g