Fix broken FileCheck prefixes

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209538 91177308-0d34-0410-b5e6-96231b3b80d8
Remove unused CHECK lines

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209539 91177308-0d34-0410-b5e6-96231b3b80d8
Use alias linkage and visibility to decide tls access mode.

This matches both what we do for the non-thread case and what gcc does.

With this patch clang would match gcc's behaviour in

static __thread int a = 42;
extern __thread int b __attribute__((alias("a")));
int *f(void) { return &a; }
int *g(void) { return &b; }

if not for pr19843. Manually writing the IL does produce the same access modes.

It is also a step in the direction of fixing pr19844.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209543 91177308-0d34-0410-b5e6-96231b3b80d8
Revert part of "Fix broken FileCheck prefixes"

This reverts part of commit r209538.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209544 91177308-0d34-0410-b5e6-96231b3b80d8
Fix and improve SCEV ComputeBackedgeTankCount.

This is a follow-up to r209358: PR19799: Indvars miscompile due to an
incorrect max backedge taken count from SCEV.

That fix was incomplete as pointed out by Arnold and Michael Z. The
code was also too confusing. It needed a careful rewrite with more
unit tests. This version will also happen to optimize more cases.

<rdar://17005101> PR19799: Indvars miscompile...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209545 91177308-0d34-0410-b5e6-96231b3b80d8