IR: Don't add inbounds to GEPs of extern_weak variables

Global variables that have `extern_weak` linkage may be null, so it's
incorrect to add `inbounds` when constant folding.

This also fixes a bug when parsing global aliases, whose forward
reference placeholders are global variables with `extern_weak` linkage.
If GEPs to these aliases are encountered before the alias itself, the
GEPs would incorrectly gain the `inbounds` keyword as well.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215803 91177308-0d34-0410-b5e6-96231b3b80d8
UseListOrder: Correctly count the number of uses

This is an off-by-one bug I found by inspection, which would only
trigger if the bitcode writer sees more uses of a `Value` than the
reader.  Since this is only relevant when an instruction gets upgraded
somehow, there unfortunately isn't a reasonable way to add test
coverage.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215804 91177308-0d34-0410-b5e6-96231b3b80d8
BitcodeReader: Only create one basic block for each blockaddress

Block address forward-references are implemented by creating a
`BasicBlock` ahead of time that gets inserted in the `Function` when
it's eventually encountered.

However, if the same blockaddress was used in two separate functions
that were parsed *before* the referenced function (and the blockaddress
was never used at global scope), two separate basic blocks would get
created, one of which would be forgotten creating invalid IR.

This commit changes the forward-reference logic to create only one basic
block (and always return the same blockaddress).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215805 91177308-0d34-0410-b5e6-96231b3b80d8
[LIT] Move display of unsupported and xfail tests to summary. 

Summary:
This patch changes the way xfail and unsupported tests are displayed. 
This output is only displayed when the --show-unsupported/--show-xfail flags are passed to lit.

Currently xfail/unsupported tests are printed during the run of the test-suite. I think its better to display this information during the summary instead.
This patch removes the printing of these tests from when they are run to the summary.


Reviewers: ddunbar, EricWF

Reviewed By: EricWF

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D4842

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215809 91177308-0d34-0410-b5e6-96231b3b80d8