X86: Custom lower zext v16i8 to v16i16.

On sandy bridge (PR17654) we now get
	vpxor	%xmm1, %xmm1, %xmm1
	vpunpckhbw	%xmm1, %xmm0, %xmm2
	vpunpcklbw	%xmm1, %xmm0, %xmm0
	vinsertf128	$1, %xmm2, %ymm0, %ymm0

On haswell it's a simple
	vpmovzxbw	%xmm0, %ymm0

There is a maze of duplicated and dead transforms and patterns in this
area. Remove the dead custom lowering of zext v8i16 to v8i32, that's
already handled by LowerAVXExtend.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193262 91177308-0d34-0410-b5e6-96231b3b80d8
Calling _chkstk is required on ELF as well as COFF on Windows. 
Without _chkstk functions requiring large stack crash in 
initialization code. Previous code tested for COFF format but 
not Mach-O and this patch modifies the code to test for Windows.

Credits to Andrew MacPherson.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193263 91177308-0d34-0410-b5e6-96231b3b80d8
Use a map instead of vector to store line counts.

There are a few motivations for this:
- Using a map allows for checking if line is in map. This differentiates
  unexecutable lines (such as comments) from unexecuted logical lines of
  code. "#####" is now outputted in this case, in line with gcov.
- Source files are no longer read in twice: once when storing the line
  counts, and once when outputting the data.
- Greatly simplifies the function FileInfo::addLineCount().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193264 91177308-0d34-0410-b5e6-96231b3b80d8
Fixed comment typo in GCOVProfiling.cpp

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193268 91177308-0d34-0410-b5e6-96231b3b80d8
X86: Custom lower sext v16i8 to v16i16, and the corresponding truncate.

Also update the cost model.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193270 91177308-0d34-0410-b5e6-96231b3b80d8
Reduce casting and use a fully covered switch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193272 91177308-0d34-0410-b5e6-96231b3b80d8
Fixed doxygen comment to match Module.cpp

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193273 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "Calling _chkstk is required on ELF as well as COFF on Windows. Without _chkstk functions requiring large stack crash in initialization code. Previous code tested for COFF format but not Mach-O and this patch modifies the code to test for Windows."

This reverts commit r193263.

It is causing CodeGen/X86/mingw-alloca.ll to fail.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193275 91177308-0d34-0410-b5e6-96231b3b80d8