(this is a corrected patch)

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 OS (both Windows target and MingW target) 
but not Mach-O object format: Looks like macho environment was used to 
build some EFI code.
 
Credits to Andrew MacPherson.

llvm-svn: 193289
diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index adcd4f7..a06ba9d 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -606,7 +606,7 @@
   // responsible for adjusting the stack pointer.  Touching the stack at 4K
   // increments is necessary to ensure that the guard pages used by the OS
   // virtual memory manager are allocated in correct sequence.
-  if (NumBytes >= 4096 && STI.isTargetCOFF() && !STI.isTargetEnvMacho()) {
+  if (NumBytes >= 4096 && STI.isOSWindows() && !STI.isTargetEnvMacho()) {
     const char *StackProbeSymbol;
     bool isSPUpdateNeeded = false;