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
diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp
index cf4e427..adcd4f7 100644
--- a/lib/Target/X86/X86FrameLowering.cpp
+++ b/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.isOSWindows()) {
+  if (NumBytes >= 4096 && STI.isTargetCOFF() && !STI.isTargetEnvMacho()) {
     const char *StackProbeSymbol;
     bool isSPUpdateNeeded = false;
 
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 694623e..cc409fb 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -631,7 +631,7 @@
   setOperationAction(ISD::STACKSAVE,          MVT::Other, Expand);
   setOperationAction(ISD::STACKRESTORE,       MVT::Other, Expand);
 
-  if (Subtarget->isTargetWindows())
+  if (Subtarget->isTargetCOFF() && !Subtarget->isTargetEnvMacho())
     setOperationAction(ISD::DYNAMIC_STACKALLOC, Subtarget->is64Bit() ?
                        MVT::i64 : MVT::i32, Custom);
   else if (TM.Options.EnableSegmentedStacks)
diff --git a/lib/Target/X86/X86Subtarget.h b/lib/Target/X86/X86Subtarget.h
index dd8c081..fb357c4 100644
--- a/lib/Target/X86/X86Subtarget.h
+++ b/lib/Target/X86/X86Subtarget.h
@@ -333,8 +333,6 @@
   }
   bool isTargetEnvMacho() const { return TargetTriple.isEnvironmentMachO(); }
 
-  bool isOSWindows() const { return TargetTriple.isOSWindows(); }
-
   bool isTargetWin64() const {
     return In64BitMode && TargetTriple.isOSWindows();
   }