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

lib/Target/X86/X86FrameLowering.cpp

@@ -606,7 +606,7 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF) const {
   // 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()) {
     const char *StackProbeSymbol;
     bool isSPUpdateNeeded = false;
 

lib/Target/X86/X86ISelLowering.cpp

@@ -631,7 +631,7 @@ void X86TargetLowering::resetOperationActions() {
   setOperationAction(ISD::STACKSAVE,          MVT::Other, Expand);
   setOperationAction(ISD::STACKRESTORE,       MVT::Other, Expand);
 
-  if (Subtarget->isTargetCOFF() && !Subtarget->isTargetEnvMacho())
+  if (Subtarget->isTargetWindows())
     setOperationAction(ISD::DYNAMIC_STACKALLOC, Subtarget->is64Bit() ?
                        MVT::i64 : MVT::i32, Custom);
   else if (TM.Options.EnableSegmentedStacks)

lib/Target/X86/X86Subtarget.h

@@ -333,6 +333,8 @@ public:
   }
   bool isTargetEnvMacho() const { return TargetTriple.isEnvironmentMachO(); }
 
+  bool isOSWindows() const { return TargetTriple.isOSWindows(); }
+
   bool isTargetWin64() const {
     return In64BitMode && TargetTriple.isOSWindows();
   }