[LLVMbugs] [Bug 8424] New: Stack probing code is only emitted on Cygwin/MinGW for alloca. Windows needs it.

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=8424

           Summary: Stack probing code is only emitted on Cygwin/MinGW for
                    alloca. Windows needs it.
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
        AssignedTo: bigcheesegs at gmail.com
        ReportedBy: bigcheesegs at gmail.com
                CC: llvmbugs at cs.uiuc.edu


On Windows when growing the stack by more than 4096 bytes you must call
_chkstk(size) or _alloca_probe[_(8|16)](size) to correctly load these pages
into memory. This is currently handled in several different places, but the
place that ends up handling calls to alloca or allocation of variable length
arrays only works on Cygwin and MinGW.

It should be trivial to support this on native Windows, alloca on CygMing just
forwards to _chkstk.

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