[LLVMbugs] [Bug 21895] New: LLVM hardcodes stack probe space to 4096 bytes

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Fri Dec 12 08:12:30 PST 2014


            Bug ID: 21895
           Summary: LLVM hardcodes stack probe space to 4096 bytes
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: clangbugs.10.mdwxzxkl at spamgourmet.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

The LLVM stack probe space (e.g. used for issuing __chkstk() calls when
compiling to Windows targets) is hard coded to 4096 bytes. However, in order to
suppress __chkstk() calls, it should be possible to specify a minimum value for
issuing stack probe calls that is greater than 4096 bytes. 

This is needed in order to properly implement the /Gs switch of the MSVC

The /Gs compiler switch is needed to suppress calls to __chkstk (the stack
probing function used by MSVC), e.g. when one carefully uses stack memory so
that all necessary stack probes are initiated, or when compiling with
/NODEFAULTLIB (as __chkstk would then be undefined). 

Reference to the hardcoded value of 4096 bytes:


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