http://llvm.org/bugs/show_bug.cgi?id=21895
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: [email protected]
Reporter: [email protected]
CC: [email protected]
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
compiler.
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:
http://llvm.org/klaus/llvm/blob/master/lib/Target/X86/X86FrameLowering.cpp#L-709
Reference:
http://msdn.microsoft.com/en-us/library/9598wk25
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