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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - LLVM hardcodes stack probe space to 4096 bytes"
href="http://llvm.org/bugs/show_bug.cgi?id=21895">21895</a>
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<th>Summary</th>
<td>LLVM hardcodes stack probe space to 4096 bytes
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>clangbugs.10.mdwxzxkl@spamgourmet.com
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>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:
<a href="http://llvm.org/klaus/llvm/blob/master/lib/Target/X86/X86FrameLowering.cpp#L-709">http://llvm.org/klaus/llvm/blob/master/lib/Target/X86/X86FrameLowering.cpp#L-709</a>
Reference:
<a href="http://msdn.microsoft.com/en-us/library/9598wk25">http://msdn.microsoft.com/en-us/library/9598wk25</a></pre>
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