https://bugs.llvm.org/show_bug.cgi?id=38679
Bug ID: 38679
Summary: -GS stack buffer checks are expensive
Product: clang
Version: unspecified
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: -New Bugs
Assignee: unassignedclangb...@nondot.org
Reporter: dma...@mozilla.com
CC: froy...@gmail.com, h...@chromium.org,
llvm-bugs@lists.llvm.org, r...@google.com
We recently observed that compiling Firefox with `-GS-` gives a 4-6%
improvement to our perf test suite in clang-cl builds. Adding the same flag to
MSVC builds gives a <1% improvement if anything.
Is there anything that can be done to improve clang's implementation? I found
this review (a bit old, not sure if it's still relevant)
https://reviews.llvm.org/D20346 that says "I think we can look into situations
where Clang emits stack guards and MSVC doesn't if that turns out to be a
problem later."
As a first guess:
https://msdn.microsoft.com/en-us/library/8dbf701c.aspx#Anchor_3 describes some
limitations on the buffers that MSVC checks. I wonder if clang that into
account?
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