efriedma added inline comments.
================
Comment at: clang/lib/Driver/ToolChains/Clang.cpp:3460
+ } else if (EffectiveTriple.isArm() || EffectiveTriple.isThumb()) {
+ CmdArgs.push_back("-mstack-probe-size=1024");
+ }
----------------
tnfchris wrote:
> efriedma wrote:
> > Why 1024?
> 1024 was experimentally determined by Arm and is part of the ABI for stack
> clash (which has not yet been published). It was determined by examining a
> large number of programs and looking at the function stack usages. 1024
> covers 80-90% of programs such that we can minimize the number of probes
> required in the average cases.
There are actually multiple numbers involved here, no? One is the spacing of
probes, i.e. if allocating a large amount of stack, how many times you need to
probe; this is basically the page size of the target. the other is how much
unprobed space a function is allowed to allocate before calling another
function. Referring to the the AArch64 patch, -mstack-probe-size is the former,
the hardcoded "1024" is the latter.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D154911/new/
https://reviews.llvm.org/D154911
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
