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| author | Tim Northover <tnorthover@apple.com> | 2014-06-10 10:49:07 +0000 |
|---|---|---|
| committer | Tim Northover <tnorthover@apple.com> | 2014-06-10 10:49:07 +0000 |
| commit | 84ad29ca1fdb6a0ec357065e05bffcfd135ed410 (patch) | |
| tree | a246c09989a79b17f794fce2020326dbec12368e /llvm/lib/CodeGen/StackMaps.cpp | |
| parent | 908180574e6d09eba543b77e76b01c06865c78ff (diff) | |
| download | llvm-84ad29ca1fdb6a0ec357065e05bffcfd135ed410.zip llvm-84ad29ca1fdb6a0ec357065e05bffcfd135ed410.tar.gz llvm-84ad29ca1fdb6a0ec357065e05bffcfd135ed410.tar.bz2 | |
X86: elide comparisons after cmpxchg instructions.
The C++ and C semantics of the compare_and_swap operations actually
require us to return a boolean "success" value. In LLVM terms this
means a second comparison of the output of "cmpxchg" against the input
desired value.
However, x86's "cmpxchg" instruction sets all flags for the comparison
formed, so we can skip any secondary comparison. (N.b. this isn't true
for cmpxchg8b/16b, which only set ZF).
rdar://problem/13201607
llvm-svn: 210523
Diffstat (limited to 'llvm/lib/CodeGen/StackMaps.cpp')
0 files changed, 0 insertions, 0 deletions