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author | Sanjay Patel <spatel@rotateright.com> | 2017-07-31 18:08:24 +0000 |
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committer | Sanjay Patel <spatel@rotateright.com> | 2017-07-31 18:08:24 +0000 |
commit | fea731a4aa6aabf270fbb9ba6401ca8826c55a9b (patch) | |
tree | 93d0d7e6532ef8f3b297548da5097f879e878312 /lldb/packages/Python/lldbsuite/test/python_api/debugger/TestDebuggerAPI.py | |
parent | 70d35e102ef8dbba10e2db84ea2dcbe95bbbfd38 (diff) | |
download | bcm5719-llvm-fea731a4aa6aabf270fbb9ba6401ca8826c55a9b.tar.gz bcm5719-llvm-fea731a4aa6aabf270fbb9ba6401ca8826c55a9b.zip |
[CGP] use subtract or subtract-of-cmps for result of memcmp expansion
As noted in the code comment, transforming this in the other direction might require
a separate transform here in CGP given the block-at-a-time DAG constraint.
Besides that theoretical motivation, there are 2 practical motivations for the
subtract-of-cmps form:
1. The codegen for both x86 and PPC is better for this IR (though PPC could be better still).
There is discussion about canonicalizing IR to the select form
( http://lists.llvm.org/pipermail/llvm-dev/2017-July/114885.html ),
so we probably need to add DAG transforms for those patterns anyway, but this improves the
memcmp output without waiting for that step.
2. If we allow vector-sized chunks for the load and compare, x86 is better prepared to convert
that to optimal code when using subtract-of-cmps, so another prerequisite patch is avoided
if we choose to enable that.
Differential Revision: https://reviews.llvm.org/D34904
llvm-svn: 309597
Diffstat (limited to 'lldb/packages/Python/lldbsuite/test/python_api/debugger/TestDebuggerAPI.py')
0 files changed, 0 insertions, 0 deletions