diff options
author | Reid Kleckner <rnk@google.com> | 2017-05-23 17:01:48 +0000 |
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committer | Reid Kleckner <rnk@google.com> | 2017-05-23 17:01:48 +0000 |
commit | 90e7ab1a9dd029511f38ae198e57061413c08c8a (patch) | |
tree | 6c8d6a2ce7e252530ae671be8ea04c48b7b45866 /lib/Bitcode | |
parent | a30e2b308bb7d8b8f5d8f0924bdd0908204e2fe2 (diff) |
[IR] Switch AttributeList to use an array for O(1) access
Summary:
Before this change, AttributeLists stored a pair of index and
AttributeSet. This is memory efficient if most arguments do not have
attributes. However, it requires doing a search over the pairs to test
an argument or function attribute. Profiling shows that this loop was
0.76% of the time in 'opt -O2' of sqlite3.c, because LLVM constantly
tests values for nullability.
This was worth about 2.5% of mid-level optimization cycles on the
sqlite3 amalgamation. Here are the full perf results:
https://reviews.llvm.org/P7995
Here are just the before and after cycle counts:
```
$ perf stat -r 5 ./opt_before -O2 sqlite3.bc -o /dev/null
13,274,181,184 cycles # 3.047 GHz ( +- 0.28% )
$ perf stat -r 5 ./opt_after -O2 sqlite3.bc -o /dev/null
12,906,927,263 cycles # 3.043 GHz ( +- 0.51% )
```
This patch *does not* change the indices used to query attributes, as
requested by reviewers. Tracking whether an index is usable for array
indexing is a huge pain that affects many of the internal APIs, so it
would be good to come back later and do a cleanup to remove this
internal adjustment.
Reviewers: pete, chandlerc
Subscribers: javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D32819
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303654 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Bitcode')
-rw-r--r-- | lib/Bitcode/Writer/BitcodeWriter.cpp | 10 | ||||
-rw-r--r-- | lib/Bitcode/Writer/ValueEnumerator.cpp | 7 |
2 files changed, 11 insertions, 6 deletions
diff --git a/lib/Bitcode/Writer/BitcodeWriter.cpp b/lib/Bitcode/Writer/BitcodeWriter.cpp index 1f8b50342c2d..e29b225adea4 100644 --- a/lib/Bitcode/Writer/BitcodeWriter.cpp +++ b/lib/Bitcode/Writer/BitcodeWriter.cpp @@ -660,10 +660,12 @@ void ModuleBitcodeWriter::writeAttributeTable() { SmallVector<uint64_t, 64> Record; for (unsigned i = 0, e = Attrs.size(); i != e; ++i) { - const AttributeList &A = Attrs[i]; - for (unsigned i = 0, e = A.getNumSlots(); i != e; ++i) - Record.push_back( - VE.getAttributeGroupID({A.getSlotIndex(i), A.getSlotAttributes(i)})); + AttributeList AL = Attrs[i]; + for (unsigned i = AL.index_begin(), e = AL.index_end(); i != e; ++i) { + AttributeSet AS = AL.getAttributes(i); + if (AS.hasAttributes()) + Record.push_back(VE.getAttributeGroupID({i, AS})); + } Stream.EmitRecord(bitc::PARAMATTR_CODE_ENTRY, Record); Record.clear(); diff --git a/lib/Bitcode/Writer/ValueEnumerator.cpp b/lib/Bitcode/Writer/ValueEnumerator.cpp index fd76400331d9..bb626baabd12 100644 --- a/lib/Bitcode/Writer/ValueEnumerator.cpp +++ b/lib/Bitcode/Writer/ValueEnumerator.cpp @@ -902,8 +902,11 @@ void ValueEnumerator::EnumerateAttributes(AttributeList PAL) { } // Do lookups for all attribute groups. - for (unsigned i = 0, e = PAL.getNumSlots(); i != e; ++i) { - IndexAndAttrSet Pair = {PAL.getSlotIndex(i), PAL.getSlotAttributes(i)}; + for (unsigned i = PAL.index_begin(), e = PAL.index_end(); i != e; ++i) { + AttributeSet AS = PAL.getAttributes(i); + if (!AS.hasAttributes()) + continue; + IndexAndAttrSet Pair = {i, AS}; unsigned &Entry = AttributeGroupMap[Pair]; if (Entry == 0) { AttributeGroups.push_back(Pair); |