Reid Kleckner 90e7ab1a9d [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		2017-05-23 17:01:48 +00:00
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llvm	[IR] Switch AttributeList to use an array for O(1) access	2017-05-23 17:01:48 +00:00
llvm-c	Introduce LLVMDIBuilderRef	2017-04-20 14:22:47 +00:00