llvm/lib/Transforms
Anthony Pesch a5fd3fdc5b Improve merging of stores from static constructors in GlobalOpt
Summary:
While working on a project I wound up generating a fairly large lookup table (10k entries) of callbacks inside of a static constructor. Clang was taking upwards of ~10 minutes to compile the lookup table. I generated a smaller test case (http://www.inolen.com/static_initializer_test.ll) that, after running with -ftime-report, pointed fingers at GlobalOpt and MemCpyOptimizer.

Running globalopt took around ~9 minutes. The slowdown came from how GlobalOpt merged stores from static constructors individually into the global initializer in EvaluateStaticConstructor. For each store it discovered and wanted to commit, it would copy the existing global initializer and then merge in the individual store. I changed this so that stores are now grouped by global, and sorted from most significant to least significant by their GEP indexes (e.g. a store to GEP 0, 0 comes before GEP 0, 0, 1). With this representation, the existing initializer can be copied and all new stores merged into it in a single pass.

With this patch and http://reviews.llvm.org/D11198, the lookup table that was taking ~10 minutes to compile now compiles in around 5 seconds. I've ran 'make check' and the test-suite, which all passed.

I'm not really sure who to tag as a reviewer, Lang mentioned that Chandler may be appropriate.

Reviewers: chandlerc, nlewycky

Subscribers: nlewycky, llvm-commits

Differential Revision: http://reviews.llvm.org/D11200

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242935 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-22 21:10:45 +00:00
..
Hello Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
InstCombine [InstCombine] Generalize sub of selects optimization to all BinaryOperators 2015-07-14 22:39:23 +00:00
Instrumentation [asan] Improve moving of non-instrumented allocas 2015-07-22 10:25:38 +00:00
IPO Improve merging of stores from static constructors in GlobalOpt 2015-07-22 21:10:45 +00:00
ObjCARC Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
Scalar [PM/AA] Remove all of the dead AliasAnalysis pointers being threaded 2015-07-22 09:52:54 +00:00
Utils Fix mem2reg to correctly handle allocas only used in a single block 2015-07-22 10:29:29 +00:00
Vectorize Fix -Wextra-semi warnings. 2015-07-22 20:46:11 +00:00
CMakeLists.txt Extracted ObjCARC.cpp into its own library libLLVMObjCARCOpts in preparation for refactoring the ARC Optimizer. 2013-01-28 01:35:51 +00:00
LLVMBuild.txt Extracted ObjCARC.cpp into its own library libLLVMObjCARCOpts in preparation for refactoring the ARC Optimizer. 2013-01-28 01:35:51 +00:00
Makefile Extracted ObjCARC.cpp into its own library libLLVMObjCARCOpts in preparation for refactoring the ARC Optimizer. 2013-01-28 01:35:51 +00:00