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This patch starts a series of patches that decrease time spent by GlobalISel in its InstructionSelect pass by roughly 60% for -O0 builds for large inputs as measured on sqlite3-amalgamation (http://sqlite.org/download.html) targeting AArch64. The performance improvements are achieved solely by reducing the number of matching GIM_* opcodes executed by the MatchTable's interpreter during the selection by approx. a factor of 30, which also brings contribution of this particular part of the selection process to the overall runtime of InstructionSelect pass down from approx. 60-70% to 5-7%, thus making further improvements in this particular direction not very profitable. The improvements described above are expected for any target that doesn't have many complex patterns. The targets that do should strictly benefit from the changes, but by how much exactly is hard to estimate beforehand. It's also likely that such target WILL benefit from further improvements to MatchTable, most likely the ones that bring it closer to a perfect decision tree. This commit specifically is rather large mostly NFC commit that does necessary preparation work and refactoring, there will be a following series of small patches introducing a specific optimization each shortly after. This commit specifically is expected to cause a small compile time regression (around 2.5% of InstructionSelect pass time), which should be fixed by the next commit of the series. Every commit planned shares the same Phabricator Review. Reviewers: qcolombet, dsanders, bogner, aemerson, javed.absar Reviewed By: qcolombet Subscribers: rovka, llvm-commits, kristof.beyls Differential Revision: https://reviews.llvm.org/D44700 llvm-svn: 332907 |
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