[llvm-dev] [RFC] Switching to MemorySSA-backed Dead Store Elimination (aka cross-bb DSE)

Florian Hahn via llvm-dev llvm-dev at lists.llvm.org
Wed Aug 19 07:37:36 PDT 2020

> On Aug 18, 2020, at 22:14, Florian Hahn via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>> On Aug 18, 2020, at 16:59, Michael Kruse <llvmdev at meinersbur.de> wrote:
>> Thanks for all the work. The reductions in stores look promising. Do you also have performance numbers how much this improves the execution time? Did you observe any regressions where MSSA resulted in fewer removed stores?
> I did not gather numbers for execution time yet, but I’ll try to share some tomorrow.

Here are some execution time results for ARM64 with -O3 -flto with the MemorySSA-DSE compared against the current DSE implementation for CINT2006 (negative % means reduction in execution time with MemorySSA-DSE). This excludes small changes within the noise (<= 0.5%)

                                                                          Exec_time  number of stores removed
 test-suite...T2006/456.hmmer/456.hmmer.test   -1.6%.     + 70.8%
 test-suite.../CINT2006/403.gcc/403.gcc.test       -1.4%.     + 35.7%
 test-suite...0.perlbench/400.perlbench.test         -1.2%.     + 33.2%
 test-suite...3.xalancbmk/483.xalancbmk.test      -1.0%.     + 3.02%
 test-suite...T2006/401.bzip2/401.bzip2.test        -0.8%.     + 70.6%

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