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

Joerg Sonnenberger via llvm-dev llvm-dev at lists.llvm.org
Tue Aug 18 12:56:08 PDT 2020

On Tue, Aug 18, 2020 at 02:35:56PM +0100, Florian Hahn via llvm-dev wrote:
> MemorySSA DSE can substantially increase the number of stores eliminated
> in many cases (e.g. across MultiSource/SPEC2000/SPEC2006 with -O3 -flto,
> the number of eliminated stores increases roughly by 45%, with some
> benchmarks seeing much larger improvements). But the improvements come
> at additional compile-time cost (CTmark geomean -O3 +0.86%, ReleaseThinLTO
> +1.59%), due to a substantially increased search space. I’d like to
> propose to switch to MemorySSA-backed DSE, as in my opinion the benefits
> in terms of store reductions outweigh the compile-time impact).

Do you also have any numbers on the impact on (peak) RSS this has?


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