[all-commits] [llvm/llvm-project] fb109c: [DSE] Switch to MemorySSA-backed DSE by default.
Florian Hahn via All-commits
all-commits at lists.llvm.org
Thu Sep 10 14:26:00 PDT 2020
Branch: refs/heads/master
Home: https://github.com/llvm/llvm-project
Commit: fb109c42d91c30c8c7497ef1fd7aff6f2969c6e7
https://github.com/llvm/llvm-project/commit/fb109c42d91c30c8c7497ef1fd7aff6f2969c6e7
Author: Florian Hahn <flo at fhahn.com>
Date: 2020-09-10 (Thu, 10 Sep 2020)
Changed paths:
M clang/test/CodeGen/thinlto-distributed-newpm.ll
M clang/test/CodeGenObjC/exceptions.m
M llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
M llvm/test/Analysis/BasicAA/modref.ll
M llvm/test/CodeGen/AMDGPU/opt-pipeline.ll
M llvm/test/Other/new-pm-defaults.ll
M llvm/test/Other/new-pm-lto-defaults.ll
M llvm/test/Other/new-pm-thinlto-defaults.ll
M llvm/test/Other/opt-O2-pipeline.ll
M llvm/test/Other/opt-O3-pipeline-enable-matrix.ll
M llvm/test/Other/opt-O3-pipeline.ll
M llvm/test/Other/opt-Os-pipeline.ll
M llvm/test/Transforms/Coroutines/ArgAddr.ll
M llvm/test/Transforms/Coroutines/coro-retcon.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/2011-03-25-DSEMiscompile.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/2011-09-06-EndOfFunction.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/2011-09-06-MemCpy.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/2016-07-17-UseAfterFree.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/OverwriteStoreBegin.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/OverwriteStoreEnd.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/PartialStore.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/PartialStore2.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/X86/gather-null-pointer.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/atomic-overlapping.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/atomic-todo.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/atomic.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/calloc-store.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/combined-partial-overwrites.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/const-pointers.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/crash.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/cs-cs-aliasing.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/debug-counter.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/debuginfo.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/dominate.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/fence-todo.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/fence.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/free.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/inst-limits.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/int_sideeffect.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/invariant.start.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/launder.invariant.group.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/libcalls.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/lifetime.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/mda-with-dbg-values.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/memcpy-complete-overwrite.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/memintrinsics.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/memoryssa-scan-limit.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/memset-and-memcpy.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/memset-missing-debugloc.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/memset-unknown-sizes.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/merge-stores-big-endian.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/merge-stores.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-captures.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-exceptions.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-loops.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-malloc-free.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-memintrinsics.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-memoryphis.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-multipath-throwing.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-multipath.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-overlap.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-partial.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-simple.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-throwing.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-unreachable.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/no-targetdata.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/noop-stores.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/operand-bundles.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/overlap.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/pr11390.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/pr47285-not-overwritten-on-all-exit-paths.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/simple-preservation.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/simple-todo.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/simple.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/stats.ll
M llvm/test/Transforms/DeadStoreElimination/MSSA/tail-byval.ll
M llvm/test/Transforms/MemCpyOpt/memcpy.ll
Log Message:
-----------
[DSE] Switch to MemorySSA-backed DSE by default.
The tests have been updated and I plan to move them from the MSSA
directory up.
Some end-to-end tests needed small adjustments. One difference to the
legacy DSE is that legacy DSE also deletes trivially dead instructions
that are unrelated to memory operations. Because MemorySSA-backed DSE
just walks the MemorySSA, we only visit/check memory instructions. But
removing unrelated dead instructions is not really DSE's job and other
passes will clean up.
One noteworthy change is in llvm/test/Transforms/Coroutines/ArgAddr.ll,
but I think this comes down to legacy DSE not handling instructions that
may throw correctly in that case. To cover this with MemorySSA-backed
DSE, we need an update to llvm.coro.begin to treat it's return value to
belong to the same underlying object as the passed pointer.
There are some minor cases MemorySSA-backed DSE currently misses, e.g. related
to atomic operations, but I think those can be implemented after the switch.
This has been discussed on llvm-dev:
http://lists.llvm.org/pipermail/llvm-dev/2020-August/144417.html
For the MultiSource/SPEC2000/SPEC2006 the number of eliminated stores
goes from ~17500 (legayc DSE) to ~26300 (MemorySSA-backed). More numbers
and details in the thread on llvm-dev.
Impact on CTMark:
```
Legacy Pass Manager
exec instrs size-text
O3 + 0.60% - 0.27%
ReleaseThinLTO + 1.00% - 0.42%
ReleaseLTO-g. + 0.77% - 0.33%
RelThinLTO (link only) + 0.87% - 0.42%
RelLO-g (link only) + 0.78% - 0.33%
```
http://llvm-compile-time-tracker.com/compare.php?from=3f22e96d95c71ded906c67067d75278efb0a2525&to=ae8be4642533ff03803967ee9d7017c0d73b0ee0&stat=instructions
```
New Pass Manager
exec instrs. size-text
O3 + 0.95% - 0.25%
ReleaseThinLTO + 1.34% - 0.41%
ReleaseLTO-g. + 1.71% - 0.35%
RelThinLTO (link only) + 0.96% - 0.41%
RelLO-g (link only) + 2.21% - 0.35%
```
http://195.201.131.214:8000/compare.php?from=3f22e96d95c71ded906c67067d75278efb0a2525&to=ae8be4642533ff03803967ee9d7017c0d73b0ee0&stat=instructions
Reviewed By: asbirlea, xbolva00, nikic
Differential Revision: https://reviews.llvm.org/D87163
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