[PATCH] D70450: [AArch64] Teach Load/Store optimizier to rename store operands for pairing.

Tue Nov 19 09:01:58 PST 2019

fhahn created this revision.
fhahn added reviewers: efriedma, thegameg, samparker, dmgreen, paquette.
Herald added subscribers: hiraditya, kristof.beyls.
Herald added a project: LLVM.

In some cases, we can rename a store operand, in order to enable pairing
of stores.  For store pairs, that cannot be merged because the first
tored register is defined in between the second store, we try to find
suitable rename register.

First, we check if we can rename the given register:

1. The first store register must be killed at the store, which means we do not have to rename instructions after the first store.
2. We scan backwards from the first store, to find the definition of the stored register and check all uses in between are renamable. Along they way, we collect the minimal register classes of the uses for overlapping (sub/super)registers.

Second, we try to find an available register from the minimal physical
register class of the original register. A suitable register must not be

1. defined before FirstMI
2. between the previous definition of the register to rename
3. a callee saved register.

We use KILL flags to clear defined registers while scanning from the
beginning to the end of the block.

This triggers quite often, here are the top changes for MultiSource,
SPEC2000, SPEC2006 compiled with -O3 for iOS:

Metric: aarch64-ldst-opt.NumPairCreated

Program                                        base     patch    diff
 test-suite...nch/fourinarow/fourinarow.test     2.00    39.00   1850.0%
 test-suite...s/ASC_Sequoia/IRSmk/IRSmk.test    46.00    80.00   73.9%
 test-suite...chmarks/Olden/power/power.test    70.00    96.00   37.1%
 test-suite...cations/hexxagon/hexxagon.test    29.00    39.00   34.5%
 test-suite...nchmarks/McCat/05-eks/eks.test   100.00   132.00   32.0%
 test-suite.../Trimaran/enc-rc4/enc-rc4.test    46.00    59.00   28.3%
 test-suite...T2006/473.astar/473.astar.test   160.00   200.00   25.0%
 test-suite.../Trimaran/enc-md5/enc-md5.test     8.00    10.00   25.0%
 test-suite...telecomm-gsm/telecomm-gsm.test   113.00   139.00   23.0%
 test-suite...ediabench/gsm/toast/toast.test   113.00   139.00   23.0%
 test-suite...Source/Benchmarks/sim/sim.test    91.00   111.00   22.0%
 test-suite...C/CFP2000/179.art/179.art.test    41.00    49.00   19.5%
 test-suite...peg2/mpeg2dec/mpeg2decode.test   245.00   279.00   13.9%
 test-suite...marks/Olden/health/health.test    16.00    18.00   12.5%
 test-suite...ks/Prolangs-C/cdecl/cdecl.test    90.00   101.00   12.2%
 test-suite...fice-ispell/office-ispell.test    91.00   100.00    9.9%
 test-suite...oxyApps-C/miniGMG/miniGMG.test   430.00   465.00    8.1%
 test-suite...lowfish/security-blowfish.test    39.00    42.00    7.7%
 test-suite.../Applications/spiff/spiff.test    42.00    45.00    7.1%
 test-suite...arks/mafft/pairlocalalign.test   2473.00  2646.00   7.0%
 test-suite.../VersaBench/ecbdes/ecbdes.test    29.00    31.00    6.9%
 test-suite...nch/beamformer/beamformer.test   220.00   235.00    6.8%
 test-suite...CFP2000/177.mesa/177.mesa.test   2110.00  2252.00   6.7%
 test-suite...ve-susan/automotive-susan.test   109.00   116.00    6.4%
 test-suite...s-C/unix-smail/unix-smail.test    65.00    69.00    6.2%
 test-suite...CI_Purple/SMG2000/smg2000.test   1194.00  1265.00   5.9%
 test-suite.../Benchmarks/nbench/nbench.test   472.00   500.00    5.9%
 test-suite...oxyApps-C/miniAMR/miniAMR.test   248.00   262.00    5.6%
 test-suite...quoia/CrystalMk/CrystalMk.test    18.00    19.00    5.6%
 test-suite...rks/tramp3d-v4/tramp3d-v4.test   7331.00  7710.00   5.2%
 test-suite.../Benchmarks/Bullet/bullet.test   5651.00  5938.00   5.1%
 test-suite...ternal/HMMER/hmmcalibrate.test   750.00   788.00    5.1%
 test-suite...T2006/456.hmmer/456.hmmer.test   764.00   802.00    5.0%
 test-suite...ications/JM/ldecod/ldecod.test   1028.00  1079.00   5.0%
 test-suite...CFP2006/444.namd/444.namd.test   1368.00  1434.00   4.8%
 test-suite...marks/7zip/7zip-benchmark.test   4471.00  4685.00   4.8%
 test-suite...6/464.h264ref/464.h264ref.test   3122.00  3271.00   4.8%
 test-suite...pplications/oggenc/oggenc.test   1497.00  1565.00   4.5%
 test-suite...T2000/300.twolf/300.twolf.test   742.00   774.00    4.3%
 test-suite.../Prolangs-C/loader/loader.test    24.00    25.00    4.2%
 test-suite...0.perlbench/400.perlbench.test   1983.00  2058.00   3.8%
 test-suite...ications/JM/lencod/lencod.test   4612.00  4785.00   3.8%
 test-suite...yApps-C++/PENNANT/PENNANT.test   995.00   1032.00   3.7%
 test-suite...arks/VersaBench/dbms/dbms.test    54.00    56.00    3.7%

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70450

Files:
  llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
  llvm/test/CodeGen/AArch64/arm64-abi_align.ll
  llvm/test/CodeGen/AArch64/arm64-variadic-aapcs.ll
  llvm/test/CodeGen/AArch64/machine-outliner-remarks.ll
  llvm/test/CodeGen/AArch64/machine-outliner.ll
  llvm/test/CodeGen/AArch64/stp-opt-with-renaming.mir

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