On some AArch64 cores, including Ampere's ampere1 and ampere1a
architectures, load and store pair instructions are faster compared to
simple loads/stores only when the alignment of the pair is at least
twice that of the individual element being loaded.
Based on that, this patch introduces four new subtarget features, two
for controlling ldp and two for controlling stp, to cover the ampere1
and ampere1a alignment needs and to enable optional fine-grained control
over ldp and stp generation in general. The latter can be utilized by
another cpu, if there are possible benefits
with a different policy than the default provided by the compiler.
More specifically, for each of the ldp and stp respectively we have:
- disable-ldp/disable-stp: Do not emit ldp/stp.
- ldp-aligned-only/stp-aligned-only: Emit ldp/stp only if the source
pointer is aligned to at least double the alignment of the type.
Therefore, for -mcpu=ampere1 and -mcpu=ampere1a
ldp-aligned-only/stp-aligned-only become the defaults, because of the
benefit from the alignment, whereas for the rest of the cpus the default
behaviour of the compiler is maintained.
This patch optimizes a pair of LDRSWpre and LDRSWui (or LDURSWi)
instructions into a single LDPSWpre instruction. This is a missing case
in D99272.
MIR test cases in D152564 are updated to verify the optimization.
Differential Revision: https://reviews.llvm.org/D152407
STG, STZG, ST2G, STZ2G are the exceptions to append 'Offset' to name the
offset format of load/store instructions. All other load/store
instructions use 'i' as the appendix. If there is no special reason to
do so, we should make the naming consistent.
Differential Revision: https://reviews.llvm.org/D141819
This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.
This is part of an effort to migrate from llvm::Optional to
std::optional:
https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716
The crash comes from mismatch between load count in epilogue and seh instruction count.
Still because of the pass AArch64LoadStoreOpt. It remove some load in the epilogue but haven't remove the corresponding seh instruction.
This patch don't optimize the load in the epilogue to fix the issue.
Fix: #58516
Reviewed By: mstorsjo
Differential Revision: https://reviews.llvm.org/D136430
AArch64LoadStoreOptimizer has a bunch of different guards to avoid
corrupting Windows SEH prologues/epilogues, but apparently we missed the
case of merging two instructions where the first instruction isn't part
of the epilogue, but the second instruction is.
Fixes issue discovered at https://reviews.llvm.org/D130049#3704064
Differential Revision: https://reviews.llvm.org/D134992
According D125377, we order STP Q's by ascending address. While on some
targets, paired 128 bit loads and stores are slow, so the STP will split
into STRQ and STUR, so I hope these stores will also be ordered.
Also add subtarget feature ascend-store-address to control the aggressive order.
Reviewed By: dmgreen, fhahn
Differential Revision: https://reviews.llvm.org/D126700
[Re-commit after fixing a dereference of "end" iterator]
The AArch64LoadStoreOptimnizer pass may merge a register
increment/decrement with a following memory operation. In doing so, it
may break CFI by moving a stack pointer adjustment past the CFI
instruction that described *that* adjustment.
This patch fixes this issue by moving said CFI instruction after the
merged instruction, where the SP increment/decrement actually takes
place.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D114547
This reverts commit ecbf32dd88fc91b4fe709dc14bb3493dda6e8854.
It's possible this patch is the reason for an asertion failure
`!NodePtr->isKnownSentinel()` in `AArch64LoadStoreOpt::mergeUpdateInsn`
(https://lab.llvm.org/buildbot/#/builders/185/builds/1555) reverting while I
investigate.
The AArch64LoadStoreOptimnizer pass may merge a register
increment/decrement with a following memory operation. In doing so, it
may break CFI by moving a stack pointer adjustment past the CFI
instruction that described *that* adjustment.
This patch fixes this issue by moving said CFI instruction after the
merged instruction, where the SP increment/decrement actually takes
place.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D114547
FirstMI is only used to get the load/store operand and the machine
function. Pass the MF and register explicitly, so the helper can be used
to find rename registers for other instructions in the future.
The content of undef registers are not used in meaningful ways, when checking
if a rename register is used between paired instructions we should ignore
undef registers.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D119305
This reverts commit ea011ec5ed53599305de62ca5fcfd31f4b3448c3.
This still causes some miscompiles, I'll follow up in the phabricator
review with a sample of that issue (which is part of the sample of
the previous issue).
This is a recommit that fixes unwanted STP generation by checking that
the base register has not been modified or used elsewhere.
Our initial motivating case was memcpy's with alignments > 16. The
loads/stores, to which small memcpy's expand, are kept together in
several places so that we get a sequence like this for a 64 bit copy:
LD w0
LD w1
ST w0
ST w1
The load/store optimiser can generate a LDP/STP w0, w1 from this because
the registers read/written are consecutive. In our case however, the
sequence is optimised during ISel, resulting in:
LD w0
ST w0
LD w0
ST w0
This instruction reordering allows reuse of registers. Since the registers
are no longer consecutive (i.e. they are the same), it inhibits LDP/STP
creation. The approach here is to perform renaming:
LD w0
ST w0
LD w1
ST w1
to enable the folding of the stores into a STP. We do not yet generate
the LDP due to a limitation in the renaming implementation, but plan to
look at that in a follow-up so that we fully support this case. While
this was initially motivated by certain memcpy's, this is a general
approach and thus is beneficial for other cases too, as can be seen
in some test changes.
Differential Revision: https://reviews.llvm.org/D103597
This reverts commit d96ea46629803641038ebe46d8cd512f8cf7e20f, as it
caused various misoptimizations, see https://reviews.llvm.org/D103597
for discussion on the issues.
Our initial motivating case was memcpy's with alignments > 16. The
loads/stores, to which small memcpy's expand, are kept together in
several places so that we get a sequence like this for a 64 bit copy:
LD w0
LD w1
ST w0
ST w1
The load/store optimiser can generate a LDP/STP w0, w1 from this because
the registers read/written are consecutive. In our case however, the
sequence is optimised during ISel, resulting in:
LD w0
ST w0
LD w0
ST w0
This instruction reordering allows reuse of registers. Since the registers
are no longer consecutive (i.e. they are the same), it inhibits LDP/STP
creation. The approach here is to perform renaming:
LD w0
ST w0
LD w1
ST w1
to enable the folding of the stores into a STP. We do not yet generate
the LDP due to a limitation in the renaming implementation, but plan to
look at that in a follow-up so that we fully support this case. While
this was initially motivated by certain memcpy's, this is a general
approach and thus is beneficial for other cases too, as can be seen
in some test changes.
Differential Revision: https://reviews.llvm.org/D103597
This patch fixes an issue where a pre-indexed store e.g.,
STR x1, [x0, #24]! with a store like STR x0, [x0, #8] are
merged into a single store: STP x1, x0, [x0, #24]!
. They shouldn’t be merged because the second store uses
x0 as both the stored value and the address and so it needs to be using the updated x0.
Therefore, it should not be folded into a STP <>pre.
Additionally a new test case is added to verify this fix.
Differential Revision: https://reviews.llvm.org/D101888
Change-Id: I26f1985ac84e970961e2cdca23c590fa6773851a
This patch merges STR<S,D,Q,W,X>pre-STR<S,D,Q,W,X>ui and
LDR<S,D,Q,W,X>pre-LDR<S,D,Q,W,X>ui instruction pairs into a single
STP<S,D,Q,W,X>pre and LDP<S,D,Q,W,X>pre instruction, respectively.
For each pair, there is a MIR test that verifies this optimization.
Differential Revision: https://reviews.llvm.org/D99272
Change-Id: Ie97a20c8c716c08492fe229c22e14e3c98ef08b7
Instead of outright disabling this completely with the noredzone attribute,
we only avoid doing the optimization if there are memory operations between
the adjustment and the load/store that the adjustment would be folded into.
This avoids the case of something like a stack cookie being corrupted if an
exception happens before the pre-increment to the SP occurs.
This also prevents the folding happening if we have a redzone, but the offset
being folded is above the redzone amount (128 bytes in this case).
rdar://73269336
Differential Revision: https://reviews.llvm.org/D95179
This matches the corresponding existing case in
AArch64LoadStoreOpt::findMatchingUpdateInsnForward.
Both cases could also be modified to check
MBBI->getFlag(FrameSetup/FrameDestroy) instead of forbidding any
optimization involving SP, but the effect is probably pretty much
the same.
Differential Revision: https://reviews.llvm.org/D88541
When pairing loads, we should check if in between the two loads the
base register has been modified. If that is the case then avoid pairing
them because the second load actually loads from a different address.
Reviewed By: fhahn
Differential Revision: https://reviews.llvm.org/D86956
When matching store instruction for ldst opt, we should make sure store instr is in 'reg+imm' form as load instr,
otherwise, it will have assertion in isLdOffsetInRangeOfSt since it will use getImm() directly.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D87905
When pairing ldr instructions to an ldp instruction, we cannot pair two ldr
destination registers where one is a sub or super register of the other.
Reviewed By: fhahn
Differential Revision: https://reviews.llvm.org/D86906
Currently aarch64-ldst-opt will incorrectly rename registers with
multiple disjunct subregisters (e.g. result of LD3). This patch updates
the canRenameUpToDef to bail out if it encounters such a register class
that contains the register to rename.
Fixes PR46105.
Reviewers: efriedma, dmgreen, paquette, t.p.northover
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D81108
Summary:
Add a check to make sure that MachineInstr::mayAlias returns prematurely if at least one of its instruction parameters does not access memory. This prevents calls to TargetInstrInfo::areMemAccessesTriviallyDisjoint with incompatible instructions.
A side effect of this change is to render the mayAlias helper in the AArch64 load/store optimizer obsolete. We can now directly call the MachineInstr::mayAlias member function.
Reviewers: hfinkel, t.p.northover, mcrosier, eli.friedman, efriedma
Reviewed By: efriedma
Subscribers: efriedma, kristof.beyls, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78823
Do not count the presence of debug insts against the limit set by
LdStLimit, and allow the optimizer to find matching insts by skipping
over debug insts.
Differential Revision: https://reviews.llvm.org/D78411
Summary:
When moving add and sub to memory operand instructions,
aarch64-ldst-opt would prematurally pop the stack pointer,
before memory instructions that do access the stack using
indirect loads.
e.g.
```
int foo(int offset){
int local[4] = {0};
return local[offset];
}
```
would generate:
```
sub sp, sp, #16 ; Push the stack
mov x8, sp ; Save stack in register
stp xzr, xzr, [sp], #16 ; Zero initialize stack, and post-increment, making it invalid
------ If an exception goes here, the stack value might be corrupted
ldr w0, [x8, w0, sxtw #2] ; Access correct position, but it is not guarded by SP
```
Reviewers: fhahn, foad, thegameg, eli.friedman, efriedma
Reviewed By: efriedma
Subscribers: efriedma, kristof.beyls, hiraditya, danielkiss, llvm-commits, simon_tatham
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D75755
This patch adds a new option to enable/disable register renaming in the
load-store optimizer. Defaults to disabled, as there is a potential
mis-compile caused by this.
If the root def of for renaming is a noop-pseudo instruction like kill,
we would end up without a correct def for the renamed register, causing
miscompiles.
This patch conservatively bails out on any pseudo instruction.
This fixes https://bugs.chromium.org/p/chromium/issues/detail?id=1037912#c70
Summary:
r347747 added support for clustering mem ops with FI base operands
including support for fixed stack objects in shouldClusterFI, but
apparently this was never tested.
This patch fixes shouldClusterFI to work with scaled as well as
unscaled load/store instructions, and fixes the ordering of memory ops
in MemOpInfo::operator< to ensure that memory addresses always
increase, regardless of which direction the stack grows.
Subscribers: MatzeB, kristof.beyls, hiraditya, javed.absar, arphaman, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D71334
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%
Reviewers: efriedma, thegameg, samparker, dmgreen, paquette, evandro
Reviewed By: paquette
Differential Revision: https://reviews.llvm.org/D70450
