When the byref attribute is added, there will need to be two similar
functions for the existing cases which have an associate value copy,
and byref which does not. Most, but not all of the existing uses will
use the existing version.
The associated size function added by D82679 also needs to
contextually differ, and will help eliminate a few places still
relying on pointee element types.
This fixes an instance where MemorySSA-using Dead Store Elimination is failing
to do a transformation that the non-MemorySSA-using version does.
Differential Revision: https://reviews.llvm.org/D83783
This patch adds support for eliminating stores by free & lifetime.end
calls. We can remove stores that are not read before calling a memory
terminator and we can eliminate all stores after a memory terminator
until we see a new lifetime.start. The second case seems to not really
trigger much in practice though.
Reviewers: dmgreen, rnk, efriedma, bryant, asbirlea, Tyker
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D72410
Summary:
Avoid exposing details about how roots are stored. This enables subsequent
type-erasure changes.
v5:
- cleanup a unit test by using EXPECT_EQ instead of EXPECT_TRUE
Change-Id: I532b774cc71f2224e543bc7d79131d97f63f093d
Reviewers: arsenm, RKSimon, mehdi_amini, courbet
Subscribers: jvesely, wdng, hiraditya, kuhar, kerbowa, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D83085
This patch add support for eliminating MemoryDefs that do not have any
aliasing users, which indicates that there are no reads/writes to the
memory location until the end of the function.
To eliminate such defs, we have to ensure that the underlying object is
not visible in the caller and does not escape via returning. We need a
separate check for that, as InvisibleToCaller does not consider returns.
Reviewers: dmgreen, rnk, efriedma, bryant, asbirlea, Tyker, george.burgess.iv
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D72631
This patch extends storeIsNoop to also detect stores of 0 to an calloced
object. This basically ports the logic from legacy DSE to the MemorySSA
backed version.
It triggers in a few cases on MultiSource, SPEC2000, SPEC2006 with -O3
LTO:
Same hash: 218 (filtered out)
Remaining: 19
Metric: dse.NumNoopStores
Program base patch2 diff
test-suite...CFP2000/177.mesa/177.mesa.test 1.00 15.00 1400.0%
test-suite...6/482.sphinx3/482.sphinx3.test 1.00 14.00 1300.0%
test-suite...lications/ClamAV/clamscan.test 2.00 28.00 1300.0%
test-suite...CFP2006/433.milc/433.milc.test 1.00 8.00 700.0%
test-suite...pplications/oggenc/oggenc.test 2.00 9.00 350.0%
test-suite.../CINT2000/176.gcc/176.gcc.test 6.00 6.00 0.0%
test-suite.../CINT2006/403.gcc/403.gcc.test NaN 137.00 nan%
test-suite...libquantum/462.libquantum.test NaN 3.00 nan%
test-suite...6/464.h264ref/464.h264ref.test NaN 7.00 nan%
test-suite...decode/alacconvert-decode.test NaN 2.00 nan%
test-suite...encode/alacconvert-encode.test NaN 2.00 nan%
test-suite...ications/JM/ldecod/ldecod.test NaN 9.00 nan%
test-suite...ications/JM/lencod/lencod.test NaN 39.00 nan%
test-suite.../Applications/lemon/lemon.test NaN 2.00 nan%
test-suite...pplications/treecc/treecc.test NaN 4.00 nan%
test-suite...hmarks/McCat/08-main/main.test NaN 4.00 nan%
test-suite...nsumer-lame/consumer-lame.test NaN 3.00 nan%
test-suite.../Prolangs-C/bison/mybison.test NaN 1.00 nan%
test-suite...arks/mafft/pairlocalalign.test NaN 30.00 nan%
Reviewers: efriedma, zoecarver, asbirlea
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D82204
This updates the MemorySSA backed implementation to treat arguments
passed by value similar to allocas: in they are assumed to be invisible
in the caller. This is similar to how they are treated in legacy DSE.
Reviewers: efriedma, asbirlea, george.burgess.iv
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D82222
Currently we stop exploring candidates too early in some cases.
In particular, we can continue checking the defining accesses of
non-removable MemoryDefs and defs without analyzable write location
(read clobbers are already ruled out using MemorySSA at this point).
As we traverse the CFG backwards, we could end up reaching unreachable
blocks. For unreachable blocks, we won't have computed post order
numbers and because DomAccess is reachable, unreachable blocks cannot be
on any path from it.
This fixes a crash with unreachable blocks.
Port partial constant store merging logic to MemorySSA backed DSE. The
heavy lifting is done by the existing helper function. It is used in
context where we already ensured that the later instruction can
eliminate the earlier one, if it is a complete overwrite.
isOverwrite expects the later location as first argument and the earlier
result later. The adjusted call is intended to check whether CC
overwrites DefLoc.
This patch relaxes the post-dominance requirement for accesses to
objects visible after the function returns.
Instead of requiring the killing def to post-dominate the access to
eliminate, the set of 'killing blocks' (= blocks that completely
overwrite the original access) is collected.
If all paths from the access to eliminate and an exit block go through a
killing block, the access can be removed.
To check this property, we first get the common post-dominator block for
the killing blocks. If this block does not post-dominate the access
block, there may be a path from DomAccess to an exit block not involving
any killing block.
Otherwise we have to check if there is a path from the DomAccess to the
common post-dominator, that does not contain a killing block. If there
is no such path, we can remove DomAccess. For this check, we start at
the common post-dominator and then traverse the CFG backwards. Paths are
terminated when we hit a killing block or a block that is not executed
between DomAccess and a killing block according to the post-order
numbering (if the post order number of a block is greater than the one
of DomAccess, the block cannot be in in a path starting at DomAccess).
This gives the following improvements on the total number of stores
after DSE for MultiSource, SPEC2K, SPEC2006:
Tests: 237
Same hash: 206 (filtered out)
Remaining: 31
Metric: dse.NumRemainingStores
Program base new100 diff
test-suite...CFP2000/188.ammp/188.ammp.test 3624.00 3544.00 -2.2%
test-suite...ch/g721/g721encode/encode.test 128.00 126.00 -1.6%
test-suite.../Benchmarks/Olden/mst/mst.test 73.00 72.00 -1.4%
test-suite...CFP2006/433.milc/433.milc.test 3202.00 3163.00 -1.2%
test-suite...000/186.crafty/186.crafty.test 5062.00 5010.00 -1.0%
test-suite...-typeset/consumer-typeset.test 40460.00 40248.00 -0.5%
test-suite...Source/Benchmarks/sim/sim.test 642.00 639.00 -0.5%
test-suite...nchmarks/McCat/09-vor/vor.test 642.00 644.00 0.3%
test-suite...lications/sqlite3/sqlite3.test 35664.00 35563.00 -0.3%
test-suite...T2000/300.twolf/300.twolf.test 7202.00 7184.00 -0.2%
test-suite...lications/ClamAV/clamscan.test 19475.00 19444.00 -0.2%
test-suite...INT2000/164.gzip/164.gzip.test 2199.00 2196.00 -0.1%
test-suite...peg2/mpeg2dec/mpeg2decode.test 2380.00 2378.00 -0.1%
test-suite.../Benchmarks/Bullet/bullet.test 39335.00 39309.00 -0.1%
test-suite...:: External/Povray/povray.test 36951.00 36927.00 -0.1%
test-suite...marks/7zip/7zip-benchmark.test 67396.00 67356.00 -0.1%
test-suite...6/464.h264ref/464.h264ref.test 31497.00 31481.00 -0.1%
test-suite...006/453.povray/453.povray.test 51441.00 51416.00 -0.0%
test-suite...T2006/401.bzip2/401.bzip2.test 4450.00 4448.00 -0.0%
test-suite...Applications/kimwitu++/kc.test 23481.00 23471.00 -0.0%
test-suite...chmarks/MallocBench/gs/gs.test 6286.00 6284.00 -0.0%
test-suite.../CINT2000/254.gap/254.gap.test 13719.00 13715.00 -0.0%
test-suite.../Applications/SPASS/SPASS.test 30345.00 30338.00 -0.0%
test-suite...006/450.soplex/450.soplex.test 15018.00 15016.00 -0.0%
test-suite...ications/JM/lencod/lencod.test 27780.00 27777.00 -0.0%
test-suite.../CINT2006/403.gcc/403.gcc.test 105285.00 105276.00 -0.0%
There might be potential to pre-compute some of the information of which
blocks are on the path to an exit for each block, but the overall
benefit might be comparatively small.
On the set of benchmarks, 15738 times out of 20322 we reach the
CFG check, the CFG check is successful. The total number of iterations
in the CFG check is 187810, so on average we need less than 10 steps in
the check loop. Bumping the threshold in the loop from 50 to 150 gives a
few small improvements, but I don't think they warrant such a big bump
at the moment. This is all pending further tuning in the future.
Reviewers: dmgreen, bryant, asbirlea, Tyker, efriedma, george.burgess.iv
Reviewed By: george.burgess.iv
Differential Revision: https://reviews.llvm.org/D78932
- Now all SalvageDebugInfo() calls will mark undef if the salvage
attempt fails.
Reviewed by: vsk, Orlando
Differential Revision: https://reviews.llvm.org/D78369
This is D77454, except for stores. All the infrastructure work was done
for loads, so the remaining changes necessary are relatively small.
Differential Revision: https://reviews.llvm.org/D79968
Using the existing NumFastStores statistic can be misleading when
comparing the impact of DSE patches.
For example, consider the case where a store gets removed from a
function before it is inlined into another function. A less
powerful DSE might only remove the store from functions it has
been inlined into, which will result in more stores being removed, but
no difference in the actual number of stores after DSE.
The new stat provides the absolute number of stores surviving after
DSE.
Reviewers: dmgreen, bryant, asbirlea, jfb
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D78830
This patch slightly improves the formatting of the debug output, adds a
few missing outputs and makes some existing outputs more consistent with
the rest.
We can eliminate MemoryDefs of objects not accessible after the function
returns (e.g. alloca), if there are no reads between the MemoryDef and
any function exits. We can stop traversing paths that completely
overwrite the memory location of the MemoryDef.
This patch was split off D73763.
Reviewers: dmgreen, bryant, asbirlea, Tyker, efriedma, george.burgess.iv
Reviewed By: asbirlea, george.burgess.iv
Differential Revision: https://reviews.llvm.org/D77736
callCapturesBefore always returns ModRef , if UseInst isn't a call. As
we only call it if we already know Mod is set, this only destroys the
Must bit for non-calls.
For MemoryPhis, we have to avoid that the MemoryPhi may be executed
before before the access we are currently looking at.
To do this we do a post-order numbering of the basic blocks in the
function and bail out once we reach a MemoryPhi with a larger (or equal)
post-order block number than the current MemoryAccess.
This changes the order in which we visit stores for elimination.
This patch also adds support for exploring multiple paths. We keep a worklist (ToCheck) of memory accesses that might be eliminated by our starting MemoryDef or MemoryPhis for further exploration. For MemoryPhis, we add the incoming values to the worklist, for MemoryDefs we add the defining access.
Reviewers: dmgreen, rnk, efriedma, bryant, asbirlea
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D72148
DSE would mistakenly remove store (2):
a = calloc(n+1)
for (int i = 0; i < n; i++) {
store 1, a[i+1] // (1)
store 0, a[i] // (2)
}
The fix is to do PHI transaltion while looking for clobbering
instructions between the store and the calloc.
Reviewed By: efriedma, bjope
Differential Revision: https://reviews.llvm.org/D68006
Add a map from BasicBlocks to overlap intervals. For partial writes, we
can keep track of those in IOLs. We only add candidates that are valid
for eliminations.
Reviewers: dmgreen, bryant, asbirlea, Tyker
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D73757
Can be used like
-debug-counter=dse-memoryssa-skip=10,dse-memoryssa-counter-count=20
Reviewers: dmgreen, rnk, efriedma, bryant, asbirlea
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D72147
Essentially, fold OrderedBasicBlock into BasicBlock, and make it
auto-invalidate the instruction ordering when new instructions are
added. Notably, we don't need to invalidate it when removing
instructions, which is helpful when a pass mostly delete dead
instructions rather than transforming them.
The downside is that Instruction grows from 56 bytes to 64 bytes. The
resulting LLVM code is substantially simpler and automatically handles
invalidation, which makes me think that this is the right speed and size
tradeoff.
The important change is in SymbolTableTraitsImpl.h, where the numbering
is invalidated. Everything else should be straightforward.
We probably want to implement a fancier re-numbering scheme so that
local updates don't invalidate the ordering, but I plan for that to be
future work, maybe for someone else.
Reviewed By: lattner, vsk, fhahn, dexonsmith
Differential Revision: https://reviews.llvm.org/D51664
This reverts commit d0c4d4fe09.
Revert "[DSE,MSSA] Move more passing test cases from todo to simple.ll."
This reverts commit 02266e64bb.
Revert "[DSE,MSSA] Adjust mda-with-dbg-values.ll to MSSA backed DSE."
This reverts commit 74f03e4ff0.
This patch adds a first version of a MemorySSA based DSE. It is missing
a lot of features, which will get added as follow-ups, to help to keep
the review manageable.
The patch uses the following general approach: given a MemoryDef, walk
upwards to find clobbering MemoryDefs that may be killed by the
starting def. Then check that there are no uses that may read the
location of the original MemoryDef in between both MemoryDefs. A bit
more concretely:
For all MemoryDefs StartDef:
1. Get the next dominating clobbering MemoryDef (DomAccess) by walking upwards.
2. Check that there no reads between DomAccess and the StartDef by checking
all uses starting at DomAccess and walking until we see StartDef.
3. For each found DomDef, check that:
1. There are no barrier instructions between DomDef and StartDef (like
throws or stores with ordering constraints).
2. StartDef is executed whenever DomDef is executed.
3. StartDef completely overwrites DomDef.
4. Erase DomDef from the function and MemorySSA.
The patch uses a very simple approach to guarantee that no throwing
instructions are between 2 stores: We only allow accesses to stack
objects, access that are in the same basic block if the block does not
contain any throwing instructions or accesses in functions that do
not contain any throwing instructions. This will get lifted later.
Besides adding support for the missing cases, there is plenty of additional
potential for improvements as follow-up work, e.g. the way we visit stores
(could be just a traversal of the MemorySSA, rather than collecting them
up-front), using the alias information discovered during walking to optimize
the MemorySSA.
This is loosely based on D40480 by Dave Green.
Reviewers: dmgreen, rnk, efriedma, bryant, asbirlea, Tyker
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D72700
This copies the DSE tests into a MSSA subdirectory to test the MemorySSA
backed DSE implementation, without disturbing the original tests.
Differential Revision: https://reviews.llvm.org/D72145
The patch makes sure that the LastThrowing pointer does not point to any instruction deleted by call to DeleteDeadInstruction.
While iterating through the instructions the pass maintains a pointer to the lastThrowing Instruction. A call to deleteDeadInstruction deletes a dead store and other instructions feeding the original dead instruction which also become dead. The instruction pointed by the lastThrowing pointer could also be deleted by the call to DeleteDeadInstruction and thus it becomes a dangling pointer. Because of this, we see an error in the next iteration.
In the patch, we maintain a list of throwing instructions encountered previously and use the last non deleted throwing instruction from the container.
Reviewers: fhahn, bcahoon, efriedma
Reviewed By: fhahn
Differential Revision: https://reviews.llvm.org/D65326
The patch makes sure that the LastThrowing pointer does not point to any instruction deleted by call to DeleteDeadInstruction.
While iterating through the instructions the pass maintains a pointer to the lastThrowing Instruction. A call to deleteDeadInstruction deletes a dead store and other instructions feeding the original dead instruction which also become dead. The instruction pointed by the lastThrowing pointer could also be deleted by the call to DeleteDeadInstruction and thus it becomes a dangling pointer. Because of this, we see an error in the next iteration.
In the patch, we maintain a list of throwing instructions encountered previously and use the last non deleted throwing instruction from the container.
Patch by Ankit <quic_aankit@quicinc.com>
Reviewers: fhahn, bcahoon, efriedma
Reviewed By: fhahn
Differential Revision: https://reviews.llvm.org/D65326
