Summary:
Some of our internal testing detected a major compile time regression which I've
tracked down to:
r278938 - Revert "Reassociate: Reprocess RedoInsts after each inst".
It appears that processing long chains of reassociatable instructions causes
non-linear (potentially exponential) growth in the number of times an
instruction is revisited. For example, the included test revisits instructions
220 times in a 20-instruction test.
It appears that r278938 reversed the order instructions were visited and that
this is preventing scheduled revisits from being cancelled as a result of
visiting the instructions naturally during normal processing. However, simply
reversing the order also harmed the generated code. Upon closer inspection, it
was discovered that revisits occurred in the opposite order to the first pass
(Thanks to escha for spotting that).
This patch makes the revisit order consistent with the first pass which allows
more revisits to be cancelled. This does appear to have a small impact on the
generated code in few cases but it significantly reduces compile-time.
After this patch, our internal test that was most affected by the regression
dropped from ~2 million revisits to ~4k resulting in Reassociate having 0.46%
of the runtime it had before (99.54% improvement).
Here's the summaries reported by lnt for the LLVM test-suite with --benchmarking-only:
| metric | geomean before patch | geomean after patch | delta |
| ----- | ----- | ----- | ----- |
| compile time | 0.1956 | 0.1261 | -35.54% |
| execution time | 0.3240 | 0.3237 | - |
| code size | 7365.4459 | 7365.6079 | - |
The results have a few wins and losses on compile-time, mostly in the +/- 2.5% range. There was one outlier though:
| Performance Regressions - compile_time | Δ | Previous | Current |
| MultiSource/Benchmarks/ASC_Sequoia/CrystalMk/CrystalMk | 9.82% | 2.0473 | 2.2483 |
Reviewers: javed.absar, dberlin
Reviewed By: dberlin
Subscribers: kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D45734
llvm-svn: 331381
The size of an object cannot be less than the emitted size of all the
contained elements. This would cause an overflow in padding size
calculation. Add an assert to catch this.
Patch by Suyog Sarda.
llvm-svn: 331376
Summary: performAddCombine should run after DAG is legalized; Otherwise generic optimization
in the DAGCombiner can optimize an addcarry+trunc into an addcarry instruction with
illegal types.
Author: FarhanaAleen
Reviewed By: rampitec
Subscribers: llvm-commits, AMDGPU
Differential Revision: https://reviews.llvm.org/D46337
llvm-svn: 331368
An input !foreach expression such as !foreach(a, lst, !add(a, 1))
would be re-emitted by llvm-tblgen -print-records with the first
argument in quotes, giving !foreach("a", lst, !add(a, 1)), which isn't
valid TableGen input syntax.
Reviewers: nhaehnle
Reviewed By: nhaehnle
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D46352
llvm-svn: 331351
It turned out that readonly argmemonly is not enough.
store 42, %p
%b = barrier(%p)
store 43, %b
the first store is dead, but because barrier was marked as
reading argument memory, it was considered alive. With
inaccessiblememonly it doesn't read the argument, but
it also can't be CSEd.
based on: https://reviews.llvm.org/D32006
llvm-svn: 331338
Summary:
This is a follow up to rL331182. A PHI node can be split up into
several MIR PHI nodes when being selected. When there is a
dbg.value intrinsic that uses the result of such a PHI node we
need to select several DBG_VALUE instructions, with fragment
expressions, in order to do a correct selection.
Reviewers: rnk, aprantl, vsk
Reviewed By: vsk
Subscribers: mattd, llvm-commits, JDevlieghere, aprantl, gbedwell, rnk
Tags: #debug-info
Differential Revision: https://reviews.llvm.org/D46329
llvm-svn: 331337
Summary:
This brings the filenames in accordance to the style guide and LLVM
conventions for C++ filenames.
As suggested by rnk@ in D46068.
Reviewers: rnk
Subscribers: mgorny, mgrang, llvm-commits
Differential Revision: https://reviews.llvm.org/D46301
llvm-svn: 331321
The logic remains the same. Eventually, I see the RCU acting as its own separate stage in the instruction pipeline.
Differential Revision: https://reviews.llvm.org/D46331
llvm-svn: 331316
and (or (lshr X, C), ...), 1 --> (X & C') != 0
I initially thought about implementing the minimal pattern in instcombine as mentioned here:
https://bugs.llvm.org/show_bug.cgi?id=37098#c6
...but we need to do better to catch the more general sequence from the motivating test
(more than 2 bits in the compare). And a test-suite run with statistics showed that this
pattern only happened 2 times currently. It would potentially happen more often if
reassociation worked better (D45842), but it's probably still not too frequent?
This is small enough that I didn't see a need to create a whole new class/file within
AggressiveInstCombine. There are likely other relatively small matchers like what was
discussed in D44266 that would slide under foldUnusualPatterns() (name suggestions welcome).
We could potentially also consolidate matchers for ctpop, bswap, etc under here.
Differential Revision: https://reviews.llvm.org/D45986
llvm-svn: 331311
As mentioned in D45986, there's a potential ordering dependency
between instcombine and aggressive-instcombine for detecting these,
so I'm adding a few tests to confirm that the expected folds occur
using -O3 (because aggressive-instcombine only runs at -O3 currently).
llvm-svn: 331308
While running the lit tests for the most recent version of D45916
(https://reviews.llvm.org/D45916), I found that a couple tests for this pass
suddenly started segfaulting. Since the outliner wasn't actually doing anything
to the code in either of these tests I got curious.
I found that the pass doesn’t completely create the machine-level constructs
necessary to actually add a MachineFunction and MachineBasicBlock to the
module. This patch adds in those missing bits. After this, adding the
outliner before this pass won’t cause it to segfault.
You can recreate this behaviour by adding the MachineOutliner directly before
the pass and having it return false immediately.
https://reviews.llvm.org/D46330
llvm-svn: 331307
This adds a some more tests, and adds some notes to tests which are using
a suboptimal lowering.
The constants with suboptimal lowerings seem to be relatively rare in
practice, but it might be a fun project to work on improvements.
llvm-svn: 331304
The logic for this combine is almost identical to the logic for a
(sext (sextload x)) combine.
This commit factors out the logic so it can be shared by both combines,
and corrects the SDLoc assigned in the zext version of the combine.
Prior to this patch, for the given test case, we would apply the
location associated with the udiv instruction to instructions which
perform the load.
Part of: llvm.org/PR37262
llvm-svn: 331303
Prior to this patch, for the given test case, we would apply the
location associated with the sdiv instruction to instructions which
perform the load.
Part of: llvm.org/PR37262.
Differential Revision: https://reviews.llvm.org/D46222
llvm-svn: 331302
In DAGCombiner, we try to simplify this pattern:
([s|z]ext (load ...))
Conceptually, a new extload which is created while splitting the load
should have the same debug location as the load.
Making this change affects the IROrder of the new load, causing some
test case churn.
In practice, the new location is never different from the location of
the [s|z]ext, at least not during check-llvm or a stage2 build.
Part of: llvm.org/PR37262
Differential Revision: https://reviews.llvm.org/D46156
llvm-svn: 331301
Setting the right SDLoc on a newly-created zextload fixes a line table
bug which resulted in non-linear stepping behavior.
Several backend tests contained CHECK lines which relied on the IROrder
inherited from the wrong SDLoc. This patch breaks that dependence where
feasbile and regenerates test cases where not.
In some cases, changing a node's IROrder may alter register allocation
and spill behavior. This can affect performance. I have chosen not to
prevent this by applying a "known good" IROrder to SDLocs, as this may
hide a more general bug in the scheduler, or cause regressions on other
test inputs.
rdar://33755881, Part of: llvm.org/PR37262
Differential Revision: https://reviews.llvm.org/D45995
llvm-svn: 331300
