The MachineOutliner has a bunch of target hooks that will call llvm_unreachable
if the target doesn't implement them. Therefore, if you enable the outliner on
such a target, it'll just crash. It'd be much better if it'd just *not* run
the outliner at all in this case.
This commit adds a hook to TargetInstrInfo that returns false by default.
Targets that implement the hook make it return true. The outliner checks the
return value of this hook to decide whether or not to continue.
llvm-svn: 329220
The linkage type on outlined functions was private before. This meant that if
you set a breakpoint in an outlined function, the debugger wouldn't be able to
give a sane name to the outlined function.
This commit changes the linkage type to internal and updates any tests that
relied on the prefixes on the names of outlined functions.
llvm-svn: 329116
Split up some of the if/else branches in runOnModule. Elaborate on some
comments. Replace a call to getOrCreateMachineFunction with getMachineFunction.
This makes it clearer what's happening in runOnModule, and ensures that the
outliner doesn't create any MachineFunctions which will never be used by the
outliner (or anything else, really).
llvm-svn: 328240
Summary:
Call MRI.freezeReservedRegs() on functions created during outlining so
that calls to isReserved() by the verifier called after this pass won't
assert.
Reviewers: MatzeB, qcolombet, paquette
Subscribers: mcrosier, javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D42749
llvm-svn: 323905
Previously, the DIBuilder didn't expose functionality to set its compile unit
in any other way than calling createCompileUnit. This meant that the outliner,
which creates new functions, had to create a new compile unit for its debug
info.
This commit adds an optional parameter in the DIBuilder's constructor which
lets you set its CU at construction.
It also changes the MachineOutliner so that it keeps track of the DISubprograms
for each outlined sequence. If debugging information is requested, then it
uses one of the outlined sequence's DISubprograms to grab a CU. It then uses
that CU to construct the DISubprogram for the new outlined function.
The test has also been updated to reflect this change.
See https://reviews.llvm.org/D42254 for more information. Also see the e-mail
discussion on D42254 in llvm-commits for more context.
llvm-svn: 322992
Before, it wasn't possible to get backtraces inside outlined functions. This
commit adds DISubprograms to the IR functions created by the outliner which
makes this possible. Also attached a test that ensures that the produced
debug information is correct. This is useful to users that want to debug
outlined code.
llvm-svn: 322789
*Mostly* NFC. Still updating the test though just for completeness.
This moves the hasAddressTaken check to MachineOutliner.cpp and replaces it
with a per-basic block test rather than a per-function test. The old test was
too conservative and was preventing functions in C programs from being
outlined even though they were safe to outline.
This was mostly a problem in C sources.
llvm-svn: 322425
This commit does two things. Firstly, it adds a collection of flags which can
be passed along to the target to encode information about the MBB that an
instruction lives in to the outliner.
Second, it adds some of those flags to the AArch64 outliner in order to add
more stack instructions to the list of legal instructions that are handled
by the outliner. The two flags added check if
- There are calls in the MachineBasicBlock containing the instruction
- The link register is available in the entire block
If the link register is available and there are no calls, then a stack
instruction can always be outlined without fixups, regardless of what it is,
since in this case, the outliner will never modify the stack to create a
call or outlined frame.
The motivation for doing this was checking which instructions are most often
missed by the outliner. Instructions like, say
%sp<def> = ADDXri %sp, 32, 0; flags: FrameDestroy
are very common, but cannot be outlined in the case that the outliner might
modify the stack. This commit allows us to outline instructions like this.
llvm-svn: 322048
Currently, the outliner considers candidates that intersect with themselves in
the candidate pruning step. That is, candidates of the form "AA" in ranges like
"AAAAAA". In that range, it looks like there are 5 instances of "AA" that could
possibly be outlined, and that's considered in the benefit calculation.
However, only at most 3 instances of "AA" could ever be outlined in "AAAAAA".
Thus, it's possible to pass through "AA" to the candidate selection step even
though it's *never* the case that "AA" could be outlined. This makes it so that
when we find candidates, we consider only non-overlapping occurrences of that
candidate.
llvm-svn: 319588
All these headers already depend on CodeGen headers so moving them into
CodeGen fixes the layering (since CodeGen depends on Target, not the
other way around).
llvm-svn: 318490
This header includes CodeGen headers, and is not, itself, included by
any Target headers, so move it into CodeGen to match the layering of its
implementation.
llvm-svn: 317647
This commit adds optimisation remarks for outlining which fire when a function
is successfully outlined.
To do this, OutlinedFunctions must now contain references to their Candidates.
Since the Candidates must still be sorted and worked on separately, this is
done by working on everything in terms of shared_ptrs to Candidates. This is
good; it means that we can easily move everything to outlining in terms of
the OutlinedFunctions rather than the individual Candidates. This is far more
intuitive than what's currently there!
(Remarks are output when a function is created for some group of Candidates.
In a later commit, all of the outlining logic should be rewritten so that we
loop over OutlinedFunctions rather than over Candidates.)
llvm-svn: 316396
Move the prune logic in pruneOverlaps to a new function, prune. This lets us
reuse the prune functionality. Makes the code a bit more readable. It'll also
make it easier to emit remarks/debug statements for pruned functions.
llvm-svn: 316031
This commit moves the decrement logic for outlined functions into the class,
and makes OccurrenceCount private. It can now be accessed via
getOccurrenceCount().
This makes it more difficult to accidentally introduce bugs by incorrectly
decrementing the occurrence count on OutlinedFunctions.
llvm-svn: 316020
Cleanup to Candidate that moves all end index calculations into
Candidate.endIdx(). For the sake of consistency, StartIdx and Len are now
private members, and can be accessed with length() and startIdx() respectively.
llvm-svn: 316019
parameterized emit() calls
Summary: This is not functional change to adopt new emit() API added in r313691.
Reviewed By: anemet
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D38285
llvm-svn: 315476
Say you have two identical linkonceodr functions, one in M1 and one in M2.
Say that the outliner outlines A,B,C from one function, and D,E,F from another
function (where letters are instructions). Now those functions are not
identical, and cannot be deduped. Locally to M1 and M2, these outlining
choices would be good-- to the whole program, however, this might not be true!
To mitigate this, this commit makes it so that the outliner sees linkonceodr
functions as unsafe to outline from. It also adds a flag,
-enable-linkonceodr-outlining, which allows the user to specify that they
want to outline from such functions when they know what they're doing.
Changing this handles most code size regressions in the test suite caused by
competing with linker dedupe. It also doesn't have a huge impact on the code
size improvements from the outliner. There are 6 tests that regress > 5% from
outlining WITH linkonceodrs to outlining WITHOUT linkonceodrs. Overall, most
tests either improve or are not impacted.
Not outlined vs outlined without linkonceodrs:
https://hastebin.com/raw/qeguxavuda
Not outlined vs outlined with linkonceodrs:
https://hastebin.com/raw/edepoqoqic
Outlined with linkonceodrs vs outlined without linkonceodrs:
https://hastebin.com/raw/awiqifiheb
Numbers generated using compare.py with -m size.__text. Tests run for AArch64
with -Oz -mllvm -enable-machine-outliner -mno-red-zone.
llvm-svn: 315136
This commit does two things. Firstly, it cleans up some of the benefit
calculation wrt outlined functions and candidates. Secondly, it fixes an
off-by-one bug in the cost model which was caused by the benefit value of
an OutlinedFunction and Candidate differing by 1. It updates the remarks test
to reflect this change.
llvm-svn: 314836
This commit yanks out the repeated sections of code in pruneCandidates into
two lambdas: ShouldSkipCandidate and Prune. This simplifies the logic in
pruneCandidates significantly, and reduces the chance of introducing bugs by
folding all of the shared logic into one place.
llvm-svn: 314475
This commit allows the outliner to avoid saving and restoring the link register
on AArch64 when it is dead within an entire class of candidates.
This introduces changes to the way the outliner interfaces with the target.
For example, the target now interfaces with the outliner using a
MachineOutlinerInfo struct rather than by using getOutliningCallOverhead and
getOutliningFrameOverhead.
This also improves several comments on the outliner's cost model.
https://reviews.llvm.org/D36721
llvm-svn: 314341
This adds missed optimization remarks which report viable candidates that
were not outlined because they would increase code size.
Other remarks will come in separate commits.
This will help to diagnose code size regressions and changes in outliner
behaviour in projects using the outliner.
https://reviews.llvm.org/D37085
llvm-svn: 312194
Since we don't factor in instruction lengths into outlining calculations
right now, it's never the case that a candidate could have length < 2.
Thus, we should quit early when we see such candidates.
llvm-svn: 310894
This commit
- Removes IsTailCall and replaces it with a target-defined unsigned
- Refactors getOutliningCallOverhead and getOutliningFrameOverhead so that they don't use IsTailCall
- Adds a call class + frame class classification to OutlinedFunction and Candidate respectively
This accomplishes a couple things.
Firstly, we don't need the notion of *tail call* in the general outlining algorithm.
Secondly, we now can have different "outlining classes" for each candidate within a set of candidates.
This will make it easy to add new ways to outline sequences for certain targets and dynamically choose
an appropriate cost model for a sequence depending on the context that that sequence lives in.
Ultimately, this should get us closer to being able to do something like, say avoid saving the link
register when outlining AArch64 instructions.
llvm-svn: 309475
This is some more cleanup in preparation for some actual
functional changes. This splits getOutliningBenefit into
two cost functions: getOutliningCallOverhead and
getOutliningFrameOverhead. These functions return the
number of instructions that would be required to call
a specific function and the number of instructions
that would be required to construct a frame for a
specific funtion. The actual outlining benefit logic
is moved into the outliner, which calls these functions.
The goal of refactoring getOutliningBenefit is to:
- Get us closer to getting rid of the IsTailCall flag
- Further split up "target-specific" things and
"general algorithm" things
llvm-svn: 309356
Doing some cleanup in preparation for some functional changes.
This commit moves findCandidates out of the suffix tree and into the
MachineOutliner class. This is much easier to follow, and removes
the burden of candidate choice from the suffix tree.
It also adds a couple FIXMEs and simplifies building outlined function
names.
llvm-svn: 309334
When parsing .mir files immediately construct the MachineFunctions and
put them into MachineModuleInfo.
This allows us to get rid of the delayed construction (and delayed error
reporting) through the MachineFunctionInitialzier interface.
Differential Revision: https://reviews.llvm.org/D33809
llvm-svn: 304758
Rename the DEBUG_TYPE to match the names of corresponding passes where
it makes sense. Also establish the pattern of simply referencing
DEBUG_TYPE instead of repeating the passname where possible.
llvm-svn: 303921
From a user prospective, it forces the use of an annoying nullptr to mark the end of the vararg, and there's not type checking on the arguments.
The variadic template is an obvious solution to both issues.
Differential Revision: https://reviews.llvm.org/D31070
llvm-svn: 299949
Module::getOrInsertFunction is using C-style vararg instead of
variadic templates.
From a user prospective, it forces the use of an annoying nullptr
to mark the end of the vararg, and there's not type checking on the
arguments. The variadic template is an obvious solution to both
issues.
llvm-svn: 299925
Module::getOrInsertFunction is using C-style vararg instead of
variadic templates.
From a user prospective, it forces the use of an annoying nullptr
to mark the end of the vararg, and there's not type checking on the
arguments. The variadic template is an obvious solution to both
issues.
Patch by: Serge Guelton <serge.guelton@telecom-bretagne.eu>
Differential Revision: https://reviews.llvm.org/D31070
llvm-svn: 299699
The old candidate collection method in the outliner caused some very large
regressions in compile time on large tests. For MultiSource/Benchmarks/7zip it
caused a 284.07 s or 1156% increase in compile time. On average, using the
SingleSource/MultiSource tests, it caused an average increase of 8 seconds in
compile time (something like 1000%).
This commit replaces that candidate collection method with a new one which
only visits each node in the tree once. This reduces the worst compile time
increase (still 7zip) to a 0.542 s overhead (22%) and the average compile time
increase on SingleSource and MultiSource to 0.018 s (4%).
llvm-svn: 298648
This commit adds tail call support to the MachineOutliner pass. This allows
the outliner to insert jumps rather than calls in areas where tail calling is
possible. Outlined tail calls include the return or terminator of the basic
block being outlined from.
Tail call support allows the outliner to take returns and terminators into
consideration while finding candidates to outline. It also allows the outliner
to save more instructions. For example, in the X86-64 outliner, a tail called
outlined function saves one instruction since no return has to be inserted.
llvm-svn: 297653
This commit changes the BumpPtrAllocator for suffix tree nodes to a SpecificBumpPtrAllocator.
Before, node construction was leaking memory because of the DenseMap in SuffixTreeNodes.
Changing this to a SpecificBumpPtrAllocator allows this memory to properly be released.
llvm-svn: 297319
Fixed the asan bot failure which led to the last commit of the outliner being reverted.
The change is in lib/CodeGen/MachineOutliner.cpp in the SuffixTree's constructor. LeafVector
is no longer initialized using reserve but just a standard constructor.
llvm-svn: 297081
This is a patch for the outliner described in the RFC at:
http://lists.llvm.org/pipermail/llvm-dev/2016-August/104170.html
The outliner is a code-size reduction pass which works by finding
repeated sequences of instructions in a program, and replacing them with
calls to functions. This is useful to people working in low-memory
environments, where sacrificing performance for space is acceptable.
This adds an interprocedural outliner directly before printing assembly.
For reference on how this would work, this patch also includes X86
target hooks and an X86 test.
The outliner is run like so:
clang -mno-red-zone -mllvm -enable-machine-outliner file.c
Patch by Jessica Paquette<jpaquette@apple.com>!
rdar://29166825
Differential Revision: https://reviews.llvm.org/D26872
llvm-svn: 296418
Jessica Paquette