This commit adds a simple verifier that tracks type indices being
touched by legalization rules' builders.
Every target will now have an opportunity to call
LegalizerInfo::verify(...) at the end of its derived LegalizerInfo's
constructor and check there are no obvious mistakes like checking only
first type for an opcode that has more than one type index and therefore
implicitly declaring any type for the second (and higher) type index
legal.
The check is only ran in assert builds and should have very minor
performance impact in assert builds and none in release builds.
This commit does not add LegalizerInfo::verify(...) calls to
target-specific legalizers, look for separate commits for that.
This commit also doesn't make the verification errors fatal, only
produces an error message, look for a later commit that does.
Reviewers: aemerson, qcolombet
Reviewed By: aemerson
Differential Revision: https://reviews.llvm.org/D46338
llvm-svn: 333576
Making LegalizeRuleSet's implementation a little more dumb and
straightforward to make it easier to read and change, in particular in
order to add the initial version of LegalizerInfo verifier
Reviewers: aemerson, qcolombet
Reviewed By: aemerson
Differential Revision: https://reviews.llvm.org/D46338
llvm-svn: 333562
This patch continues a series of patches started by r332907 (reapplied
as r332917).
In this commit we introduce new matching opcode for the MatchTable:
GIM_SwitchType, similar to GIM_SwitchOpcode, and use it to switch over
LLTs of def operands of root instructions on the 2nd level of the
MatchTable within GIM_SwitchOpcode's cases.
This is expected to decrease time GlobalISel spends in its
InstructionSelect pass by about 6.5% for an -O0 build as measured on
sqlite3-amalgamation (http://sqlite.org/download.html) targeting
AArch64 (cross-compile on x86).
Reviewers: qcolombet, dsanders, bogner, aemerson, javed.absar
Reviewed By: qcolombet
Subscribers: rovka, llvm-commits, kristof.beyls
Differential Revision: https://reviews.llvm.org/D44700
llvm-svn: 333146
This patch continues a series of patches started by r332907 (reapplied
as r332917)
In this commit we introduce a new matching opcode GIM_SwitchOpcode
that implements a jump table over opcodes and start emitting them for
root instructions.
This is expected to decrease time GlobalISel spends in its
InstructionSelect pass by roughly 20% for an -O0 build as measured on
sqlite3-amalgamation (http://sqlite.org/download.html) targeting
AArch64.
To some degree, we assume here that the opcodes form a dense set,
which is true at the moment for all upstream targets given the
limitations of our rule importing mechanism.
It might not be true for out of tree targets, specifically due to
pseudo's. If so, we might noticeably increase the size of the
MatchTable with this patch due to padding zeros. This will be
addressed later.
Reviewers: qcolombet, dsanders, bogner, aemerson, javed.absar
Reviewed By: qcolombet
Subscribers: rovka, llvm-commits, kristof.beyls
Differential Revision: https://reviews.llvm.org/D44700
llvm-svn: 333017
Apparently the compile time problem was caused by the fact that not
all compilers / STL implementations can automatically convert
std::unique_ptr<Derived> to std::unique_ptr<Base>. Fixed (hopefully)
by making sure it's std::unique_ptr<Derived>&& (rvalue ref) to
std::unique_ptr<Base> conversion instead.
llvm-svn: 332917
This patch starts a series of patches that decrease time spent by
GlobalISel in its InstructionSelect pass by roughly 60% for -O0 builds
for large inputs as measured on sqlite3-amalgamation
(http://sqlite.org/download.html) targeting AArch64.
The performance improvements are achieved solely by reducing the
number of matching GIM_* opcodes executed by the MatchTable's
interpreter during the selection by approx. a factor of 30, which also
brings contribution of this particular part of the selection process
to the overall runtime of InstructionSelect pass down from approx.
60-70% to 5-7%, thus making further improvements in this particular
direction not very profitable.
The improvements described above are expected for any target that
doesn't have many complex patterns. The targets that do should
strictly benefit from the changes, but by how much exactly is hard to
estimate beforehand. It's also likely that such target WILL benefit
from further improvements to MatchTable, most likely the ones that
bring it closer to a perfect decision tree.
This commit specifically is rather large mostly NFC commit that does
necessary preparation work and refactoring, there will be a following
series of small patches introducing a specific optimization each
shortly after.
This commit specifically is expected to cause a small compile time
regression (around 2.5% of InstructionSelect pass time), which should
be fixed by the next commit of the series.
Every commit planned shares the same Phabricator Review.
Reviewers: qcolombet, dsanders, bogner, aemerson, javed.absar
Reviewed By: qcolombet
Subscribers: rovka, llvm-commits, kristof.beyls
Differential Revision: https://reviews.llvm.org/D44700
llvm-svn: 332907
We currently handle all aggregates by creating one large LLT, and letting the
legalizer deal with splitting them up. However using this approach means that
we can't support big endian code correctly.
This patch changes the way that the IRTranslator deals with aggregate values,
by splitting them up into their constituent element values. To do this, parts
of the translator need to be modified to deal with multiple VRegs for a single
Value.
A new Value to VReg mapper is introduced to help keep compile time under
control, currently there is no measurable impact on CTMark despite the extra
code being generated in some cases.
Patch is based on the original work of Tim Northover.
Differential Revision: https://reviews.llvm.org/D46018
llvm-svn: 332449
The DEBUG() macro is very generic so it might clash with other projects.
The renaming was done as follows:
- git grep -l 'DEBUG' | xargs sed -i 's/\bDEBUG\s\?(/LLVM_DEBUG(/g'
- git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM
- Manual change to APInt
- Manually chage DOCS as regex doesn't match it.
In the transition period the DEBUG() macro is still present and aliased
to the LLVM_DEBUG() one.
Differential Revision: https://reviews.llvm.org/D43624
llvm-svn: 332240
Reverting this to see if the clang-cmake-aarch64-global-isel and
clang-cmake-aarch64-quick bots are failing because of this commit.
We know it wasn't r331819.
llvm-svn: 331846
Refactoring LegalizerHelper::widenScalar member function reducing its
size by approximately a factor of 2 and (hopefuly) making it more
straightforward and regular by introducing widenScalarSrc and
widenScalarDst helper methods.
The new widenScalar* methods mutate the instructions in place instead
of recreating them from scratch and removing the originals. The
compile time implications of this were measured on sqlite3
amalgamation, targeting AArch64 in -O0:
LegalizerHelper::widenScalar: > 25% faster
Legalizer::runOnMachineFunction: ~ 4.0 - 4.5% faster
Also adding MachineOperand::setCImm and refactoring out
MachineIRBuilder::recordInsertion methods to make the change possible.
Reviewers: aditya_nandakumar, bogner, javed.absar, t.p.northover, ab, dsanders, arsenm
Reviewed By: aditya_nandakumar
Subscribers: wdng, rovka, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D46414
llvm-svn: 331819
Summary:
Previously, a extending load was represented at (G_*EXT (G_LOAD x)).
This had a few drawbacks:
* G_LOAD had to be legal for all sizes you could extend from, even if
registers didn't naturally hold those sizes.
* All sizes you could extend from had to be allocatable just in case the
extend went missing (e.g. by optimization).
* At minimum, G_*EXT and G_TRUNC had to be legal for these sizes. As we
improve optimization of extends and truncates, this legality requirement
would spread without considerable care w.r.t when certain combines were
permitted.
* The SelectionDAG importer required some ugly and fragile pattern
rewriting to translate patterns into this style.
This patch changes the representation to:
* (G_[SZ]EXTLOAD x)
* (G_LOAD x) any-extends when MMO.getSize() * 8 < ResultTy.getSizeInBits()
which resolves these issues by allowing targets to work entirely in their
native register sizes, and by having a more direct translation from
SelectionDAG patterns.
Each extending load can be lowered by the legalizer into separate extends
and loads, however a target that supports s1 will need the any-extending
load to extend to at least s8 since LLVM does not represent memory accesses
smaller than 8 bit. The legalizer can widenScalar G_LOAD into an
any-extending load but sign/zero-extending loads need help from something
else like a combiner pass. A follow-up patch that adds combiner helpers for
for this will follow.
The new representation requires that the MMO correctly reflect the memory
access so this has been corrected in a couple tests. I've also moved the
extending loads to their own tests since they are (mostly) separate opcodes
now. Additionally, the re-write appears to have invalidated two tests from
select-with-no-legality-check.mir since the matcher table no longer contains
loads that result in s1's and they aren't legal in AArch64 anymore.
Depends on D45540
Reviewers: ab, aditya_nandakumar, bogner, rtereshin, volkan, rovka, javed.absar
Reviewed By: rtereshin
Subscribers: javed.absar, llvm-commits, kristof.beyls
Differential Revision: https://reviews.llvm.org/D45541
llvm-svn: 331601
The main goal is to share getMatchTable between the Instruction
Selector and the Testgen.
The commit also contains some NFC only loosely related to refactoring
out the getMatchTable, but strongly related to the initial Testgen
patch (see https://reviews.llvm.org/D43962)
Reviewers: dsanders, aemerson
Reviewed By: dsanders
Subscribers: rovka, kristof.beyls, llvm-commits, dsanders
Differential Revision: https://reviews.llvm.org/D46096
llvm-svn: 331395
Summary:
Previously, a extending load was represented at (G_*EXT (G_LOAD x)).
This had a few drawbacks:
* G_LOAD had to be legal for all sizes you could extend from, even if
registers didn't naturally hold those sizes.
* All sizes you could extend from had to be allocatable just in case the
extend went missing (e.g. by optimization).
* At minimum, G_*EXT and G_TRUNC had to be legal for these sizes. As we
improve optimization of extends and truncates, this legality requirement
would spread without considerable care w.r.t when certain combines were
permitted.
* The SelectionDAG importer required some ugly and fragile pattern
rewriting to translate patterns into this style.
This patch begins changing the representation to:
* (G_[SZ]EXTLOAD x)
* (G_LOAD x) any-extends when MMO.getSize() * 8 < ResultTy.getSizeInBits()
which resolves these issues by allowing targets to work entirely in their
native register sizes, and by having a more direct translation from
SelectionDAG patterns.
This patch introduces the new generic instructions and new variation on
G_LOAD and adds lowering for them to convert back to the existing
representations.
Depends on D45466
Reviewers: ab, aditya_nandakumar, bogner, rtereshin, volkan, rovka, aemerson, javed.absar
Reviewed By: aemerson
Subscribers: aemerson, kristof.beyls, javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D45540
llvm-svn: 331115
Some of the bots were failing in a different way to the others. These were
unable to compare tuples. Fix this by changing to a struct, thereby avoiding
the quirks of tuples.
llvm-svn: 331081
Summary:
Currently only the memory size is supported but others can be added as
needed.
narrowScalar for G_LOAD and G_STORE now correctly update the
MachineMemOperand and will refuse to legalize atomics since those need more
careful expansions to maintain atomicity.
Reviewers: ab, aditya_nandakumar, bogner, rtereshin, aemerson, javed.absar
Reviewed By: aemerson
Subscribers: aemerson, rovka, kristof.beyls, javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D45466
llvm-svn: 331071
As we're becoming stricter w/ respect to not allowing vregs having LLTs
and regclasses assigned both mid-globalisel pipeline, the number of
extra copies grows, some of which separate G_UNMERGE's from their
corresponding G_MERGE's, becoming a performance concern.
It's worth mentioning that we're already looking through copies while
combining legalization artifacts for every kind of artifact but
G_UNMERGE.
Reviewed By: aditya_nandakumar
Reviewers: ab, t.p.northover, volkan, javed.absar
Subscribers: rovka, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D45644
llvm-svn: 330660
Lower is slightly odd. It often doesn't change the type but the lowerings
do use the new type to decide what code to create. Treat it like a mutation
but provide convenience functions that re-use the existing type.
Re-uses the existing tests:
test/CodeGen/AArch64/GlobalISel/legalize-rem.mir
test/CodeGen/AArch64/GlobalISel//legalize-mul.mir
test/CodeGen/AArch64/GlobalISel//legalize-cmpxchg-with-success.mir
llvm-svn: 329623
building.
https://reviews.llvm.org/D45067
This change attempts to do two things:
1) It separates out the state that is stored in the
MachineIRBuilder(InsertionPt, MF, MRI, InsertFunction etc) into a
separate object called MachineIRBuilderState.
2) Add the ability to constant fold operations while building instructions
(optionally). MachineIRBuilder is now refactored into a MachineIRBuilderBase
which contains lots of non foldable build methods and their implementation.
Instructions which can be constant folded/transformed are now in a class
called FoldableInstructionBuilder which uses CRTP to use the implementation
of the derived class for buildBinaryOps. Additionally buildInstr in the derived
class can be used to implement other kinds of transformations.
Also because of separation of state, given a MachineIRBuilder in an API,
if one wishes to use another MachineIRBuilder, a new one can be
constructed from the state locally. For eg,
void doFoo(MachineIRBuilder &B) {
MyCustomBuilder CustomB(B.getState());
// Use CustomB for building.
}
reviewed by : aemerson
llvm-svn: 329596
This is used by llvm tblgen as well as by LLVM Targets, so the only
common place is Support for now. (maybe we need another target for these
sorts of things - but for now I'm at least making them correct & we can
make them better if/when people have strong feelings)
llvm-svn: 328395
Added helpers to build G_FCONSTANT, along with matching ConstantFP and
unit tests for the same.
Sample usage.
auto MIB = Builder.buildFConstant(s32, 0.5); // Build IEEESingle
For Matching the above
const ConstantFP* Tmp;
mi_match(DstReg, MRI, m_GFCst(Tmp));
https://reviews.llvm.org/D44128
reviewed by: volkan
llvm-svn: 327152
Summary:
Fabs is a common floating-point operation, especially for some expansions. This patch adds
a new generic opcode for llvm.fabs.* intrinsic in order to avoid building/matching this intrinsic.
Reviewers: qcolombet, aditya_nandakumar, dsanders, rovka
Reviewed By: aditya_nandakumar
Subscribers: kristof.beyls, javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D43864
llvm-svn: 326749
Currently it's impossible to test InstructionSelect pass with MIR which
is considered illegal by the Legalizer in Assert builds. In early stages
of porting an existing backend from SelectionDAG ISel to GlobalISel,
however, we would have very basic CallLowering, Legalizer, and
RegBankSelect implementations, but rather functional Instruction Select
with quite a few patterns selectable due to the semi-automatic porting
process borrowing them from SelectionDAG ISel.
As we are trying to define legality as a property of being selectable by
the instruction selector, it would be nice to be able to easily check
what the selector can do in its current state w/o the legality check
provided by the Legalizer getting in the way.
It also seems beneficial to have a regression testing set up that would
not allow the selector to silently regress in its support of the MIR not
supported yet by the previous passes in the GlobalISel pipeline.
This commit adds -disable-gisel-legality-check command line option to
llc that disables those legality checks in RegBankSelect and
InstructionSelect passes.
It also adds quite a few MIR test cases for AArch64's Instruction
Selector. Every one of them would fail on the legality check at the
moment, but will select just fine if the check is disabled. Every test
MachineFunction is intended to exercise a specific selection rule and
that rule only, encoded in the MachineFunction's name by the rule's
number, ID, and index of its GIM_Try opcode in TableGen'erated
MatchTable (-optimize-match-table=false).
Reviewers: ab, dsanders, qcolombet, rovka
Reviewed By: bogner
Subscribers: kristof.beyls, volkan, aditya_nandakumar, aemerson,
rengolin, t.p.northover, javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D42886
llvm-svn: 326396
Currently we assert that only non target specific opcodes can have
missing RegisterClass constraints in the MCDesc. The backend can have
instructions with register operands but don't have RegisterClass
constraints (say using unknown_class) in which case the instruction
defining the register will constrain it.
Change the assert to only fire if a def has no regclass.
https://reviews.llvm.org/D43409
llvm-svn: 326142
The base case for any_of was incorrectly returning true. Also add test
case which uses m_any_of(preds...) where none of the predicates are
true.
llvm-svn: 325848
Summary:
This patch adds templated functions to MachineIRBuilder for some opcodes
and adds pattern matcher support for G_AND and G_OR.
Reviewers: aditya_nandakumar
Reviewed By: aditya_nandakumar
Subscribers: rovka, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D43309
llvm-svn: 325162
* Document most API's
* Delete a useless function call
* Fix a discrepancy between the single and multi-opcode variants of
getActionDefinitions().
The multi-opcode variant now requires that more than one opcode is requested.
Previously it acted much like the single-opcode form but unnecessarily
enforced the requirements of the multi-opcode form.
llvm-svn: 325067
Summary:
Some of the commands tries to get the register without checking
if the specified operands is a register and causing crash. All commands
should check the type of the operand first and reject if the type is
not expected.
Reviewers: dsanders, qcolombet
Reviewed By: qcolombet
Subscribers: qcolombet, rovka, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D42984
llvm-svn: 324442
Start using the new LegalizerInfo API introduced in r323681.
Keep the old API for opcodes that need Lowering in some circumstances
(G_FNEG and G_UREM/G_SREM).
llvm-svn: 323876
Prior to committing r323681, we decided to change pick() to identity() since
it wasn't clear from the name what pick() did. However, identity() isn't a very
good name either since it implies that no changes are made. For some reason,
naming it changeTo() didn't occur to me until just after the commit. This
should resolve the lack of clarity that pick() had while still implying that
it changes the MIR.
llvm-svn: 323689
Summary:
As discussed in D42244, we have difficulty describing the legality of some
operations. We're not able to specify relationships between types.
For example, declaring the following
setAction({..., 0, s32}, Legal)
setAction({..., 0, s64}, Legal)
setAction({..., 1, s32}, Legal)
setAction({..., 1, s64}, Legal)
currently declares these type combinations as legal:
{s32, s32}
{s64, s32}
{s32, s64}
{s64, s64}
but we currently have no means to say that, for example, {s64, s32} is
not legal. Some operations such as G_INSERT/G_EXTRACT/G_MERGE_VALUES/
G_UNMERGE_VALUES have relationships between the types that are currently
described incorrectly.
Additionally, G_LOAD/G_STORE currently have no means to legalize non-atomics
differently to atomics. The necessary information is in the MMO but we have no
way to use this in the legalizer. Similarly, there is currently no way for the
register type and the memory type to differ so there is no way to cleanly
represent extending-load/truncating-store in a way that can't be broken by
optimizers (resulting in illegal MIR).
It's also difficult to control the legalization strategy. We've added support
for legalizing non-power of 2 types but there's still some hardcoded assumptions
about the strategy. The main one I've noticed is that type0 is always legalized
before type1 which is not a good strategy for `type0 = G_EXTRACT type1, ...` if
you need to widen the container. It will converge on the same result eventually
but it will take a much longer route when legalizing type0 than if you legalize
type1 first.
Lastly, the definition of legality and the legalization strategy is kept
separate which is not ideal. It's helpful to be able to look at a one piece of
code and see both what is legal and the method the legalizer will use to make
illegal MIR more legal.
This patch adds a layer onto the LegalizerInfo (to be removed when all targets
have been migrated) which resolves all these issues.
Here are the rules for shift and division:
for (unsigned BinOp : {G_LSHR, G_ASHR, G_SDIV, G_UDIV})
getActionDefinitions(BinOp)
.legalFor({s32, s64}) // If type0 is s32/s64 then it's Legal
.clampScalar(0, s32, s64) // If type0 is <s32 then WidenScalar to s32
// If type0 is >s64 then NarrowScalar to s64
.widenScalarToPow2(0) // Round type0 scalars up to powers of 2
.unsupported(); // Otherwise, it's unsupported
This describes everything needed to both define legality and describe how to
make illegal things legal.
Here's an example of a complex rule:
getActionDefinitions(G_INSERT)
.unsupportedIf([=](const LegalityQuery &Query) {
// If type0 is smaller than type1 then it's unsupported
return Query.Types[0].getSizeInBits() <= Query.Types[1].getSizeInBits();
})
.legalIf([=](const LegalityQuery &Query) {
// If type0 is s32/s64/p0 and type1 is a power of 2 other than 2 or 4 then it's legal
// We don't need to worry about large type1's because unsupportedIf caught that.
const LLT &Ty0 = Query.Types[0];
const LLT &Ty1 = Query.Types[1];
if (Ty0 != s32 && Ty0 != s64 && Ty0 != p0)
return false;
return isPowerOf2_32(Ty1.getSizeInBits()) &&
(Ty1.getSizeInBits() == 1 || Ty1.getSizeInBits() >= 8);
})
.clampScalar(0, s32, s64)
.widenScalarToPow2(0)
.maxScalarIf(typeInSet(0, {s32}), 1, s16) // If type0 is s32 and type1 is bigger than s16 then NarrowScalar type1 to s16
.maxScalarIf(typeInSet(0, {s64}), 1, s32) // If type0 is s64 and type1 is bigger than s32 then NarrowScalar type1 to s32
.widenScalarToPow2(1) // Round type1 scalars up to powers of 2
.unsupported();
This uses a lambda to say that G_INSERT is unsupported when type0 is bigger than
type1 (in practice, this would be a default rule for G_INSERT). It also uses one
to describe the legal cases. This particular predicate is equivalent to:
.legalFor({{s32, s1}, {s32, s8}, {s32, s16}, {s64, s1}, {s64, s8}, {s64, s16}, {s64, s32}})
In terms of performance, I saw a slight (~6%) performance improvement when
AArch64 was around 30% ported but it's pretty much break even right now.
I'm going to take a look at constexpr as a means to reduce the initialization
cost.
Future work:
* Make it possible for opcodes to share rulesets. There's no need for
G_LSHR/G_ASHR/G_SDIV/G_UDIV to have separate rule and ruleset objects. There's
no technical barrier to this, it just hasn't been done yet.
* Replace the type-index numbers with an enum to get .clampScalar(Type0, s32, s64)
* Better names for things like .maxScalarIf() (clampMaxScalar?) and the vector rules.
* Improve initialization cost using constexpr
Possible future work:
* It's possible to make these rulesets change the MIR directly instead of
returning a description of how to change the MIR. This should remove a little
overhead caused by parsing the description and routing to the right code, but
the real motivation is that it removes the need for LegalizeAction::Custom.
With Custom removed, there's no longer a requirement that Custom legalization
change the opcode to something that's considered legal.
Reviewers: ab, t.p.northover, qcolombet, rovka, aditya_nandakumar, volkan, reames, bogner
Reviewed By: bogner
Subscribers: hintonda, bogner, aemerson, mgorny, javed.absar, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D42251
llvm-svn: 323681
Summary:
The improvements to the LegalizerInfo discussed in D42244 require that
LegalizerInfo::LegalizeAction be available for use in other classes. As such,
it needs to be moved out of LegalizerInfo. This has been done separately to the
next patch to minimize the noise in that patch.
llvm-svn: 323669
https://reviews.llvm.org/D41373
The various components are
GICombinerHelper contains transformations that are common to all
targets. Targets can pick and choose which transformations (at
function/opcode granularity) each pass uses via configuring a
GICombinerInfo.
GICombiner contains some common code and it does the traversal,
driving of combines, worklist management and iterating until
convergence.
GICombinerInfo is an interface with a virtual method called combine.
The combiner info will allow targets to pick and choose (or
implement their own specific combines). CombineInfos can make
use of available combines in GICombineHelper to configure the
transformations for a particular pass. Currently this approach allows
cherry picking transformations from helpers (at function/opcode
granularity) and also allows early returning on specific
transformations. Targets also get to prioritize whether target specific
combines run before/after the opt-in generic combines. Ideally we would
like this part to be configured by both C++ and Tablegen. The
CombinerInfo also has a field which indicates how to deal with
IllegalOps (ie - should we allow to create them/or legalize them?).
A CombinerPass would configure a CombinerInfo, create the GICombiner
with the Info, and call
GICombiner::combineMachineInstrs(MachineFunction&).
This organization is very similar to the GISelLegalizer.
llvm-svn: 323392
Summary:
`getAction(const InstrAspect &) const` breaks encapsulation by exposing
the smaller components that are used to decide how to legalize an
instruction.
This is a problem because we need to change the implementation of
LegalizerInfo so that it's able to describe particular type combinations
rather than just cartesian products of types.
For example, declaring the following
setAction({..., 0, s32}, Legal)
setAction({..., 0, s64}, Legal)
setAction({..., 1, s32}, Legal)
setAction({..., 1, s64}, Legal)
currently declares these type combinations as legal:
{s32, s32}
{s64, s32}
{s32, s64}
{s64, s64}
but we currently have no means to say that, for example, {s64, s32} is
not legal. Some operations such as G_INSERT/G_EXTRACT/G_MERGE_VALUES/
G_UNMERGE_VALUES has relationships between the types that are currently
described incorrectly.
Additionally, G_LOAD/G_STORE currently have no means to legalize non-atomics
differently to atomics. The necessary information is in the MMO but we have no
way to use this in the legalizer. Similarly, there is currently no way for the
register type and the memory type to differ so there is no way to cleanly
represent extending-load/truncating-store in a way that can't be broken by
optimizers (resulting in illegal MIR).
This patch introduces LegalityQuery which provides all the information
needed by the legalizer to make a decision on whether something is legal
and how to legalize it.
Reviewers: ab, t.p.northover, qcolombet, rovka, aditya_nandakumar, volkan, reames, bogner
Reviewed By: bogner
Subscribers: bogner, llvm-commits, kristof.beyls
Differential Revision: https://reviews.llvm.org/D42244
llvm-svn: 323342
Right now, it is not possible to run MachineCSE in the middle of the
GlobalISel pipeline. Being able to run generic optimizations between the
core passes of GlobalISel was one of the goals of the new ISel framework.
This is the first attempt to do it.
The problem is that MachineCSE pass assumes all register operands have a
register class, which, in GlobalISel context, won't be true until after the
InstructionSelect pass. The reason for this behaviour is that before
replacing one virtual register with another, MachineCSE pass (and most of
the other optimization machine passes) must check if the virtual registers'
constraints have a (sufficiently large) intersection, and constrain the
resulting register appropriately if such intersection exists.
GlobalISel extends the representation of such constraints from just a
register class to a triple (low-level type, register bank, register
class).
This commit adds MachineRegisterInfo::constrainRegAttrs method that extends
MachineRegisterInfo::constrainRegClass to such a triple.
The idea is that going forward we should use:
- RegisterBankInfo::constrainGenericRegister within GlobalISel's
InstructionSelect pass
- MachineRegisterInfo::constrainRegClass within SelectionDAG ISel
- MachineRegisterInfo::constrainRegAttrs everywhere else regardless
the target and instruction selector it uses.
Patch by Roman Tereshin. Thanks!
llvm-svn: 322805
