There is a subtle problem with new statepoint lowering scheme
when base and pointers are the same (see PR46917 for more context):
%1 = STATEPOINT ... %0, %0(tied-def 0)...
if, for some reason, register allocator desides to put two instances
of %0 into two different objects (registers or spill slots), we may
end up with
$reg3 = STATEPOINT ... $reg2, $reg1(tied-def 0)...
and nothing will prevent later passes to sink uses of $reg2 below
statepoint, which is incorrect.
As a short term solution, always put base pointers on stack during
lowering.
A longer term solution may be to rework MIR statepoint format to
avoid GC pointer duplication in statepoint argument list.
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D86712
This change is mechanical, it just removes the restriction and updates tests. The key building blocks were submitted in 31342eb and 8fe2abc.
Note that this (and preceeding changes) entirely subsumes D83965. I did includes a couple of it's tests.
From the codegen changes, an interesting observation: this doesn't actual reduce spilling, it just let's the register allocator do it's job. That results in a slightly different overall result which has both pros and cons over the eager spill lowering. (i.e. We'll have some perf tuning to do once this is stable.)
Change the way we track how a particular pointer was relocated at a statepoint in selection dag. Previously, we used an optional<location> for the spill lowering, and a block local Register for the newly introduced vreg lowering. Combine all three lowerings (norelocate, spill, and vreg) into a single helper class, and keep a single copy of the information.
This is submitted separately as it really does make the code more readible on it's own, but the indirect motivation is to move vreg tracking from StatepointLowering to FunctionLoweringInfo. This is the last piece needed to support cross block relocations with vregs; that will follow in a separate (non-NFC) patch.
This builds on 3da1a96 on the path towards supporting invokes and cross block relocations. The actual change attempts to be NFC, but does fail in one corner-case explained below.
The change itself is fairly mechanical. Rather than remember SDValues - which are inherently block local - immediately produce a virtual register copy and remember that.
Once this lands, we'll update the FunctionLoweringInfo::StatepointSpillMap map to allow register based lowerings, delete VirtRegs from StatepointLowering, and drop the restriction against cross block relocations. I deliberately separate the semantic part into it's own change for easy of understanding and fault isolation.
The corner-case which isn't quite NFC is that the old implementation implicitly CSEd gc.relocates of the same SDValue regardless of type. The new implementation still only relocates once, but it produces distinct vregs for the bitcast and it's source, whereas SelectionDAG's generic CSE was able to remove the bitcast in the old implementation. Note that the final assembly doesn't change (at least in the test), as our MI level optimizations catch the duplication.
I assert that this is an uninteresting corner-case. It's functionally correct, and if we find a case where this influences performance, we should really be canonicalizing types to i8* at the IR level.
Differential Revision: https://reviews.llvm.org/D84692
(Disabled under flag for the moment)
This is part of a larger project wherein we are finally integrating lowering of gc live operands with the register allocator. Today, we force spill all operands in SelectionDAG. The code to do so is distinctly non-optimal. The approach this patch is working towards is to instead lower the relocations directly into the MI form, and let the register allocator pick which ones get spilled and which stack slots they get spilled to. In terms of performance, the later part is actually more important as it avoids redundant shuffling of values between stack slots.
This particular change adds ISEL support to produce the variadic def STATEPOINT form required by the above. In particular, the first N are lowered to variadic tied def/use pairs. So new statepoint looks like this:
reloc1,reloc2,... = STATEPOINT ..., base1, derived1<tied-def0>, base2, derived2<tied-def1>, ...
N is limited by the maximal number of tied registers machine instruction can have (15 at the moment).
The current patch is restricted to handling relocations within a single basic block. Cross block relocations (e.g. invokes) are handled via the legacy mechanism. This restriction will be relaxed in future patches.
Patch By: dantrushin
Differential Revision: https://reviews.llvm.org/D81648
This is inspired by D81648. The basic idea is to have the set of SDValues which are lowered as either constants or direct frame references explicit in one place, and to separate them clearly from the spilling logic.
This is not NFC in that the handling of constants larger than > 64 bit has changed. The old lowering would crash on values which could not be encoded as a sign extended 64 bit value. The new lowering just spills all constants > 64 bits. We could be consistent about doing the sext(Con64) optimization, but I happen to know that this code path is utterly unexercised in practice, so simple is better for now.
To do so, I had to sink the old school inline operand handling into GCStatepointInst which is non ideal. This code should be removed shortly and I was able to at least clean it up a bunch.
Do not spill UNDEF GC values. Instead, replace corresponding
gc.relocate intrinsic with an (arbitrary, but recognizable) constant.
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D80714
These are the two operand sets which are expected to survive more than another week or so. Instead of bothering to update the deopt and gc-transition operands, we'll just wait until those are removed and delete the code.
For those following along, this is likely to be the last (major) change in this sequence for about a week. I want to wait until all of this has been merged downstream to ensure I haven't introduced any bugs (and migrate some downstream code to the new interfaces). Once that's done, we should be able to delete Statepoint/ImmutableStatepoint without too much work.
I'd apparently only grepped in the lib directories and missed a few used in the Statepoint header itself. Beyond simple mechanical cleanup, changed the type of one routine to reflect the fact it also returns a statepoint.
Sinking logic around actual callee from Statepoint to GCStatepointInst. While doing so, adjust naming to be consistent about refering to "actual" callee and follow precedent on naming from CallBase otherwise.
Use the result to simplify one consumer. This is mostly just to ensure the new code is exercised, but is also a helpful cleanup on it's own.
In the current statepoint design, we have four distinct groups of operands to the call: call args, gc transition args, deopt args, and gc args. This format prexisted the support in IR for operand bundles and was in fact one of the inspirations for the extension. However, we never went back and rearchitected statepoints to fully leverage bundles.
This change is the first in a small sequence to do so. All this does is extend the SelectionDAG lowering code to allow deopt and gc transition operands to be specified in either inline argument bundles or operand bundles.
Differential Revision: https://reviews.llvm.org/D8059
We do not have any special handling for constant FP deopt arguments.
They are just spilled to stack or generated in register by MOVS
instruction. This is inefficient and, when we have too many such
constant arguments, may result in register allocation failure.
Instead, we can bitcast such constant FP operands to appropriately
sized integer and record as constant into statepoint and later, into
StackMap.
Reviewed By: skatkov
Differential Revision: https://reviews.llvm.org/D80318
Remove a number of includes that aren't necessary (nor are we relying on the remaining includes to provide the declarations), we just needed a llvm::Instruction forward declaration.
This exposed a couple of source files that were implicitly replying on the includes for their use of llvm::SmallSet or std::set, requiring local includes to be added there instead.
The change introduces the usage of physical registers for non-gc deopt values.
This require runtime support to know how to take a value from register.
By default usage is off and can be switched on by option.
The change also introduces additional fix-up patch which forces the spilling
of caller saved registers (clobbered after the call) and re-writes statepoint
to use spill slots instead of caller saved registers.
Reviewers: reames, danstrushin
Reviewed By: dantrushin
Subscribers: mgorny, hiraditya, mgrang, llvm-commits
Differential Revision: https://reviews.llvm.org/D77797
The change introduces the usage of physical registers for non-gc deopt values.
This require runtime support to know how to take a value from register.
By default usage is off and can be switched on by option.
The change also introduces additional fix-up patch which forces the spilling
of caller saved registers (clobbered after the call) and re-writes statepoint
to use spill slots instead of caller saved registers.
Reviewers: reames, dantrushin
Reviewed By: reames, dantrushin
Subscribers: mgorny, hiraditya, mgrang, llvm-commits
Differential Revision: https://reviews.llvm.org/D77371
Move the logic whether lowering of deopt value requires a spill slot in
a separate lambda.
Reviewers: reames, dantrushin
Reviewed By: dantrushin
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D77629
The newly-created constant zero will need an extra register to hold it
in the current statepoint lowering implementation. Remove it if there
exists one.
isGCValue should detect whether the deopt value is a GC pointer.
Currently it checks by finding the value in SI.Bases and SI.Ptrs.
However these data structures contain only those values which
have corresponding gc.relocate call. So we can miss GC value if it
does not have gc.relocate call (dead after the call).
Check GC strategy whether pointer is GC one or consider any pointer
to be GC one conservatively.
Reviewers: reames, dantrushin
Reviewed By: reames
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D77130
Summary:
In method SelectionDAGBuilder::LowerStatepoint, array SI.GCTransitionArgs
is initialized from wrong part of ImmutableStatepoint class.
We copy gc args instead of transitions args.
Reviewers: reames, skatkov
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D77075
Summary:
This is patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790
Reviewers: courbet
Subscribers: jyknight, sdardis, nemanjai, hiraditya, kbarton, fedor.sergeev, asb, rbar, johnrusso, simoncook, sabuasal, niosHD, jrtc27, MaskRay, zzheng, edward-jones, atanasyan, rogfer01, MartinMosbeck, brucehoult, the_o, jfb, PkmX, jocewei, Jim, lenary, s.egerton, pzheng, sameer.abuasal, apazos, luismarques, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D77059
This is a reimplementation of the optimization removed in D75964. The actual spill/fill optimization is handled by D76013, this one just worries about reducing the stackmap section size itself by eliminating redundant entries. As noted in the comments, we could go a lot further here, but avoiding the degenerate invoke case as we did before is probably "enough" in practice.
Differential Revision: https://reviews.llvm.org/D76021
We just removed a broken duplicate elimination algorithm in D75964, and after landed that it occurred to me that duplicate elimination is simply CSE. SelectionDAG has a build in CSE, so why wasn't that triggering? Well, it turns out we were overly conservative in the memory states for our reloads and CSE (rightly) considers the incoming memory state for a load part of the identity of the load.
By loosening the chain and allowing reordering, we also allow CSE. As shown in the test case, doing iterative CSE as we go is enough to eliminate duplicate stores in later statepoints as well. We key our (block local) slot map by SDValue, so commoning a previous pair of loads at construction time means we also common following stores.
Differential Revision: https://reviews.llvm.org/D76013
A downstream test case (see included reduced test) revealed that we have a bug in how we handle duplicate relocations. If we have the same SDValue relocated twice, and that value happens to be a constant (such as null), we only export one of the two llvm::Values. Exporting on a per llvm::Value basis is required to allow lowering of gc.relocates in following basic blocks (e.g. invokes). Without it, we end up with a use of an undefined vreg and bad things happen.
Rather than fixing the optimization - which appears to be hard - I propose we simply remove it. There are no tests in tree that change with this code removed. If we find out later that this did matter for something, we can reimplement a variation of this in CodeGenPrepare to catch the easy cases without complicating the lowering code.
Thanks to Denis and Serguei who did all the hard work of figuring out what went wrong here. The patch is by far the easy part. :)
Differential Revision: https://reviews.llvm.org/D75964
Patchable statepoint is lowered into sequence of nops, so zeroed call target
should not be on register. It is better to use getTargetConstant instead
of getConstant to select zero constant for call target.
Reviewers: reames
Reviewed By: reames
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D74465
* Implements scalable size queries for MVTs, split out from D53137.
* Contains a fix for FindMemType to avoid using scalable vector type
to contain non-scalable types.
* Explicit casts for several places where implicit integer sign
changes or promotion from 32 to 64 bits caused problems.
* CodeGenDAGPatterns will treat scalable and non-scalable vector types
as different.
Reviewers: greened, cameron.mcinally, sdesmalen, rovka
Reviewed By: rovka
Differential Revision: https://reviews.llvm.org/D66871
This really should have been part of 366765. For some reason, I forgot to handle the corresponding load side, and the readable test cases (using deopt vs statepoints) turned out to be overly reduced. Oops.
As seen in the test change, the problem was that we were using a load with alignment expectations rather than the unaligned variant when the stack alignment was less than that prefered type alignment.
llvm-svn: 367718
We were silently using the ABI alignment for all of the stores generated for deopt and gc values. We'd gotten the alignment of the stack slot itself properly reduced (via MachineFrameInfo's clamping), but having the MMO on the store incorrect was enough for us to generate an aligned store to a unaligned location.
The simplest fix would have been to just pass the alignment to the helper function, but once we do that, the helper function doesn't really help. So, inline it and directly call the MMO version of DAG.getStore with a properly constructed MMO.
Note that there's a separate performance possibility here. Even if we *can* realign stacks, we probably don't *want to* if all of the stores are in slowpaths. But that's a later patch, if at all. :)
llvm-svn: 366765
The existing statepoint lowering code does something odd; it adds machine memory operands post instruction selection. This was copied from the stackmap/patchpoint implementation, but appears to be non-idiomatic.
This change is largely NFC. It moves the MMO creation logic into SelectionDAG building. It ends up not quite being NFC because the size of the stack slot is reflected in the MMO. The old code blindly used pointer size for the MMO size, which appears to have always been incorrect for larger values. It just happened nothing actually relied on the MMOs, so it worked out okay.
For context, I'm planning on removing the MOVolatile flag from these in a future commit, and then removing the MOStore flag from deopt spill slots in a separate one. Doing so is motivated by a small test case where we should be able to better schedule spill slots, but don't do so due to a memory use/def implied by the statepoint.
Differential Revision: https://reviews.llvm.org/D59106
llvm-svn: 355953
`CallBase` class rather than `CallSite` wrappers.
I pushed this change down through most of the statepoint infrastructure,
completely removing the use of CallSite where I could reasonably do so.
I ended up making a couple of cut-points: generic call handling
(instcombine, TLI, SDAG). As soon as it hit truly generic handling with
users outside the immediate code, I simply transitioned into or out of
a `CallSite` to make this a reasonable sized chunk.
Differential Revision: https://reviews.llvm.org/D56122
llvm-svn: 353660
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
Summary:
If a given liveness arg of STATEPOINT is at a fixed frame index
(e.g. a function argument passed on stack), prefer to use this
fixed location even the address is also in a register. If we use
the register it will generate a spill, which is not necessary
since the fixed frame index can be directly recorded in the stack
map.
Patch by Cherry Zhang <cherryyz@google.com>.
Reviewers: thanm, niravd, reames
Reviewed By: reames
Subscribers: cherryyz, reames, anna, arphaman, llvm-commits
Differential Revision: https://reviews.llvm.org/D53889
llvm-svn: 347998
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
This is needed for cases when the memory access is not as big as the width of
the data type. For instance, storing i1 (1 bit) would be done in a byte (8
bits).
Using 'BitSize >> 3' (or '/ 8') would e.g. give the memory access of an i1 a
size of 0, which for instance makes alias analysis return NoAlias even when
it shouldn't.
There are no tests as this was done as a follow-up to the bugfix for the case
where this was discovered (r318824). This handles more similar cases.
Review: Björn Petterson
https://reviews.llvm.org/D40339
llvm-svn: 319173
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
Denis Antrushin