into Analysis as a standalone function, since there's no need for
it to be in VMCore. Also, update it to use isKnownNonZero and
other goodies available in Analysis, making it more precise,
enabling more aggressive optimization.
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On ARM, peephole optimization for ABS creates a trivial cfg triangle which tempts machine sink to sink instructions in code which is really straight line code. Sometimes this sinking may alter register allocator input such that use and def of a reg is divided by a branch in between, which may result in extra spills. Now mahine sink avoids sinking if final sink destination is post dominator.
Radar 10266272.
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r0 = mov #0
r0 = moveq #1
Then the second instruction has an implicit data dependency on the first
instruction. Sadly I have yet to come up with a small test case that
demonstrate the post-ra scheduler taking advantage of this.
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to finalize MI bundles (i.e. add BUNDLE instruction and computing register def
and use lists of the BUNDLE instruction) and a pass to unpack bundles.
- Teach more of MachineBasic and MachineInstr methods to be bundle aware.
- Switch Thumb2 IT block to MI bundles and delete the hazard recognizer hack to
prevent IT blocks from being broken apart.
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Fast ISel isn't able to handle 'insertvalue' and it causes a large slowdown
during -O0 compilation. We don't necessarily need to generate an aggregate of
the values here if they're just going to be extracted directly afterwards.
<rdar://problem/10530851>
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undefined result. This adds new ISD nodes for the new semantics,
selecting them when the LLVM intrinsic indicates that the undef behavior
is desired. The new nodes expand trivially to the old nodes, so targets
don't actually need to do anything to support these new nodes besides
indicating that they should be expanded. I've done this for all the
operand types that I could figure out for all the targets. Owners of
various targets, please review and let me know if any of these are
incorrect.
Note that the expand behavior is *conservatively correct*, and exactly
matches LLVM's current behavior with these operations. Ideally this
patch will not change behavior in any way. For example the regtest suite
finds the exact same instruction sequences coming out of the code
generator. That's why there are no new tests here -- all of this is
being exercised by the existing test suite.
Thanks to Duncan Sands for reviewing the various bits of this patch and
helping me get the wrinkles ironed out with expanding for each target.
Also thanks to Chris for clarifying through all the discussions that
this is indeed the approach he was looking for. That said, there are
likely still rough spots. Further review much appreciated.
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subdirectories to traverse into.
- Originally I wanted to avoid this and just autoscan, but this has one key
flaw in that new subdirectories can not automatically trigger a rerun of the
llvm-build tool. This is particularly a pain when switching back and forth
between trees where one has added a subdirectory, as the dependencies will
tend to be wrong. This will also eliminates FIXME implicitly.
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If we create new intervals for a variable that is being spilled, then those new intervals are not guaranteed to also spill. This means that anything reading from the original spilling value might not get the correct value if spills were missed.
Fixes <rdar://problem/10546864>
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clients to decide whether to look inside bundled instructions and whether
the query should return true if any / all bundled instructions have the
queried property.
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We must not issue a bitcast operation for integer-promotion of vector types, because the
location of the values in the vector may be different.
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generator to it. For non-bundle instructions, these behave exactly the same
as the MC layer API.
For properties like mayLoad / mayStore, look into the bundle and if any of the
bundled instructions has the property it would return true.
For properties like isPredicable, only return true if *all* of the bundled
instructions have the property.
For properties like canFoldAsLoad, isCompare, conservatively return false for
bundles.
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This flag is used when bundling machine instructions. It indicates
whether the operand reads a value defined inside or outside its bundle.
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1. Added opcode BUNDLE
2. Taught MachineInstr class to deal with bundled MIs
3. Changed MachineBasicBlock iterator to skip over bundled MIs; added an iterator to walk all the MIs
4. Taught MachineBasicBlock methods about bundled MIs
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The new register allocator is much more able to split back up ranges too constrained by register classes.
Fixes <rdar://problem/10466609>
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This was actually a bit of a mess. TLI.setPrefLoopAlignment was clearly
documented as taking log2(bytes) units, but the x86 target would still
set a preferred loop alignment of '16'.
CodePlacementOpt passed this number on to the basic block, and
AsmPrinter interpreted it as bytes.
Now both MachineFunction and MachineBasicBlock use logarithmic
alignments.
Obviously, MachineConstantPool still measures alignments in bytes, so we
can emulate the thrill of using as.
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change, now you need a TargetOptions object to create a TargetMachine. Clang
patch to follow.
One small functionality change in PTX. PTX had commented out the machine
verifier parts in their copy of printAndVerify. That now calls the version in
LLVMTargetMachine. Users of PTX who need verification disabled should rely on
not passing the command-line flag to enable it.
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non_lazy_symbol_pointers section (__IMPORT,__pointers). Ignore the 'hidden' part
since that will place it in the wrong section.
<rdar://problem/10443720>
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Conservatively returns zero when the GV does not specify an alignment nor is it
initialized. Previously it returns ABI alignment for type of the GV. However, if
the type is a "packed" type, then the under-specified alignments is attached to
the load / store instructions. In that case, the alignment of the type cannot be
trusted.
rdar://10464621
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than ABI alignment. These are loads / stores from / to "packed" data structures.
Their alignments are intentionally under-specified.
rdar://10301431
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fallthrough) in cases where we might fail to rotate an exit to an outer
loop onto the end of the loop chain.
Having *some* rotation, but not performing this rotation, is the primary
fix of thep performance regression with -enable-block-placement for
Olden/em3d (a whopping 30% regression). Still working on reducing the
test case that actually exercises this and the new rotation strategy out
of this code, but I want to check if this regresses other test cases
first as that may indicate it isn't the correct fix.
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was centered around the premise of laying out a loop in a chain, and
then rotating that chain. This is good for preserving contiguous layout,
but bad for actually making sane rotations. In order to keep it safe,
I had to essentially make it impossible to rotate deeply nested loops.
The information needed to correctly reason about a deeply nested loop is
actually available -- *before* we layout the loop. We know the inner
loops are already fused into chains, etc. We lose information the moment
we actually lay out the loop.
The solution was the other alternative for this algorithm I discussed
with Benjamin and some others: rather than rotating the loop
after-the-fact, try to pick a profitable starting block for the loop's
layout, and then use our existing layout logic. I was worried about the
complexity of this "pick" step, but it turns out such complexity is
needed to handle all the important cases I keep teasing out of benchmarks.
This is, I'm afraid, a bit of a work-in-progress. It is still
misbehaving on some likely important cases I'm investigating in Olden.
It also isn't really tested. I'm going to try to craft some interesting
nested-loop test cases, but it's likely to be extremely time consuming
and I don't want to go there until I'm sure I'm testing the correct
behavior. Sadly I can't come up with a way of getting simple, fine
grained test cases for this logic. We need complex loop structures to
even trigger much of it.
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heavily on AnalyzeBranch. That routine doesn't behave as we want given
that rotation occurs mid-way through re-ordering the function. Instead
merely check that there are not unanalyzable branching constructs
present, and then reason about the CFG via successor lists. This
actually simplifies my mental model for all of this as well.
The concrete result is that we now will rotate more loop chains. I've
added a test case from Olden highlighting the effect. There is still
a bit more to do here though in order to regain all of the performance
in Olden.
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pass. This is designed to achieve one of the important optimizations
that the old code placement pass did, but more simply.
This is a somewhat rough and *very* conservative version of the
transform. We could get a lot fancier here if there are profitable cases
to do so. In particular, this only looks for a single pattern, it
insists that the loop backedge being rotated away is the last backedge
in the chain, and it doesn't provide any means of doing better in-loop
placement due to the rotation. However, it appears that it will handle
the important loops I am finding in the LLVM test suite.
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need lots of fanciness around retaining a reference to a Chain's slot in
the BlockToChain map, but that's all gone now. We can just go directly
to allocating the new chain (which will update the mapping for us) and
using it.
Somewhat gross mechanically generated test case replicates the issue
Duncan spotted when actually testing this out.
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conflicts, we should only be adding the first block of the chain to the
list, lest we try to merge into the middle of that chain. Most of the
places we were doing this we already happened to be looking at the first
block, but there is no reason to assume that, and in some cases it was
clearly wrong.
I've added a couple of tests here. One already worked, but I like having
an explicit test for it. The other is reduced from a test case Duncan
reduced for me and used to crash. Now it is handled correctly.
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further. This invariant just wasn't going to work in the face of
unanalyzable branches; we need to be resillient to the phenomenon of
chains poking into a loop and poking out of a loop. In fact, we already
were, we just needed to not assert on it.
This was found during a bootstrap with block placement turned on.
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successors, they just are all landing pad successors. We handle this the
same way as no successors. Comments attached for the next person to wade
through here and another lovely test case courtesy of Benjamin Kramer's
bugpoint reduction.
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This was a bug in keeping track of the available domains when merging
domain values.
The wrong domain mask caused ExecutionDepsFix to try to move VANDPSYrr
to the integer domain which is only available in AVX2.
Also add an assertion to catch future attempts at emitting AVX2
instructions.
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reversed in the function's original ordering, and we happened to
encounter it while handling an outer unnatural CFG structure.
Thanks to the test case reduced from GCC's source by Benjamin Kramer.
This may also fix a crasher in gzip that Duncan reduced for me, but
I haven't yet gotten to testing that one.
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updateTerminator code didn't correctly handle EH terminators in one very
specific case. AnalyzeBranch would find no terminator instruction, and
so the fallback in updateTerminator is to assume fallthrough. This is
correct, but the destination of the fallthrough was assumed to be the
first successor.
This is *almost always* true, but in certain cases the loop
transformations will cause the landing pad to be the first successor!
Instead of this brittle logic, actually look through the successors for
a non-landing-pad accessor, and to assert if more than one is found.
This will hopefully fix some (if not all) of the self host miscompiles
with block placement. Thanks to Benjamin Kramer for reporting, Nick
Lewycky for an initial stab at a reduction, and Duncan for endless
advice on EH (which I know nothing about) as well as reviewing the
actual fix.
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dropping weights on the floor for invokes. This was impeding my writing
further test cases for invoke when interacting with probabilities and
block placement.
No test case as there doesn't appear to be a way to test this stuff. =/
Suggestions for a test case of course welcome. I hope to be able to add
test cases that indirectly cover this eventually by adding probabilities
to the exceptional edge and reordering blocks as a result.
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properly account for the *global* probability of the edge being taken.
This manifested as a very large number of unconditional branches to
blocks being merged against the CFG even though they weren't
particularly hot within the CFG.
The fix is to check whether the edge being merged is both locally hot
relative to other successors for the source block, and globally hot
compared to other (unmerged) predecessors of the destination block.
This introduces a new crasher on GCC single-source, but it's currently
behind a flag, and Ben has offered to work on the reduction. =]
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formation phase and into the initial walk of the basic blocks. We
essentially pre-merge all blocks where unanalyzable fallthrough exists,
as we won't be able to update the terminators effectively after any
reorderings. This is quite a bit more principled as there may be CFGs
where the second half of the unanalyzable pair has some analyzable
predecessor that gets placed first. Then it may get placed next,
implicitly breaking the unanalyzable branch even though we never even
looked at the part that isn't analyzable. I've included a test case that
triggers this (thanks Benjamin yet again!), and I'm hoping to synthesize
some more general ones as I dig into related issues.
Also, to make this new scheme work we have to be able to handle branches
into the middle of a chain, so add this check. We always fallback on the
incoming ordering.
Finally, this starts to really underscore a known limitation of the
current implementation -- we don't consider broken predecessors when
merging successors. This can caused major missed opportunities, and is
something I'm planning on looking at next (modulo more bug reports).
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ADDs. MaxOffs is used as a threshold to limit the size of the offset. Tradeoffs
being: (1) If we can't materialize the large constant then we'll cause fast-isel
to bail. (2) Too large of an offset can't be directly encoded in the ADD
resulting in a MOV+ADD. Generally not a bad thing because otherwise we would
have had ADD+ADD, but on Thumb this turns into a MOVS+MOVT+ADD. Working on a fix
for that. (3) Conversely, too low of a threshold we'll miss opportunities to
coalesce ADDs.
rdar://10412592
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for a single miss and not all predecessor instructions that get selected by
the selection DAG instruction selector. This is still not exact (e.g., over
states misses when folded/dead instructions are present), but it is a step in
the right direction.
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and code model. This eliminates the need to pass OptLevel flag all over the
place and makes it possible for any codegen pass to use this information.
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There may be many invokes that share one landing pad, and the previous code
would record the landing pad once for each invoke. Besides the wasted
effort, a pair of volatile loads gets inserted every time the landing pad is
processed. The rest of the code can get optimized away when a landing pad
is processed repeatedly, but the volatile loads remain, resulting in code like:
LBB35_18:
Ltmp483:
ldr r2, [r7, #-72]
ldr r2, [r7, #-68]
ldr r2, [r7, #-72]
ldr r2, [r7, #-68]
ldr r2, [r7, #-72]
ldr r2, [r7, #-68]
ldr r2, [r7, #-72]
ldr r2, [r7, #-68]
ldr r2, [r7, #-72]
ldr r2, [r7, #-68]
ldr r2, [r7, #-72]
ldr r2, [r7, #-68]
ldr r2, [r7, #-72]
ldr r2, [r7, #-68]
ldr r2, [r7, #-72]
ldr r2, [r7, #-68]
ldr r4, [r7, #-72]
ldr r2, [r7, #-68]
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This same basic code was in the older version of the SjLj exception handling,
but it was removed in the recent revisions to that code. It needs to be there.
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%arrayidx135 = getelementptr inbounds [4 x [4 x [4 x [4 x i32]]]]* %M0, i32 0, i64 0
%arrayidx136 = getelementptr inbounds [4 x [4 x [4 x i32]]]* %arrayidx135, i32 0, i64 %idxprom134
Prior to this commit, the GEP instruction that defines %arrayidx136 thought that
%arrayidx135 was a trivial kill. The GEP that defines %arrayidx135 doesn't
generate any code and thus %M0 gets folded into the second GEP. Thus, we need
to look through GEPs with all zero indices.
rdar://10443319
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has a reference to it. Unfortunately, that doesn't work for codegen passes
since we don't get notified of MBB's being deleted (the original BB stays).
Use that fact to our advantage and after printing a function, check if
any of the IL BBs corresponds to a symbol that was not printed. This fixes
pr11202.
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block sequence when recovering from unanalyzable control flow
constructs, *always* use the function sequence. I'm not sure why I ever
went down the path of trying to use the loop sequence, it is
fundamentally not the correct sequence to use. We're trying to preserve
the incoming layout in the cases of unreasonable control flow, and that
is only encoded at the function level. We already have a filter to
select *exactly* the sub-set of blocks within the function that we're
trying to form into a chain.
The resulting code layout is also significantly better because of this.
In several places we were ending up with completely unreasonable control
flow constructs due to the ordering chosen by the loop structure for its
internal storage. This change removes a completely wasteful vector of
basic blocks, saving memory allocation in the common case even though it
costs us CPU in the fairly rare case of unnatural loops. Finally, it
fixes the latest crasher reduced out of GCC's single source. Thanks
again to Benjamin Kramer for the reduction, my bugpoint skills failed at
it.
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Two new TargetInstrInfo hooks lets the target tell ExecutionDepsFix
about instructions with partial register updates causing false unwanted
dependencies.
The ExecutionDepsFix pass will break the false dependencies if the
updated register was written in the previoius N instructions.
The small loop added to sse-domains.ll runs twice as fast with
dependency-breaking instructions inserted.
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Keep track of the last instruction to define each register individually
instead of per DomainValue. This lets us track more accurately when a
register was last written.
Also track register ages across basic blocks. When entering a new
basic block, use the least stale predecessor def as a worst case
estimate for register age.
The register age is used to arbitrate between conflicting domains. The
most recently defined register wins.
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"kill". This looks like a bug upstream. Since that's going to take some time
to understand, loosen the assertion and disable the optimization when
multiple kills are seen.
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instructions of the two-address operands) in order to avoid inserting copies.
This fixes the few regressions introduced when the two-address hack was
disabled (without regressing the improvements).
rdar://10422688
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cleans up all the chains allocated during the processing of each
function so that for very large inputs we don't just grow memory usage
without bound.
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tests when I forcibly enabled block placement.
It is apparantly possible for an unanalyzable block to fallthrough to
a non-loop block. I don't actually beleive this is correct, I believe
that 'canFallThrough' is returning true needlessly for the code
construct, and I've left a bit of a FIXME on the verification code to
try to track down why this is coming up.
Anyways, removing the assert doesn't degrade the correctness of the algorithm.
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this pass. We're leaving already merged blocks on the worklist, and
scanning them again and again only to determine each time through that
indeed they aren't viable. We can instead remove them once we're going
to have to scan the worklist. This is the easy way to implement removing
them. If this remains on the profile (as I somewhat suspect it will), we
can get a lot more clever here, as the worklist's order is essentially
irrelevant. We can use swapping and fold the two loops to reduce
overhead even when there are many blocks on the worklist but only a few
of them are removed.
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time it is queried to compute the probability of a single successor.
This makes computing the probability of every successor of a block in
sequence... really really slow. ;] This switches to a linear walk of the
successors rather than a quadratic one. One of several quadratic
behaviors slowing this pass down.
I'm not really thrilled with moving the sum code into the public
interface of MBPI, but I don't (at the moment) have ideas for a better
interface. My direction I'm thinking in for a better interface is to
have MBPI actually retain much more state and make *all* of these
queries cheap. That's a lot of work, and would require invasive changes.
Until then, this seems like the least bad (ie, least quadratic)
solution. Suggestions welcome.
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correctly handle blocks whose successor weights sum to more than
UINT32_MAX. This is slightly less efficient, but the entire thing is
already linear on the number of successors. Calling it within any hot
routine is a mistake, and indeed no one is calling it. It also
simplifies the code.
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the sum of the edge weights not overflowing uint32, and crashed when
they did. This is generally safe as BranchProbabilityInfo tries to
provide this guarantee. However, the CFG can get modified during codegen
in a way that grows the *sum* of the edge weights. This doesn't seem
unreasonable (imagine just adding more blocks all with the default
weight of 16), but it is hard to come up with a case that actually
triggers 32-bit overflow. Fortuately, the single-source GCC build is
good at this. The solution isn't very pretty, but its no worse than the
previous code. We're already summing all of the edge weights on each
query, we can sum them, check for an overflow, compute a scale, and sum
them again.
I've included a *greatly* reduced test case out of the GCC source that
triggers it. It's a pretty lame test, as it clearly is just barely
triggering the overflow. I'd like to have something that is much more
definitive, but I don't understand the fundamental pattern that triggers
an explosion in the edge weight sums.
The buggy code is duplicated within this file. I'll colapse them into
a single implementation in a subsequent commit.
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get loop info structures associated with them, and so we need some way
to make forward progress selecting and placing basic blocks. The
technique used here is pretty brutal -- it just scans the list of blocks
looking for the first unplaced candidate. It keeps placing blocks like
this until the CFG becomes tractable.
The cost is somewhat unfortunate, it requires allocating a vector of all
basic block pointers eagerly. I have some ideas about how to simplify
and optimize this, but I'm trying to get the logic correct first.
Thanks to Benjamin Kramer for the reduced test case out of GCC. Sadly
there are other bugs that GCC is tickling that I'm reducing and working
on now.
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This makes no difference for normal defs, but early clobber dead defs
now look like:
[Slot_EarlyClobber; Slot_Dead)
instead of:
[Slot_EarlyClobber; Slot_Register).
Live ranges for normal dead defs look like:
[Slot_Register; Slot_Dead)
as before.
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when we fail to place all the blocks of a loop. Currently this is
happening for unnatural loops, and this logic helps more immediately
point to the problem.
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The old naming scheme (load/use/def/store) can be traced back to an old
linear scan article, but the names don't match how slots are actually
used.
The load and store slots are not needed after the deferred spill code
insertion framework was deleted.
The use and def slots don't make any sense because we are using
half-open intervals as is customary in C code, but the names suggest
closed intervals. In reality, these slots were used to distinguish
early-clobber defs from normal defs.
The new naming scheme also has 4 slots, but the names match how the
slots are really used. This is a purely mechanical renaming, but some
of the code makes a lot more sense now.
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branches that also may involve fallthrough. In the case of blocks with
no fallthrough, we can still re-order the blocks profitably. For example
instruction decoding will in some cases continue past an indirect jump,
making laying out its most likely successor there profitable.
Note, no test case. I don't know how to write a test case that exercises
this logic, but it matches the described desired semantics in
discussions with Jakob and others. If anyone has a nice example of IR
that will trigger this, that would be lovely.
Also note, there are still assertion failures in real world code with
this. I'm digging into those next, now that I know this isn't the cause.
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second algorithm, but only loosely. It is more heavily based on the last
discussion I had with Andy. It continues to walk from the inner-most
loop outward, but there is a key difference. With this algorithm we
ensure that as we visit each loop, the entire loop is merged into
a single chain. At the end, the entire function is treated as a "loop",
and merged into a single chain. This chain forms the desired sequence of
blocks within the function. Switching to a single algorithm removes my
biggest problem with the previous approaches -- they had different
behavior depending on which system triggered the layout. Now there is
exactly one algorithm and one basis for the decision making.
The other key difference is how the chain is formed. This is based
heavily on the idea Andy mentioned of keeping a worklist of blocks that
are viable layout successors based on the CFG. Having this set allows us
to consistently select the best layout successor for each block. It is
expensive though.
The code here remains very rough. There is a lot that needs to be done
to clean up the code, and to make the runtime cost of this pass much
lower. Very much WIP, but this was a giant chunk of code and I'd rather
folks see it sooner than later. Everything remains behind a flag of
course.
I've added a couple of tests to exercise the issues that this iteration
was motivated by: loop structure preservation. I've also fixed one test
that was exhibiting the broken behavior of the previous version.
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Most of this stuff was supporting the old deferred spill code insertion
mechanism. Modern spillers just edit machine code in place.
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It was off by default.
The new register allocators don't have the problems that made it
necessary to reallocate registers during stack slot coloring.
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It is worth noting that the old spiller would split live ranges around
basic blocks. The new spiller doesn't do that.
PBQP should do its own live range splitting with
SplitEditor::splitSingleBlock() if desired. See
RAGreedy::tryBlockSplit().
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RegAllocGreedy has been the default for six months now.
Deleting RegAllocLinearScan makes it possible to also delete
VirtRegRewriter and clean up the spiller code.
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instance and a concrete inlined instance are the use of DW_TAG_subprogram
instead of DW_TAG_inlined_subroutine and the who owns the tree.
We were also omitting DW_AT_inline from the abstract roots. To fix this,
make sure we mark abstract instance roots with DW_AT_inline even when
we have only out-of-line instances referring to them with DW_AT_abstract_origin.
FileCheck is not a very good tool for tests like this, maybe we should add
a -verify mode to llvm-dwarfdump.
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instruction lower optimization" in the pre-RA scheduler.
The optimization, rather the hack, was done before MI use-list was available.
Now we should be able to implement it in a better way, perhaps in the
two-address pass until a MI scheduler is available.
Now that the scheduler has to backtrack to handle call sequences. Adding
artificial scheduling constraints is just not safe. Furthermore, the hack
is not taking all the other scheduling decisions into consideration so it's just
as likely to pessimize code. So I view disabling this optimization goodness
regardless of PR11314.
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The TII.foldMemoryOperand hook preserves implicit operands from the
original instruction. This is not what we want when those implicit
operands refer to the register being spilled.
Implicit operands referring to other registers are preserved.
This fixes PR11347.
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dragonegg self-host buildbot will recover (it is complaining about object
files differing between different build stages). Original commit message:
Add a hack to the scheduler to disable pseudo-two-address dependencies in
basic blocks containing calls. This works around a problem in which
these artificial dependencies can get tied up in calling seqeunce
scheduling in a way that makes the graph unschedulable with the current
approach of using artificial physical register dependencies for calling
sequences. This fixes PR11314.
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During the initial RPO traversal of the basic blocks, remember the ones
that are incomplete because of back-edges from predecessors that haven't
been visited yet.
After the initial RPO, revisit all those loop headers so the incoming
DomainValues on the back-edges can be properly collapsed.
This will properly fix execution domains on software pipelined code,
like the included test case.
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When merging two uncollapsed DomainValues, place a link to the active
DomainValue from the passive DomainValue. This allows old stale
references to the passive DomainValue to be updated to point to the
active DomainValue.
The new resolve() function finds the active DomainValue and updates the
pointer.
This change makes old live-out lists more useful since they may contain
uncollapsed DomainValues that have since been merged into other
DomainValues.
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This new function will decrement the reference count, and collapse a
domain value when the last reference is gone.
This simplifies DomainValue reference counting, and decouples it from
the LiveRegs array.
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basic blocks containing calls. This works around a problem in which
these artificial dependencies can get tied up in calling seqeunce
scheduling in a way that makes the graph unschedulable with the current
approach of using artificial physical register dependencies for calling
sequences. This fixes PR11314.
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The old value may still be referenced by some live-out list, and we
don't wan't to collapse those instructions twice.
This fixes the "Can only swizzle VMOVD" assertion in some armv7 SPEC
builds.
<rdar://problem/10413292>
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Add support for trimming constants to GetDemandedBits. This fixes some funky
constant generation that occurs when stores are expanded for targets that don't
support unaligned stores natively.
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When this field is true it means that the load is from constant (runt-time or compile-time) and so can be hoisted from loops or moved around other memory accesses
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DomainValues that are only used by "don't care" instructions are now
collapsed to the first possible execution domain after all basic blocks
have been processed. This typically means the PS domain on x86.
For example, the vsel_i64 and vsel_double functions in sse2-blend.ll are
completely collapsed to the PS domain instead of containing a mix of
execution domains created by isel.
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The enterBasicBlock() function is combining live-out values from
predecessor blocks. The RPO traversal means that more predecessors
have been visited when that happens, only back-edges are missing.
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to fix the types section (all types, not just global types), and testcases.
The code to do the final emission is disabled by default.
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the pubnames and pubtypes tables. LLDB can currently use this format
and a full spec is forthcoming and submission for standardization is planned.
A basic summary:
The dwarf accelerator tables are an indirect hash table optimized
for null lookup rather than access to known data. They are output into
an on-disk format that looks like this:
.-------------.
| HEADER |
|-------------|
| BUCKETS |
|-------------|
| HASHES |
|-------------|
| OFFSETS |
|-------------|
| DATA |
`-------------'
where the header contains a magic number, version, type of hash function,
the number of buckets, total number of hashes, and room for a special
struct of data and the length of that struct.
The buckets contain an index (e.g. 6) into the hashes array. The hashes
section contains all of the 32-bit hash values in contiguous memory, and
the offsets contain the offset into the data area for the particular
hash.
For a lookup example, we could hash a function name and take it modulo the
number of buckets giving us our bucket. From there we take the bucket value
as an index into the hashes table and look at each successive hash as long
as the hash value is still the same modulo result (bucket value) as earlier.
If we have a match we look at that same entry in the offsets table and
grab the offset in the data for our final match.
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into the function. Reflect that here so that the array will be placed next to
the SP.
<rdar://problem/10128329>
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the mailing list. Suggestions for other statistics to collect would be
awesome. =]
Currently these are implemented as a separate pass guarded by a separate
flag. I'm not thrilled by that, but I wanted to be able to collect the
statistics for the old code placement as well as the new in order to
have a point of comparison. I'm planning on folding them into the single
pass if / when there is only one pass of interest.
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If all of the inputs are zero/any_extended, create a new simple BV
which can be further optimized by other BV optimizations.
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fixes: Use a separate register, instead of SP, as the
calling-convention resource, to avoid spurious conflicts with
actual uses of SP. Also, fix unscheduling of calling sequences,
which can be triggered by pseudo-two-address dependencies.
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Don't assume APInt::getRawData() would hold target-aware endianness nor host-compliant endianness. rawdata[0] holds most lower i64, even on big endian host.
FIXME: Add a testcase for big endian target.
FIXME: Ditto on CompileUnit::addConstantFPValue() ?
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it fixes the dragonegg self-host (it looks like gcc is miscompiled).
Original commit messages:
Eliminate LegalizeOps' LegalizedNodes map and have it just call RAUW
on every node as it legalizes them. This makes it easier to use
hasOneUse() heuristics, since unneeded nodes can be removed from the
DAG earlier.
Make LegalizeOps visit the DAG in an operands-last order. It previously
used operands-first, because LegalizeTypes has to go operands-first, and
LegalizeTypes used to be part of LegalizeOps, but they're now split.
The operands-last order is more natural for several legalization tasks.
For example, it allows lowering code for nodes with floating-point or
vector constants to see those constants directly instead of seeing the
lowered form (often constant-pool loads). This makes some things
somewhat more complicated today, though it ought to allow things to be
simpler in the future. It also fixes some bugs exposed by Legalizing
using RAUW aggressively.
Remove the part of LegalizeOps that attempted to patch up invalid chain
operands on libcalls generated by LegalizeTypes, since it doesn't work
with the new LegalizeOps traversal order. Instead, define what
LegalizeTypes is doing to be correct, and transfer the responsibility
of keeping calls from having overlapping calling sequences into the
scheduler.
Teach the scheduler to model callseq_begin/end pairs as having a
physical register definition/use to prevent calls from having
overlapping calling sequences. This is also somewhat complicated, though
there are ways it might be simplified in the future.
This addresses rdar://9816668, rdar://10043614, rdar://8434668, and others.
Please direct high-level questions about this patch to management.
Delete #if 0 code accidentally left in.
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on every node as it legalizes them. This makes it easier to use
hasOneUse() heuristics, since unneeded nodes can be removed from the
DAG earlier.
Make LegalizeOps visit the DAG in an operands-last order. It previously
used operands-first, because LegalizeTypes has to go operands-first, and
LegalizeTypes used to be part of LegalizeOps, but they're now split.
The operands-last order is more natural for several legalization tasks.
For example, it allows lowering code for nodes with floating-point or
vector constants to see those constants directly instead of seeing the
lowered form (often constant-pool loads). This makes some things
somewhat more complicated today, though it ought to allow things to be
simpler in the future. It also fixes some bugs exposed by Legalizing
using RAUW aggressively.
Remove the part of LegalizeOps that attempted to patch up invalid chain
operands on libcalls generated by LegalizeTypes, since it doesn't work
with the new LegalizeOps traversal order. Instead, define what
LegalizeTypes is doing to be correct, and transfer the responsibility
of keeping calls from having overlapping calling sequences into the
scheduler.
Teach the scheduler to model callseq_begin/end pairs as having a
physical register definition/use to prevent calls from having
overlapping calling sequences. This is also somewhat complicated, though
there are ways it might be simplified in the future.
This addresses rdar://9816668, rdar://10043614, rdar://8434668, and others.
Please direct high-level questions about this patch to management.
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trying to legalize the operand types when only the result type
is required to be legalized - the type legalization machinery
will get round to the operands later if they need legalizing.
There can be a point to legalizing operands in parallel with
the result: when this saves compile time or results in better
code. There was only one case in which this was true: when
the operand is also split, so keep the logic for that bit.
As a result of this change, additional operand legalization
methods may need to be introduced to handle nodes where the
result and operand types can differ, like SIGN_EXTEND, but
the testsuite doesn't contain any tests where this is the case.
In any case, it seems better to require such methods (and die
with an assert if they doesn't exist) than to quietly produce
wrong code if we forgot to special case the node in
SplitVecRes_UnaryOp.
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This code makes different decisions when compiled into x87 instructions
because of different rounding behavior. That caused phase 2/3
miscompares on 32-bit Linux when the phase 1 compiler was built with gcc
(using x87), and the phase 2 compiler was built with clang (using SSE).
This fixes PR11200.
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An MBB which branches to an EH landing pad shouldn't be considered for tail merging.
In SjLj EH, the jump to the landing pad is not done explicitly through a branch
statement. The EH landing pad is added as a successor to the throwing
BB. Because of that however, the branch folding pass could mistakenly think that
it could merge the throwing BB with another BB. This isn't safe to do.
<rdar://problem/10334833>
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down to this commit. Original commit message:
An MBB which branches to an EH landing pad shouldn't be considered for tail merging.
In SjLj EH, the jump to the landing pad is not done explicitly through a branch
statement. The EH landing pad is added as a successor to the throwing
BB. Because of that however, the branch folding pass could mistakenly think that
it could merge the throwing BB with another BB. This isn't safe to do.
<rdar://problem/10334833>
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In SjLj EH, the jump to the landing pad is not done explicitly through a branch
statement. The EH landing pad is added as a successor to the throwing
BB. Because of that however, the branch folding pass could mistakenly think that
it could merge the throwing BB with another BB. This isn't safe to do.
<rdar://problem/10334833>
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to get important constant branch probabilities and use them for finding
the best branch out of a set of possibilities.
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discussions with Andy. Fundamentally, the previous algorithm is both
counter productive on several fronts and prioritizing things which
aren't necessarily the most important: static branch prediction.
The new algorithm uses the existing loop CFG structure information to
walk through the CFG itself to layout blocks. It coalesces adjacent
blocks within the loop where the CFG allows based on the most likely
path taken. Finally, it topologically orders the block chains that have
been formed. This allows it to choose a (mostly) topologically valid
ordering which still priorizes fallthrough within the structural
constraints.
As a final twist in the algorithm, it does violate the CFG when it
discovers a "hot" edge, that is an edge that is more than 4x hotter than
the competing edges in the CFG. These are forcibly merged into
a fallthrough chain.
Future transformations that need te be added are rotation of loop exit
conditions to be fallthrough, and better isolation of cold block chains.
I'm also planning on adding statistics to model how well the algorithm
does at laying out blocks based on the probabilities it receives.
The old tests mostly still pass, and I have some new tests to add, but
the nested loops are still behaving very strangely. This almost seems
like working-as-intended as it rotated the exit branch to be
fallthrough, but I'm not convinced this is actually the best layout. It
is well supported by the probabilities for loops we currently get, but
those are pretty broken for nested loops, so this may change later.
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The assumption in the back-end is that PHIs are not allowed at the start of the
landing pad block for SjLj exceptions.
<rdar://problem/10313708>
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ZExtPromotedInteger and SExtPromotedInteger based on the operation we legalize.
SetCC return type needs to be legalized via PromoteTargetBoolean.
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it's a bit more plausible to use this instead of CodePlacementOpt. The
code for this was shamelessly stolen from CodePlacementOpt, and then
trimmed down a bit. There doesn't seem to be much utility in returning
true/false from this pass as we may or may not have rewritten all of the
blocks. Also, the statistic of counting how many loops were aligned
doesn't seem terribly important so I removed it. If folks would like it
to be included, I'm happy to add it back.
This was probably the most egregious of the missing features, and now
I'm going to start gathering some performance numbers and looking at
specific loop structures that have different layout between the two.
Test is updated to include both basic loop alignment and nested loop
alignment.
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block frequency analyses. This differs substantially from the existing
block-placement pass in LLVM:
1) It operates on the Machine-IR in the CodeGen layer. This exposes much
more (and more precise) information and opportunities. Also, the
results are more stable due to fewer transforms ocurring after the
pass runs.
2) It uses the generalized probability and frequency analyses. These can
model static heuristics, code annotation derived heuristics as well
as eventual profile loading. By basing the optimization on the
analysis interface it can work from any (or a combination) of these
inputs.
3) It uses a more aggressive algorithm, both building chains from tho
bottom up to maximize benefit, and using an SCC-based walk to layout
chains of blocks in a profitable ordering without O(N^2) iterations
which the old pass involves.
The pass is currently gated behind a flag, and not enabled by default
because it still needs to grow some important features. Most notably, it
needs to support loop aligning and careful layout of loop structures
much as done by hand currently in CodePlacementOpt. Once it supports
these, and has sufficient testing and quality tuning, it should replace
both of these passes.
Thanks to Nick Lewycky and Richard Smith for help authoring & debugging
this, and to Jakob, Andy, Eric, Jim, and probably a few others I'm
forgetting for reviewing and answering all my questions. Writing
a backend pass is *sooo* much better now than it used to be. =D
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When checking the availability of instructions using the TLI, a 'promoted'
instruction IS available. It means that the value is bitcasted to another type
for which there is an operation. The correct check for the availablity of an
instruction is to check if it should be expanded.
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svn r139159 caused SelectionDAG::getConstant() to promote BUILD_VECTOR operands
with illegal types, even before type legalization. For this testcase, that led
to one BUILD_VECTOR with i16 operands and another with promoted i32 operands,
which triggered the assertion.
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.file filenumber "directory" "filename"
This removes one join+split of the directory+filename in MC internals. Because
bitcode files have independent fields for directory and filenames in debug info,
this patch may change the .o files written by existing .bc files.
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Use the custom inserter for the ARM setjmp intrinsics. Instead of creating the
SjLj dispatch table in IR, where it frequently violates serveral assumptions --
in particular assumptions made by the landingpad instruction about what can
branch to a landing pad and what cannot. Performing this in the back-end allows
us to violate these assumptions without the IR getting angry at us.
It also allows us to perform a small optimization. We can shove the address of
the dispatch's basic block into the function context and not have to add code
around the setjmp to check for the return value and jump to the dispatch.
Neat, huh?
<rdar://problem/10116753>
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to match its final use.
With this change, all of test-suite compiles for Thumb2 with -verify-coalescing
enabled.
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Some code want to check that *any* call within a function has the 'returns
twice' attribute, not just that the current function has one.
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This isn't put into the 'clear()' method because the information needs to stick
around (at least for a little bit) after the selection DAG is built.
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When spilling around an instruction with a dead def, remember to add a
value number for the def.
The missing value number wouldn't normally create problems since there
would be an incoming live range as well. However, due to another bug
we could spill a dead V_SET0 instruction which doesn't read any values.
The missing value number caused an empty live range to be created which
is dangerous since it doesn't interfere with anything.
This fixes part of PR11125.
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have the same address as the one we deleted, and we don't want that in the set
yet. Noticed by inspection.
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Now that MI->getRegClassConstraint() can also handle inline assembly,
don't bail when recomputing the register class of a virtual register
used by inline asm.
This fixes PR11078.
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Most instructions have some requirements for their register operands.
Usually, this is expressed as register class constraints in the
MCInstrDesc, but for inline assembly the constraints are encoded in the
flag words.
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The inline asm operand constraint is initially encoded in the virtual
register for the operand, but that register class may change during
coalescing, and the original constraint is lost.
Encode the original register class as part of the flag word for each
inline asm operand. This makes it possible to recover the actual
constraint required by inline asm, just like we can for normal
instructions.
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our current machine instruction defines a register with the same register class
as what's being replaced. This showed up in the SPEC 403.gcc benchmark, where it
would ICE because a tail call was expecting one register class but was given
another. (The machine instruction verifier catches this situation.)
<rdar://problem/10270968>
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rather than the previous index. If a block has a single instruction, the
previous index may be in a different basic block.
I have no clue how this used to work on all of test-suite, because now this
failure is seen quite often when trying to compile code with -strong-phi-elim.
This fixes PR10252.
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containing loop's header to see if that's a landing pad. If it is, then we don't
want to hoist instructions out of the loop and above the header.
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1. The speculation check may not have been performed if the BB hasn't had a load
LICM candidate.
2. If the candidate would be CSE'ed, then go ahead and speculatively LICM the
instruction even if it's in high register pressure situation.
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file. Since it should only be used when necessary propagate it through
the backend code generation and tweak testcases accordingly.
This helps with code like in clang's test/CodeGen/debug-info-line.c where
we have multiple #line directives within a single lexical block and want
to generate only a single block that contains each file change.
Part of rdar://10246360
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The blocks with invokes have branches to the dispatch block, because that more
correctly models the behavior of the CFG. The dispatch of course has edges to
the landing pads. Those landing pads could contain invokes, which then have
branches back to the dispatch. This creates a loop. The machine LICM pass looks
at this loop and thinks it can hoist elements out of it. But because the
dispatch is an alternate entry point into the program, the hoisted instructions
won't be executed.
I wasn't able to get a testcase which was small and could reproduce all of the
time. The function_try_block.cpp in llvm-test was where this showed up.
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For example, MachineLICM should not hoist a load that is not guaranteed to be executed.
Radar 10254254.
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Allow targets to expand COPY and other standard pseudo-instructions
before they are expanded with copyPhysReg().
This allows the target to examine the COPY instruction for extra
operands indicating it can be widened to a preferable super-register
copy. See the ARM -widen-vmovs option.
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For example, MachineLICM should not hoist a load that is not guaranteed to be executed.
Radar 10254254.
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across unwind edges. This is for the back-end which expects such things.
The code is from the original SjLj EH pass.
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to the landing pad. This will be used by the back-end to generate the jump
tables for dispatching the arriving longjmp in sjlj eh.
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PhysReg operands are not allowed to have sub-register indices at all.
For virtual registers with sub-reg indices, check that all registers in
the register class support the sub-reg index.
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EXTRACT_SUBREG is emitted as %dst = COPY %src:sub, so there is no need to
constrain the %dst register class. RegisterCoalescer will apply the
necessary constraints if it decides to eliminate the COPY.
The %src register class does need to be constrained to something with
the right sub-registers, though. This is currently done manually with
COPY_TO_REGCLASS nodes. They can possibly be removed after this patch.
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The register class created by INSERT_SUBREG and SUBREG_TO_REG must be
legal and support the SubIdx sub-registers.
The new getSubClassWithSubReg() hook can compute that.
This may create INSERT_SUBREG instructions defining a larger register
class than the sub-register being inserted. That is OK,
RegisterCoalescer will constrain the register class as needed when it
eliminates the INSERT_SUBREG instructions.
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TwoAddressInstructionPass should annotate instructions with <undef>
flags when it lower REG_SEQUENCE instructions. LiveIntervals should not
be in the business of modifying code (except for kill flags, perhaps).
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For example:
%vreg10:dsub_0<def,undef> = COPY %vreg1
%vreg10:dsub_1<def> = COPY %vreg2
is rewritten as:
%D2<def> = COPY %D0, %Q1<imp-def>
%D3<def> = COPY %D1, %Q1<imp-use,kill>, %Q1<imp-def>
The first COPY doesn't care about the previous value of %Q1, so it
doesn't read that register.
The second COPY is a partial redefinition of %Q1, so it implicitly kills
and redefines that register.
This makes it possible to recognize instructions that can harmlessly
clobber the full super-register. The write and don't read the
super-register.
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RegisterCoalescer can create sub-register defs when it is joining a
register with a sub-register. Add <undef> flags to these new
sub-register defs where appropriate.
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The <undef> flag says that a MachineOperand doesn't read its register,
or doesn't depend on the previous value of its register.
A full register def never depends on the previous register value. A
partial register def may depend on the previous value if it is intended
to update part of a register.
For example:
%vreg10:dsub_0<def,undef> = COPY %vreg1
%vreg10:dsub_1<def> = COPY %vreg2
The first copy instruction defines the full %vreg10 register with the
bits not covered by dsub_0 defined as <undef>. It is not considered a
read of %vreg10.
The second copy modifies part of %vreg10 while preserving the rest. It
has an implicit read of %vreg10.
This patch adds a MachineOperand::readsReg() method to determine if an
operand reads its register.
Previously, this was modelled by adding a full-register <imp-def>
operand to the instruction. This approach makes it possible to
determine directly from a MachineOperand if it reads its register. No
scanning of MI operands is required.
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and the alignment is 0 (i.e., it's defined globally in one file and declared in
another file) it could get an alignment which is larger than the ABI allows for
that type, resulting in aligned moves being used for unaligned loads.
For instance, in file A.c:
struct S s;
In file B.c:
struct {
// something long
};
extern S s;
void foo() {
struct S p = s;
// ...
}
this copy is a 'memcpy' which is turned into a series of 'movaps' instructions
on X86. But this is wrong, because 'struct S' has alignment of 4, not 16.
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This helps with porting code from 2.9 to 3.0 as TargetSelect.h changed location,
and if you include the old one by accident you will trigger this assert.
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The function needs to scan the implicit operands anyway, so no
performance is won by caching the number of implicit operands added to
an instruction.
This also fixes a bug when adding operands after an implicit operand has
been added manually. The NumImplicitOps count wasn't kept up to date.
MachineInstr::addOperand() will now consistently place all explicit
operands before all the implicit operands, regardless of the order they
are added. It is possible to change an MI opcode and add additional
explicit operands. They will be inserted before any existing implicit
operands.
The only exception is inline asm instructions where operands are never
reordered. This is because of a hack that marks explicit clobber regs
on inline asm as <implicit-def> to please the fast register allocator.
This hack can go away when InstrEmitter and FastIsel can add exact
<dead> flags to physreg defs.
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Upon further review, most of the EH code should remain written at the IR
level. The part which breaks SSA form is the dispatch table, so that part will
be moved to the back-end.
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This intrinsic is used to pass the index of the function context to the back-end
for further processing. The back-end is in charge of filling in the rest of the
entries.
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The DWARF exception pass uses the call site information, which is set up here. A
pre-RA pass is too late for it to use this information. So create and setup the
function context here, and then insert the call site values here (and map the
call sites for the DWARF EH pass). This is simpler than the original pass, and
doesn't make the CFG lose its SSA-ness.
It's a win-win-win-win-lose-win-win situation.
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current IR-level pass.
The old SjLj EH pass has some problems, especially with the new EH model. Most
significantly, it violates some of the new restrictions the new model has. For
instance, the 'dispatch' table wants to jump to the landing pad, but we cannot
allow that because only an invoke's unwind edge can jump to a landing pad. This
requires us to mangle the code something awful. In addition, we need to keep the
now dead landingpad instructions around instead of CSE'ing them because the
DWARF emitter uses that information (they are dead because no control flow edge
will execute them - the control flow edge from an invoke's unwind is superceded
by the edge coming from the dispatch).
Basically, this pass belongs not at the IR level where SSA is king, but at the
code-gen level, where we have more flexibility.
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Many targets use pseudo instructions to help register allocation. Like
the COPY instruction, these pseudos can be expanded after register
allocation. The early expansion can make life easier for PEI and the
post-ra scheduler.
This patch adds a hook that is called for all remaining pseudo
instructions from the ExpandPostRAPseudos pass.
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SDNodes may return values which are wider than the incoming element types. In
this patch we fix the integer promotion of these nodes.
Fixes spill-q.ll when running -promote-elements.
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I'll fix the file contents in the next commit.
This pass is currently expanding the COPY and SUBREG_TO_REG pseudos. I
am going to add a hook so targets can expand more pseudo-instructions
after register allocation.
Many targets have pseudo-instructions that assist the register
allocator. They can be expanded after register allocation, before PEI
and PostRA scheduling.
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(this is always the case for scalars), otherwise use the promoted result type.
Fix test/CodeGen/X86/vsplit-and.ll when promote-elements is enabled.
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When generating the trunc-store of i1's, we need to use the vector type and not
the scalar type.
This patch fixes the assertion in CodeGen/Generic/bool-vector.ll when
running with -promote-elements.
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DecomposeMERGE_VALUES to "know" that results are legalized in
a particular order, by passing it the number of the result
being legalized (the type legalization core provides this, it
just needs to be passed on).
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integer-promotion of CONCAT_VECTORS.
Test: test/CodeGen/X86/widen_shuffle-1.ll
This patch fixes the above tests (when running in with -promote-elements).
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Sometimes register class constraints are trivial, like GR32->GR32_NOSP,
or GPR->rGPR. Teach InstrEmitter to simply constrain the virtual
register instead of emitting a copy in these cases.
Normally, these copies are handled by the coalescer. This saves some
coalescer work.
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The function will refuse to use a register class with fewer registers
than MinNumRegs. This can be used by clients to avoid accidentally
increase register pressure too much.
The default value of MinNumRegs=0 doesn't affect how constrainRegClass()
works.
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Few weeks ago, llvm completely inverted the debug info graph. Earlier each debug info node used to keep track of its compile unit, now compile unit keeps track of important nodes. One impact of this change is that the global variable's do not have any context, which should be checked before deciding to use AT_specification DIE.
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Vector SetCC result types need to be type-legalized.
This code worked before because scalar result types are known to be legal.
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This is still a hack until we can teach tblgen to generate the
optional CPSR operand rather than an implicit CPSR def. But the
strangeness is now limited to the selection DAG. ADD/SUB MI's no
longer have implicit CPSR defs, nor do we allow flag setting variants
of these opcodes in machine code. There are several corner cases to
consider, and getting one wrong would previously lead to nasty
miscompilation. It's not the first time I've debugged one, so this
time I added enough verification to ensure it won't happen again.
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No functionality change. The hook makes it explicit which patterns
require "special" handling. i.e. it self-documents tblgen
deficiencies. I plan to add verification in ExpandISelPseudos and
Thumb2SizeReduce to catch any missing hasPostISelHooks. Otherwise it's
too fragile.
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Modified ARMISelLowering::AdjustInstrPostInstrSelection to handle the
full gamut of CPSR defs/uses including instructins whose "optional"
cc_out operand is not really optional. This allowed removal of the
hasPostISelHook to simplify the .td files and make the implementation
more robust.
Fixes rdar://10137436: sqlite3 miscompile
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