A release fence acts as a publication barrier for stores within the current thread to become visible to other threads which might observe the release fence. It does not require the current thread to observe stores performed on other threads. As a result, we can allow store-load and load-load forwarding across a release fence.
We choose to be much more conservative about stores. In theory, nothing prevents us from shifting a store from after a release fence to before it, and then eliminating the preceeding (previously fenced) store. Doing this without actually moving the second store is likely also legal, but we chose to be conservative at this time.
The LangRef indicates only atomic loads and stores are effected by fences. This patch chooses to be far more conservative then that.
This is the GVN companion to http://reviews.llvm.org/D11434 which applied the same logic in EarlyCSE and has been baking in tree for a while now.
Differential Revision: http://reviews.llvm.org/D11436
llvm-svn: 264472
The implementation of SDLoc has an extra layer of indirection here for
no particular reason, and was leading to problems where we were
dereferencing pointers to SDNodes that had already been deleted so
that we could get at the DebugLoc for a new SDNode. This is one of the
errors that came up often in PR26808.
Instead, we can just track the DebugLoc and IROrder directly. This
makes the code both easier to understand and more correct. It's also
basically NFC other than fixing a large number of places where we were
reading the memory of deleted SDNodes.
llvm-svn: 264470
method instead.
This is not quite a named constructor: Construction may fail, and
MachOObjectFiles are usually passed by unique_ptr anyway, so create
returns an Expected<std::unique_ptr<MachOObjectFile>>.
llvm-svn: 264469
This helper method creates a pre-checked Error suitable for use as an out
parameter in a constructor. This avoids the need to have the constructor
check a known-good error before assigning to it.
llvm-svn: 264467
When encountering instructions with regmasks, instead of cleaning up all the
elements in MaybeDeadCopies map, remove only the instructions erased. By keeping
more instruction in MaybeDeadCopies, this change will expose more dead copies
across instructions with regmasks.
llvm-svn: 264462
When merging stores in DAGCombiner, add check to ensure that no
dependenices exist that would cause the construction of a cycle in our
DAG. This may happen if one store has a data dependence on another
instruction (e.g. a load) which itself has a (chain) dependence on
another store being merged. These stores cannot be merged safely and
doing so results in a cycle that is discovered in LegalizeDAG.
This test is only done in cases where Antialias analysis is used (UseAA)
as non-AA store merge candidates will be merged logically after all
loads which have been checked to not alias.
Reviewers: ahatanak, spatel, niravd, arsenm, hfinkel, tstellarAMD, jyknight
Subscribers: llvm-commits, tberghammer, danalbert, srhines
Differential Revision: http://reviews.llvm.org/D18336
llvm-svn: 264461
I didn't notice any significant changes in the actual checks here;
all of these tests already used FileCheck, so a script can batch
update them in one shot.
This commit is just to show the value of automating this process:
We have uniform formatting as opposed to a mish-mash of check
structure that changes based on individual prefs and the current
fashion. This makes it simpler to update when we find a bug or
make an enhancement.
llvm-svn: 264457
This changes RS4GC to lower calls to ``@llvm.experimental.deoptimize``
to gc.statepoints wrapping ``__llvm_deoptimize``, and changes
``callsGCLeafFunction`` to recognize ``@llvm.experimental.deoptimize``
as a non GC leaf function.
I've had to hard code the ``"__llvm_deoptimize"`` name in
RewriteStatepointsForGC; since ``TargetLibraryInfo`` is available only
during codegen. This isn't without precedent in the codebase, so I'm
not overtly concerned.
llvm-svn: 264456
This fixes a use-after-free introduced 3 years ago, in r182872 ;)
The code more or less worked because the memory that CopyMI was
pointing to happened to still be valid, but lots of tests would crash
if you ran under ASAN with the recycling allocator changes from
llvm.org/PR26808
llvm-svn: 264455
It is possible to have a fallthrough MBB prior to MBB placement. The original
addition of the BB would result in reordering the BB as not preceding the
successor. Because of the fallthrough nature of the BB, we could end up
executing incorrect code or even a constant pool island! Insert the spliced BB
into the same location to avoid that.
Thanks to Tim Northover for invaluable hints and Fiora for the discussion on
what may have been occurring!
llvm-svn: 264454
This is a recommit of r264414 after fixing the buildbot failure caused by
incompatible use of std::vector.erase().
The original message:
Add erase() which returns an iterator pointing to the next element after the
erased one. This makes it possible to erase selected elements while iterating
over the SetVector :
while (I != E)
if (test(*I))
I = SetVector.erase(I);
else
++I;
Reviewers: qcolombet, mcrosier, MatzeB, dblaikie
Subscribers: dberlin, dblaikie, mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D18281
llvm-svn: 264450
We're erasing MI here, but then immediately using it again inside the
`if`. This moves the erase after we're done using it.
Doing that reveals a second problem though - this case is missing a
break, so we fall through to the default and dereference MI again.
This is obviously a bug, though I don't know how to write a test that
triggers it - all we do in the error case is print some extra debug
output.
Both of these issue crash on lots of tests under ASAN with the
recycling allocator changes from PR26808 applied.
llvm-svn: 264442
64-bit, 32-bit and 16-bit move-immediate instructions are 7, 6, and 5 bytes,
respectively, whereas and/or with 8-bit immediate is only three bytes.
Since these instructions imply an additional memory read (which the CPU could
elide, but we don't think it does), restrict these patterns to minsize functions.
Differential Revision: http://reviews.llvm.org/D18374
llvm-svn: 264440
Now register parameters that aren't saved to the stack or CSRs are
considered dead after the first call. Previously the debugger would show
whatever was in the register.
Fixes PR26589
Reviewers: aprantl
Differential Revision: http://reviews.llvm.org/D17211
llvm-svn: 264429
This keeps the naming consistent with Chapters 6-8, where Error was renamed to
LogError in r264426 to avoid clashes with the new Error class in libSupport.
llvm-svn: 264427
Summary:
Add erase() which returns an iterator pointing to the next element after the
erased one. This makes it possible to erase selected elements while iterating
over the SetVector :
while (I != E)
if (test(*I))
I = SetVector.erase(I);
else
++I;
Reviewers: qcolombet, mcrosier, MatzeB, dblaikie
Subscribers: dberlin, dblaikie, mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D18281
llvm-svn: 264414
Optimize output of MDStrings in bitcode. This emits them in big blocks
(currently 1024) in a pair of records:
- BULK_STRING_SIZES: the sizes of the strings in the block, and
- BULK_STRING_DATA: a single blob, which is the concatenation of all
the strings.
Inspired by Mehdi's similar patch, http://reviews.llvm.org/D18342, this
should (a) slightly reduce bitcode size, since there is less record
overhead, and (b) greatly improve reading speed, since blobs are super
cheap to deserialize.
I needed to add support for blobs to streaming input to get the test
suite passing.
- StreamingMemoryObject::getPointer reads ahead and returns the
address of the blob.
- To avoid a possible reallocation of StreamingMemoryObject::Bytes,
BitstreamCursor::readRecord needs to move the call to JumpToEnd
forward so that getPointer is the last bitstream operation.
llvm-svn: 264409
LowerShift was using the same code as Lower256IntArith to split 256-bit vectors into 2 x 128-bit vectors, so now we just call Lower256IntArith.
llvm-svn: 264403
