There can be a need for some optimizations to get (base, offset)
for any GC pointer. The base can be calculated by generating
needed instructions as it is done by the
RewriteStatepointsForGC::findBasePointer() function. The offset
can be calculated in the same way. Though to not expose the base
calculation and to make the offset calculation as simple as
ptrtoint(derived_ptr) - ptrtoint(base_ptr), which is illegal
outside RS4GC, this patch introduces 2 intrinsics:
@llvm.experimental.gc.get.pointer.base(%derived_ptr)
@llvm.experimental.gc.get.pointer.offset(%derived_ptr)
These intrinsics are inlined by RS4GC along with generation of
statepoint sequences.
With these new intrinsics the GC parseable lowering for atomic
memcpy intrinsics (6ec2c5e402)
could be implemented as a separate pass.
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D100445
This change introduces a GC parseable lowering for element atomic
memcpy/memmove intrinsics. This way runtime can provide an
implementation which can take a safepoint during copy operation.
See "GC-parseable element atomic memcpy/memmove" thread on llvm-dev
for the background and details:
https://groups.google.com/g/llvm-dev/c/NnENHzmX-b8/m/3PyN8Y2pCAAJ
Differential Revision: https://reviews.llvm.org/D88861
The "gc-live" operand bundles were recently added, and all tests have been updated to use that format. A migration period was provided, though it's worth noting these intrinsics are experimental, so formally there is no compatibile requirement.
This is an extension to a96fc46. "gc-live" hadn't been implemented at the point that patch was initially posted.
(Forgot to land this a couple of weeks back.)
In a recent series of changes, I've introduced support for using the respective operand bundle kinds on the statepoint. At the moment, code supports either/or, but there's no need to keep the old support around. For the moment, I am simply changing the specification and verifier to require zero length argument sets in the intrinsic.
The intrinsic itself is experimental. Given that, there's no forward serialization needed. The in tree uses and generation have already been updated to use the new operand bundle based forms, the only folks broken by the change will be those with frontends generating statepoints directly and the updates should be easy.
Why not go ahead and just remove the arguments entirely? Well, I plan to. But while working on this I've found that almost all of the arguments to the statepoint can be expressed via operand bundles or attributes. Given that, I'm planning a radical simplification of the arguments and figured I'd do one update not several small ones.
Differential Revision: https://reviews.llvm.org/D80892
Currently, gc.relocates are defined in terms of indices into the statepoint's operand list. Given the gc args are at the end of a variable length list of operands, this makes interpreting their indices by hand a tad challenging. We can simplify the statepoint sequence and improve readability quite a bit by pulling these new operands into their own named operand bundle.
This patch defines a new operand bundle tag "gc-live". The semantics of the bundle are the same as the existing gc arguments of a statepoint. This patch simply introduces the definition and codegen for the bundle, future patches will migrate RS4GC to emitting the new form.
Interestingly, with this done and the recent migration to using deopt and gc-transition bundles, we really don't have much left in the statepoint itself. It really looks like the existing ID and flags fields are redundant; we have (existing!) attributes for all of them. I think we'll be able to reduce the gc.statepoint signature to simply a wrapped call (e.g. actual target and actual arguments).
Differential Revision: https://reviews.llvm.org/D80937
The requirement for deopt parameter to be in gc parameter if it can
be modified by GC is very strong and difficult to follow.
The key example of why this can't work:
%p1 = bitcast i8* %p to i8*
statepoint [gc = (%p1)], [deopt = (%p1)]
The optimizer is allowed to replace either use (or both) of %p1 with %p.
If it updates only one of the two (entirely legal), the two sets do not overlap.
So this change removes the strong wording.
Reviewers: reames, dantrushin
Reviewed By: reames
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D77122
The documentation had gotten a bit stale. The revised one are by no means perfect, but I tried to remove the obvious incorrect or misleading statements.
llvm-svn: 300782
Lots of blocks had "llvm" or "nasm" syntax types but either weren't following
the syntax, or the syntax has changed (and sphinx hasn't keep up) or the type
doesn't even exist (nasm?).
Other documents had :options: what were invalid. I only removed those that had
warnings, and left the ones that didn't, in order to follow the principle of
least surprise.
This is like this for ages, but the buildbot is now failing on errors. It may
take a while to upgrade the buildbot's sphinx, if that's even possible, but
that shouldn't stop us from getting docs updates (which seem down for quite
a while).
Also, we're not losing any syntax highlight, since when it doesn't parse, it
doesn't colour. Ie. those blocks are not being highlighted anyway.
I'm trying to get all docs in one go, so that it's easy to revert later if we
do fix, or at least easy to know what's to fix.
llvm-svn: 276109
Summary:
This adds a new kind of operand bundle to LLVM denoted by the
`"gc-transition"` tag. Inputs to `"gc-transition"` operand bundle are
lowered into the "transition args" section of `gc.statepoint` by
`RewriteStatepointsForGC`.
This removes the last bit of functionality that was unsupported in the
deopt bundle based code path in `RewriteStatepointsForGC`.
Reviewers: pgavlin, JosephTremoulet, reames
Subscribers: sanjoy, mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D16342
llvm-svn: 258338
The previous text was hard to understand even for me and I wrote it. Hopefully the new structure makes it a bit more clear what's going on. If anyone has word smithing suggestion or clarification questions, please let me know.
llvm-svn: 257847
Summary: This patch changes gc.statepoint intrinsic's return type to token type instead of i32 type. Using token types could prevent LLVM to merge different gc.statepoint nodes into PHI nodes and cause further problems with gc relocations. The patch also changes the way on how gc.relocate and gc.result look for their corresponding gc.statepoint on unwind path. The current implementation uses the selector value extracted from a { i8*, i32 } landingpad as a hook to find the gc.statepoint, while the patch directly uses a token type landingpad (http://reviews.llvm.org/D15405) to find the gc.statepoint.
Reviewers: sanjoy, JosephTremoulet, pgavlin, igor-laevsky, mjacob
Subscribers: reames, mjacob, sanjoy, llvm-commits
Differential Revision: http://reviews.llvm.org/D15662
llvm-svn: 256443
Summary: This fixes a variety of typos in docs, code and headers.
Subscribers: jholewinski, sanjoy, arsenm, llvm-commits
Differential Revision: http://reviews.llvm.org/D12626
llvm-svn: 247495
Expand the information on base pointers to include an example, the assumptions a collector is allowed to make, legal optimizations over gc.relocates, and the assumptions made by RewriteStatepointsForGC. This is the result of a recent conversation with folks from LLIC and the confusions that came to light therein.
llvm-svn: 246103
Summary:
As added initially, statepoints required their call targets to be a
constant pointer null if ``numPatchBytes`` was non-zero. This turns out
to be a problem ergonomically, since there is no way to mark patchable
statepoints as calling a (readable) symbolic value.
This change remove the restriction of requiring ``null`` call targets
for patchable statepoints, and changes PlaceSafepoints to maintain the
symbolic call target through its transformation.
Reviewers: reames, swaroop.sridhar
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D11550
llvm-svn: 243502
Summary:
This patch teaches the PlaceSafepoints pass about two `CallSite`
function attributes:
* "statepoint-id": if the string value of this attribute can be parsed
as an integer, then it is propagated to the ID parameter of the
statepoint created.
* "statepoint-num-patch-bytes": if the string value of this attribute
can be parsed as an integer, then it is propagated to the `num patch
bytes` parameter of the statepoint created.
This change intentionally does not assert on a malformed value for these
attributes, given that they're not "official" attributes.
Reviewers: reames, pgavlin
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D9735
llvm-svn: 237286
Summary:
This change adds two new parameters to the statepoint intrinsic, `i64 id`
and `i32 num_patch_bytes`. `id` gets propagated to the ID field
in the generated StackMap section. If the `num_patch_bytes` is
non-zero then the statepoint is lowered to `num_patch_bytes` bytes of
nops instead of a call (the spill and reload code remains unchanged).
A non-zero `num_patch_bytes` is useful in situations where a language
runtime requires complete control over how a call is lowered.
This change brings statepoints one step closer to patchpoints. With
some additional work (that is not part of this patch) it should be
possible to get rid of `TargetOpcode::STATEPOINT` altogether.
PlaceSafepoints generates `statepoint` wrappers with `id` set to
`0xABCDEF00` (the old default value for the ID reported in the stackmap)
and `num_patch_bytes` set to `0`. This can be made more sophisticated
later.
Reviewers: reames, pgavlin, swaroop.sridhar, AndyAyers
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D9546
llvm-svn: 237214
This changes the shape of the statepoint intrinsic from:
@llvm.experimental.gc.statepoint(anyptr target, i32 # call args, i32 unused, ...call args, i32 # deopt args, ...deopt args, ...gc args)
to:
@llvm.experimental.gc.statepoint(anyptr target, i32 # call args, i32 flags, ...call args, i32 # transition args, ...transition args, i32 # deopt args, ...deopt args, ...gc args)
This extension offers the backend the opportunity to insert (somewhat) arbitrary code to manage the transition from GC-aware code to code that is not GC-aware and back.
In order to support the injection of transition code, this extension wraps the STATEPOINT ISD node generated by the usual lowering lowering with two additional nodes: GC_TRANSITION_START and GC_TRANSITION_END. The transition arguments that were passed passed to the intrinsic (if any) are lowered and provided as operands to these nodes and may be used by the backend during code generation.
Eventually, the lowering of the GC_TRANSITION_{START,END} nodes should be informed by the GC strategy in use for the function containing the intrinsic call; for now, these nodes are instead replaced with no-ops.
Differential Revision: http://reviews.llvm.org/D9501
llvm-svn: 236888
When I originally committed the statepoint docs, I left placeholders for example IR fragments. I'm finally getting around to filling those in.
I also added IR fragments to illustrate the usage of the PlaceSafepoints pass while I was at it.
llvm-svn: 230601
Shao-Ce SUN