The stack slot reuse code had a really amusing bug. We ended up only reusing a stack slot exact once (initial use + reuse) within a basic block. If we had a third statepoint to process, we ended up allocating a new set of stack slots. If we crossed a basic block boundary, the set got cleared. As a result, code which is invoke heavy doesn't see the problem, but multiple calls within a basic block does. Net result: as we optimize invokes into calls, lowering gets worse.
The root error here is that the bitmap uses by the custom allocator wasn't kept in sync. The result was that we ended up resizing the bitmap on the next statepoint (to handle the cross block case), reset the bit once, but then never reset it again.
Differential Revision: https://reviews.llvm.org/D25243
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@289509 91177308-0d34-0410-b5e6-96231b3b80d8
This is a first step towards supporting deopt value lowering and reporting entirely with the register allocator. I hope to build on this in the near future to support live-on-return semantics, but I have a use case which allows me to test and investigate code quality with just the live-in semantics so I've chosen to start there. For those curious, my use cases is our implementation of the "__llvm_deoptimize" function we bind to @llvm.deoptimize. I'm choosing not to hard code that fact in the patch and instead make it configurable via function attributes.
The basic approach here is modelled on what is done for the "Live In" values on stackmaps and patchpoints. (A secondary goal here is to remove one of the last barriers to merging the pseudo instructions.) We start by adding the operands directly to the STATEPOINT SDNode. Once we've lowered to MI, we extend the remat logic used by the register allocator to fold virtual register uses into StackMap::Indirect entries as needed. This does rely on the fact that the register allocator rematerializes. If it didn't along some code path, we could end up with more vregs than physical registers and fail to allocate.
Today, we *only* fold in the register allocator. This can create some weird effects when combined with arguments passed on the stack because we don't fold them appropriately. I have an idea how to fix that, but it needs this patch in place to work on that effectively. (There's some weird interaction with the scheduler as well, more investigation needed.)
My near term plan is to land this patch off-by-default, experiment in my local tree to identify any correctness issues and then start fixing codegen problems one by one as I find them. Once I have the live-in lowering fully working (both correctness and code quality), I'm hoping to move on to the live-on-return semantics. Note: I don't have any *known* miscompiles with this patch enabled, but I'm pretty sure I'll find at least a couple. Thus, the "experimental" tag and the fact it's off by default.
Differential Revision: https://reviews.llvm.org/D24000
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280250 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Instead, we take a single flags arg (a bitset).
Also add a default 0 alignment, and change the order of arguments so the
alignment comes before the flags.
This greatly simplifies many callsites, and fixes a bug in
AMDGPUISelLowering, wherein the order of the args to getLoad was
inverted. It also greatly simplifies the process of adding another flag
to getLoad.
Reviewers: chandlerc, tstellarAMD
Subscribers: jholewinski, arsenm, jyknight, dsanders, nemanjai, llvm-commits
Differential Revision: http://reviews.llvm.org/D22249
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275592 91177308-0d34-0410-b5e6-96231b3b80d8
Previously, we were using isGCRelocate predicates. Using a subclass of IntrinsicInst is far more idiomatic. The refactoring also enables a couple of minor simplifications and code sharing.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266098 91177308-0d34-0410-b5e6-96231b3b80d8
While preserving the return value for @llvm.experimental.deoptimize at
the IR level is useful during mid-level optimization, doing so at the
machine instruction level requires generating some extra code and a
return that is non-ideal. This change has LLVM lower
```
%val = call @llvm.experimental.deoptimize
ret %val
```
to effectively
```
call @__llvm_deoptimize()
unreachable
```
instead.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265502 91177308-0d34-0410-b5e6-96231b3b80d8
Earlier we were ignoring varargs in LowerCallSiteWithDeoptBundle because
populateCallLoweringInfo does not set CallLoweringInfo::IsVarArg.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264354 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Only adds support for "naked" calls to llvm.experimental.deoptimize.
Support for round-tripping through RewriteStatepointsForGC will come
as a separate patch (should be simpler than this one).
Reviewers: reames
Subscribers: sanjoy, mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D18429
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264329 91177308-0d34-0410-b5e6-96231b3b80d8
Given that StatepointLowering now uniques derived pointers before
putting them in the per-statepoint spill map, we may end up with missing
entries for derived pointers when we visit a gc.relocate on a pointer
that was de-duplicated away.
Fix this by keeping two maps, one mapping gc pointers to their
de-duplicated values, and one mapping a de-duplicated value to the slot
it is spilled in.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264320 91177308-0d34-0410-b5e6-96231b3b80d8
Now that StatepointLoweringInfo represents base pointers, derived
pointers and gc relocates as SmallVectors and not ArrayRefs, we no
longer need to allocate "backing storage" on stack in LowerStatepoint.
So elide the backing storage, and inline the trivial body of
getIncomingStatepointGCValues.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264128 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
After this change, deopt operand bundles can be lowered directly by
SelectionDAG into STATEPOINT instructions (which are then lowered to a
call or sequence of nop, with an associated __llvm_stackmaps entry0.
This obviates the need to round-trip deoptimization state through
gc.statepoint via RewriteStatepointsForGC.
Reviewers: reames, atrick, majnemer, JosephTremoulet, pgavlin
Subscribers: sanjoy, mcrosier, majnemer, llvm-commits
Differential Revision: http://reviews.llvm.org/D18257
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264015 91177308-0d34-0410-b5e6-96231b3b80d8
This way we have a single entry point into StatepointLowering. The
method was a direct dispatch to LowerStatepoint anyway.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@263682 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
This is a step towards implementing "direct" lowering of calls and
invokes with deopt operand bundles into STATEPOINT nodes (as opposed to
having them mandatorily pass through RewriteStatepointsForGC, which is
the case today).
This change extracts out a `SelectionDAGBuilder::LowerAsStatepoint`
helper function that is able to lower a "statepoint like thing", and
uses it to lower `gc.statepoint` calls. This is an NFC now, but in a
later change we will use `LowerAsStatepoint` to directly lower calls and
invokes with operand bundles without going through an intermediate
`gc.statepoint` IR representation.
FYI: I expect `SelectionDAGBuilder::StatepointInfo` will evolve as I add
support for lowering non gc.statepoints, right now it is fairly tightly
coupled with an IR level `gc.statepoint`.
Reviewers: reames, pgavlin, JosephTremoulet
Subscribers: sanjoy, mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D18106
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@263671 91177308-0d34-0410-b5e6-96231b3b80d8
SelectionDAGBuilder::populateCallLoweringInfo is now used instead of
SelectionDAGBuilder::lowerCallOperands. The populateCallLoweringInfo
interface is more composable in face of design changes like
http://reviews.llvm.org/D18106
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@263663 91177308-0d34-0410-b5e6-96231b3b80d8
Instead of running an explicit loop over `gc.relocate` calls hanging off
of a `gc.statepoint`, assert the validity of the type of the value being
relocated in `visitRelocate`.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@263516 91177308-0d34-0410-b5e6-96231b3b80d8
Now that we don't always add an element to AllocatedStackSlots if we
don't find a pre-existing unallocated stack slot, bumping
StatepointMaxSlotsRequired to `NumSlots + 1` is not correct. Instead
bump the statistic near the push_back, to
Builder.FuncInfo.StatepointStackSlots.size().
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261348 91177308-0d34-0410-b5e6-96231b3b80d8
Philip Reames
Simon Pilgrim
Sanjay Patel
Matthias Braun
Justin Lebar
Sanjoy Das