When memory operations are outstanding on function calls, either the
caller or the callee can insert a waitcnt to ensure that all reads are
finished.
Calls need some time to be executed, so if the callee inserts the
waitcnt, filling the instruction buffer and waiting for memory will be
interleaved, hiding some latency. This comes at the cost of having a
waitcnt inside functions that may not be needed as no memory operations
are outstanding.
For function calls, this is already implemented. The same principal
applies to returns: If the caller inserts a waitcnt after the call, the
callee does not have to wait and the return and memory operation can be
run in parallel.
This commit implements waiting in the caller after returning from a
function call.
Differential Revision: https://reviews.llvm.org/D87674
GlobalISel let through a call to null, which would then fold into the
source operand like any other inline immediate. The SelectionDAG
lowering deletes calls to null and undef as a workaround from before
calls were supported. We should probably drop the special handling
case in the DAG lowering now, since the middle end optimizers delete
null calls anyway.
Summary:
CFI emitted during PEI at the beginning of the prologue needs to apply
to any inserted waitcnts on function entry.
Reviewers: arsenm, t-tye, RamNalamothu
Reviewed By: arsenm
Subscribers: arsenm, kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, kerbowa, llvm-commits
Tags: #llvm, #debug-info
Differential Revision: https://reviews.llvm.org/D76881
VMEM loads of the same type (sampler vs no sampler) are guaranteed to
write their result registers in order, so there is no need for an
s_waitcnt even if they write to overlapping vgprs.
Differential Revision: https://reviews.llvm.org/D79176
Summary:
Up to gfx9, writes to vcc_lo and vcc_hi by instructions like
v_readlane and v_readfirstlane do not update vccz to reflect the new
value of vcc. Fix it by reusing part of the existing vccz bug handling
code, which inserts an "s_mov_b64 vcc, vcc" instruction to restore vccz
just before an instruction that needs the correct value.
Subscribers: arsenm, kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69661
Summary:
The waitcnt pass can overflow the counters when the number of outstanding events
for a type exceed the capacity of the counter. This can lead to inefficient
insertion of waitcnts, or to waitcnt instructions with max values for each type.
The last situation can cause an instruction which when disassembled appears to
be an illegal waitcnt without an operand.
In these cases we should add a wait for the 'counter maximum' - 1, and update the
waitcnt brackets accordingly.
Reviewers: rampitec, arsenm
Reviewed By: rampitec
Subscribers: kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70418
Summary:
VCCZBugHandledSet was used to make sure we don't apply the same
workaround more than once to a single cbranch instruction, but it's not
necessary because the workaround involves inserting an s_waitcnt
instruction, which is enough for subsequent iterations to detect that no
further workaround is necessary.
Also beef up the test case to check that the workaround was only applied
once. I have also manually verified that the test still passes even if I
hack the big do-while loop in runOnMachineFunction to run a minimum of
five iterations.
Subscribers: arsenm, kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69621
Summary:
An outstanding load with same destination sgpr as call could cause PC to be
updated with junk value on return.
Reviewers: arsenm, rampitec
Reviewed By: arsenm
Subscribers: kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69474
Now that we've moved to C++14, we no longer need the llvm::make_unique
implementation from STLExtras.h. This patch is a mechanical replacement
of (hopefully) all the llvm::make_unique instances across the monorepo.
llvm-svn: 369013
This is incomplete, and ideally these would all be removed, but it's
better to localize them to the subtarget first with comments about
what they're for.
llvm-svn: 363902
This reapplies r363678, using the correct chain for the CopyToReg for
v0. glueCopyToM0 counterintuitively changes the operands of the
original node.
llvm-svn: 363870
Currently you get extra waits, because waits are inserted for the
register dependencies of the call, and the function prolog waits on
everything.
Currently waits are still inserted on returns. It may make sense to
not do this, and wait in the caller instead.
llvm-svn: 363465
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
Summary:
Fix an issue where VGPR/SGPR bounds are not properly extended when brackets are merged.
This manifests as missing waitcnt insertions when multiple brackets are forwarded to a successor block and the first forward has lower VGPR/SGPR bounds.
Irreducible loop test has been extended based on a CTS failure detected for GFX9.
Reviewers: nhaehnle
Reviewed By: nhaehnle
Subscribers: arsenm, kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, t-tye, jfb, llvm-commits
Differential Revision: https://reviews.llvm.org/D55602
llvm-svn: 349611
Summary:
MachineLoopInfo cannot be relied on for correctness, because it cannot
properly recognize loops in irreducible control flow which can be
introduced by late machine basic block optimization passes. See the new
test case for the reduced form of an example that occurred in practice.
Use a simple fixpoint iteration instead.
In order to facilitate this change, refactor WaitcntBrackets so that it
only tracks pending events and registers, rather than also maintaining
state that is relevant for the high-level algorithm. Various accessor
methods can be removed or made private as a consequence.
Affects (in radv):
- dEQP-VK.glsl.loops.special.{for,while}_uniform_iterations.select_iteration_count_{fragment,vertex}
Fixes: r345719 ("AMDGPU: Rewrite SILowerI1Copies to always stay on SALU")
Reviewers: msearles, rampitec, scott.linder, kanarayan
Subscribers: arsenm, kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, t-tye, llvm-commits, hakzsam
Differential Revision: https://reviews.llvm.org/D54231
llvm-svn: 347853
Summary:
There is one obsolete reference to using -1 as an indication of "unknown",
but this isn't actually used anywhere.
Using unsigned makes robust wrapping checks easier.
Reviewers: msearles, rampitec, scott.linder, kanarayan
Subscribers: arsenm, kzhuravl, jvesely, wdng, yaxunl, dstuttard, llvm-commits, tpr, t-tye, hakzsam
Differential Revision: https://reviews.llvm.org/D54230
llvm-svn: 347852
Summary:
Instead of storing the "score" (last time point) of the various relevant
events, only store whether an event is pending or not.
This is sufficient, because whenever only one event of a count type is
pending, its last time point is naturally the upper bound of all time
points of this count type, and when multiple event types are pending,
the count type has gone out of order and an s_waitcnt to 0 is required
to clear any pending event type (and will then clear all pending event
types for that count type).
This also removes the special handling of GDS_GPR_LOCK and EXP_GPR_LOCK.
I do not understand what this special handling ever attempted to achieve.
It has existed ever since the original port from an internal code base,
so my best guess is that it solved a problem related to EXEC handling in
that internal code base.
Reviewers: msearles, rampitec, scott.linder, kanarayan
Subscribers: arsenm, kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, t-tye, llvm-commits, hakzsam
Differential Revision: https://reviews.llvm.org/D54228
llvm-svn: 347850
Summary:
It hides the type casting ugliness, and I happened to have to add a new
such loop (in a later patch).
Reviewers: msearles, rampitec, scott.linder, kanarayan
Subscribers: arsenm, kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, t-tye, llvm-commits, hakzsam
Differential Revision: https://reviews.llvm.org/D54227
llvm-svn: 347849
Sebastian Neubauer