The machine scheduler currently biases register copies to/from
physical registers to be closer to their point of use / def to
minimize their live ranges. This change extends this to also physical
register assignments from immediate values.
This causes a reduction in reduction in overall register pressure and
minor reduction in spills and indirectly fixes an out-of-registers
assertion (PR39391).
Most test changes are from minor instruction reorderings and register
name selection changes and direct consequences of that.
Reviewers: MatzeB, qcolombet, myatsina, pcc
Subscribers: nemanjai, jvesely, nhaehnle, eraman, hiraditya,
javed.absar, arphaman, jfb, jsji, llvm-commits
Differential Revision: https://reviews.llvm.org/D54218
llvm-svn: 346894
Summary:
Instead of writing boolean values temporarily into 32-bit VGPRs
if they are involved in PHIs or are observed from outside a loop,
we use bitwise masking operations to combine lane masks in a way
that is consistent with wave control flow.
Move SIFixSGPRCopies to before this pass, since that pass
incorrectly attempts to move SGPR phis to VGPRs.
This should recover most of the code quality that was lost with
the bug fix in "AMDGPU: Remove PHI loop condition optimization".
There are still some relevant cases where code quality could be
improved, in particular:
- We often introduce redundant masks with EXEC. Ideally, we'd
have a generic computeKnownBits-like analysis to determine
whether masks are already masked by EXEC, so we can avoid this
masking both here and when lowering uniform control flow.
- The criterion we use to determine whether a def is observed
from outside a loop is conservative: it doesn't check whether
(loop) branch conditions are uniform.
Change-Id: Ibabdb373a7510e426b90deef00f5e16c5d56e64b
Reviewers: arsenm, rampitec, tpr
Subscribers: kzhuravl, jvesely, wdng, mgorny, yaxunl, dstuttard, t-tye, eraman, llvm-commits
Differential Revision: https://reviews.llvm.org/D53496
llvm-svn: 345719
This was introducing unnecessary padding after the explicit
arguments, depending on the alignment of the total struct type.
Also has the side effect of avoiding creating an extra GEP for
the offset from the base kernel argument to the explicit kernel
argument offset.
llvm-svn: 335999
This replaces most argument uses with loads, but for
now not all.
The code in SelectionDAG for calling convention lowering
is actively harmful for amdgpu_kernel. It attempts to
split the argument types into register legal types, which
results in low quality code for arbitary types. Since
all kernel arguments are passed in memory, we just want the
raw types.
I've tried a couple of methods of mitigating this in SelectionDAG,
but it's easier to just bypass this problem alltogether. It's
possible to hack around the problem in the initial lowering,
but the real problem is the DAG then expects to be able to use
CopyToReg/CopyFromReg for uses of the arguments outside the block.
Exposing the argument loads in the IR also has the advantage
that the LoadStoreVectorizer can merge them.
I'm not sure the best approach to dealing with the IR
argument list is. The patch as-is just leaves the IR arguments
in place, so all the existing code will still compute the same
kernarg size and pointlessly lowers the arguments.
Arguably the frontend should emit kernels with an empty argument
list in the first place. Alternatively a dummy array could be
inserted as a single argument just to reserve space.
This does have some disadvantages. Local pointer kernel arguments can
no longer have AssertZext placed on them as the equivalent !range
metadata is not valid on pointer typed loads. This is mostly bad
for SI which needs to know about the known bits in order to use the
DS instruction offset, so in this case this is not done.
More importantly, this skips noalias arguments since this pass
does not yet convert this to the equivalent !alias.scope and !noalias
metadata. Producing this metadata correctly seems to be tricky,
although this logically is the same as inlining into a function which
doesn't exist. Additionally, exposing these loads to the vectorizer
may result in degraded aliasing information if a pointer load is
merged with another argument load.
I'm also not entirely sure this is preserving the current clover
ABI, although I would greatly prefer if it would stop widening
arguments and match the HSA ABI. As-is I think it is extending
< 4-byte arguments to 4-bytes but doesn't align them to 4-bytes.
llvm-svn: 335650
Summary:
Previously, all DS ops forced WQM in a pixel shader. That was a hack to
allow for graphics frontends using ds_swizzle to implement explicit
derivatives, on SI/CI at least where DPP is not available. But it forced
WQM for _any_ DS op.
With this commit, DS ops no longer force WQM. Both graphics frontends
(Mesa and LLPC) need to change to issue an explicit llvm.amdgcn.wqm
intrinsic call when calculating explicit derivatives.
The required Mesa change is: "amd/common: use llvm.amdgcn.wqm for
explicit derivatives".
Subscribers: qcolombet, arsenm, kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, t-tye, llvm-commits
Differential Revision: https://reviews.llvm.org/D46051
Change-Id: I9b745b626fa91bbd66456e6cf41ee07eeea42f81
llvm-svn: 331633
Currently SI_IF results in a s_and_saveexec_b64 followed by s_xor_b64.
The xor is used to extract only the changed bits. In case of a simple
if region where the only use of that value is in the SI_END_CF to
restore the old exec mask, we can omit the xor and perform an or of
the exec mask with the original exec value saved by the
s_and_saveexec_b64.
Differential Revision: https://reviews.llvm.org/D35861
llvm-svn: 309185
-enable-si-insert-waitcnts=1 becomes the default
-enable-si-insert-waitcnts=0 to use old pass
Differential Revision: https://reviews.llvm.org/D33730
llvm-svn: 304551
This reverts commit r300732. This breaks a few tests.
I think the problem is related to adding more uses of
the condition that don't yet exist at this point.
llvm-svn: 301242
The most common case for a branch condition is
a single use compare. Directly invert the branch
predicate rather than adding a lot of xor i1 true
which the DAG will have to fold later.
This produces nicer to read structurizer output.
This produces some random changes in codegen
due to the DAG swapping branch conditions itself,
and then does a poor job of dealing with those
inverts.
llvm-svn: 300732
StructurizeCFG can't handle cases with multiple
returns creating regions with multiple exits.
Create a copy of UnifyFunctionExitNodes that only
unifies exit nodes that skips exit nodes
with uniform branch sources.
llvm-svn: 298729
Stanislav Mekhanoshin