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
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
Currently the default C calling convention functions are treated
the same as compute kernels. Make this explicit so the default
calling convention can be changed to a non-kernel.
Converted with perl -pi -e 's/define void/define amdgpu_kernel void/'
on the relevant test directories (and undoing in one place that actually
wanted a non-kernel).
llvm-svn: 298444
This switches to the workaround that HSA defaults to
for the mesa path.
This should be applied to the 4.0 branch.
Patch by Vedran Miletić <vedran@miletic.net>
llvm-svn: 292982
For some reason there are both of these available, except
for scalar 64-bit compares which only has u64. I'm not sure
why there are both (I'm guessing it's for the one bit inputs we
don't use), but for consistency always using the
unsigned one.
llvm-svn: 282832
Nicolai Haehnle