This is a follow-up to r302611, which moved an -O0 computation of DT
from SDAGISel to TwoAddress.
Don't use it here either, and avoid computing it completely. The only
use was forwarding the analysis as an optional argument to utility
functions.
Differential Revision: https://reviews.llvm.org/D32766
llvm-svn: 302612
Before r247167, the pass manager builder controlled which AA
implementations were used, exporting them all in the AliasAnalysis
analysis group.
Now, AAResultsWrapperPass always uses BasicAA, but still uses other AA
implementations if made available in the pass pipeline.
But regardless, SDAGISel is required at O0, and really doesn't need to
be doing fancy optimizations based on useful AA results.
Don't require AA at CodeGenOpt::None, and only use it otherwise.
This does have a functional impact (and one testcase is pessimized
because we can't reuse a load). But I think that's desirable no matter
what.
Note that this alone doesn't result in less DT computations: TwoAddress
was previously able to reuse the DT we computed for SDAG. That will be
fixed separately.
Differential Revision: https://reviews.llvm.org/D32766
llvm-svn: 302611
We currently require SCEV, which requires DT/LI. Those are expensive to
compute, but the pass only runs for functions that have the safestack
attribute.
Compute DT/LI to build SCEV lazily, only when the pass is actually going
to transform the function.
Differential Revision: https://reviews.llvm.org/D31302
llvm-svn: 302610
This should hopefully makes changes to the O0 pipeline obvious; it's
easy to require expensive passes, and this helps make informed
decisions.
Case in point: in the few weeks separating the time when I initially
wrote this patch to the time when I committed, the test regressed as
r302103 added another use of DT!
llvm-svn: 302608
Ahmed Bougacha