Darwin platforms for both AArch64 and X86 can provide optimized `bzero()`
routines. In this case, it may be preferable to use `bzero` in place of a
memset of 0.
This adds a G_BZERO generic opcode, similar to G_MEMSET et al. This opcode can
be generated by platforms which may want to use bzero.
To emit the G_BZERO, this adds a pre-legalize combine for AArch64. The
conditions for this are largely a port of the bzero case in
`AArch64SelectionDAGInfo::EmitTargetCodeForMemset`.
The only difference in comparison to the SelectionDAG code is that, when
compiling for minsize, this will fire for all memsets of 0. The original code
notes that it's not beneficial to do this for small memsets; however, using
bzero here will save a mov from wzr. For minsize, I think that it's preferable
to prioritise omitting the mov.
This also fixes a bug in the libcall legalization code which would delete
instructions which could not be legalized. It also adds a check to make sure
that we actually get a libcall name.
Code size improvements (Darwin):
- CTMark -Os: -0.0% geomean (-0.1% on pairlocalalign)
- CTMark -Oz: -0.2% geomean (-0.5% on bullet)
Differential Revision: https://reviews.llvm.org/D99358
This reverts commit 962b73dd0f.
This commit was reverted because of some internal SPEC test failures.
It turns out that this wasn't actually relevant to anything in open source, so
it's safe to recommit this.
This is pretty much just ports `performGlobalAddressCombine` from
AArch64ISelLowering. (AArch64 doesn't use the generic DAG combine for this.)
This adds a pre-legalize combine which looks for this pattern:
```
%g = G_GLOBAL_VALUE @x
%ptr1 = G_PTR_ADD %g, cst1
%ptr2 = G_PTR_ADD %g, cst2
...
%ptrN = G_PTR_ADD %g, cstN
```
And then, if possible, transforms it like so:
```
%g = G_GLOBAL_VALUE @x
%offset_g = G_PTR_ADD %g, -min(cst)
%ptr1 = G_PTR_ADD %offset_g, cst1
%ptr2 = G_PTR_ADD %offset_g, cst2
...
%ptrN = G_PTR_ADD %offset_g, cstN
```
Where min(cst) is the smallest out of the G_PTR_ADD constants.
This means we should save at least one G_PTR_ADD.
This also updates code in the legalizer + selector which assumes that
G_GLOBAL_VALUE will never have an offset and adds/updates relevant tests.
Differential Revision: https://reviews.llvm.org/D96624
We try to do this optimization if we can determine that testing for the
truncated bits with an eq/ne predicate results in the same thing as testing
the lower bits.
Differential Revision: https://reviews.llvm.org/D95645
There are a lot of combines in AArch64PostLegalizerCombiner which exist to
facilitate instruction matching in the selector. (E.g. matching for G_ZIP and
other shuffle vector pseudos)
It still makes sense to select these instructions at -O0.
Matching earlier in a combiner can reduce complexity in the selector
significantly. For example, a good portion of our selection code for compares
would be a lot easier to represent in a combine.
This patch moves matching combines into a "AArch64PostLegalizerLowering"
combiner which runs at all optimization levels.
Also, while we're here, improve the documentation for the
AArch64PostLegalizerCombiner, and fix up the filepath in its file comment.
And also add a 'r' which somehow got dropped from a bunch of function names.
https://reviews.llvm.org/D89820
AArch64, X86 and Mips currently directly consumes these and custom
lowering to produce a libcall, but really these should follow the
normal legalization process through the libcall/lower action.
Summary:
Adds the ability to add members to a generated combiner via
a State base class. In the current AArch64PreLegalizerCombiner
this is used to make Helper available without having to
provide it to every call.
As part of this, split the command line processing into a
separate object so that it still only runs once even though
the generated combiner is constructed more frequently.
Depends on D81862
Reviewers: aditya_nandakumar, bogner, volkan, aemerson, paquette, arsenm
Reviewed By: arsenm
Subscribers: jvesely, wdng, nhaehnle, kristof.beyls, hiraditya, kerbowa, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D81863
Jessica Paquette