The Zicond extension was ratified in the last few months, with no
changes that affect the LLVM implementation. Although there's surely
more tuning that could be done about when to select Zicond or not, there
are no known correctness issues. Therefore, we should mark support as
non-experimental.
R_RISCV_CALL/R_RISCV_CALL_PLT distinction is not necessary and
R_RISCV_CALL has been deprecated. Since https://reviews.llvm.org/D132530
`call foo` assembles to R_RISCV_CALL_PLT. The `@plt` suffix is not
useful and can be removed now (matching AArch64 and PowerPC).
GNU assembler assembles `call foo` to RISCV_CALL_PLT since 2022-09
(70f35d72ef04cd23771875c1661c9975044a749c).
Without this patch, unconditionally changing MO_CALL to MO_PLT could
create `jump .L1@plt, a0`, which is invalid in LLVM integrated assembler
and GNU assembler.
PR #72978 disabled transformation (select_cc seteq (and x, C), 0, 0, A)
-> (and (sra(shl x)), A) for better Zicond codegen. It still enables the
combine when C is not fit into 12-bits. This patch disables the combine
when Zbs enabled.
Currently, llvm can transform (setcc ne (and x, c)) to (bexti x,
log2(c)) where c is power of 2.
This patch transform (select (setcc ne (and x, c)), T, F) into (select
(setcc eq (and x, c)), F, T).
It is benefit to the case c is not fit to 12-bits.
DAGCombiner folds (select_cc seteq (and x, y), 0, 0, A) to (and (sra
(shl x)) A) where y has a single bit set. Previously, DAGCombiner relies
on `shouldAvoidTransformToShift` to decide when to do the combine, but
`shouldAvoidTransformToShift` is only about shift cost. This patch
introuduces a specific hook to decide when to do the combine and disable
the combine when Zicond enabled and AndMask <= 1024.
This removes selectSETCC and adds isel patterns for seteq/setne
conditions.
This removes the duplication of selectSETCC between lowering and
isel. This also gets some cases in xaluo.ll that we missed previously.
Reviewed By: wangpc
Differential Revision: https://reviews.llvm.org/D156250
If we are selecting between two setccs that need to be legalized
with xor, the select will be legalized first. Detect this pattern
so we can pull the xor through to expose it to additional
optimizations.
We could generalize this to other operations, but those normally
get handled in DAG combine before select legalization.
Reviewed By: asb
Differential Revision: https://reviews.llvm.org/D156159
If we're selecting the result of two setccs that have been legalized
by introducing an xor with 1, we can pull the xor with 1 through the
select to enable more optimizations.
We could generalize this to other binary operators with identical
conditions, but those are usually caught before we legalize the select.
Reviewed By: asb
Differential Revision: https://reviews.llvm.org/D156144
This test is copied from select-cc.ll. It wasn't worth adding
Zicond RUN lines to that file.
Reviewed By: asb, wangpc
Differential Revision: https://reviews.llvm.org/D156083
This is an alternative to D155288 that can handle other sources of
xori like FP compares. Unfortunately, it misses the i64 setge case
on RV32 in condops.ll.
Reviewed By: asb
Differential Revision: https://reviews.llvm.org/D155328
This makes Zicond and XVentanaCondOps use the same code path.
The instructions have identical semantics.
Reviewed By: wangpc
Differential Revision: https://reviews.llvm.org/D155391
This patch is a step towards altering how we handle the emission of
condops. Marking ISD::SELECT as legal is a major change in the codegen
path, and gives few options for maintaining the old codegen path when
it is believed to be better (e.g. a better branchless sequence is
possible using non-zicond instructions, or the branch-based sequence is
preferable).
This removes the existing SelectionDAG patterns and moves the logic into
lowerSELECT. Along some small codegen changes you'll note a few minor
regressions in the generated code quality - this are due to the fact
that by lowering the SELECT node early we miss out on combines that
would kick in later when setcc condcodes that aren't natively supported
have been expanded (thus exposing opportunities for optimisation by
performing logical negation and swapping truev/falsev). I've opted to
split out work that addresses these into follow-on patches (especially
as zicond is still 'experimental').
matchSetCC is a straight-forward translation from the version in
RISCVISelDAGToDAG. Ideally, in the future it can be converted to a
helper shared between both files.
Differential Revision: https://reviews.llvm.org/D155083
This directly matches the codegen for xventanacondops with vt.maskcn =>
czero.nez and vt.maskc => czero.eqz. An additional difference is that
zicond is available on RV32 in addition to RV64 (xventanacondops is RV64
only).
Differential Revision: https://reviews.llvm.org/D147147
