There is a bunch of similar bitfield extraction code throughout *ISelDAGToDAG.
E.g, ARMISelDAGToDAG, AArch64ISelDAGToDAG, and AMDGPUISelDAGToDAG all contain
code that matches a bitfield extract from an and + right shift.
Rather than duplicating code in the same way, this adds two opcodes:
- G_UBFX (unsigned bitfield extract)
- G_SBFX (signed bitfield extract)
They work like this
```
%x = G_UBFX %y, %lsb, %width
```
Where `lsb` and `width` are
- The least-significant bit of the extraction
- The width of the extraction
This will extract `width` bits from `%y`, starting at `lsb`. G_UBFX zero-extends
the result, while G_SBFX sign-extends the result.
This should allow us to use the combiner to match the bitfield extraction
patterns rather than duplicating pattern-matching code in each target.
Differential Revision: https://reviews.llvm.org/D98464
It is good to have a combined `divrem` instruction when the
`div` and `rem` are computed from identical input operands.
Some targets can lower them through a single expansion that
computes both division and remainder. It effectively reduces
the number of instructions than individually expanding them.
Reviewed By: arsenm, paquette
Differential Revision: https://reviews.llvm.org/D96013
This adds a G_ASSERT_SEXT opcode, similar to G_ASSERT_ZEXT. This instruction
signifies that an operation was already sign extended from a smaller type.
This is useful for functions with sign-extended parameters.
E.g.
```
define void @foo(i16 signext %x) {
...
}
```
This adds verifier, regbankselect, and instruction selection support for
G_ASSERT_SEXT equivalent to G_ASSERT_ZEXT.
Differential Revision: https://reviews.llvm.org/D96890
This adds a generic opcode which communicates that a type has already been
zero-extended from a narrower type.
This is intended to be similar to AssertZext in SelectionDAG.
For example,
```
%x_was_extended:_(s64) = G_ASSERT_ZEXT %x, 16
```
Signifies that the top 48 bits of %x are known to be 0.
This is useful in cases like this:
```
define i1 @zeroext_param(i8 zeroext %x) {
%cmp = icmp ult i8 %x, -20
ret i1 %cmp
}
```
In AArch64, `%x` must use a 32-bit register, which is then truncated to a 8-bit
value.
If we know that `%x` is already zero-ed out in the relevant high bits, we can
avoid the truncate.
Currently, in GISel, this looks like this:
```
_zeroext_param:
and w8, w0, #0xff ; We don't actually need this!
cmp w8, #236
cset w0, lo
ret
```
While SDAG does not produce the truncation, since it knows that it's
unnecessary:
```
_zeroext_param:
cmp w0, #236
cset w0, lo
ret
```
This patch
- Adds G_ASSERT_ZEXT
- Adds MIRBuilder support for it
- Adds MachineVerifier support for it
- Documents it
It also puts G_ASSERT_ZEXT into its own class of "hint instruction." (There
should be a G_ASSERT_SEXT in the future, maybe a G_ASSERT_ALIGN as well.)
This allows us to skip over hints in the legalizer etc. These can then later
be selected like COPY instructions or removed.
Differential Revision: https://reviews.llvm.org/D95564
Some of the lower implementations were relying on this, however the
type was not set depending on which form .lower* helper form you were
using. For instance, if you used an unconditonal lower(), the type was
never set. Most of the lower actions do not benefit from a type
parameter, and just expand in terms of the original operation's types.
However, some lowerings could benefit from an additional type hint to
combine a promotion and an expansion. An example of this is for
add/sub sat. The DAG integer legalization tries to use smarter
expansions directly when promoting the integer type, and doesn't
always produce the same instruction with a wider type.
Treat this as an optional hint argument, that only means something for
specific lower actions. It may be useful to generalize this mechanism
to pass a full list of type indexes and desired types, but I haven't
run into a case like that yet.
Before the fix the build of docs-llvm-html would fail.
The rG8bc03d216824 introduced a reference to an undefined label,
so we have warning as:
llvm-project/llvm/docs/GlobalISel/GenericOpcode.rst:295:\
undefined label: i_intr_llvm_ptrmask (if the link has no\
caption the label must precede a section header)
Confusingly, these were unrelated and had different semantics. The
G_PTR_MASK instruction predates the llvm.ptrmask intrinsic, but has a
different format. G_PTR_MASK only allows clearing the low bits of a
pointer, and only a constant number of bits. The ptrmask intrinsic
allows an arbitrary mask. Replace G_PTR_MASK to match the intrinsic.
Only selects the cases that look like the old instruction. More work
is needed to select the general case. Also new legalization code is
still needed to deal with the case where the incoming mask size does
not match the pointer size, which has a specified behavior in the
langref.
Summary: I think it would be better to require the alignment to be >= 1. It is currently confusing to allow both values.
Reviewers: courbet
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D77372
Summary:
Add new generic MIR opcodes G_SADDSAT etc. Add support in IRTranslator
for translating the saturating add/subtract intrinsics to the new
opcodes.
Reviewers: aemerson, dsanders, paquette, arsenm
Subscribers: jvesely, wdng, nhaehnle, rovka, hiraditya, volkan, kerbowa, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D76600
It looks like I pushed an older version of this commit without the review
fixups earlier. This applies the review changes
Differential Revision: https://reviews.llvm.org/D69545
Summary:
Rework the GMIR documentation to focus more on the end user than the
implementation and tie it in to the MIR document. There was also some
out-of-date information which has been removed.
The quality of the GenericOpcode reference is highly variable and drops
sharply as I worked through them all but we've got to start somewhere :-).
It would be great if others could expand on this too as there is an awful
lot to get through.
Also fix a typo in the definition of G_FLOG. Previously, the comments said
we had two base-2's (G_FLOG and G_FLOG2).
Reviewers: aemerson, volkan, rovka, arsenm
Reviewed By: rovka
Subscribers: wdng, arphaman, jfb, Petar.Avramovic, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69545
Summary:
This is largely based off of the slides from the keynote
Depends on D69545
Reviewers: volkan, rovka, arsenm
Subscribers: wdng, arphaman, Petar.Avramovic, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69644
The legalizer page was in a fairly good state. I've mostly just inlined
some information as a note and removed a reference to potential future
work that I think is very unlikely to be done (it's very hard to tell if
a pattern or set of patterns fully covers a node due to C++ predicates).
Also added a note that 'selectable' doesn't mean that InstructionSelect
must do it.
I had hoped that I could have some
```
.. code-block:: MIR
```
sections for MIR examples which causes a warning about pygments not
supporting it but we have warnings treated as errors
Summary:
I haven't refreshed the Function Calls section as I don't feel I have
sufficient knowledge of that area. It would be appreciated if someone could
review that section.
Note: I'm aware that pygments doesn't support 'mir' as used in one of the
code-block directives. This currently emits a warning and I decided to
keep it to enable finding them later. Maybe we can teach pygments to
support it.
Depends on D69456
Reviewers: volkan, aditya_nandakumar
Subscribers: rovka, Petar.Avramovic, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69457
Summary:
Rewrite the pipeline overview to be more focused on the structure and
flexibility as well as highlight the increased usefulness of
MachineVerifier and increased testability resulting from the smaller
incremental passes approach.
The diagrams are lifted from the slides for the LLVMDev 2019 talk
'Generating Optimized Code with GlobalISel' and adapted to be readable on
the white background used in the docs.
Reviewers: volkan
Subscribers: rovka, Petar.Avramovic, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69456
Matt Arsenault