Without this check, COPY instructions can actually be one of the generic casts
in disguise. That's confusing and bad.
At some point during ISel this restriction has to be relaxed since the fully
selected instructions will usually use COPY for those purposes. Right now I
think it's possible that relaxation occurs during RegBankSelect (hence the
change there). I'm not convinced that's where it belongs long-term though.
llvm-svn: 306470
G_SEQUENCE is going away soon so as a first step the MachineIRBuilder needs to
be taught how to emulate it with alternatives. We use G_MERGE_VALUES where
possible, and a sequence of G_INSERTs if not.
llvm-svn: 306119
Summary:
When legalizing G_LOAD/G_STORE using NarrowScalar, we should avoid emitting
%0 = G_CONSTANT ty 0
%1 = G_GEP %x, %0
since it's cheaper to not emit the redundant instructions than it is to fold them
away later.
Reviewers: qcolombet, t.p.northover, ab, rovka, aditya_nandakumar, kristof.beyls
Reviewed By: qcolombet
Subscribers: javed.absar, llvm-commits, igorb
Differential Revision: https://reviews.llvm.org/D32746
llvm-svn: 305340
This fixes PR32471.
As comment 10 on that bug report highlights
(https://bugs.llvm.org//show_bug.cgi?id=32471#c10), there are quite a
few different defendable design tradeoffs that could be made, including
not representing pointers at all in LLT.
I decided to go for representing vector-of-pointer as a concept in LLT,
while keeping the size of the LLT type 64 bits (this is an increase from
48 bits before). My rationale for keeping pointers explicit is that on
some targets probably it's very handy to have the distinction between
pointer and non-pointer (e.g. 68K has a different register bank for
pointers IIRC). If we keep a scalar pointer, it probably is easiest to
also have a vector-of-pointers to keep LLT relatively conceptually clean
and orthogonal, while we don't have a very strong reason to break that
orthogonality. Once we gain more experience on the use of LLT, we can
of course reconsider this direction.
Rejecting vector-of-pointer types in the IRTranslator is also an option
to avoid the crash reported in PR32471, but that is only a very
short-term solution; also needs quite a bit of code tweaks in places,
and is probably fragile. Therefore I didn't consider this the best
option.
llvm-svn: 300664
This reverts r300535 and r300537.
The newly added tests in test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll
produces slightly different code between LLVM versions being built with different compilers.
E.g., dependent on the compiler LLVM is built with, either one of the following
can be produced:
remark: <unknown>:0:0: unable to legalize instruction: %vreg0<def>(p0) = G_EXTRACT_VECTOR_ELT %vreg1, %vreg2; (in function: vector_of_pointers_extractelement)
remark: <unknown>:0:0: unable to legalize instruction: %vreg2<def>(p0) = G_EXTRACT_VECTOR_ELT %vreg1, %vreg0; (in function: vector_of_pointers_extractelement)
Non-determinism like this is clearly a bad thing, so reverting this until
I can find and fix the root cause of the non-determinism.
llvm-svn: 300538
This fixes PR32471.
As comment 10 on that bug report highlights
(https://bugs.llvm.org//show_bug.cgi?id=32471#c10), there are quite a
few different defendable design tradeoffs that could be made, including
not representing pointers at all in LLT.
I decided to go for representing vector-of-pointer as a concept in LLT,
while keeping the size of the LLT type 64 bits (this is an increase from
48 bits before). My rationale for keeping pointers explicit is that on
some targets probably it's very handy to have the distinction between
pointer and non-pointer (e.g. 68K has a different register bank for
pointers IIRC). If we keep a scalar pointer, it probably is easiest to
also have a vector-of-pointers to keep LLT relatively conceptually clean
and orthogonal, while we don't have a very strong reason to break that
orthogonality. Once we gain more experience on the use of LLT, we can
of course reconsider this direction.
Rejecting vector-of-pointer types in the IRTranslator is also an option
to avoid the crash reported in PR32471, but that is only a very
short-term solution; also needs quite a bit of code tweaks in places,
and is probably fragile. Therefore I didn't consider this the best
option.
llvm-svn: 300535
For vector operands, the `select` instruction supports both vector and
non-vector conditions. The MIR builder had an overly restrictive
assertion, that only accepted vector conditions for vector selects
(in effect implementing ISD::VSELECT).
Make it possible to express the full range of G_SELECTs.
llvm-svn: 297207
When a dbg_value has a constant operand that isn't representable in MI,
there isn't much we can do. Use %noreg (0) for those situations.
This matches the SelectionDAG behavior.
llvm-svn: 297200
A bit more painful than G_INSERT because it was more widely used, but this
should simplify the handling of extract operations in most locations.
llvm-svn: 297100
Before, we were producing G_INSERT instructions that were actually closer to a
cast or even a COPY when both input and output sizes are the same. This doesn't
really make sense and means that everything interpreting a G_INSERT also has to
handle all these kinds of casts.
So now we detect these degenerate cases and emit real casts instead.
llvm-svn: 297051
These are simplified variants of the current G_SEQUENCE and G_EXTRACT, which
assume the individual parts will be contiguous, homogeneous, and occupy the
entirity of the larger register. This makes reasoning about them much easer
since you only have to look at the first register being merged and the result
to know what the instruction is doing.
I intend to gradually replace all uses of the more complicated sequence/extract
with these (or single-element insert/extracts), and then remove the older
variants. For now we start with legalization.
llvm-svn: 296921
This instruction clears the low bits of a pointer without requiring (possibly
dodgy if pointers aren't ints) conversions to and from an integer. Since (as
far as I'm aware) all masks are statically known, the instruction takes an
immediate operand rather than a register to specify the mask.
llvm-svn: 295103
The translation scheme is mostly cribbed from FastISel, and it's not entirely
convincing semantically. But it does seem to work in the common cases and allow
variables to be printed so it can't be all wrong.
llvm-svn: 293228
MachineIRBuilder had weird before/after and beginning/end flags for the insert
point. Unfortunately the non-default means that instructions will be inserted
in reverse order which is almost never what anyone wants.
Really, I think we just want (like IRBuilder has) the ability to insert at any
C++ iterator-style point (i.e. before any instruction or before MBB.end()). So
this fixes MIRBuilders to behave like IRBuilders in this respect.
llvm-svn: 288980
This makes it more similar to the floating-point constant, and also allows for
larger constants to be translated later. There's no real functional change in
this patch though, just syntax updates.
llvm-svn: 288712
This should match the existing behaviour for passing complicated struct and
array types, in particular HFAs come through like that from Clang.
For C & C++ we still need to somehow support all the weird ABI flags, or at
least those that are present in the IR (signext, byval, ...), and stack-based
parameter passing.
llvm-svn: 281977
Unlike SDag, we use a separate G_GEP instruction (much simplified, only taking
a single byte offset) to preserve the pointer type information through
selection.
llvm-svn: 281205
We want each register to have a canonical type, which means the best place to
store this is in MachineRegisterInfo rather than on every MachineInstr that
happens to use or define that register.
Most changes following from this are pretty simple (you need an MRI anyway if
you're going to be doing any transformations, so just check the type there).
But legalization doesn't really want to check redundant operands (when, for
example, a G_ADD only ever has one type) so I've made use of MCInstrDesc's
operand type field to encode these constraints and limit legalization's work.
As an added bonus, more validation is possible, both in MachineVerifier and
MachineIRBuilder (coming soon).
llvm-svn: 281035
More preparation for dropping source types from MachineInstrs: regsters coming
out of already-selected code (i.e. non-generic instructions) don't have a type,
but that information is needed so we must add it manually.
This is done via a new G_TYPE instruction.
llvm-svn: 280292
Legalization ends up creating many G_SEQUENCE/G_EXTRACT pairs which leads to
inefficient codegen (even for -O0), so add a quick pass over the function to
remove them again.
llvm-svn: 280155
They really should have both types represented, but early variants were created
before MachineInstrs could have multiple types so they're rather ambiguous.
llvm-svn: 279567
First, make sure all types involved are represented, rather than being implicit
from the register width.
Second, canonicalize all types to scalar. These operations just act in bits and
don't care about vectors.
Also standardize spelling of Indices in the MachineIRBuilder (NFC here).
llvm-svn: 279294
Unsigned addition and subtraction can reuse the instructions created to
legalize large width operations (i.e. both produce and consume a carry flag).
Signed operations and multiplies get a dedicated op-with-overflow instruction.
Once this is produced the two values are combined into a struct register (which
will almost always be merged with a corresponding G_EXTRACT as part of
legalization).
llvm-svn: 279278
These come in two variants for now: G_INTRINSIC and G_INTRINSIC_W_SIDE_EFFECTS.
We may decide to split the latter up with finer-grained restrictions later, if
necessary.
llvm-svn: 277224
For MachineInstrBuilder, having to manually use RegState::Define is ugly and
makes register definitions clunkier than they need to be, so this adds two
convenience functions: addDef and addUse.
For MachineIRBuilder, we want to avoid BuildMI's first-reg-is-def rule because
it's hidden away and causes bugs. So this patch switches buildInstr to
returning a MachineInstrBuilder and adding *all* operands via addDef/addUse.
NFC.
llvm-svn: 277176
Instead of an ad-hoc collection of "buildInstr" functions with varying numbers
of registers, this uses variadic templates to provide for as many regs as
needed!
Also make IRtranslator use new "buildBr" function instead of some weird generic
one that no-one else would really use.
llvm-svn: 276762
This adds LLVM's 3 main cast instructions (inttoptr, ptrtoint, bitcast) to the
IRTranslator. The first two are direct translations (with 2 MachineInstr types
each). Since LLT discards information, a bitcast might become trivial and we
emit a COPY in those cases instead.
llvm-svn: 276690
This adds the actual MachineLegalizeHelper to do the work and a trivial pass
wrapper that legalizes all instructions in a MachineFunction. Currently the
only transformation supported is splitting up a vector G_ADD into one acting on
smaller vectors.
llvm-svn: 276461
This should be all the low-level instruction selection needs to determine how
to implement an operation, with the remaining context taken from the opcode
(e.g. G_ADD vs G_FADD) or other flags not based on type (e.g. fast-math).
llvm-svn: 276158
Tim Northover