Unfortunately the current call lowering code is built on top of the
legacy MVT/DAG based code. However, GlobalISel was not using it the
same way. In short, the DAG passes legalized types to the assignment
function, and GlobalISel was passing the original raw type if it was
simple.
I do believe the DAG lowering is conceptually broken since it requires
picking a type up front before knowing how/where the value will be
passed. This ends up being a problem for AArch64, which wants to pass
i1/i8/i16 values as a different size if passed on the stack or in
registers.
The argument type decision is split across 3 different places which is
hard to follow. SelectionDAG builder uses
getRegisterTypeForCallingConv to pick a legal type, tablegen gives the
illusion of controlling the type, and the target may have additional
hacks in the C++ part of the call lowering. AArch64 hacks around this
by not using the standard AnalyzeFormalArguments and special casing
i1/i8/i16 by looking at the underlying type of the original IR
argument.
I believe people have generally assumed the calling convention code is
processing the original types, and I've discovered a number of dead
paths in several targets.
x86 actually relies on the opposite behavior from AArch64, and relies
on x86_32 and x86_64 sharing calling convention code where the 64-bit
cases implicitly do not work on x86_32 due to using the pre-legalized
types.
AMDGPU targets without legal i16/f16 have always used a broken ABI
that promotes to i32/f32. GlobalISel accidentally fixed this to be the
ABI we should have, but this fixes it so we're using the worse ABI
that is compatible with the DAG. Ideally we would fix the DAG to match
the old GlobalISel behavior, but I don't wish to fight that battle.
A new native GlobalISel call lowering framework should let the target
process the incoming types directly.
CCValAssigns select a "ValVT" and "LocVT" but the meanings of these
aren't entirely clear. Different targets don't use them consistently,
even within their own call lowering code. My current belief is the
intent was "ValVT" is supposed to be the legalized value type to use
in the end, and and LocVT was supposed to be the ABI passed type
(which is also legalized).
With the default CCState::Analyze functions always passing the same
type for these arguments, these only differ when the TableGen part of
the lowering decide to promote the type from one legal type to
another. AArch64's i1/i8/i16 hack ends up inverting the meanings of
these values, so I had to add an additional hack to let the target
interpret how large the argument memory is.
Since targets don't consistently interpret ValVT and LocVT, this
doesn't produce quite equivalent code to the initial DAG
lowerings. I've opted to consistently interpret LocVT as the in-memory
size for stack passed values, and ValVT as the register type to assign
from that memory. We therefore produce extending loads directly out of
the IRTranslator, whereas the DAG would emit regular loads of smaller
values. This will also produce loads/stores that are wider than the
argument value if the allocated stack slot is larger (and there will
be undef padding bytes). If we had the optimizations to reduce
load/stores based on truncated values, this wouldn't produce a
different end result.
Since ValVT/LocVT are more consistently interpreted, we now will emit
more G_BITCASTS as requested by the CCAssignFn. For example AArch64
was directly assigning types to some physical vector registers which
according to the tablegen spec should have been casted to a vector
with a different element type.
This also moves the responsibility for inserting
G_ASSERT_SEXT/G_ASSERT_ZEXT from the target ValueHandlers into the
generic code, which is closer to how SelectionDAGBuilder works.
I had to xfail an x86 test since I don't see a quick way to fix it
right now (I filed bug 50035 for this). It's broken independently of
this change, and only triggers since now we end up with more ands
which hit the improperly handled selection pattern.
I also observed that FP arguments that need promotion (e.g. f16 passed
as f32) are broken, and use regular G_TRUNC and G_ANYEXT.
TLDR; the current call lowering infrastructure is bad and nobody has
ever understood how it chooses types.
G_SELECT uses a 1-bit scalar for the condition, and is currently
implemented with a plain CMPri against 0. This means that values such as
0x1110 are interpreted as true, when instead the higher bits should be
treated as undefined and therefore ignored. Replace the CMPri with a
TSTri against 0x1, which performs an implicit AND, yielding the expected
result.
llvm-svn: 357153
When lowering a G_BRCOND, we generate a TSTri of the condition against
1, which sets the flags, and then a Bcc which branches based on the
value of the flags.
Unfortunately, we were using the wrong condition code to check whether
we need to branch (EQ instead of NE), which caused all our branches to
do the opposite of what they were intended to do. This patch fixes the
issue by using the correct condition code.
llvm-svn: 319313
artifacts along with DCE
Legalization Artifacts are all those insts that are there to make the
type system happy. Currently, the target needs to say all combinations
of extends and truncs are legal and there's no way of verifying that
post legalization, we only have *truly* legal instructions. This patch
changes roughly the legalization algorithm to process all illegal insts
at one go, and then process all truncs/extends that were added to
satisfy the type constraints separately trying to combine trivial cases
until they converge. This has the added benefit that, the target
legalizerinfo can only say which truncs and extends are okay and the
artifact combiner would combine away other exts and truncs.
Updated legalization algorithm to roughly the following pseudo code.
WorkList Insts, Artifacts;
collect_all_insts_and_artifacts(Insts, Artifacts);
do {
for (Inst in Insts)
legalizeInstrStep(Inst, Insts, Artifacts);
for (Artifact in Artifacts)
tryCombineArtifact(Artifact, Insts, Artifacts);
} while(!Insts.empty());
Also, wrote a simple wrapper equivalent to SetVector, except for
erasing, it avoids moving all elements over by one and instead just
nulls them out.
llvm-svn: 318210
We were generating BLX for all the calls, which was incorrect in most
cases. Update ARMCallLowering to generate BL for direct calls, and BLX,
BX_CALL or BMOVPCRX_CALL for indirect calls.
llvm-svn: 316570
Insert a TSTri to set the flags and a Bcc to branch based on their
values. This is a bit inefficient in the (common) cases where the
condition for the branch comes from a compare right before the branch,
since we set the flags both as part of the compare lowering and as part
of the branch lowering. We're going to live with that until we settle on
a principled way to handle this kind of situation, which occurs with
other patterns as well (combines might be the way forward here).
llvm-svn: 308009
This boils down to not crashing in reg bank select due to the lack of
register operands on this instruction, and adding some tests. The
instruction selection is already covered by the TableGen'erated code.
llvm-svn: 307904
* Mark as legal for (s32, i1, s32, s32)
* Map everything into GPRs
* Select to two instructions: a CMP of the condition against 0, to set
the flags, and a MOVCCr to select between the two inputs based on the
flags that we've just set
llvm-svn: 306382
Add support throughout the pipeline:
- mark as legal for s32 and pointers
- map to GPRs
- lower to a sequence of instructions, which moves 0 or 1 into the
result register based on the flags set by a CMPrr
We have copied from FastISel a helper function which maps CmpInst
predicates into ARMCC codes. Ideally, we should be able to move it
somewhere that both FastISel and GlobalISel can use.
llvm-svn: 305672
According to the commit message from r296921, G_MERGE_VALUES and
G_INSERT are to be preferred over G_SEQUENCE. Therefore, stop generating
G_SEQUENCE in the ARM backend and remove the code dealing with it.
This boils down to the code breaking up double values for the soft float
calling convention. Use G_MERGE_VALUES + G_UNMERGE_VALUES instead of
G_SEQUENCE + G_EXTRACT for it. This maps very nicely to VMOVDRR +
VMOVRRD and simplifies the code in the instruction selector.
There's one occurence of G_SEQUENCE left in arm-irtranslator.ll, but
that is part of the target-independent code for translating constant
structs. Therefore, it is beyond the scope of this commit.
llvm-svn: 304902
This is identical to the support for the other binary operators:
- widen to s32
- map into GPR
- select ANDrr (via TableGen'erated code)
llvm-svn: 304885
Fix a crash when trying to extend a value passed as a sign- or
zero-extended stack parameter. The cause of the crash was that we were
setting the size of the loaded value to 32 bits, and then tyring to
extend again to 32 bits.
This patch addresses the issue by also introducing a G_TRUNC after the
load. This will leave the unused bits to their original values set by
the caller, while being consistent about the types. For values that are
not extended, we just use a smaller load.
llvm-svn: 301531
When selecting a G_CONSTANT to a MOVi, we need the value to be an Imm
operand. We used to just leave the G_CONSTANT operand unchanged, which
works in some cases (such as the GEP offsets that we create when
referring to stack slots). However, in many other places the G_CONSTANTs
are created with CImm operands. This patch makes sure to handle those as
well, and to error out gracefully if in the end we don't end up with an
Imm operand.
Thanks to Oliver Stannard for reporting this issue.
llvm-svn: 301162
Select them as copies. We only select if both the source and the
destination are on the same register bank, so this shouldn't cause any
trouble.
llvm-svn: 300971
Support G_MUL, very similar to G_ADD and G_SUB. The only difference is
in the instruction selector, where we have to select either MUL or MULv5
depending on the target.
llvm-svn: 300665
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
It is important to change the ArgInfo's type from pointer to integer, otherwise
the CC assign function won't know what to do. Instead of hacking it up, we use
ComputeValueVTs and introduce some of the helpers that we will need later on for
lowering more complex types.
llvm-svn: 293889
Add support for loading i1, i8 and i16 arguments from the stack, with or without
the ABI extension flags.
When the ABI extension flags are present, we load a 4-byte value, otherwise we
preserve the size of the load and let the instruction selector replace it with a
LDRB/LDRH. This generates the same thing as DAGISel.
Differential Revision: https://reviews.llvm.org/D27803
llvm-svn: 293163
Add support for:
* i1 add
* i1 function arguments, if passed through registers
* i1 returns, with ABI signext/zeroext
Differential Revision: https://reviews.llvm.org/D27706
llvm-svn: 293035
At the moment, this means supporting the signext/zeroext attribute on the return
type of the function. For function arguments, signext/zeroext should be handled
by the caller, so there's nothing for us to do until we start lowering calls.
Note that this does not include support for other extensions (i8 to i16), those
will be added later.
Differential Revision: https://reviews.llvm.org/D27705
llvm-svn: 293034
This allows lowering i8 and i16 arguments if they can fit in the registers. Note
that the lowering is incomplete - ABI extensions are handled in a subsequent
patch.
(Last part of)
Differential Revision: https://reviews.llvm.org/D27704
llvm-svn: 290106
This adds support for lowering more than 4 arguments (although still i32 only).
It uses the handleAssignments / ValueHandler infrastructure extracted from
the AArch64 backend in r288658.
Differential Revision: https://reviews.llvm.org/D27195
llvm-svn: 290098
Add the minimal support necessary to select a function that returns the sum of
two i32 values.
This includes some support for argument/return lowering of i32 values through
registers, as well as the handling of copy and add instructions throughout the
GlobalISel pipeline.
Differential Revision: https://reviews.llvm.org/D26677
llvm-svn: 289940
