For some reductions like G_VECREDUCE_OR on AArch64, we need to scalarize
completely if the source is <= 64b. This change adds support for that in
the legalizer. If the source has a pow-2 num elements, then we can do
a tree reduction using the scalar operation in the individual elements.
Otherwise, we just create a sequential chain of operations.
For AArch64, we only need to scalarize if the input is <64b. If it's great than
64b then we can first do a fewElements step to 64b, taking advantage of vector
instructions until we reach the point of scalarization.
I also had to relax the verifier checks for reductions because the intrinsics
support <1 x EltTy> types, which we lower to scalars for GlobalISel.
Differential Revision: https://reviews.llvm.org/D108276
When support for copying vector s8 lanes was added recently, this also
had the side effect of fixing a fallback for <16 x s8> extracts since
both used the same helper. However, there was a bug in another helper
to get the regclass for a specific FPR-native type, which was assigning
FPR16 to s8 instead of FPR8.
This allows the instruction selector to realize that it can directly
broadcast the low byte of the memset value, rather than replicating
it to a 64-bit GPR before broadcasting.
This fixes PR50985.
Differential Revision: https://reviews.llvm.org/D108354
This changes the lowering of saddsat and ssubsat so that instead of
using:
r,o = saddo x, y
c = setcc r < 0
s = c ? INTMAX : INTMIN
ret o ? s : r
into using asr and xor to materialize the INTMAX/INTMIN constants:
r,o = saddo x, y
s = ashr r, BW-1
x = xor s, INTMIN
ret o ? x : r
https://alive2.llvm.org/ce/z/TYufgD
This seems to reduce the instruction count in most testcases across most
architectures. X86 has some custom lowering added to compensate for
cases where it can increase instruction count.
Differential Revision: https://reviews.llvm.org/D105853
We need to ensure that these end up on FPR to allow imported patterns to
select them.
This will also ensure that we get good regbank selection when dealing with
instructions like G_PHI/G_LOAD/G_STORE which deduce their banks from their
uses/users.
Differential Revision: https://reviews.llvm.org/D108260
For subtargets with full FP16, this is legal for s16, s32, and s64. Without
full FP16, it's legal for s32 and s64.
For s128, this is a libcall.
We also support some vector types, but for now, let's just support scalars.
Differential Revision: https://reviews.llvm.org/D108259
Translate the `@llvm.isnan` intrinsic to G_ISNAN when we see it.
This is pretty much the same as the associated SelectionDAGBuilder code. Main
difference is that we don't expand it here. It makes more sense to do that
during legalization in GlobalISel. GlobalISel will just legalize the generated
illegal types.
Differential Revision: https://reviews.llvm.org/D108226
visitEXTRACT_SUBVECTOR can sometimes create illegal BITCASTs when
removing "redundant" INSERT_SUBVECTOR operations. This patch adds
an extra check to ensure such combines only occur after operation
legalisation if any resulting BITBAST is itself legal.
Differential Revision: https://reviews.llvm.org/D108086
This is a non-intrusive fix for
https://bugs.llvm.org/show_bug.cgi?id=51476 intended for backport
to the 13.x release branch. It expands on the current hack by
distinguishing between CmpValue of 0, 1 and 2, where 0 and 1 have
the obvious meaning and 2 means "anything else". The new optimization
from D98564 should only be performed for CmpValue of 0 or 1.
For main, I think we should switch the analyzeCompare() and
optimizeCompare() APIs to use int64_t instead of int, which is in
line with MachineOperand's notion of an immediate, and avoids this
problem altogether.
Differential Revision: https://reviews.llvm.org/D108076
This is a fairly common pattern:
```
%mask = G_CONSTANT iN <mask val>
%add = G_ADD %lhs, %rhs
%and = G_AND %add, %mask
```
We have combines to eliminate G_AND with a mask that does nothing.
If we combined the above to this:
```
%mask = G_CONSTANT iN <mask val>
%narrow_lhs = G_TRUNC %lhs
%narrow_rhs = G_TRUNC %rhs
%narrow_add = G_ADD %narrow_lhs, %narrow_rhs
%ext = G_ZEXT %narrow_add
%and = G_AND %ext, %mask
```
We'd be able to take advantage of those combines using the trunc + zext.
For this to work (or be beneficial in the best case)
- The operation we want to narrow then widen must only be used by the G_AND
- The G_TRUNC + G_ZEXT must be free
- Performing the operation at a narrower width must not produce a different
value than performing it at the original width *after masking.*
Example comparison between SDAG + GISel: https://godbolt.org/z/63jzb1Yvj
At -Os for AArch64, this is a 0.2% code size improvement on CTMark/pairlocalign.
Differential Revision: https://reviews.llvm.org/D107929
These are lowered, matching SDAG behaviour. (See
llvm/test/CodeGen/AArch64/ssub_sat.ll and llvm/test/CodeGen/AArch64/sadd_sat.ll)
These fall back ~159 times on a build of clang with GISel enabled.
Differential Revision: https://reviews.llvm.org/D107777
This patch enables extending loads for fixed length SVE code generation.
There is a slight regression here in the mulh tests; since these tests
load the parameter and then extend it these are treated as extending
loads which are merged, preventing the mulh instruction from being
generated. As this affects scalable SVE codegen as well this should be
addressed in a separate patch.
Reviewed By: bsmith
Differential Revision: https://reviews.llvm.org/D107057
These rules were originally written when the new predicate based legalizer
was introduced in an attempt to preserve existing behaviour. It wasn't
properly kept up to date as things like vector support was split out into
G_CONCAT_VECTORS, and frankly, even if it was, it was too complex.
It's much easier to start from scratch with what we can actually support,
which is just a few type combinations. Anything illegal we should either
legalize, or should be eliminated as a side effect of artifact combination.
Differential Revision: https://reviews.llvm.org/D107937
The assertion can fail in some cases when an i16 constant is promoted
to i32.
e.g. in the added test case the value `i16 -32768` is within the range
of i16 but the assert fails when the constant is promoted to positive
`i32 32768` by an earlier call to DAG.getConstant().
Differential Revision: https://reviews.llvm.org/D107880
Change-Id: I2f6179783cbc9630e6acab149a762b43c65664de
If a G_SHL is fed by a G_CONSTANT, the lower and upper bits of the source can be
shifted individually by the constant shift amount.
However in case the shift amount came from a G_TRUNC(G_CONSTANT), the generic shift legalization
code was used, producing intermediate shifts that are potentially illegal on some targets.
This change teaches narrowScalarShift to look through G_TRUNCs and G_*EXTs.
Reviewed By: paquette
Differential Revision: https://reviews.llvm.org/D89100
I was originally going to try to implement this in target-independent
code, but it's actually sort of tricky to generate the correct sequence
for vectors like nxv2f32. So just stick this in target-specific code,
at least for now.
Differential Revision: https://reviews.llvm.org/D107608
The patterns for fixed length gather/scatter with 32-bit offsets and
64-bit memory type are slightly different that the rest of the patterns,
as such the lowering needs to be slightly different to ensure the
correct types are used.
Differential Revision: https://reviews.llvm.org/D107576
We should use MachineInstr::eraseFromParentAndMarkDBGValuesForRemoval()
instead of eraseFromParent().
We should probably use that in other places too but fix this issue which
affects clang bootstrap builds for now.
This is recommit of the patch 16ff91ebcc,
reverted in 0c28a7c990 because it had
an error in call of getFastMathFlags (base type should be FPMathOperator
but not Instruction). The original commit message is duplicated below:
Clang has builtin function '__builtin_isnan', which implements C
library function 'isnan'. This function now is implemented entirely in
clang codegen, which expands the function into set of IR operations.
There are three mechanisms by which the expansion can be made.
* The most common mechanism is using an unordered comparison made by
instruction 'fcmp uno'. This simple solution is target-independent
and works well in most cases. It however is not suitable if floating
point exceptions are tracked. Corresponding IEEE 754 operation and C
function must never raise FP exception, even if the argument is a
signaling NaN. Compare instructions usually does not have such
property, they raise 'invalid' exception in such case. So this
mechanism is unsuitable when exception behavior is strict. In
particular it could result in unexpected trapping if argument is SNaN.
* Another solution was implemented in https://reviews.llvm.org/D95948.
It is used in the cases when raising FP exceptions by 'isnan' is not
allowed. This solution implements 'isnan' using integer operations.
It solves the problem of exceptions, but offers one solution for all
targets, however some can do the check in more efficient way.
* Solution implemented by https://reviews.llvm.org/D96568 introduced a
hook 'clang::TargetCodeGenInfo::testFPKind', which injects target
specific code into IR. Now only SystemZ implements this hook and it
generates a call to target specific intrinsic function.
Although these mechanisms allow to implement 'isnan' with enough
efficiency, expanding 'isnan' in clang has drawbacks:
* The operation 'isnan' is hidden behind generic integer operations or
target-specific intrinsics. It complicates analysis and can prevent
some optimizations.
* IR can be created by tools other than clang, in this case treatment
of 'isnan' has to be duplicated in that tool.
Another issue with the current implementation of 'isnan' comes from the
use of options '-ffast-math' or '-fno-honor-nans'. If such option is
specified, 'fcmp uno' may be optimized to 'false'. It is valid
optimization in general, but it results in 'isnan' always returning
'false'. For example, in some libc++ implementations the following code
returns 'false':
std::isnan(std::numeric_limits<float>::quiet_NaN())
The options '-ffast-math' and '-fno-honor-nans' imply that FP operation
operands are never NaNs. This assumption however should not be applied
to the functions that check FP number properties, including 'isnan'. If
such function returns expected result instead of actually making
checks, it becomes useless in many cases. The option '-ffast-math' is
often used for performance critical code, as it can speed up execution
by the expense of manual treatment of corner cases. If 'isnan' returns
assumed result, a user cannot use it in the manual treatment of NaNs
and has to invent replacements, like making the check using integer
operations. There is a discussion in https://reviews.llvm.org/D18513#387418,
which also expresses the opinion, that limitations imposed by
'-ffast-math' should be applied only to 'math' functions but not to
'tests'.
To overcome these drawbacks, this change introduces a new IR intrinsic
function 'llvm.isnan', which realizes the check as specified by IEEE-754
and C standards in target-agnostic way. During IR transformations it
does not undergo undesirable optimizations. It reaches instruction
selection, where is lowered in target-dependent way. The lowering can
vary depending on options like '-ffast-math' or '-ffp-model' so the
resulting code satisfies requested semantics.
Differential Revision: https://reviews.llvm.org/D104854
Similar cleanup to G_EXTRACT (51bd4e874f).
Also swap the order of clamp/widen to avoid unnecessary complex merges.
Add a bunch of missing testcases to legalize-inserts while we're at it.
Differential Revision: https://reviews.llvm.org/D107601
Similar to other cleanup commits which widen instructions before clamping
during legalization. Purpose of this is to avoid weird type breakdowns.
In terms of G_IMPLICIT_DEF, this simplifies legalization for other instructions.
The legalizer has to emit G_IMPLICIT_DEF to legalize certain instructions, so
this can help with emitting merges elsewhere.
Differential Revision: https://reviews.llvm.org/D107604
In some cases, like with inserts, we may have a matching size register already,
but still decide to try to look further. This change adds a CurrentBest
register to the value finder state, and any time a method fails to make progress,
returns that register (which may just be an empty Register).
To facilitate this, add a new entry point to the findValueFromDef() function
which initializes this state.
Also fix the build vector finder to return the current build_vector if all
sources are being requested.
Differential Revision: https://reviews.llvm.org/D107017
This allows us to avoid odd type breakdowns + allows us to legalize types like
s88 in the first place.
Add some testcases for known legal types + testcases for s4 and s88.
Differential Revision: https://reviews.llvm.org/D107607
This simplifies our existing G_EXTRACT rules and adds some test coverage. Mostly
changing this because it should make it easier to improve legalization for
instructions which use G_EXTRACT as part of the legalization process.
This also adds support for legalizing some weird types. Similar to other recent
legalizer changes, this changes the order of widening/clamping.
There was some dead code in our existing rules (e.g. the p0 case would never get
hit), so this knocks those out and makes the types we want to handle explicit.
This also removes some checks which, nowadays, are handled by the
MachineVerifier.
Differential Revision: https://reviews.llvm.org/D107505
This is re-landing the same patch again, but without the changes to
LegalizerHelper that regressed the Mips test:
test/CodeGen/Mips/GlobalISel/llvm-ir/ctpop.ll
Differential revision: https://reviews.llvm.org/D106494
G_CONCAT_VECTORS shows up from time to time when legalizing other instructions.
We actually import patterns for the v16s8 <- v8s8, v8s8 case so marking it
as legal gives us selection for free.
Differential Revision: https://reviews.llvm.org/D107512
IR typically creates INSERT_SUBVECTOR patterns as a widening of the subvector with undefs to pad to the destination size, followed by a shuffle for the actual insertion - SelectionDAGBuilder has to do something similar for shuffles when source/destination vectors are different sizes.
This combine attempts to recognize these patterns by looking for a shuffle of a subvector (from a CONCAT_VECTORS) that starts at a modulo of its size into an otherwise identity shuffle of the base vector.
This uncovered a couple of target-specific issues as we haven't often created INSERT_SUBVECTOR nodes in generic code - aarch64 could only handle insertions into the bottom of undefs (i.e. a vector widening), and x86-avx512 vXi1 insertion wasn't keeping track of undef elements in the base vector.
Fixes PR50053
Differential Revision: https://reviews.llvm.org/D107068
Clamp the max number of elements when legalizing G_PHI. This allows us to
legalize some common fallbacks like 4 x s64.
Here's an example: https://godbolt.org/z/6YocsEYTd
Had to add -global-isel-abort=0 to legalize-phi.mir to account for the
G_EXTRACT_VECTOR_ELT from the 32 x s8 G_PHI.
Differential Revision: https://reviews.llvm.org/D107508
This allows us to handle weird types like s88; we first widen to s128, then
clamp back down to s64.
https://godbolt.org/z/9xqbP46Mz
Also this makes it possible for GISel to legalize the case in pr48188.ll. It
now does the same thing as SDAG, although regalloc chooses different registers.
Differential Revision: https://reviews.llvm.org/D107417
Going through our legalization rules and doing some cleanup.
Widening and then clamping is usually easier than clamping and then widening.
This allows us to legalize some weird types like s88.
Differential Revision: https://reviews.llvm.org/D107413
An insert subvector that is inserting the result of a vector predicate
sized load into undef at index 0, whose result is casted to a predicate
type, can be combined into a direct predicate load. Likewise the same
applies to extract subvector but in reverse.
The purpose of this optimization is to clean up cases that will be
introduced in a later patch where casts to/from predicate types from i8
types will use insert subvector, rather than going through memory early.
This optimization is done in SVEIntrinsicOpts rather than InstCombine to
re-introduce scalable loads as late as possible, to give other
optimizations the best chance possible to do a good job.
Differential Revision: https://reviews.llvm.org/D106549
Don't know how to custom expand this
UNREACHABLE executed at llvm-project/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp:16788
The fix is to provide missing expansions for:
case ISD::STRICT_FP_TO_UINT:
case ISD::STRICT_FP_TO_SINT:
A test case is provided.
Reviewed By: dmgreen
Differential Revision: https://reviews.llvm.org/D107452
Clang has builtin function '__builtin_isnan', which implements C
library function 'isnan'. This function now is implemented entirely in
clang codegen, which expands the function into set of IR operations.
There are three mechanisms by which the expansion can be made.
* The most common mechanism is using an unordered comparison made by
instruction 'fcmp uno'. This simple solution is target-independent
and works well in most cases. It however is not suitable if floating
point exceptions are tracked. Corresponding IEEE 754 operation and C
function must never raise FP exception, even if the argument is a
signaling NaN. Compare instructions usually does not have such
property, they raise 'invalid' exception in such case. So this
mechanism is unsuitable when exception behavior is strict. In
particular it could result in unexpected trapping if argument is SNaN.
* Another solution was implemented in https://reviews.llvm.org/D95948.
It is used in the cases when raising FP exceptions by 'isnan' is not
allowed. This solution implements 'isnan' using integer operations.
It solves the problem of exceptions, but offers one solution for all
targets, however some can do the check in more efficient way.
* Solution implemented by https://reviews.llvm.org/D96568 introduced a
hook 'clang::TargetCodeGenInfo::testFPKind', which injects target
specific code into IR. Now only SystemZ implements this hook and it
generates a call to target specific intrinsic function.
Although these mechanisms allow to implement 'isnan' with enough
efficiency, expanding 'isnan' in clang has drawbacks:
* The operation 'isnan' is hidden behind generic integer operations or
target-specific intrinsics. It complicates analysis and can prevent
some optimizations.
* IR can be created by tools other than clang, in this case treatment
of 'isnan' has to be duplicated in that tool.
Another issue with the current implementation of 'isnan' comes from the
use of options '-ffast-math' or '-fno-honor-nans'. If such option is
specified, 'fcmp uno' may be optimized to 'false'. It is valid
optimization in general, but it results in 'isnan' always returning
'false'. For example, in some libc++ implementations the following code
returns 'false':
std::isnan(std::numeric_limits<float>::quiet_NaN())
The options '-ffast-math' and '-fno-honor-nans' imply that FP operation
operands are never NaNs. This assumption however should not be applied
to the functions that check FP number properties, including 'isnan'. If
such function returns expected result instead of actually making
checks, it becomes useless in many cases. The option '-ffast-math' is
often used for performance critical code, as it can speed up execution
by the expense of manual treatment of corner cases. If 'isnan' returns
assumed result, a user cannot use it in the manual treatment of NaNs
and has to invent replacements, like making the check using integer
operations. There is a discussion in https://reviews.llvm.org/D18513#387418,
which also expresses the opinion, that limitations imposed by
'-ffast-math' should be applied only to 'math' functions but not to
'tests'.
To overcome these drawbacks, this change introduces a new IR intrinsic
function 'llvm.isnan', which realizes the check as specified by IEEE-754
and C standards in target-agnostic way. During IR transformations it
does not undergo undesirable optimizations. It reaches instruction
selection, where is lowered in target-dependent way. The lowering can
vary depending on options like '-ffast-math' or '-ffp-model' so the
resulting code satisfies requested semantics.
Differential Revision: https://reviews.llvm.org/D104854
This changes the lowering of f32 and f64 COPY from a 128bit vector ORR to
a fmov of the appropriate type. At least on some CPU's with 64bit NEON
data paths this is expected to be faster, and shouldn't be slower on any
CPU that treats fmov as a register rename.
Differential Revision: https://reviews.llvm.org/D106365
Add a comment when there is a shifted value,
add x9, x0, #291, lsl #12 ; =1191936
but not when the immediate value is unshifted,
subs x9, x0, #256 ; =256
when the comment adds nothing additional to the reader.
Differential Revision: https://reviews.llvm.org/D107196
Amara Emerson