Previously, InstCombine detected a pair of llvm.stacksave/stackrestore
instructions that are adjacent modulo debug instructions in order to
eliminate the llvm.stackrestore. This precludes situations where
intervening instructions (e.g. loads) preclude the llvm.stacksave and
llvm.stackrestore from becoming adjacent. This commit extends the logic
and allows for eliminating the llvm.stackrestore when the range of
instructions between them does not include any alloca or side-effect
causing instructions.
Signed-off-by: Itay Bookstein <itay.bookstein@nextsilicon.com>
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D113105
Hoist the instruction classification logic outside the loop
in preparation for reuse in a future commit.
Signed-off-by: Itay Bookstein <itay.bookstein@nextsilicon.com>
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D113464
This patch continues unblocking optimizations that are blocked by pseudo probe instrumentation.
Not exactly like DbgIntrinsics, PseudoProbe intrinsic has other attributes (such as mayread, maywrite, mayhaveSideEffect) that can block optimizations. The issues fixed are:
- Flipped default param of getFirstNonPHIOrDbg API to skip pseudo probes
- Unblocked CSE by avoiding pseudo probe from clobbering memory SSA
- Unblocked induction variable simpliciation
- Allow empty loop deletion by treating probe intrinsic isDroppable
- Some refactoring.
Reviewed By: wenlei
Differential Revision: https://reviews.llvm.org/D110847
Stop using APInt constructors and methods that were soft-deprecated in
D109483. This fixes all the uses I found in llvm, except for the APInt
unit tests which should still test the deprecated methods.
Differential Revision: https://reviews.llvm.org/D110807
This is another regression noted with the proposal to canonicalize
to the min/max intrinsics in D98152.
Here are Alive2 attempts to show correctness without specifying
exact constants:
https://alive2.llvm.org/ce/z/bvfCwh (smax)
https://alive2.llvm.org/ce/z/of7eqy (smin)
https://alive2.llvm.org/ce/z/2Xtxoh (umax)
https://alive2.llvm.org/ce/z/Rm4Ad8 (umin)
(if you comment out the assume and/or no-wrap, you should see failures)
The different output for the umin test is due to a fold added with
c4fc2cb5b2 :
// umin(x, 1) == zext(x != 0)
We probably want to adjust that, so it applies more generally
(umax --> sext or patterns where we can fold to select-of-constants).
Some folds that were ok when starting with cmp+select may increase
instruction count for the equivalent intrinsic, so we have to decide
if it's worth altering a min/max.
Differential Revision: https://reviews.llvm.org/D110038
InstCombine's worklist can be re-used by other passes like
VectorCombine. Move it to llvm/Transform/Utils and rename it to
InstructionWorklist.
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D110181
This renames the primary methods for creating a zero value to `getZero`
instead of `getNullValue` and renames predicates like `isAllOnesValue`
to simply `isAllOnes`. This achieves two things:
1) This starts standardizing predicates across the LLVM codebase,
following (in this case) ConstantInt. The word "Value" doesn't
convey anything of merit, and is missing in some of the other things.
2) Calling an integer "null" doesn't make any sense. The original sin
here is mine and I've regretted it for years. This moves us to calling
it "zero" instead, which is correct!
APInt is widely used and I don't think anyone is keen to take massive source
breakage on anything so core, at least not all in one go. As such, this
doesn't actually delete any entrypoints, it "soft deprecates" them with a
comment.
Included in this patch are changes to a bunch of the codebase, but there are
more. We should normalize SelectionDAG and other APIs as well, which would
make the API change more mechanical.
Differential Revision: https://reviews.llvm.org/D109483
We're trying to get the parameter index of sret and see if it's part of
a function's varargs.
Reviewed By: rnk
Differential Revision: https://reviews.llvm.org/D109335
Please refer to
https://lists.llvm.org/pipermail/llvm-dev/2021-September/152440.html
(and that whole thread.)
TLDR: the original patch had no prior RFC, yet it had some changes that
really need a proper RFC discussion. It won't be productive to discuss
such an RFC, once it's actually posted, while said patch is already
committed, because that introduces bias towards already-committed stuff,
and the tree is potentially in broken state meanwhile.
While the end result of discussion may lead back to the current design,
it may also not lead to the current design.
Therefore i take it upon myself
to revert the tree back to last known good state.
This reverts commit 4c4093e6e3.
This reverts commit 0a2b1ba33a.
This reverts commit d9873711cb.
This reverts commit 791006fb8c.
This reverts commit c22b64ef66.
This reverts commit 72ebcd3198.
This reverts commit 5fa6039a5f.
This reverts commit 9efda541bf.
This reverts commit 94d3ff09cf.
isFreeToInvert allows min/max with 'not' on both operands,
so easing the argument restriction catches the case where
that operand has one use.
We already handle the sub-patterns when there are less uses:
https://alive2.llvm.org/ce/z/8Jatm_
...but this is another step towards parity with the
equivalent icmp+select idioms ( D98152 ).
Differential Revision: https://reviews.llvm.org/D109059
This mimics the code for the corresponding cmp-select idiom.
This also prevents an infinite loop because isFreeToInvert
does not match constant expressions.
So this patch solves the same problem as D108814 and obsoletes
it, but my main motivation is to enhance the pattern matching
to allow more invertible ops. That change will be a follow-up
patch on top of this one.
Differential Revision: https://reviews.llvm.org/D109058
If both operands are negated, we can invert the min/max and do
the negation after:
smax (neg nsw X), (neg nsw Y) --> neg nsw (smin X, Y)
smin (neg nsw X), (neg nsw Y) --> neg nsw (smax X, Y)
This is visible as a remaining regression in D98152. I don't see
a way to generalize this for 'unsigned' or adapt Negator to
handle it. This only appears to be safe with 'nsw':
https://alive2.llvm.org/ce/z/GUy1zJ
Differential Revision: https://reviews.llvm.org/D108165
This adds a call to matchSAddSubSat from smin/smax instrinsics, allowing
the same patterns to match if the canonical form of a min/max is an
intrinsics, not a icmp/select.
Differential Revision: https://reviews.llvm.org/D108077
This is a re-try of 6de1dbbd09 which was reverted because
it missed a null check. Extra test for that failure added.
Original commit message:
This is an adaptation of D41603 and another step on the way
to canonicalizing to the intrinsic forms of min/max.
See D98152 for status.
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
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
Some of the SPEC tests end up with reduction+(sext/zext(<n x i1>) to <n x im>) pattern, which can be transformed to [-]zext/trunc(ctpop(bitcast <n x i1> to in)) to im.
Also, reduction+(<n x i1>) can be transformed to ctpop(bitcast <n x i1> to in) & 1 != 0.
Differential Revision: https://reviews.llvm.org/D105587
We already implemented this for the select form, but the intrinsic form was missing. Note that this doesn't change poison behavior as 1 is non-poison, and the optimized form is still poison exactly when x is.
After SLP + LTO we may have have reduction(shuffle V, poison,
mask). This can be simplified to just reduction(V) if the mask is only
for single vector and just all elements from this vector are permuted,
without reusing, replacing with undefs and/or other values, etc.
Differential Revision: https://reviews.llvm.org/D105053
This is an extension of the handling for unary intrinsics and
follows the logic that we use for binary ops.
We don't canonicalize to min/max intrinsics yet, but this might
help unlock other folds seen in D98152.
The whole transform can be dropped once we have fully transitioned
to opaque pointers (as it's purpose is to remove no-op pointer
casts). For now, make sure that it handles opaque pointers correctly.
This is part of improving floating-point patterns seen in:
https://llvm.org/PR39480
We don't require any FMF because the 2 potential corner cases
(-0.0 and NaN) are correctly handled without FMF:
1. -0.0 is treated as strictly less than +0.0 with
maximum/minimum, so fabs/fneg work as expected.
2. +/- 0.0 with maxnum/minnum is indeterminate, so
transforming to fabs/fneg is more defined.
3. The sign of a NaN may be altered by this transform,
but that is allowed in the default FP environment.
If there are FMF, they are propagated from the min/max call to
one or both new operands which seems to agree with Alive2:
https://alive2.llvm.org/ce/z/bem_xC
With regards to overrunning, the langref (llvm/docs/LangRef.rst)
specifies:
(llvm.experimental.vector.insert)
Elements ``idx`` through (``idx`` + num_elements(``subvec``) - 1)
must be valid ``vec`` indices. If this condition cannot be determined
statically but is false at runtime, then the result vector is
undefined.
(llvm.experimental.vector.extract)
Elements ``idx`` through (``idx`` + num_elements(result_type) - 1)
must be valid vector indices. If this condition cannot be determined
statically but is false at runtime, then the result vector is
undefined.
For the non-mixed cases (e.g. inserting/extracting a scalable into/from
another scalable, or inserting/extracting a fixed into/from another
fixed), it is possible to statically check whether or not the above
conditions are met. This was previously missing from the verifier, and
if the conditions were found to be false, the result of the
insertion/extraction would be replaced with an undef.
With regards to invalid indices, the langref (llvm/docs/LangRef.rst)
specifies:
(llvm.experimental.vector.insert)
``idx`` represents the starting element number at which ``subvec``
will be inserted. ``idx`` must be a constant multiple of
``subvec``'s known minimum vector length.
(llvm.experimental.vector.extract)
The ``idx`` specifies the starting element number within ``vec``
from which a subvector is extracted. ``idx`` must be a constant
multiple of the known-minimum vector length of the result type.
Similarly, these conditions were not previously enforced in the
verifier. In some circumstances, invalid indices were permitted
silently, and in other circumstances, an undef was spawned where a
verifier error would have been preferred.
This commit adds verifier checks to enforce the constraints above.
Differential Revision: https://reviews.llvm.org/D104468
This is no outwardly-visible-difference-intended,
but it is obviously better to have all transforms
for an intrinsic housed together since we already
have helper functions in place.
It is also potentially more efficient to zap a
simple pattern match before trying to do expensive
computeKnownBits() calls.
Itay Bookstein