This patch adds NoUndef to Intrinsics.td.
The attribute is attached to llvm.assume's operand, because llvm.assume(undef)
is UB.
It is attached to pointer operands of several memory accessing intrinsics
as well.
This change makes ValueTracking::getGuaranteedNonPoisonOps' intrinsic check
unnecessary, so it is removed.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D86576
This patch helps getGuaranteedNonPoisonOp find multiple non-poison operands.
Instead of special-casing llvm.assume, I think it is also a viable option to
add noundef to Intrinsics.td. If it makes sense, I'll make a patch for that.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D86477
There's a potential motivating case to increase this limit in PR47191:
http://bugs.llvm.org/PR47191
But first we should make it less hacky. The limit in InstCombine is directly tied
to this value because an increase there can cause asserts in the underlying value
tracking calls if not changed together. The usage in VectorUtils is independent,
but the comment suggests that we should use the same value unless there's a known
reason to diverge. There are similar limits in codegen analysis, but I think we
should leave those independent in case we intentionally want the optimization
power/cost to be different there.
Differential Revision: https://reviews.llvm.org/D86113
In GlobalISel, if you have a load into a small type with a range, you'll hit
an assert if you try to compute known bits on it starting at a larger type.
e.g.
```
%x:_(s8) = G_LOAD %whatever(p0) :: (load 1 ... !range !n)
...
%y:_(s32) = G_SOMETHING %x
```
When we walk through G_SOMETHING and hit the load, the width of our known bits
is 32. However, the width of the range is going to be 8. This will cause us
to hit an assert.
To fix this, make computeKnownBitsFromRangeMetadata zero extend or truncate
the range type to match the bitwidth of the known bits we're calculating.
Add a testcase in CodeGen/GlobalISel/KnownBitsTest.cpp to reflect that this
works now.
https://reviews.llvm.org/D85375
Add the optimizations we have in the SelectionDAG version.
Known non-negative copies all known bits. Any known one other than
the sign bit makes result non-negative.
Differential Revision: https://reviews.llvm.org/D85000
If absolute value needs turn a negative number into a positive number it reduces the number of sign bits by at most 1.
Differential Revision: https://reviews.llvm.org/D84971
findAllocaForValue uses AllocaForValue to cache resolved values.
The function is used only to resolve arguments of lifetime
intrinsic which usually are not fare for allocas. So result reuse
is likely unnoticeable.
In followup patches I'd like to replace the function with
GetUnderlyingObjects.
Depends on D84616.
Differential Revision: https://reviews.llvm.org/D84617
This includes basic support for computeKnownBits on abs. I've left FIXMEs for more complicated things we could do.
Differential Revision: https://reviews.llvm.org/D84963
This is a simple patch that makes canCreateUndefOrPoison use
Instruction::isBinaryOp because BinaryOperator inherits Instruction.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D84596
This is the first of two patches to address PR46753. We basically allow
mem2reg to promote allocas that are used in doppable instructions, for
now that means `llvm.assume`. The uses of the alloca (or a bitcast or
zero offset GEP from there) are replaced by `undef` in the droppable
instructions.
Reviewed By: Tyker
Differential Revision: https://reviews.llvm.org/D83976
Make sure we do not call
constainsConstantExpression/containsUndefElement on ConstantExpression,
which is not supported.
In particular, containsUndefElement/constainsConstantExpression are only
supported on constants which are supported by getAggregateElement.
Unfortunately there's no convenient way to check if a constant supports
getAggregateElement, so just check for non-constantexpressions with
vector type. Other users of those functions do so too.
Reviewers: spatel, nikic, craig.topper, lebedev.ri, jdoerfert, aqjune
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D84512
.. in isGuaranteedNotToBeUndefOrPoison.
This caused early exit of isGuaranteedNotToBeUndefOrPoison, making it return
imprecise result.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D84251
This patch
- adds `canCreateUndefOrPoison`
- refactors `canCreatePoison` so it can deal with constantexprs
`canCreateUndefOrPoison` will be used at D83926.
Reviewed By: nikic, jdoerfert
Differential Revision: https://reviews.llvm.org/D84007
When the byref attribute is added, there will need to be two similar
functions for the existing cases which have an associate value copy,
and byref which does not. Most, but not all of the existing uses will
use the existing version.
The associated size function added by D82679 also needs to
contextually differ, and will help eliminate a few places still
relying on pointee element types.
The IR doesn't have a proper concept of invalid pointers, and "null"
constants are just all zeros (though it really needs one).
I think it's not possible to break this for AMDGPU due to the copy
semantics of byval. If you have an original stack object at 0, the
byval copy will be placed above it so I don't think it's really
possible to hit a 0 address.
GetUnderlyingObject() (and by required symmetry
DecomposeGEPExpression()) will call SimplifyInstruction() on the
passed value if other checks fail. This simplification is very
expensive, but has little effect in practice. This patch removes
the SimplifyInstruction call(), and replaces it with a check for
single-argument phis (which can occur in canonical IR in LCSSA
form), which is the only useful simplification case I was able to
identify.
At O3 the geomean CTMark improvement is -1.7%. The largest
improvement is SPASS with ThinLTO at -6%.
In test-suite, I see only two tests with a hash difference and
no code size difference (PAQ8p, Ptrdist), which indicates that
the simplification only ends up being useful very rarely. (I would
have liked to figure out which simplification is responsible here,
but wasn't able to spot it looking at transformation logs.)
The AMDGPU test case that is update was using two selects with
undef condition, in which case GetUnderlyingObject will return
the first select operand as the underlying object. This will of
course not happen with non-undef conditions, so this was not
testing anything realistic. Additionally this illustrates potential
unsoundness: While GetUnderlyingObject will pick the first operand,
the select might be later replaced by the second operand, resulting
in inconsistent assumptions about the undef value.
Differential Revision: https://reviews.llvm.org/D82261
This intrinsic implements IEEE-754 operation roundToIntegralTiesToEven,
and performs rounding to the nearest integer value, rounding halfway
cases to even. The intrinsic represents the missed case of IEEE-754
rounding operations and now llvm provides full support of the rounding
operations defined by the standard.
Differential Revision: https://reviews.llvm.org/D75670
This patch updates computeConstantRange to optionally take an assumption
cache as argument and use the available assumptions to limit the range
of the result.
Currently this is limited to assumptions that are comparisons.
Reviewers: reames, nikic, spatel, jdoerfert, lebedev.ri
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D76193
If we don't know anything about the alignment of a pointer, Align(1) is
still correct: all pointers are at least 1-byte aligned.
Included in this patch is a bugfix for an issue discovered during this
cleanup: pointers with "dereferenceable" attributes/metadata were
assumed to be aligned according to the type of the pointer. This
wasn't intentional, as far as I can tell, so Loads.cpp was fixed to
stop making this assumption. Frontends may need to be updated. I
updated clang's handling of C++ references, and added a release note for
this.
Differential Revision: https://reviews.llvm.org/D80072
computeKnownBitsFromAssume() currently asserts if m_V matches a
ptrtoint that changes the bitwidth. Because InstCombine
canonicalizes ptrtoint instructions to use explicit zext/trunc,
we never ran into the issue in practice. I'm adding unit tests,
as I don't know if this can be triggered via IR anywhere.
Fix this by calling anyextOrTrunc(BitWidth) on the computed
KnownBits. Note that we are going from the KnownBits of the
ptrtoint result to the KnownBits of the ptrtoint operand,
so we need to truncate if the ptrtoint zexted and anyext if
the ptrtoint truncated.
Differential Revision: https://reviews.llvm.org/D79234
Summary:
This fixes PR45885 by fixing isGuaranteedNotToBeUndefOrPoison so it does not look into dominating
branch conditions of V when V is an instruction in an unreachable block.
Reviewers: spatel, nikic, lebedev.ri
Reviewed By: nikic
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D79790
Summary:
This patch makes propagatesPoison be more accurate by returning true on
more bin ops/unary ops/casts/etc.
The changed test in ScalarEvolution/nsw.ll was introduced by
a19edc4d15 .
IIUC, the goal of the tests is to show that iv.inc's SCEV expression still has
no-overflow flags even if the loop isn't in the wanted form.
It becomes more accurate with this patch, so think this is okay.
Reviewers: spatel, lebedev.ri, jdoerfert, reames, nikic, sanjoy
Reviewed By: spatel, nikic
Subscribers: regehr, nlopes, efriedma, fhahn, javed.absar, llvm-commits, hiraditya
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78615
Summary:
Any function in this module that make use of DemandedElts laregely does
not work with scalable vectors. DemandedElts is used to define which
elements of the vector to look at. At best, for scalable vectors, we can
express the first N elements of the vector. However, in practice, most
code that uses these functions expect to be able to talk about the
entire vector. In principle, this module should be able to be extended
to work with scalable vectors. However, before we can do that, we should
ensure that it does not cause code with scalable vectors to miscompile.
All functions that use a DemandedElts will bail out if the vector is
scalable. Usages of getNumElements() are updated to go through
FixedVectorType pointers.
Reviewers: rengolin, efriedma, sdesmalen, c-rhodes, spatel
Reviewed By: efriedma
Subscribers: david-arm, tschuett, kristof.beyls, hiraditya, rkruppe, psnobl, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D79053
The 'nsz' flag is different than 'nnan' or 'ninf' in that it does not create poison.
Make that explicit in the LangRef and fix ValueTracking analysis that misinterpreted
the definition.
This manifests as bugs in InstSimplify shown in the test diffs and as discussed in
PR45778:
https://bugs.llvm.org/show_bug.cgi?id=45778
Differential Revision: https://reviews.llvm.org/D79422
Summary:
This patch helps isGuaranteedNotToBeUndefOrPoison look into more constants and instructions (bitcast/alloca/gep/fcmp).
To deal with bitcast, Depth is added to isGuaranteedNotToBeUndefOrPoison.
This patch is splitted from https://reviews.llvm.org/D75808.
Checked with Alive2
Reviewers: reames, jdoerfert
Reviewed By: jdoerfert
Subscribers: sanwou01, spatel, llvm-commits, hiraditya
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D76010
Summary:
This is RFC for fixes in poison-related functions of ValueTracking.
These functions assume that a value can be poison bitwisely, but the semantics
of bitwise poison is not clear at the moment.
Allowing a value to have bitwise poison adds complexity to reasoning about
correctness of optimizations.
This patch makes the analysis functions simply assume that a value is
either fully poison or not, which has been used to understand the correctness
of a few previous optimizations.
The bitwise poison semantics seems to be only used by these functions as well.
In terms of implementation, using value-wise poison concept makes existing
functions do more precise analysis, which is what this patch contains.
Reviewers: spatel, lebedev.ri, jdoerfert, reames, nikic, nlopes, regehr
Reviewed By: nikic
Subscribers: fhahn, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78503
Summary:
This is RFC for fixes in poison-related functions of ValueTracking.
These functions assume that a value can be poison bitwisely, but the semantics
of bitwise poison is not clear at the moment.
Allowing a value to have bitwise poison adds complexity to reasoning about
correctness of optimizations.
This patch makes the analysis functions simply assume that a value is
either fully poison or not, which has been used to understand the correctness
of a few previous optimizations.
The bitwise poison semantics seems to be only used by these functions as well.
In terms of implementation, using value-wise poison concept makes existing
functions do more precise analysis, which is what this patch contains.
Reviewers: spatel, lebedev.ri, jdoerfert, reames, nikic, nlopes, regehr
Reviewed By: nikic
Subscribers: fhahn, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78503
