The initial implementation just delegates to APInt's implementation of
XOR for single element ranges and conservatively returns the full set
otherwise.
Reviewers: nikic, spatel, lebedev.ri
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D76453
Summary:
To be used in `ConstantRange::mulWithNoOverflow()`,
may in future be useful for when saturating shift/mul ops are added.
These are precise as far as i can tell.
I initially though i will need `APInt::[us]mul_sat()` for these,
but it turned out much simpler to do what `ConstantRange::multiply()`
does - perform multiplication in twice the bitwidth, and then truncate.
Though here we want saturating signed truncation.
Reviewers: nikic, reames, spatel
Reviewed By: nikic
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69994
Summary:
To be used in `ConstantRange::shlWithNoOverflow()`,
may in future be useful for when saturating shift/mul ops are added.
Unlike `ConstantRange::shl()`, these are precise.
Reviewers: nikic, spatel, reames
Reviewed By: nikic
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69960
Summary:
Much like D67339, adds ConstantRange handling for
when we know no-wrap behavior of the `sub`.
Unlike addWithNoWrap(), we only get lucky re returning empty set
for signed wrap. For unsigned, we must perform overflow check manually.
A patch that makes use of this in LVI (CVP) to be posted later.
Reviewers: nikic, shchenz, efriedma
Reviewed By: nikic
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69918
The implementation is conceptually simple: We separate the LHS and
RHS into positive and negative components and then also compute the
positive and negative components of the result, taking into account
that e.g. only pos/pos and neg/neg will give a positive result.
However, there's one significant complication: SignedMin / -1 is UB
for sdiv, and we can't just ignore it, because the APInt result of
SignedMin would break the sign segregation. Instead we drop SignedMin
or -1 from the corresponding ranges, taking into account some edge
cases with wrapped ranges.
Because of the sign segregation, the implementation ends up being
nearly fully precise even for wrapped ranges (the remaining
imprecision is due to ranges that are both signed and unsigned
wrapping and are divided by a trivial divisor like 1). This means
that the testing cannot just check the signed envelope as we
usually do. Instead we collect all possible results in a bitvector
and construct a better sign wrapped range (than the full envelope).
Differential Revision: https://reviews.llvm.org/D61238
llvm-svn: 362430
In order to fold an always overflowing signed saturating add/sub,
we need to know in which direction the always overflow occurs.
This patch splits up AlwaysOverflows into AlwaysOverflowsLow and
AlwaysOverflowsHigh to pass through this information (but it is
not used yet).
Differential Revision: https://reviews.llvm.org/D62463
llvm-svn: 361858
Add support for srem() to ConstantRange so we can use it in LVI. For
srem the sign of the result matches the sign of the LHS. For the RHS
only the absolute value is important. Apart from that the logic is
like urem.
Just like for urem this is only an approximate implementation. The tests
check a few specific cases and run an exhaustive test for conservative
correctness (but not exactness).
Differential Revision: https://reviews.llvm.org/D61207
llvm-svn: 360055
I got confused on the terminology, and the change in D60598 was not
correct. I was thinking of "exact" in terms of the result being
non-approximate. However, the relevant distinction here is whether
the result is
* Largest range such that:
Forall Y in Other: Forall X in Result: X BinOp Y does not wrap.
(makeGuaranteedNoWrapRegion)
* Smallest range such that:
Forall Y in Other: Forall X not in Result: X BinOp Y wraps.
(A hypothetical makeAllowedNoWrapRegion)
* Both. (makeExactNoWrapRegion)
I'm adding a separate makeExactNoWrapRegion method accepting a
single APInt (same as makeExactICmpRegion) and using it in the
places where the guarantee is relevant.
Differential Revision: https://reviews.llvm.org/D60960
llvm-svn: 359402
Add support for abs() to ConstantRange. This will allow to handle
SPF_ABS select flavor in LVI and will also come in handy as a
primitive for the srem implementation.
The implementation is slightly tricky, because a) abs of signed min
is signed min and b) sign-wrapped ranges may have an abs() that is
smaller than a full range, so we need to explicitly handle them.
Differential Revision: https://reviews.llvm.org/D61084
llvm-svn: 359321
Add urem support to ConstantRange, so we can handle in in LVI. This
is an approximate implementation that tries to capture the most useful
conditions: If the LHS is always strictly smaller than the RHS, then
the urem is a no-op and the result is the same as the LHS range.
Otherwise the lower bound is zero and the upper bound is
min(LHSMax, RHSMax - 1).
Differential Revision: https://reviews.llvm.org/D60952
llvm-svn: 359019
This reverts commit 7bf4d7c07f2fac862ef34c82ad0fef6513452445.
After thinking about this more, this isn't right, the range is not exact
in the same sense as makeExactICmpRegion(). This needs a separate
function.
llvm-svn: 358876
Following D60632 makeGuaranteedNoWrapRegion() always returns an
exact nowrap region. Rename the function accordingly. This is in
line with the naming of makeExactICmpRegion().
llvm-svn: 358875
Add support for uadd_sat and friends to ConstantRange, so we can
handle uadd.sat and friends in LVI. The implementation is forwarding
to the corresponding APInt methods with appropriate bounds.
One thing worth pointing out here is that the handling of wrapping
ranges is not maximally accurate. A simple example is that adding 0
to a wrapped range will return a full range, rather than the original
wrapped range. The tests also only check that the non-wrapping
envelope is correct and minimal.
Differential Revision: https://reviews.llvm.org/D60946
llvm-svn: 358855
ConstantRanges have an annoying special case: If upper and lower are
the same, it can be either an empty or a full set. When constructing
constant ranges nearly always a full set is intended, but this still
requires an explicit check in many places.
This revision adds a getNonEmpty() constructor that disambiguates this
case: If upper and lower are the same, a full set is created.
Differential Revision: https://reviews.llvm.org/D60947
llvm-svn: 358854
getSetSize returns an APInt that is 1 bit wider. The APInt is typically 65-bit and requires memory allocation. isSizeStrictlySmallerThan and isSizeLargerThan are preferred. The last use of this helper method was removed by rL302385.
llvm-svn: 358347
As motivated in D60598, this drops support for specifying both NUW and
NSW in makeGuaranteedNoWrapRegion(). None of the users of this function
currently make use of this.
When both NUW and NSW are specified, the exact nowrap region has two
disjoint parts and makeGNWR() returns one of them. This result doesn't
seem to be useful for anything, but makes the semantics of the function
fuzzier.
Differential Revision: https://reviews.llvm.org/D60632
llvm-svn: 358340
makeGuaranteedNoWrapRegion() is actually makeExactNoWrapRegion() as
long as only one of NUW or NSW is specified. This is not obvious from
the current documentation, and some code seems to think that it is
only exact for single-element ranges. Clarify docs and add tests to
be more confident this really holds.
There are currently no users of makeGuaranteedNoWrapRegion() that
pass both NUW and NSW. I think it would be best to drop support for
this entirely and then rename the function to makeExactNoWrapRegion().
Knowing that the no-wrap region is exact is useful, because we can
backwards-constrain values. What I have in mind in particular is
that LVI should be able to constrain values on edges where the
with.overflow overflow flag is false.
Differential Revision: https://reviews.llvm.org/D60598
llvm-svn: 358305
Same as the other ConstantRange overflow checking methods, but for
unsigned mul. In this case there is no cheap overflow criterion, so
using umul_ov for the implementation.
Differential Revision: https://reviews.llvm.org/D60574
llvm-svn: 358228
This extends D59959 to unionWith(), allowing to specify that a
non-wrapping unsigned/signed range is preferred. This is somewhat
less useful than the intersect case, because union operations are
rarer. An example use would the the phi union computed in SCEV.
The implementation is mostly a straightforward use of getPreferredRange(),
but I also had to adjust some <=/< checks to make sure that no ranges with
lower==upper get constructed before they're passed to getPreferredRange(),
as these have additional constraints.
Differential Revision: https://reviews.llvm.org/D60377
llvm-svn: 357876
The intersection of two ConstantRanges may consist of two disjoint
ranges. As we can only return one range as the result, we need to
return one of the two possible ranges that cover both. Currently the
result is picked based on set size. However, this is not always
optimal: If we're in an unsigned context, we'd prefer to get a large
unsigned range over a small signed range -- the latter effectively
becomes a full set in the unsigned domain.
This revision adds a PreferredRangeType, which can be either Smallest,
Unsigned or Signed. Smallest is the current behavior and Unsigned and
Signed are new variants that prefer not to wrap the unsigned/signed
domain. The new type isn't used anywhere yet (but SCEV will be a good
first user, see D60035).
I've also added some comments to illustrate the various cases in
intersectWith(), which should hopefully make it more obvious what is
going on.
Differential Revision: https://reviews.llvm.org/D59959
llvm-svn: 357873
Add isAllNegative() and isAllNonNegative() methods to ConstantRange,
which determine whether all values in the constant range are
negative/non-negative.
This is useful for replacing KnownBits isNegative() and isNonNegative()
calls when changing code to use constant ranges.
Differential Revision: https://reviews.llvm.org/D60264
llvm-svn: 357871
Split off from D59749. This adds isWrappedSet() and
isUpperSignWrapped() set with the same behavior as isSignWrappedSet()
and isUpperWrapped() for the respectively other domain.
The methods isWrappedSet() and isSignWrappedSet() will not consider
ranges of the form [X, Max] == [X, 0) and [X, SignedMax] == [X, SignedMin)
to be wrapping, while isUpperWrapped() and isUpperSignWrapped() will.
Also replace the checks in getUnsignedMin() and friends with method
calls that implement the same logic.
llvm-svn: 357112
Split out from D59749. The current implementation of isWrappedSet()
doesn't do what it says on the tin, and treats ranges like
[X, Max] as wrapping, because they are represented as [X, 0) when
using half-inclusive ranges. This also makes it inconsistent with
the semantics of isSignWrappedSet().
This patch renames isWrappedSet() to isUpperWrapped(), in preparation
for the introduction of a new isWrappedSet() method with corrected
behavior.
llvm-svn: 357107
Split off from D59749. This uses a simpler and more efficient
implementation of isSignWrappedSet(), and considers full sets
as non-wrapped, to be consistent with isWrappedSet(). Otherwise
the behavior is unchanged.
There are currently only two users of this function and both already
check for isFullSet() || isSignWrappedSet(), so this is not going to
cause a change in overall behavior.
Differential Revision: https://reviews.llvm.org/D59848
llvm-svn: 357039
This adds ConstantRange::getFull(BitWidth) and
ConstantRange::getEmpty(BitWidth) named constructors as more readable
alternatives to the current ConstantRange(BitWidth, /* full */ false)
and similar. Additionally private getFull() and getEmpty() member
functions are added which return a full/empty range with the same bit
width -- these are commonly needed inside ConstantRange.cpp.
The IsFullSet argument in the ConstantRange(BitWidth, IsFullSet)
constructor is now mandatory for the few usages that still make use of it.
Differential Revision: https://reviews.llvm.org/D59716
llvm-svn: 356852
Following the suggestion in D59450, I'm moving the code for constructing
a ConstantRange from KnownBits out of ValueTracking, which also allows us
to test this code independently.
I'm adding this method to ConstantRange rather than KnownBits (which
would have been a bit nicer API wise) to avoid creating a dependency
from Support to IR, where ConstantRange lives.
Differential Revision: https://reviews.llvm.org/D59475
llvm-svn: 356339
Add functions to ConstantRange that determine whether the
unsigned/signed addition/subtraction of two ConstantRanges
may/always/never overflows. This will allow checking overflow
conditions based on known constant ranges in addition to known bits.
I'm implementing these methods on ConstantRange to allow them to be
unit tested independently of any ValueTracking machinery. The tests
include exhaustive testing on 4-bit ranges, to make sure the result
is both conservatively correct and maximally precise.
The OverflowResult enum is redeclared on ConstantRange, because
I wanted to avoid a dependency in either direction between
ValueTracking.h and ConstantRange.h.
Differential Revision: https://reviews.llvm.org/D59193
llvm-svn: 356276
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
This is a follow-up to r331272.
We've been running doxygen with the autobrief option for a couple of
years now. This makes the \brief markers into our comments
redundant. Since they are a visual distraction and we don't want to
encourage more \brief markers in new code either, this patch removes
them all.
Patch produced by
for i in $(git grep -l '\@brief'); do perl -pi -e 's/\@brief //g' $i & done
https://reviews.llvm.org/D46290
llvm-svn: 331275
Extend the ConstantRange implementation to compute the range of possible values resulting from an arithmetic right shift operation.
There will be a follow up patch to leverage this constant range infrastructure in LazyValueInfo.
Patch by Surya Kumari Jangala!
Differential Revision: https://reviews.llvm.org/D40881
llvm-svn: 320976
Previously ConstantRange::makeGuaranteedNoWrapRegion only handled addition. This adds support for subtraction.
Differential Revision: https://reviews.llvm.org/D40036
llvm-svn: 319806
Previously SimplifyCFG used getSetSize which returns an APInt that is 1 bit wider than the ConstantRange's bit width. In the reasonably common case that the ConstantRange is 64-bits wide, this requires returning a 65-bit APInt. APInt's can only store 64-bits without a memory allocation so this is inefficient.
The new method takes the 8 as an input and tells if the range contains more than that many elements without requiring any wider math.
llvm-svn: 302385
This typedef used to be conditional based on whether rvalue references were supported. Looks like it got left behind when we switched to always having rvalue references with c++11. I don't think it provides any value now.
llvm-svn: 300146
Summary:
ConstantRange class currently has a method getSetSize, which is mostly used to
compare set sizes of two constant ranges (there is only one spot where it's used
in a slightly different scenario). This patch introduces setSizeSmallerThanOf
method, which does such comparison in a more efficient way. In the original
method we have to extend our types to (BitWidth+1), which can result it using
slow case of APInt, extra memory allocations, etc.
The change is supposed to not change any functionality, but it slightly improves
compile time. Here is compile time improvements that I observed on CTMark:
* tramp3d-v4 -2.02%
* pairlocalalign -1.82%
* lencod -1.67%
Reviewers: sanjoy, atrick, pete
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D31104
llvm-svn: 298236
This just extracts out the transfer rules for constant ranges into a single shared point. As it happens, neither bit of code actually overlaps in terms of the handled operators, but with this change that could easily be tweaked in the future.
I also want to have this separated out to make experimenting with a eager value info implementation and possibly a ValueTracking-like fixed depth recursion peephole version. There's no reason all four of these can't share a common implementation which reduces the chances of bugs.
Differential Revision: https://reviews.llvm.org/D27294
llvm-svn: 288413
This change teaches getEquivalentICmp to be smarter about generating
ICMP_NE and ICMP_EQ predicates.
An earlier version of this change was landed as rL283057 which had a
use-after-free bug. This new version has a fix for that bug, and a (C++
unittests/) test case that would have triggered it rL283057.
llvm-svn: 283078
This reapplies commit r268521, that was reverted in r268530 due to a test failure in select-implied.ll
Modified the test case to reflect the new change.
llvm-svn: 268557
