The shift argument is defined to be modulo the bitwidth, so if that argument
is a constant, we can always reduce the constant to its minimal form to allow
better CSE and other follow-on transforms.
We need to be careful to ignore constant expressions here, or we will likely
infinite loop. I'm adding a general vector constant query for that case.
Differential Revision: https://reviews.llvm.org/D59374
llvm-svn: 356192
InstructionSimplify currently has some code to determine the constant
range of integer instructions for some simple cases. It is used to
simplify icmps.
This change moves the relevant code into ValueTracking as
llvm::computeConstantRange(), so it can also be reused for other
purposes.
In particular this is with the optimization of overflow checks in
mind (ref D59071), where constant ranges cover some cases that
known bits don't.
llvm-svn: 355781
As discussed on llvm-dev:
http://lists.llvm.org/pipermail/llvm-dev/2019-February/130491.html
We can't remove the compare+select in the general case because
we are treating funnel shift like a standard instruction (as
opposed to a special instruction like select/phi).
That means that if one of the operands of the funnel shift is
poison, the result is poison regardless of whether we know that
the operand is actually unused based on the instruction's
particular semantics.
The motivating case for this transform is the more specific
rotate op (rather than funnel shift), and we are preserving the
fold for that case because there is no chance of introducing
extra poison when there is no anonymous extra operand to the
funnel shift.
llvm-svn: 354905
The m_APFloat matcher does not work with anything but strict
splat vector constants, so we could miss these folds and then
trigger an assertion in instcombine:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=13201
The previous attempt at this in rL354406 had a logic bug that
actually triggered a regression test failure, but I failed to
notice it the first time.
llvm-svn: 354467
The m_APFloat matcher does not work with anything but strict
splat vector constants, so we could miss these folds and then
trigger an assertion in instcombine:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=13201
llvm-svn: 354406
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
If a saturating add/sub has one constant operand, then we can
determine the possible range of outputs it can produce, and simplify
an icmp comparison based on that.
The implementation is based on a similar existing mechanism for
simplifying binary operator + icmps.
Differential Revision: https://reviews.llvm.org/D55735
llvm-svn: 349369
We were duplicating code around the existing isImpliedCondition() that
checks for a predecessor block/dominating condition, so make that a
wrapper call.
llvm-svn: 348088
This is an almost direct move of the functionality from InstCombine to
InstSimplify. There's no reason not to do this in InstSimplify because
we never create a new value with this transform.
(There's a question of whether any dominance-based transform belongs in
either of these passes, but that's a separate issue.)
I've changed 1 of the conditions for the fold (1 of the blocks for the
branch must be the block we started with) into an assert because I'm not
sure how that could ever be false.
We need 1 extra check to make sure that the instruction itself is in a
basic block because passes other than InstCombine may be using InstSimplify
as an analysis on values that are not wired up yet.
The 3-way compare changes show that InstCombine has some kind of
phase-ordering hole. Otherwise, we would have already gotten the intended
final result that we now show here.
llvm-svn: 347896
This is a problem seen in common rotate idioms as noted in:
https://bugs.llvm.org/show_bug.cgi?id=34924
Note that we are not canonicalizing standard IR (shifts and logic) to the intrinsics yet.
(Although I've written this before...) I think this is the last step before we enable
that transform. Ie, we could regress code by doing that transform without this
simplification in place.
In PR34924, I questioned whether this is a valid transform for target-independent IR,
but I convinced myself this is ok. If we're speculating a funnel shift by turning cmp+br
into select, then SimplifyCFG has already determined that the transform is justified.
It's possible that SimplifyCFG is not taking into account profile or other metadata,
but if that's true, then it's a bug independent of funnel shifts.
Also, we do have CGP code to restore a guard like this around an intrinsic if it can't
be lowered cheaply. But that isn't necessary for funnel shift because the default
expansion in SelectionDAGBuilder includes this same cmp+select.
Differential Revision: https://reviews.llvm.org/D54552
llvm-svn: 346960
This is NFCI for InstCombine because it calls InstSimplify,
so I left the tests for this transform there. As noted in
the code comment, we can allow this fold more often by using
FMF and/or value tracking.
llvm-svn: 346169
This is a bit awkward in a handful of places where we didn't even have
an instruction and now we have to see if we can build one. But on the
whole, this seems like a win and at worst a reasonable cost for removing
`TerminatorInst`.
All of this is part of the removal of `TerminatorInst` from the
`Instruction` type hierarchy.
llvm-svn: 340701
Remove duplicate tests from InstCombine that were added with
D50582. I left negative tests there to verify that nothing
in InstCombine tries to go overboard. If isKnownNeverNaN is
improved to handle the FP binops or other cases, we should
have coverage under InstSimplify, so we could remove more
duplicate tests from InstCombine at that time.
llvm-svn: 340279
NewGVN uses InstructionSimplify for simplifications of leaders of
congruence classes. It is not guaranteed that the metadata or other
flags/keywords (like nsw or exact) of the leader is available for all members
in a congruence class, so we cannot use it for simplification.
This patch adds a InstrInfoQuery struct with a boolean field
UseInstrInfo (which defaults to true to keep the current behavior as
default) and a set of helper methods to get metadata/keywords for a
given instruction, if UseInstrInfo is true. The whole thing might need a
better name, to avoid confusion with TargetInstrInfo but I am not sure
what a better name would be.
The current patch threads through InstrInfoQuery to the required
places, which is messier then it would need to be, if
InstructionSimplify and ValueTracking would share the same Query struct.
The reason I added it as a separate struct is that it can be shared
between InstructionSimplify and ValueTracking's query objects. Also,
some places do not need a full query object, just the InstrInfoQuery.
It also updates some interfaces that do not take a Query object, but a
set of optional parameters to take an additional boolean UseInstrInfo.
See https://bugs.llvm.org/show_bug.cgi?id=37540.
Reviewers: dberlin, davide, efriedma, sebpop, hiraditya
Reviewed By: hiraditya
Differential Revision: https://reviews.llvm.org/D47143
llvm-svn: 340031
This is the second patch of the series which intends to enable jump threading for an inlined method whose return type is std::pair<int, bool> or std::pair<bool, int>.
The first patch is https://reviews.llvm.org/rL338485.
This patch handles code sequences that merges two values using `shl` and `or`, then extracts one value using `and`.
Differential Revision: https://reviews.llvm.org/D49981
llvm-svn: 338817
This patch intends to enable jump threading when a method whose return type is std::pair<int, bool> or std::pair<bool, int> is inlined.
For example, jump threading does not happen for the if statement in func.
std::pair<int, bool> callee(int v) {
int a = dummy(v);
if (a) return std::make_pair(dummy(v), true);
else return std::make_pair(v, v < 0);
}
int func(int v) {
std::pair<int, bool> rc = callee(v);
if (rc.second) {
// do something
}
SROA executed before the method inlining replaces std::pair by i64 without splitting in both callee and func since at this point no access to the individual fields is seen to SROA.
After inlining, jump threading fails to identify that the incoming value is a constant due to additional instructions (like or, and, trunc).
This series of patch add patterns in InstructionSimplify to fold extraction of members of std::pair. To help jump threading, actually we need to optimize the code sequence spanning multiple BBs.
These patches does not handle phi by itself, but these additional patterns help NewGVN pass, which calls instsimplify to check opportunities for simplifying instructions over phi, apply phi-of-ops optimization to result in successful jump threading.
SimplifyDemandedBits in InstCombine, can do more general optimization but this patch aims to provide opportunities for other optimizers by supporting a simple but common case in InstSimplify.
This first patch in the series handles code sequences that merges two values using shl and or and then extracts one value using lshr.
Differential Revision: https://reviews.llvm.org/D48828
llvm-svn: 338485
This fold is repeated/misplaced in instcombine, but I'm
not sure if it's safe to remove that yet because some
other folds appear to be asserting that the transform
has occurred within instcombine itself.
This isn't the best fix for PR37776, but it probably
hides the bug with the given code example:
https://bugs.llvm.org/show_bug.cgi?id=37776
We have another test to demonstrate the more general bug.
llvm-svn: 337127
Summary:
Support for this option is needed for building Linux kernel.
This is a very frequently requested feature by kernel developers.
More details : https://lkml.org/lkml/2018/4/4/601
GCC option description for -fdelete-null-pointer-checks:
This Assume that programs cannot safely dereference null pointers,
and that no code or data element resides at address zero.
-fno-delete-null-pointer-checks is the inverse of this implying that
null pointer dereferencing is not undefined.
This feature is implemented in LLVM IR in this CL as the function attribute
"null-pointer-is-valid"="true" in IR (Under review at D47894).
The CL updates several passes that assumed null pointer dereferencing is
undefined to not optimize when the "null-pointer-is-valid"="true"
attribute is present.
Reviewers: t.p.northover, efriedma, jyknight, chandlerc, rnk, srhines, void, george.burgess.iv
Reviewed By: efriedma, george.burgess.iv
Subscribers: eraman, haicheng, george.burgess.iv, drinkcat, theraven, reames, sanjoy, xbolva00, llvm-commits
Differential Revision: https://reviews.llvm.org/D47895
llvm-svn: 336613
Sanjay Patel