We might want to use it when creating SCEV proper in createSCEV(),
now that we don't `forgetValue()` in `SimplifyIndvar::strengthenOverflowingOperation()`,
which might have caused us to loose some optimization potential.
When SimplifyIndVars infers IR nowrap flags from SCEV, this may
happen in two ways: Either nowrap flags were already present in
SCEV and just get transferred to IR. Or zero/sign extension of
addrecs infers additional nowrap flags, and those get transferred
to IR. In the latter case, calling forgetValue() ensures that the
newly inferred nowrap flags get propagated to any other SCEV
expressions based on the addrec. However, the invalidation can
also have a major compile-time effect in some cases. For
https://bugs.llvm.org/show_bug.cgi?id=50384 with n=512 compile-
time drops from 7.1s to 0.8s without this invalidation. At the
same time, removing the invalidation doesn't affect any codegen
in test-suite.
Differential Revision: https://reviews.llvm.org/D103424
When eliminating comparisons, we can use common dominator of
all its users as context. This gives better results when ICMP is not
computed right before the branch that uses it.
Differential Revision: https://reviews.llvm.org/D98924
Reviewed By: lebedev.ri
We can prove more predicates when we have a context when eliminating ICmp.
As first (and very obvious) approximation we can use the ICmp instruction itself,
though in the future we are going to use a common dominator of all its users.
Need some refactoring before that.
Observed ~0.5% negative compile time impact.
Differential Revision: https://reviews.llvm.org/D98697
Reviewed By: lebedev.ri
This reverts commit 4bd35cdc3ae1874c6d070c5d410b3f591de54ee6.
The patch was reverted during the investigation. The investigation
shown that the patch did not cause any trouble, but just exposed
the existing problem that is addressed by the previous patch
"[IndVars] Quick fix LHS/RHS bug". Returning without changes.
The code relies on fact that LHS is the NarrowDef but never
really checks it. Adding the conservative restrictive check,
will follow-up with handling of case where RHS is a NarrowDef.
This reverts commit 0c9c6ddf17bb01ae350a899b3395bb078aa0c62e.
We are seeing some failures with this patch locally. Not clear
if it's causing them or just triggering a problem in another
place. Reverting while investigating.
If we decided to widen IV with zext, then unsigned comparisons
should not prevent widening (same for sext/sign comparisons).
The result of comparison in wider type does not change in this case.
Differential Revision: https://reviews.llvm.org/D92207
Reviewed By: nikic
When widening an IndVar that has LCSSA Phi users outside
the loop, we can safely widen it as usual and then truncate
the result outside the loop without hurting the performance.
Differential Revision: https://reviews.llvm.org/D91593
Reviewed By: skatkov
When deciding to widen narrow use, we may need to prove some facts
about it. For proof, the context is used. Currently we take the instruction
being widened as the context.
However, we may be more precise here if we take as context the point that
dominates all users of instruction being widened.
Differential Revision: https://reviews.llvm.org/D90456
Reviewed By: skatkov
Sometimes the an instruction we are trying to widen is used by the IV
(which means the instruction is the IV increment). Currently this may
prevent its widening. We should ignore such user because it will be
dead once the transform is done anyways.
Differential Revision: https://reviews.llvm.org/D90920
Reviewed By: fhahn
InstCombine canonicalizes 'sub nuw' instructions to 'add' without the
`nuw` flag. The typical case where we see it is decrementing induction
variables. For them, IndVars fails to prove that it's legal to widen them,
and inserts unprofitable `zext`'s.
This patch adds recognition of such pattern using SCEV.
Differential Revision: https://reviews.llvm.org/D89550
Reviewed By: fhahn, skatkov
This moves WidenIV from IndVarSimplify to Utils/SimplifyIndVar so that we have
createWideIV available as a generic helper utility. I.e., this is not only
useful in IndVarSimplify, but could be useful for loop transformations. For
example, motivation for this refactoring is the loop flatten transformation: if
induction variables in a loop nest can be widened, we can avoid having to
perform certain overflow checks, enabling this transformation.
Differential Revision: https://reviews.llvm.org/D90421
While we haven't encountered an earth-shattering problem with this yet,
by now it is pretty evident that trying to model the ptr->int cast
implicitly leads to having to update every single place that assumed
no such cast could be needed. That is of course the wrong approach.
Let's back this out, and re-attempt with some another approach,
possibly one originally suggested by Eli Friedman in
https://bugs.llvm.org/show_bug.cgi?id=46786#c20
which should hopefully spare us this pain and more.
This reverts commits 1fb610429308a7c29c5065f5cc35dcc3fd69c8b1,
7324616660fc0995fa8c166e3c392361222d5dbc,
aaafe350bb65dfc24c2cdad4839059ac81899fbe,
e92a8e0c743f83552fac37ecf21e625ba3a4b11e.
I've kept&improved the tests though.
This relands commit 1c021c64caef83cccb719c9bf0a2554faa6563af which was
reverted in commit 17cec6a11a12f815052d56a17ef738cf246a2d9a because
an assertion was being triggered, since `BuildConstantFromSCEV()`
wasn't updated to handle the case where the constant we want to truncate
is actually a pointer. I was unsuccessful in coming up with a test case
where we'd end there with constant zext/sext of a pointer,
so i didn't handle those cases there until there is a test case.
Original commit message:
While we indeed can't treat them as no-ops, i believe we can/should
do better than just modelling them as `unknown`. `inttoptr` story
is complicated, but for `ptrtoint`, it seems straight-forward
to model it just as a zext-or-trunc of unknown.
This may be important now that we track towards
making inttoptr/ptrtoint casts not no-op,
and towards preventing folding them into loads/etc
(see D88979/D88789/D88788)
Reviewed By: mkazantsev
Differential Revision: https://reviews.llvm.org/D88806
> While we indeed can't treat them as no-ops, i believe we can/should
> do better than just modelling them as `unknown`. `inttoptr` story
> is complicated, but for `ptrtoint`, it seems straight-forward
> to model it just as a zext-or-trunc of unknown.
>
> This may be important now that we track towards
> making inttoptr/ptrtoint casts not no-op,
> and towards preventing folding them into loads/etc
> (see D88979/D88789/D88788)
>
> Reviewed By: mkazantsev
>
> Differential Revision: https://reviews.llvm.org/D88806
It caused the following assert during Chromium builds:
llvm/lib/IR/Constants.cpp:1868:
static llvm::Constant *llvm::ConstantExpr::getTrunc(llvm::Constant *, llvm::Type *, bool):
Assertion `C->getType()->isIntOrIntVectorTy() && "Trunc operand must be integer"' failed.
See code review for a link to a reproducer.
This reverts commit 1c021c64caef83cccb719c9bf0a2554faa6563af.
While we indeed can't treat them as no-ops, i believe we can/should
do better than just modelling them as `unknown`. `inttoptr` story
is complicated, but for `ptrtoint`, it seems straight-forward
to model it just as a zext-or-trunc of unknown.
This may be important now that we track towards
making inttoptr/ptrtoint casts not no-op,
and towards preventing folding them into loads/etc
(see D88979/D88789/D88788)
Reviewed By: mkazantsev
Differential Revision: https://reviews.llvm.org/D88806
When removing an overflow intrinsic the Changed status in SimplifyIndvar
was not set, leading to the IndVarSimplify pass returning an incorrect
status.
This was caught using the check introduced by D80916.
As pointed out in the code review, a similar bug may exist for
eliminateTrunc().
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D85971
Summary:
As [[ https://bugs.llvm.org/show_bug.cgi?id=45360 | PR45360 ]] reports,
with new cost-model we can sometimes end up being able to expand `udiv`/`urem` instructions.
And that exposes at least one instance of when we do that
regardless of whether or not it is safe to do.
In this particular case, it's `SimplifyIndvar::replaceIVUserWithLoopInvariant()`.
It seems to me, we simply need to check with `isSafeToExpandAt()` first.
The test isn't great. I'm not sure how to make it only run `-indvars`.
Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=45360 | PR45360 ]].
Reviewers: mkazantsev, reames, helloqirun
Reviewed By: mkazantsev
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D82108
SCEVExpander modifies the underlying function so it is more suitable in
Transforms/Utils, rather than Analysis. This allows using other
transform utils in SCEVExpander.
This patch was originally committed as b8a3c34eee06, but broke the
modules build, as LoopAccessAnalysis was using the Expander.
The code-gen part of LAA was moved to lib/Transforms recently, so this
patch can be landed again.
Reviewers: sanjoy.google, efriedma, reames
Reviewed By: sanjoy.google
Differential Revision: https://reviews.llvm.org/D71537
Summary:
In future patches`SCEVExpander::isHighCostExpansionHelper()` will respect the budget allocated by performing TTI cost modelling.
This is a fully NFC patch to make things reviewable.
Reviewers: reames, mkazantsev, wmi, sanjoy
Reviewed By: mkazantsev
Subscribers: hiraditya, zzheng, javed.absar, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D73705
Summary:
Future patches will make use of TTI to perform cost-model-driven `SCEVExpander::isHighCostExpansionHelper()`
This is a fully NFC patch to make things reviewable.
Reviewers: reames, mkazantsev, wmi, sanjoy
Reviewed By: mkazantsev
Subscribers: hiraditya, zzheng, javed.absar, dmgreen, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D73704
SCEVExpander modifies the underlying function so it is more suitable in
Transforms/Utils, rather than Analysis. This allows using other
transform utils in SCEVExpander.
Reviewers: sanjoy.google, efriedma, reames
Reviewed By: sanjoy.google
Differential Revision: https://reviews.llvm.org/D71537
If we can detect that saturating math that depends on an IV cannot
overflow, replace it with simple math. This is similar to the CVP
optimization from D62703, just based on a different underlying
analysis (SCEV vs LVI) that catches different cases.
Differential Revision: https://reviews.llvm.org/D62792
llvm-svn: 363489
We were only matching RHS being a loop invariant value, not the inverse. Since there's nothing which appears to canonicalize loop invariant values to RHS, this means we missed cases.
Differential Revision: https://reviews.llvm.org/D63112
llvm-svn: 363108
Extract a willNotOverflow() helper function that is shared between
eliminateOverflowIntrinsic() and strengthenOverflowingOperation().
Use WithOverflowInst for the former.
We'll be able to reuse the same code for saturating intrinsics as
well.
llvm-svn: 362305
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
There is a transform that may replace `lshr (x+1), 1` with `lshr x, 1` in case
if it can prove that the result will be the same. However the initial instruction
might have an `exact` flag set, and it now should be dropped unless we prove
that it may hold. Incorrectly set `exact` attribute may then produce poison.
Differential Revision: https://reviews.llvm.org/D53061
Reviewed By: sanjoy
llvm-svn: 344223
This is a follow-up for the patch rL335020. When we replace compares against
trunc with compares against wide IV, we can also replace signed predicates with
unsigned where it is legal.
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D48763
llvm-svn: 338115
If a trunc has a user in a block which is not reachable from entry,
we can safely perform trunc elimination as if this user didn't exist.
llvm-svn: 335816
This patch adds logic to deal with the following constructions:
%iv = phi i64 ...
%trunc = trunc i64 %iv to i32
%cmp = icmp <pred> i32 %trunc, %invariant
Replacing it with
%iv = phi i64 ...
%cmp = icmp <pred> i64 %iv, sext/zext(%invariant)
In case if it is legal. Specifically, if `%iv` has signed comparison users, it is
required that `sext(trunc(%iv)) == %iv`, and if it has unsigned comparison
uses then we require `zext(trunc(%iv)) == %iv`. The current implementation
bails if `%trunc` has other uses than `icmp`, but in theory we can handle more
cases here (e.g. if the user of trunc is bitcast).
Differential Revision: https://reviews.llvm.org/D47928
Reviewed By: reames
llvm-svn: 335020
IndVarSimplify sometimes makes transforms basing on users that are trivially dead. In particular,
if DCE wasn't run before it, there may be a dead `sext/zext` in loop that will trigger widening
transforms, however it makes no sense to do it.
This patch teaches IndVarsSimplify ignore the mist trivial cases of that.
Differential Revision: https://reviews.llvm.org/D47974
Reviewed By: sanjoy
llvm-svn: 334567
The DEBUG() macro is very generic so it might clash with other projects.
The renaming was done as follows:
- git grep -l 'DEBUG' | xargs sed -i 's/\bDEBUG\s\?(/LLVM_DEBUG(/g'
- git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM
- Manual change to APInt
- Manually chage DOCS as regex doesn't match it.
In the transition period the DEBUG() macro is still present and aliased
to the LLVM_DEBUG() one.
Differential Revision: https://reviews.llvm.org/D43624
llvm-svn: 332240
Turns out we can have comparisons which are indirect users of the induction variable that we can make invariant. In this case, there is no loop invariant value contributing and we'd fail an assert.
The test case was found by a java fuzzer and reduced. It's a real cornercase. You have to have a static loop which we've already proven only executes once, but haven't broken the backedge on, and an inner phi whose result can be constant folded by SCEV using exit count reasoning but not proven by isKnownPredicate. To my knowledge, only the fuzzer has hit this case.
llvm-svn: 319583
