As discussed in:
https://llvm.org/PR49055
We invert instcombine's add->or transform here
because it makes it easier to identify factorization
transforms like the mul in the motivating test.
This extends the logic added with:
https://reviews.llvm.org/rG70472f3https://reviews.llvm.org/rG93f3d7f
(I intentionally kept the formatting fix in this patch
to provide more context about the calling logic.)
With the addition of the `willreturn` attribute, functions that may
not return (e.g. due to an infinite loop) are well defined, if they are
not marked as `willreturn`.
This patch updates `wouldInstructionBeTriviallyDead` to not consider
calls that may not return as dead.
This patch still provides an escape hatch for intrinsics, which are
still assumed as willreturn unconditionally. It will be removed once
all intrinsics definitions have been reviewed and updated.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D94106
As Wei Mi is reporting in post-commit review
https://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20201116/853479.html
teaching -reassociate about add-like-or's (70472f3) results in breaking apart
load widening patterns, and reassociating them.
For now, simply exclude any such `or` that appears to be a root of
load widening idiom from the or->add transformation.
Note that the heuristic is greedy, it doesn't ensure that loads
can *actually* be widened into a single load.
As Wei Mi is reporting in post-commit review:
https://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20201116/853479.html
teaching -reassociate about add-like-or's (70472f3) results in breaking apart
load widening patterns, and reassociating them.
While that's great, it prevents the actual load widening in backend,
and that is not good. We should have load widening in middle-end,
but for now we should at least not regress the naive patterns..
This is slightly better compile-time wise,
since we avoid potentially-costly knownbits analysis that will
ultimately not allow us to actually do anything with said `add`.
InstCombine is quite aggressive in doing the opposite transform,
folding `add` of operands with no common bits set into an `or`,
and that not many things support that new pattern..
In this case, teaching Reassociate about it is easy,
there's preexisting art for `sub`/`shl`:
just convert such an `or` into an `add`:
https://rise4fun.com/Alive/Xlyv
The two tests rely on LegacyInlinerBase::doFinalization to remove
Function::isDefTriviallyDead() functions. The new PM does not have the behavior.
The -NEXT patterns checking the emptiness are actually sufficient.
Note, reassociate-deadinst.ll has become stale - it no longer catches
the problem r285380 intended. Unfortunately it is difficult to craft a
new test because it is actually pretty difficult to break it with
`MadeChange = true;` all over the file.
This pass is like DeadCodeEliminationPass, but only does one pass
through a function instead of iterating on users of eliminated
instructions.
DeadCodeEliminationPass should be used in all cases.
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D87933
As discussed in D86843, -earlycse-debug-hash should be used in more regression
tests to catch inconsistency between the hashing and the equivalence check.
Differential Revision: https://reviews.llvm.org/D86863
To match NewPM pass name, and also for readability.
Also rename rpo-functionattrs -> rpo-function-attrs while we're here.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D84694
For IR generated by a compiler, this is really simple: you just take the
datalayout from the beginning of the file, and apply it to all the IR
later in the file. For optimization testcases that don't care about the
datalayout, this is also really simple: we just use the default
datalayout.
The complexity here comes from the fact that some LLVM tools allow
overriding the datalayout: some tools have an explicit flag for this,
some tools will infer a datalayout based on the code generation target.
Supporting this properly required plumbing through a bunch of new
machinery: we want to allow overriding the datalayout after the
datalayout is parsed from the file, but before we use any information
from it. Therefore, IR/bitcode parsing now has a callback to allow tools
to compute the datalayout at the appropriate time.
Not sure if I covered all the LLVM tools that want to use the callback.
(clang? lli? Misc IR manipulation tools like llvm-link?). But this is at
least enough for all the LLVM regression tests, and IR without a
datalayout is not something frontends should generate.
This change had some sort of weird effects for certain CodeGen
regression tests: if the datalayout is overridden with a datalayout with
a different program or stack address space, we now parse IR based on the
overridden datalayout, instead of the one written in the file (or the
default one, if none is specified). This broke a few AVR tests, and one
AMDGPU test.
Outside the CodeGen tests I mentioned, the test changes are all just
fixing CHECK lines and moving around datalayout lines in weird places.
Differential Revision: https://reviews.llvm.org/D78403
Use UnaryOperator::CreateFNeg instead.
Summary:
With the introduction of the native fneg instruction, the
fsub -0.0, %x idiom is obsolete. This patch makes LLVM
emit fneg instead of the idiom in all places.
Reviewed By: cameron.mcinally
Differential Revision: https://reviews.llvm.org/D75130
As discussed in the motivating PR44509:
https://bugs.llvm.org/show_bug.cgi?id=44509
...we can end up with worse code using fast-math than without.
This is because the reassociate pass greedily transforms fsub
into fneg/fadd and apparently (based on the regression tests
seen here) expects instcombine to clean that up if it wasn't
profitable. But we were missing this fold:
(X - Y) - Z --> X - (Y + Z)
There's another, more specific case that I think we should
handle as shown in the "fake" fneg test (but missed with a real
fneg), but that's another patch. That may be tricky to get
right without conflicting with existing transforms for fneg.
Differential Revision: https://reviews.llvm.org/D72521
This is an extension of a transform that tries to produce positive floating-point
constants to improve canonicalization (and hopefully lead to more reassociation
and CSE).
The original patches were:
D4904
D5363 (rL221721)
But as the test diffs show, these were limited to basic patterns by walking from
an instruction to its single user rather than recursively moving up the def-use
sequence. No fast-math is required here because we're only rearranging implicit
FP negations in intermediate ops.
A motivating bug is:
https://bugs.llvm.org/show_bug.cgi?id=32939
Differential Revision: https://reviews.llvm.org/D65954
llvm-svn: 368512
Reverse the canonicalization of fneg relative to fmul/fdiv. That makes it
easier to implement the transforms (and possibly other fneg transforms) in
1 place because we can always start the pattern match from fneg (either the
legacy binop or the new unop).
There's a secondary practical benefit seen in PR21914 and PR42681:
https://bugs.llvm.org/show_bug.cgi?id=21914https://bugs.llvm.org/show_bug.cgi?id=42681
...hoisting fneg rather than sinking seems to play nicer with LICM in IR
(although this change may expose analysis holes in the other direction).
1. The instcombine test changes show the expected neutral IR diffs from
reversing the order.
2. The reassociation tests show that we were missing an optimization
opportunity to fold away fneg-of-fneg. My reading of IEEE-754 says
that all of these transforms are allowed (regardless of binop/unop
fneg version) because:
"For all other operations [besides copy/abs/negate/copysign], this
standard does not specify the sign bit of a NaN result."
In all of these transforms, we always have some other binop
(fadd/fsub/fmul/fdiv), so we are free to flip the sign bit of a
potential intermediate NaN operand.
(If that interpretation is wrong, then we must already have a bug in
the existing transforms?)
3. The clang tests shouldn't exist as-is, but that's effectively a
revert of rL367149 (the test broke with an extension of the
pre-existing fneg canonicalization in rL367146).
Differential Revision: https://reviews.llvm.org/D65399
llvm-svn: 367447
Also, add a FIXME for the unsafe transform on a unary FNeg. A unary FNeg can only be transformed to a FMul by -1.0 when the nnan flag is present. The unary FNeg project is a WIP, so the unsafe transformation is acceptable until that work is complete.
The bogus assert with introduced in D63445.
llvm-svn: 363998
Reassociation's NegateValue moved instructions to the beginning of
blocks (after PHIs) without checking for exception handling pads.
It's possible for reassociation to move something into an exception
handling block so we need to make sure we don't move things too early
in the block. This change advances the insertion point past any
exception handling pads.
If the block we want to move into contains a catchswitch, we cannot
move into it. In that case just create a new neg as if we had not
found an existing neg to move.
Differential Revision: https://reviews.llvm.org/D61089
llvm-svn: 360262
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
Summary:
Between building the pair map and querying it there are a few places that
erase and create Values. It's rare but the address of these newly created
Values is occasionally the same as a just-erased Value that we already
have in the pair map. These coincidences should be accounted for to avoid
non-determinism.
Thanks to Roman Tereshin for the test case.
Reviewers: rtereshin, bogner
Reviewed By: rtereshin
Subscribers: mgrang, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59401
llvm-svn: 356803
This patch fixes the issue noticed in D54532.
The problem is that cst_pred_ty-based matchers like m_Zero() currently do not match
scalar undefs (as expected), but *do* match vector undefs. This may lead to optimization
inconsistencies in rare cases.
There is only one existing test for which output changes, reverting the change from D53205.
The reason here is that vector fsub undef, %x is no longer matched as an m_FNeg(). While I
think that the new output is technically worse than the previous one, it is consistent with
scalar, and I don't think it's really important either way (generally that undef should have
been folded away prior to reassociation.)
I've also added another test case for this issue based on InstructionSimplify. It took some
effort to find that one, as in most cases undef folds are either checked first -- and in the
cases where they aren't it usually happens to not make a difference in the end. This is the
only case I was able to come up with. Prior to this patch the test case simplified to undef
in the scalar case, but zeroinitializer in the vector case.
Patch by: @nikic (Nikita Popov)
Differential Revision: https://reviews.llvm.org/D54631
llvm-svn: 347318
This work is to avoid regressions when we seperate FNeg from the FSub IR instruction.
Differential Revision: https://reviews.llvm.org/D53205
llvm-svn: 345146
We need to update this code before introducing an 'fneg' instruction in IR,
so we might as well kill off the integer neg/not queries too.
This is no-functional-change-intended for scalar code and most vector code.
For vectors, we can see that the 'match' API allows for undef elements in
constants, so we optimize those cases better.
Ideally, there would be a test for each code diff, but I don't see evidence
of that for the existing code, so I didn't try very hard to come up with new
vector tests for each code change.
Differential Revision: https://reviews.llvm.org/D53533
llvm-svn: 345042
I was trying to provide test coverage for D53533
with rL344964, but these don't do it...and I don't
think they add any value, so deleting.
llvm-svn: 344969
Also, regenerate checks for these files. We should do better
on the vector tests by using the PatternMatch API instead of
BinaryOperator::isNot/isNeg.
llvm-svn: 344964
If we have a pair of binops feeding another pair of binops, rearrange the operands so
the matching pair are together because that allows easy factorization folds to happen
in instcombine:
((X << S) & Y) & (Z << S) --> ((X << S) & (Z << S)) & Y (reassociation)
--> ((X & Z) << S) & Y (factorize shift from 'and' ops optimization)
This is part of solving PR37098:
https://bugs.llvm.org/show_bug.cgi?id=37098
Note that there's an instcombine version of this patch attached there, but we're trying
to make instcombine have less responsibility to improve compile-time efficiency.
For reasons I still don't completely understand, reassociate does this kind of transform
sometimes, but misses everything in my motivating cases.
This patch on its own is gluing an independent cleanup chunk to the end of the existing
RewriteExprTree() loop. We can build on it and do something stronger to better order the
full expression tree like D40049. That might be an alternative to the proposal to add a
separate reassociation pass like D41574.
Differential Revision: https://reviews.llvm.org/D45842
llvm-svn: 341288
As the test diffs show, the current users of getBinOpIdentity()
are InstCombine and Reassociate. SLP vectorizer is a candidate
for using this functionality too (D28907).
The InstCombine shuffle improvements are part of the planned
enhancements noted in D48830.
InstCombine actually has several other uses of getBinOpIdentity()
via SimplifyUsingDistributiveLaws(), but we don't call that for
any FP ops. Fixing that might be another part of removing the
custom reassociation in InstCombine that is only done for fadd+fmul.
llvm-svn: 336215
Sanjay Patel