[LLVM][IR] Use splat syntax when printing Constant[Data]Vector. (#112548)

[PatternMatch] Do not accept undef elements in m_AllOnes() and friends (#88217)

Change all the cstval_pred_ty based PatternMatch helpers (things like
m_AllOnes and m_Zero) to only allow poison elem

[PatternMatch] Do not accept undef elements in m_AllOnes() and friends (#88217)

Change all the cstval_pred_ty based PatternMatch helpers (things like
m_AllOnes and m_Zero) to only allow poison elements inside vector
splats, not undef elements.

Historically, we used to represent non-demanded elements in vectors
using undef. Nowadays, we use poison instead. As such, I believe that
support for undef in vector splats is no longer useful.

At the same time, while poison splat elements are pretty much always
safe to ignore, this is not generally the case for undef elements. We
have existing miscompiles in our tests due to this (see the
masked-merge-*.ll tests changed here) and it's easy to miss such cases
in the future, now that we write tests using poison instead of undef
elements.

I think overall, keeping support for undef elements no longer makes
sense, and we should drop it. Once this is done consistently, I think we
may also consider allowing poison in m_APInt by default, as doing that
change is much less risky than doing the same with undef.

This change involves a substantial amount of test changes. For most
tests, I've just replaced undef with poison, as I don't think there is
value in retaining both. For some tests (where the distinction between
undef and poison is important), I've duplicated tests.

show more ...

[InstCombine] Extend `(lshr/shl (shl/lshr -1, x), x)` -> `(lshr/shl -1, x)` for multi-use

We previously did this iff the inner `(shl/lshr -1, x)` was
one-use. No instructions are added even if the i

[InstCombine] Extend `(lshr/shl (shl/lshr -1, x), x)` -> `(lshr/shl -1, x)` for multi-use

We previously did this iff the inner `(shl/lshr -1, x)` was
one-use. No instructions are added even if the inner `(shl/lshr -1,
x)` is multi-use and this canonicalization both makes the resulting
instruction easier to analyze and shrinks its dependency chain.

Closes #81576

show more ...

[InstCombine] Infer shift flags with unknown shamt (#72535)

Alive2: https://alive2.llvm.org/ce/z/82Wr3q

Related patch:
https://github.com/llvm/llvm-project/commit/2dd52b4527667837cc525aa48435ab5

[InstCombine] Infer shift flags with unknown shamt (#72535)

Alive2: https://alive2.llvm.org/ce/z/82Wr3q

Related patch:
https://github.com/llvm/llvm-project/commit/2dd52b4527667837cc525aa48435ab5cbfa30a0b

show more ...

[InstCombine] Add exact flags for ext idiom `shr (shl X, Y), Y` (#72483)

This patch adds exact flags for sext/zext idiom `shr (shl X, Y), Y`.
Alive2: https://alive2.llvm.org/ce/z/xYFpfB

We can g

[InstCombine] Add exact flags for ext idiom `shr (shl X, Y), Y` (#72483)

This patch adds exact flags for sext/zext idiom `shr (shl X, Y), Y`.
Alive2: https://alive2.llvm.org/ce/z/xYFpfB

We can generalize it to handle pattern `shr (shl X, Y), Z` with `Y u>=
Z` (e.g., non-splat vectors). But I don't think it's worth the effort.

This missed optimization is discovered with the help of
https://github.com/AliveToolkit/alive2/pull/962.

show more ...

[test] Use -passes=instcombine instead of -instcombine in lots of tests. NFC

Another step moving away from the deprecated syntax of specifying
pass pipeline in opt.

Differential Revision: https://r

[test] Use -passes=instcombine instead of -instcombine in lots of tests. NFC

Another step moving away from the deprecated syntax of specifying
pass pipeline in opt.

Differential Revision: https://reviews.llvm.org/D119081

show more ...

[InstCombine] use redirect of input file in regression tests; NFC

This is a repeat of 1880092722 from 2009. We should have less risk
of hitting bugs at this point because we auto-generate positive C

[InstCombine] use redirect of input file in regression tests; NFC

This is a repeat of 1880092722 from 2009. We should have less risk
of hitting bugs at this point because we auto-generate positive CHECK
lines only, but this makes things consistent.

Copying the original commit msg:
"Change tests from "opt %s" to "opt < %s" so that opt doesn't see the
input filename so that opt doesn't print the input filename in the
output so that grep lines in the tests don't unintentionally match
strings in the input filename."

show more ...

[NFC][InstCombine] More tests for PR42563 "Dropping pointless masking before left shift"

For patterns c/d/e we too can deal with the pattern even if we can't
just drop the mask, we can just apply it

[NFC][InstCombine] More tests for PR42563 "Dropping pointless masking before left shift"

For patterns c/d/e we too can deal with the pattern even if we can't
just drop the mask, we can just apply it afterwars:
https://rise4fun.com/Alive/gslRa

llvm-svn: 372244

show more ...

[NFC][InstCombine] Redundant masking before left-shift: tests with assume

If the legality check is `(shiftNbits-maskNbits) s>= 0`,
then we can simplify it to `shiftNbits u>= maskNbits`,
which is eas

[NFC][InstCombine] Redundant masking before left-shift: tests with assume

If the legality check is `(shiftNbits-maskNbits) s>= 0`,
then we can simplify it to `shiftNbits u>= maskNbits`,
which is easier to check for.

However, currently switching the `dropRedundantMaskingOfLeftShiftInput()`
to `SimplifyICmpInst()` does not catch these cases and regresses
currently-handled cases, so i'll leave it as is for now.

https://rise4fun.com/Alive/25P

llvm-svn: 366564

show more ...

[InstCombine] Dropping redundant masking before left-shift [3/5] (PR42563)

Summary:
If we have some pattern that leaves only some low bits set, and then performs
left-shift of those bits, if none of

[InstCombine] Dropping redundant masking before left-shift [3/5] (PR42563)

Summary:
If we have some pattern that leaves only some low bits set, and then performs
left-shift of those bits, if none of the bits that are left after the final
shift are modified by the mask, we can omit the mask.

There are many variants to this pattern:
d. `(x & ((-1 << MaskShAmt) >> MaskShAmt)) << ShiftShAmt`
All these patterns can be simplified to just:
`x << ShiftShAmt`
iff:
d. `(ShiftShAmt-MaskShAmt) s>= 0` (i.e. `ShiftShAmt u>= MaskShAmt`)

alive proofs:
d: https://rise4fun.com/Alive/I5Y

For now let's start with patterns where both shift amounts are variable,
with trivial constant "offset" between them, since i believe this is
both simplest to handle and i think this is most common.
But again, there are likely other variants where we could use
ValueTracking/ConstantRange to handle more cases.

https://bugs.llvm.org/show_bug.cgi?id=42563

Differential Revision: https://reviews.llvm.org/D64519

llvm-svn: 366538

show more ...

[NFC][InstCombine] Comb through just-added "omit mask before left-shift" tests once more

llvm-svn: 365694

[NFC][InstCombine] Redundant masking before left-shift (PR42563)

alive proofs:
a,b: https://rise4fun.com/Alive/4zsf
c,d,e,f: https://rise4fun.com/Alive/RC49

Indeed, not all of these patterns ar

[NFC][InstCombine] Redundant masking before left-shift (PR42563)

alive proofs:
a,b: https://rise4fun.com/Alive/4zsf
c,d,e,f: https://rise4fun.com/Alive/RC49

Indeed, not all of these patterns are canonical.
But since this fold will only produce a single instruction
i'm really interested in handling even uncanonical patterns.

Other than these 6 patterns, i can't think of any other
reasonable variants right now, although i'm sure they exist.

For now let's start with patterns where both shift amounts are variable,
with trivial constant "offset" between them, since i believe this is
both simplest to handle and i think this is most common.
But again, there are likely other variants where we could use
ValueTracking/ConstantRange to handle more cases.

https://bugs.llvm.org/show_bug.cgi?id=42563

llvm-svn: 365641

show more ...