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Revision tags: llvmorg-21-init, llvmorg-19.1.7, llvmorg-19.1.6, llvmorg-19.1.5, llvmorg-19.1.4, llvmorg-19.1.3, llvmorg-19.1.2, llvmorg-19.1.1, llvmorg-19.1.0, llvmorg-19.1.0-rc4 |
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| #
a1058776 |
| 21-Aug-2024 |
Nikita Popov <npopov@redhat.com> |
[InstCombine] Remove some of the complexity-based canonicalization (#91185)
The idea behind this canonicalization is that it allows us to handle less
patterns, because we know that some will be can
[InstCombine] Remove some of the complexity-based canonicalization (#91185)
The idea behind this canonicalization is that it allows us to handle less
patterns, because we know that some will be canonicalized away. This is
indeed very useful to e.g. know that constants are always on the right.
However, this is only useful if the canonicalization is actually
reliable. This is the case for constants, but not for arguments: Moving
these to the right makes it look like the "more complex" expression is
guaranteed to be on the left, but this is not actually the case in
practice. It fails as soon as you replace the argument with another
instruction.
The end result is that it looks like things correctly work in tests,
while they actually don't. We use the "thwart complexity-based
canonicalization" trick to handle this in tests, but it's often a
challenge for new contributors to get this right, and based on the
regressions this PR originally exposed, we clearly don't get this right
in many cases.
For this reason, I think that it's better to remove this complexity
canonicalization. It will make it much easier to write tests for
commuted cases and make sure that they are handled.
show more ...
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Revision tags: llvmorg-19.1.0-rc3, llvmorg-19.1.0-rc2, llvmorg-19.1.0-rc1, llvmorg-20-init, llvmorg-18.1.8, llvmorg-18.1.7, llvmorg-18.1.6, llvmorg-18.1.5, llvmorg-18.1.4, llvmorg-18.1.3, llvmorg-18.1.2, llvmorg-18.1.1, llvmorg-18.1.0, llvmorg-18.1.0-rc4, llvmorg-18.1.0-rc3, llvmorg-18.1.0-rc2, llvmorg-18.1.0-rc1, llvmorg-19-init, llvmorg-17.0.6, llvmorg-17.0.5, llvmorg-17.0.4, llvmorg-17.0.3, llvmorg-17.0.2, llvmorg-17.0.1, llvmorg-17.0.0, llvmorg-17.0.0-rc4, llvmorg-17.0.0-rc3, llvmorg-17.0.0-rc2, llvmorg-17.0.0-rc1, llvmorg-18-init, llvmorg-16.0.6 |
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| #
5189eff3 |
| 10-Jun-2023 |
Noah Goldstein <goldstein.w.n@gmail.com> |
[InstCombine] Canonicalize (icmp eq/ne X, rotate(X)) to always use rotate-left
We canonicalize rotate-right -> rotate-left in other places. Makes
sense to do so here as well.
Proof: https://alive2.l
[InstCombine] Canonicalize (icmp eq/ne X, rotate(X)) to always use rotate-left
We canonicalize rotate-right -> rotate-left in other places. Makes
sense to do so here as well.
Proof: https://alive2.llvm.org/ce/z/HL3TpK
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D152349
show more ...
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| #
2df63095 |
| 07-Jun-2023 |
Noah Goldstein <goldstein.w.n@gmail.com> |
[InstCombine] Transform (icmp eq/ne rotate(X,AX),rotate(Y,AY)) -> (icmp eq/ne rotate(Y,AX-AY))
Only do so if we don't create more instructions, so either both
rotates have one use or one of the rota
[InstCombine] Transform (icmp eq/ne rotate(X,AX),rotate(Y,AY)) -> (icmp eq/ne rotate(Y,AX-AY))
Only do so if we don't create more instructions, so either both
rotates have one use or one of the rotates has one use and both `AX`
and `AY` are constant.
Proof: https://alive2.llvm.org/ce/z/rVmJgz
Differential Revision: https://reviews.llvm.org/D152348
show more ...
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| #
1ce02652 |
| 07-Jun-2023 |
Noah Goldstein <goldstein.w.n@gmail.com> |
[InstCombine] Add tests for equality `icmp` with rotates; NFC
Differential Revision: https://reviews.llvm.org/D152347
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