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Revision tags: llvmorg-20.1.0, llvmorg-20.1.0-rc3, llvmorg-20.1.0-rc2, llvmorg-20.1.0-rc1, 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, 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, llvmorg-16.0.5, llvmorg-16.0.4, llvmorg-16.0.3, llvmorg-16.0.2, llvmorg-16.0.1, llvmorg-16.0.0, llvmorg-16.0.0-rc4, llvmorg-16.0.0-rc3, llvmorg-16.0.0-rc2, llvmorg-16.0.0-rc1, llvmorg-17-init, llvmorg-15.0.7, llvmorg-15.0.6, llvmorg-15.0.5, llvmorg-15.0.4, llvmorg-15.0.3, llvmorg-15.0.2, llvmorg-15.0.1, llvmorg-15.0.0, llvmorg-15.0.0-rc3, llvmorg-15.0.0-rc2, llvmorg-15.0.0-rc1, llvmorg-16-init, llvmorg-14.0.6, llvmorg-14.0.5 |
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| #
8b0d7634 |
| 25-May-2022 |
Alex Zhikhartsev <[email protected]> |
[DFAJumpThreading] Relax analysis to handle unpredictable initial values
Responding to a feature request from the Rust community:
https://github.com/rust-lang/rust/issues/80630
void foo(X) {
[DFAJumpThreading] Relax analysis to handle unpredictable initial values
Responding to a feature request from the Rust community:
https://github.com/rust-lang/rust/issues/80630
void foo(X) {
for (...)
switch (X)
case A
X = B
case B
X = C
}
Even though the initial switch value is non-constant, the switch
statement can still be threaded: the initial value will hit the switch
statement but the rest of the state changes will proceed by jumping
unconditionally.
The early predictability check is relaxed to allow unpredictable values
anywhere, but later, after the paths through the switch statement have
been enumerated, no non-constant state values are allowed along the
paths. Any state value not along a path will be an initial switch value,
which can be safely ignored.
Differential Revision: https://reviews.llvm.org/D124394
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Revision tags: llvmorg-14.0.4, llvmorg-14.0.3, llvmorg-14.0.2, llvmorg-14.0.1, llvmorg-14.0.0, llvmorg-14.0.0-rc4, llvmorg-14.0.0-rc3, llvmorg-14.0.0-rc2, llvmorg-14.0.0-rc1, llvmorg-15-init, llvmorg-13.0.1, llvmorg-13.0.1-rc3, llvmorg-13.0.1-rc2, llvmorg-13.0.1-rc1, llvmorg-13.0.0, llvmorg-13.0.0-rc4, llvmorg-13.0.0-rc3, llvmorg-13.0.0-rc2, llvmorg-13.0.0-rc1, llvmorg-14-init |
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| #
02077da7 |
| 27-Jul-2021 |
Alexey Zhikhartsev <[email protected]> |
Add jump-threading optimization for deterministic finite automata
The current JumpThreading pass does not jump thread loops since it can
result in irreducible control flow that harms other optimizat
Add jump-threading optimization for deterministic finite automata
The current JumpThreading pass does not jump thread loops since it can
result in irreducible control flow that harms other optimizations. This
prevents switch statements inside a loop from being optimized to use
unconditional branches.
This code pattern occurs in the core_state_transition function of
Coremark. The state machine can be implemented manually with goto
statements resulting in a large runtime improvement, and this transform
makes the switch implementation match the goto version in performance.
This patch specifically targets switch statements inside a loop that
have the opportunity to be threaded. Once it identifies an opportunity,
it creates new paths that branch directly to the correct code block.
For example, the left CFG could be transformed to the right CFG:
```
sw.bb sw.bb
/ | \ / | \
case1 case2 case3 case1 case2 case3
\ | / / | \
latch.bb latch.2 latch.3 latch.1
br sw.bb / | \
sw.bb.2 sw.bb.3 sw.bb.1
br case2 br case3 br case1
```
Co-author: Justin Kreiner @jkreiner
Co-author: Ehsan Amiri @amehsan
Reviewed By: SjoerdMeijer
Differential Revision: https://reviews.llvm.org/D99205
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