| Issue |
175465
|
| Summary |
[rust] Performance degradation from LLVM14->15 still present in 21
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
kika
|
This is LLVM performance issue isolated from https://github.com/rust-lang/rust/issues/129713
LLVM14 runs the `opt -O2` phase on this file in about 3 minutes on my machine (M1 Max Macbook Pro) and LLVM15 runs it in about 70minutes. LLVM 18-21 "improved" it to about 40min. The Rust code is at the link, bytecode is attached.
Since the performance degradation is superlinear, the smaller repro bytecodes are also attached (the _150 and _300 versions). On my machine `opt -O2` for `bug_150.bc` runs in 2 seconds on LLVM14 and 7.3 s on LLVM15.
(files with -14 suffix are for LLVM14, it can't process bytecode from 15 and higher)
The fix will follow once I rebuild this elephant and test. I brought the compile time from 40 min to 3, which is also a bit high for a struct with 621 fields and initialization code, but baby steps.
[repro.zip](https://github.com/user-attachments/files/24555172/repro.zip)
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