When the new LLVM Pass Manager is enabled, -Z verify-llvm-ir=yes is ignored if -C no-prepopulate-passes is also given
#95874
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luqmana
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…s, r=nikic Respect -Z verify-llvm-ir and other flags that add extra passes when combined with -C no-prepopulate-passes in the new LLVM Pass Manager. As part of the switch to the new LLVM Pass Manager the behaviour of flags such as `-Z verify-llvm-ir` (e.g. sanitizer, instrumentation) was modified when combined with `-C no-prepopulate-passes`. With the old PM, rustc was the one manually constructing the pipeline and respected those flags but in the new pass manager, those flags are used to build a list of callbacks that get invoked at certain extension points in the pipeline. Unfortunately, `-C no-prepopulate-passes` would skip building the pipeline altogether meaning we'd never add the corresponding passes. The fix here is to just manually invoke those callbacks as needed. Fixes rust-lang#95874 Demonstrating the current vs fixed behaviour using the bug in rust-lang#95864 ```console $ rustc +nightly asm-miscompile.rs --edition 2021 --emit=llvm-ir -C no-prepopulate-passes -Z verify-llvm-ir $ echo $? 0 $ rustc +stage1 asm-miscompile.rs --edition 2021 --emit=llvm-ir -C no-prepopulate-passes -Z verify-llvm-ir Basic Block in function '_ZN14asm_miscompile3foo28_$u7b$$u7b$closure$u7d$$u7d$17h360e2f7eee1275c5E' does not have terminator! label %bb1 LLVM ERROR: Broken module found, compilation aborted! ```
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While investigating the issue fixed in #95864 I came across some surprising behaviour. In trying to figure out whether
rustcwas generating invalid IR or it was some subsequent LLVM pass, I realized that-Z verify-llvm-irwas essentially ignored with-C no-prepopulate-passesin the new LLVM Pass Manager. This lead me to (incorrectly) assume that the IRrustcgenerated was valid when it got to LLVM.It looks like a subtle change in behaviour due to the way the new Pass Manager is constructed in
LLVMRustOptimizeWithNewPassManager.The text was updated successfully, but these errors were encountered: