Emit optimization remarks to the final binary, not the console #96705

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1. matthiaskrgr commented on May 4, 2022

   

   matthiaskrgr

   on May 4, 2022

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   RUSTFLAGS="-C llvm-args=--pass-remarks=.* -Cdebuginfo=2" cargo build --release

   does that work for you?
2. tschuett commented on May 4, 2022

   

   tschuett

   on May 4, 2022

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   It still pollutes my console.
3. tschuett commented on May 4, 2022

   

   tschuett

   on May 4, 2022

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   RUSTFLAGS="-C llvm-args=--pass-remarks-output=filename -Cdebuginfo=2" cargo build --release

   This fails because rustc does not know about: pass-remarks-output
4. jyn514

   changed the title [-]remarks[/-] [+]Emit optimization remarks to the final binary, not the console[/+] on Apr 9, 2023
5. jyn514

   added

   A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.

   T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

   A-codegenArea: Code generationArea: Code generation

   on Apr 9, 2023
6. matthiaskrgr

   added 3 commits that reference this issue on May 6, 2023

   Rollup merge of rust-lang#111203 - Kobzol:remark-print-kind, r=tmiasko

   ...

   bd9924b

   Rollup merge of rust-lang#111203 - Kobzol:remark-print-kind, r=tmiasko

   ...

   3959d47

   Rollup merge of rust-lang#111203 - Kobzol:remark-print-kind, r=tmiasko

   ...

   e4eaf31
7. Kobzol commented on Jul 6, 2023

   

   Kobzol

   on Jul 6, 2023

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   With #113040, remarks can now be outputted into a directory, in the same (YAML) format as clang outputs them.
8. yugr commented on Jun 9, 2025

   

   yugr

   on Jun 9, 2025

   Last edited by yugr

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   There seems to be something fishy about -C remark. This code

   $ cat test.rs
   #[no_mangle]
   pub fn foo(v: &[i32], n: usize) -> i32 {
       let mut ans = 0;
       for i in 0..n {
           ans += v[i];
       }
       ans
   }
   

   is clearly vectorized:

   $ rustc --crate-type=rlib -O -C target-cpu=native test.rs
   $ objdump -d libtest.rlib
   ...
     50:   c5 fd fe 04 87          vpaddd (%rdi,%rax,4),%ymm0,%ymm0
     55:   c5 f5 fe 4c 87 20       vpaddd 0x20(%rdi,%rax,4),%ymm1,%ymm1
     5b:   c5 ed fe 54 87 40       vpaddd 0x40(%rdi,%rax,4),%ymm2,%ymm2
     61:   c5 e5 fe 5c 87 60       vpaddd 0x60(%rdi,%rax,4),%ymm3,%ymm3
     67:   48 83 c0 20             add    $0x20,%rax
     6b:   48 39 c1                cmp    %rax,%rcx
     6e:   75 e0                   jne    50 <foo+0x50>
   ...
   

   and -C llvm-args=--pass-remarks=.* tells me that (and nothing else):

   $ rustc --crate-type=rlib -O -C target-cpu=native -C debuginfo=1 -C llvm-args=--pass-remarks=.* test.rs
   remark: /rustc/17067e9ac6d7ecb70e50f92c1944e545188d2359/library/core/src/iter/range.rs:764:12: vectorized loop (vectorization width: 8, interleaved count: 4)
   

   On the other hand -C remark=all tells me a lot of other things but nothing about vectorization:

   $ rustc --crate-type=rlib -O -C target-cpu=native -C debuginfo=1 -C remark=all test.rs  |& wc -l
   $ rustc --crate-type=rlib -O -C target-cpu=native -C debuginfo=1 -C remark=all test.rs  |& grep -i vector
   

   Moreover trying to ask about Loop Vectorizer also fails:

   $ rustc  --crate-type=rlib -O -C target-cpu=native -C debuginfo=1 -C remark=loop-vectorize test.rs  | wc -l
   0
   

   I'm on

   yugr@cfarm13:~/src/rust/llvm-tool/tests$ rustc --version
   rustc 1.87.0 (17067e9ac 2025-05-09)
   
9. Enselic

   added

   C-enhancementCategory: An issue proposing an enhancement or a PR with one.Category: An issue proposing an enhancement or a PR with one.

   on Oct 18, 2025