Add logging support for debugging ISLE rules

[bongjunj]

resolves #11971

Run the following command to check:

RUST_LOG=cranelift_codegen::opts::generated_code=trace cargo run -p cranelift-tools --bin clif-util -- compile --target x86_64-unknown-linux-gnu --set opt_level=speed <input.clif>

Should print logs such as:

[2025-12-31T06:48:33Z DEBUG cranelift_codegen::opts::generated_code] ISLE simplify src/opts/remat.isle line 23
[2025-12-31T06:48:33Z DEBUG cranelift_codegen::opts::generated_code] ISLE bnot <OUT_DIR>/clif_opt.isle line 1322
[2025-12-31T06:48:33Z DEBUG cranelift_codegen::opts::generated_code] ISLE bnot <OUT_DIR>/clif_opt.isle line 1322
[2025-12-31T06:48:33Z DEBUG cranelift_codegen::opts::generated_code] ISLE simplify src/opts/remat.isle line 17
[2025-12-31T06:48:33Z DEBUG cranelift_codegen::opts::generated_code] ISLE bor <OUT_DIR>/clif_opt.isle line 1304
[2025-12-31T06:48:33Z DEBUG cranelift_codegen::opts::generated_code] ISLE simplify src/opts/bitops.isle line 48
[2025-12-31T06:48:33Z DEBUG cranelift_codegen::opts::generated_code] ISLE simplify src/opts/remat.isle line 23
[2025-12-31T06:48:33Z DEBUG cranelift_codegen::opts::generated_code] ISLE bnot <OUT_DIR>/clif_opt.isle line 1322

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[cfallin]

Thanks! Happy to merge with the one question below answered/addressed. This will definitely be helpful tracing rule applications!

[cfallin]

I don't think we need the #[cfg(feature = "trace-log")] here, since we are already conditionalizing this bit of codegen on the trace-log feature via the emit_logging option, right?

[bongjunj]

No, the feature guard isn't necessary as you pointed out, and the test below demonstrates you can safely remove the guard.

> RUST_LOG=cranelift_codegen::opts::generated_code=trace cargo run -p cranelift-tools --bin clif-util -- co
mpile --target x86_64-unknown-linux-gnu --set opt_level=speed ../../keccak-no-opts.clif 2>&1 | head -n10
...
[2026-01-04T04:52:21Z DEBUG cranelift_codegen::opts::generated_code] ISLE simplify src/opts/remat.isle line 25
[2026-01-04T04:52:21Z DEBUG cranelift_codegen::opts::generated_code] ISLE simplify src/opts/remat.isle line 5
[2026-01-04T04:52:21Z DEBUG cranelift_codegen::opts::generated_code] ISLE simplify src/opts/remat.isle line 25
[2026-01-04T04:52:21Z DEBUG cranelift_codegen::opts::generated_code] ISLE simplify src/opts/remat.isle line 5
[2026-01-04T04:52:21Z DEBUG cranelift_codegen::opts::generated_code] ISLE simplify src/opts/remat.isle line 25
[2026-01-04T04:52:21Z DEBUG cranelift_codegen::opts::generated_code] ISLE simplify src/opts/remat.isle line 5
[2026-01-04T04:52:21Z DEBUG cranelift_codegen::opts::generated_code] ISLE simplify src/opts/remat.isle line 25
[2026-01-04T04:52:21Z DEBUG cranelift_codegen::opts::generated_code] ISLE simplify src/opts/remat.isle line 5

> cargo run -p cranelift-tools --bin clif-util -- compile --target x86_64-unknown-linux-gnu --set opt_level
=speed ../../data/clif/keccak-no-opts.clif 2>&1 | head -n10

[No output]

I didn't catch this. Thanks!

[cfallin]

@bongjunj it looks like this fails on Windows (see this CI job) because the paths have backslashes, and when embedding those into strings, they become (ill-formed) escapes. Could you address by either replacing \ with / or by properly escaping somehow?

[bongjunj]

I have changed the string embedding from Display trait to Debug trait, as Debug trait can automatically place escapes and quotes.