Don't ICE in `might_permit_raw_init` if reference is polymorphic
Emitting optimized MIR for a polymorphic function may require computing layout of a type that isn't (yet) known. This happens in the instcombine pass, for example. Let's fail gracefully in that condition.
cc `@saethlin`
fixes#107999
This slightly improves performance on systems with many cores and
barely affects systems with few cores.
My laptop (2 core + HT):
Before:
Benchmark 2: RUSTC=rustc /home/bjorn/Projects/cg_clif2/./dist/cargo-clif build --manifest-path /home/bjorn/Projects/cg_clif2/./download/simple-raytracer/Cargo.toml --target-dir /home/bjorn/Projects/cg_clif2/./build/simple_raytracer
Time (mean ± σ): 12.042 s ± 0.313 s [User: 29.434 s, System: 4.720 s]
Range (min … max): 11.670 s … 12.795 s 10 runs
After:
Benchmark 2: RUSTC=rustc /home/bjorn/Projects/cg_clif2/./dist/cargo-clif build --manifest-path /home/bjorn/Projects/cg_clif2/./download/simple-raytracer/Cargo.toml --target-dir /home/bjorn/Projects/cg_clif2/./build/simple_raytracer
Time (mean ± σ): 12.037 s ± 0.384 s [User: 29.960 s, System: 4.722 s]
Range (min … max): 11.673 s … 12.769 s 10 runs
Dev desktop (32 cores)
Before:
Benchmark 2: RUSTC=rustc /home/gh-bjorn3/cg_clif/./dist/cargo-clif build --manifest-path /home/gh-bjorn3/cg_clif/./download/simple-raytracer/Cargo.toml --target-dir /home/gh-bjorn3/cg_clif/./build/simple_raytracer
Time (mean ± σ): 10.425 s ± 0.104 s [User: 25.877 s, System: 5.513 s]
Range (min … max): 10.267 s … 10.640 s 10 runs
After:
Benchmark 2: RUSTC=rustc /home/gh-bjorn3/cg_clif/./dist/cargo-clif build --manifest-path /home/gh-bjorn3/cg_clif/./download/simple-raytracer/Cargo.toml --target-dir /home/gh-bjorn3/cg_clif/./build/simple_raytracer
Time (mean ± σ): 10.212 s ± 0.100 s [User: 25.918 s, System: 5.555 s]
Range (min … max): 10.079 s … 10.362 s 10 runs
This significantly improves performance. For example for the
simple-raytracer benchmark it goes from a 13% improvement over LLVM to
39% improvement over LLVM.
