`lto=fat` results in compressed RV64 instructions even when they are explicitly disabled

I tried to compile a shared library with the following custom target:

{
  "arch": "riscv64",
  "code-model": "medium",
  "cpu": "generic-rv64",
  "crt-objects-fallback": "false",
  "data-layout": "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128",
  "only-cdylib": true,
  "eh-frame-header": false,
  "emit-debug-gdb-scripts": false,
  "features": "+m,+b,+zbc,+zknh,+unaligned-scalar-mem",
  "linker": "rust-lld",
  "linker-flavor": "ld.lld",
  "llvm-abiname": "lp64",
  "llvm-target": "riscv64",
  "max-atomic-width": 64,
  "panic-strategy": "immediate-abort",
  "position-independent-executables": true,
  "relro-level": "full",
  "static-position-independent-executables": true,
  "target-pointer-width": 64,
  "relocation-model": "pie",
  "singlethread": true,
  "dynamic-linking": true,
  "default-visibility": "hidden",
  "pre-link-args": {
    "ld": [
      "-Bsymbolic"
    ]
  },
  "dll-prefix": "",
  "dll-suffix": ".contract.so",
  "env": "abundance"
}

It works as expected with release profile, producing the code according to the specification, file says:

ELF 64-bit LSB shared object, UCB RISC-V, soft-float ABI, version 1 (GNU/Linux), static-pie linked, not stripped

Things change when I compile it for this custom profile:

[profile.contract]
inherits = "release"
lto = "fat"

I expected to see this happen:

Same kind of shared library is produced.

Instead, this happened:

ELF 64-bit LSB shared object, UCB RISC-V, RVC, soft-float ABI, version 1 (GNU/Linux), static-pie linked, not stripped

RVC is not what I requested though. Moreover, adding -c,-zca,-zcb to features explicitly makes no difference, I still see compressed instructions like c.or, c.sd, c.li, etc.

Possibly related to https://github.com/rust-lang/rust/issues/147667 ?

Meta

rustc --version --verbose:

rustc 1.96.0-nightly (3b1b0ef4d 2026-03-11)
binary: rustc
commit-hash: 3b1b0ef4d80d3117924d91352c8b6ca528708b3c
commit-date: 2026-03-11
host: x86_64-unknown-linux-gnu
release: 1.96.0-nightly
LLVM version: 22.1.0

Reproduce the custom RISC-V target with the release profile and with profile.contract using lto = "fat"; compare the file output and generated instructions. Start by tracing how the target feature settings are passed through the compiler's LTO/codegen path. Done means compressed instructions are not emitted when the relevant compressed extensions are disabled.