If the original code was written in Rust, then I don't think the Rust compiler is allowed to do any of these "optimizations" of rewriting floating point expressions.
The C compiler also isn't allowed to do all of them. However some people use fast-math or compilers that default to fast-math to break the rules. Some older targets also may use the 80 bit fpu, which is its own mess and any sane compiler will default to properly sized SSE instructions instead.
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If the original code was written in Rust, then I don't think the Rust compiler is allowed to do any of these "optimizations" of rewriting floating point expressions.
The C compiler also isn't allowed to do all of them. However some people use fast-math or compilers that default to fast-math to break the rules. Some older targets also may use the 80 bit fpu, which is its own mess and any sane compiler will default to properly sized SSE instructions instead.
On x86, LLVM does not follow strict IEEE 754 behavior all the time.
IIRC it also depends on the CPU's storage and capabilities.