Function generate_llvm_ir 

pub fn generate_llvm_ir(
    functions: &[FunctionWithCfg],
    type_pool: &TypeInternPool,
    strings: &[String],
    interner: &ThreadedRodeo,
    opt_level: OptLevel,
) -> CompileResult<String>

Generate LLVM textual IR from analyzed functions.

Returns the LLVM IR in human-readable .ll format. Used by --emit asm to produce inspectable IR in place of native assembly.