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 3.1.2. Function call linkage

Code generated to implement direct function calls must adhere to the rules in section 2.2.1 "Function Call Linkage Protocols" of the ELFv2 ABI specification. In particular, direct calls must be implemented using a bl instruction directly followed by a nop instruction, where the nop may be omitted if either the bl is marked with a R_PPC64_REL24_NOTOC relocation or the callee is in the same compilation unit and is guaranteed to preserve r2.