True if it is OK to do sibling call optimization for the specified
call expression exp. decl will be the called function,
NULL if this is an indirect call.
It is not uncommon for limitations of calling conventions to prevent
tail calls to functions outside the current unit of translation, or
during PIC compilation. The hook is used to enforce these restrictions,
sibcall md pattern can not fail, or fall over to a
“normal” call. The criteria for successful sibling call optimization
may vary greatly between different architectures.
Add any hard registers to regs that are live on entry to the function. This hook only needs to be defined to provide registers that cannot be found by examination of FUNCTION_ARG_REGNO_P, the callee saved registers, STATIC_CHAIN_INCOMING_REGNUM, STATIC_CHAIN_REGNUM, TARGET_STRUCT_VALUE_RTX, FRAME_POINTER_REGNUM, EH_USES, FRAME_POINTER_REGNUM, ARG_POINTER_REGNUM, and the PIC_OFFSET_TABLE_REGNUM.
This hook should add additional registers that are computed by the prologue to the hard regset for shrink-wrapping optimization purposes.
True if a function’s return statements should be checked for matching the function’s return type. This includes checking for falling off the end of a non-void function. Return false if no such check should be made.