On Thu, Oct 01, 2020 at 12:42:39PM +0000, Christophe Leroy wrote: > On PPC64, we have mftb(). > On PPC32, we have mftbl() and an #define mftb() mftbl(). > > mftb() and mftbl() are equivalent, their purpose is to read the > content of SPRN_TRBL, as returned by 'mftb' simplified instruction. > > binutils seems to define 'mftbl' instruction as an equivalent > of 'mftb'. > > However in both 32 bits and 64 bits documentation, only 'mftb' is > defined, and when performing a disassembly with objdump, the displayed > instruction is 'mftb' > > No need to have two ways to do the same thing with different > names, rename mftbl() to have only mftb().
There are mttbl and mttbu insns (and no mttb insn); they write a 32-bit half for the time base. There is an mftb, and an mftbu. mftbu reads the upper half, while mftb reads the *whole* register. SPR 269 is the TBU register, while SPR 268 is called both TB and TBL. Yes, it is confusing :-) The "mftb" name is much clearer than "mftbl" (on 64-bit), because it reads the whole 64-bit register. On 32-bit mftbl is clearer (but not defined in the architecture, not officially an insn or even an extended mnemonic). Segher
