"Amker.Cheng" <amker.ch...@gmail.com> writes: > I found the temp register used for saving registers when expanding > prologue is defined by > macro MIPS_PROLOGUE_TEMP_REGNUM on mips target, like: > > #define MIPS_PROLOGUE_TEMP_REGNUM \ > (cfun->machine->interrupt_handler_p ? K0_REG_NUM : GP_REG_FIRST + 3) > > I don't understand why using registers starting from $3? > in my application, I have to save DFmode fpu regs through gpr regs, > that is $3,$4 in this case, > just like : > mfc1 $3, $fpr > sw $3, addr > mfc1 $4, $fpr+1 > sw $4, addr+4 > > apparently this would crush the argument in $4.
Why not use $3 in all cases? Why switch to $4? > why don't use $8 for MIPS_PROLOGUE_TEMP_REGNUM like EPILOGUE_TEMP? $8 can hold an argument value. I think $13 would be a possibility, but I don't see anything wrong with $3. Ian
