>>
>> +/* Generate insns to zero all st/mm registers together.
>> + Return true when zeroing instructions are generated.
>> + Assume the number of st registers that are zeroed is num_of_st,
>> + we will emit the following sequence to zero them together:
>> + fldz; \
>> + fldz; \
>> + ...
>> + fldz; \
>> + fstp %%st(0); \
>> + fstp %%st(0); \
>> + ...
>> + fstp %%st(0);
>> + i.e., num_of_st fldz followed by num_of_st fstp to clear the stack
>> + mark stack slots empty. */
>> +
>> +static bool
>> +zero_all_st_mm_registers (HARD_REG_SET need_zeroed_hardregs)
>> +{
>> + unsigned int num_of_st = 0;
>> + for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
>> + if (STACK_REGNO_P (regno)
>> + && TEST_HARD_REG_BIT (need_zeroed_hardregs, regno)
>> + /* When the corresponding mm register also need to be cleared too.
>> */
>> + && TEST_HARD_REG_BIT (need_zeroed_hardregs,
>> + (regno - FIRST_STACK_REG + FIRST_MMX_REG)))
>> + num_of_st++;
>
> I don't think the above logic is correct. It should go like this:
>
> - If the function is returning an MMX register,
How to check on this? Is the following correct?
If (GET_CODE(crtl->return_rtx) == REG
&& (MMX_REG_P (REGNO (crtl->return_rtx)))
The function is returning an MMX register.
> then the function
> exits in MMX mode, and MMX registers should be cleared in the same way
> as XMM registers.
When clearing XMM registers, we used V4SFmode, what’s the mode we should use to
clearing
mmx registers?
> Otherwise the ABI specifies that the function exits
> in x87 mode and x87 stack should be cleared (but see below).
>
> - There is no direct mapping of stack registers to hard register
> numbers. If a stack register is used, we don't know where in the stack
> the value remains. So, if _any_ stack register is touched, the whole
> stack should be cleared (value, returning in x87 stack register should
> obviously be excluded).
Then, how to exclude the x87 stack register that returns the function return
value when we need to
Clear the whole stack?
I am a little confused here? Could you explain a little more details?
>
> - There is no x87 argument register. 32bit targets use MMX0-3 argument
> registers and return value in the XMM register. Please also note that
> complex values take two stack slots in x87 stack.
You mean the complex return value will be returned in two x87 registers?
thanks.
Qing
>
> Uros.
>
>> +
>> + if (num_of_st == 0)
