Re: [Qemu-devel] [PATCH v10 01/10] target-avr: AVR cores support is added.

[Richard Henderson]

On 07/13/2016 05:35 AM, Michael Rolnik wrote:
> a. a helper function sets a flag within env

... and exits the cpu loop.

> b. cpu_get_tb_cpu_state introduces this flag, though tb.flags, for code
> generation by gen_intermediate_code
> c. the code is generated 

Yep.

> d. the flag remains to be set within env. Who clear it?

Presumably this flag is only usefully set for one instruction, the one we've
just determined accesses the registers.  So I'd clear the flag within
helper_fullwr / helper_fullrd.

In translate.c, when you notice tb->flags & HF_FULLACC is set, you'd interpret
one instruction and then exit the TB.  That way we'll start the next TB with
HF_FULLACC cleared.

Thus for a series of instructions like

        insn1
        insn2
        insn3 (writes to register)
        insn4
        branch

we will generate 3 TB:

TB1: (flags = 0)
        insn1
        insn2
        insn3
        insn4
        branch

TB2: (flags = HF_FULLACC)
        insn3

TB3: (flags = 0)
        insn4
        branch

Most importantly, when we come to execute TB1 for the second time, we will find
TB2 and TB3 quickly, with the right set of flags.


r~