On 09/08/2011 03:08 PM, Richard Sandiford wrote:
> Bernd Schmidt <ber...@codesourcery.com> writes:
>> @@ -10227,17 +10236,30 @@ mips_expand_prologue (void)
>> emit_insn (gen_blockage ());
>> }
>>
>> -/* Emit instructions to restore register REG from slot MEM. */
>> +/* Emit instructions to restore register REG from slot MEM. Also update
>> + the cfa_restores list. */
>>
>> static void
>> mips_restore_reg (rtx reg, rtx mem)
>> {
>> + rtx orig_reg = reg;
>> + rtx last;
>> +
>> /* There's no MIPS16 instruction to load $31 directly. Load into
>> $7 instead and adjust the return insn appropriately. */
>> if (TARGET_MIPS16 && REGNO (reg) == RETURN_ADDR_REGNUM)
>> reg = gen_rtx_REG (GET_MODE (reg), GP_REG_FIRST + 7);
>>
>> mips_emit_save_slot_move (reg, mem, MIPS_EPILOGUE_TEMP (GET_MODE (reg)));
>> + if (reg == orig_reg)
>> + cfa_restores = alloc_reg_note (REG_CFA_RESTORE, reg, cfa_restores);
>> +
>> + if (!frame_pointer_needed || REGNO (reg) != HARD_FRAME_POINTER_REGNUM)
>> + return;
>> + last = get_last_insn ();
>> + add_reg_note (last, REG_CFA_DEF_CFA, plus_constant (stack_pointer_rtx,
>> + cfa_sp_offset));
>> + RTX_FRAME_RELATED_P (last) = 1;
>
> I suppose I still don't get why this is OK but this:
>
>> @@ -10324,12 +10350,26 @@ mips_expand_epilogue (bool sibcall_p)
>> if (!TARGET_MIPS16)
>> target = stack_pointer_rtx;
>>
>> - emit_insn (gen_add3_insn (target, base, adjust));
>> + insn = emit_insn (gen_add3_insn (target, base, adjust));
>> + if (!frame_pointer_needed && target == stack_pointer_rtx)
>> + {
>> + RTX_FRAME_RELATED_P (insn) = 1;
>> + add_reg_note (insn, REG_CFA_DEF_CFA,
>> + plus_constant (stack_pointer_rtx, step2));
>> + }
>
> triggered ICEs without the !frame_pointer_required. I think I need
> to play around with it a bit before I understand enough to review.
> I'll try to find time this weekend.
I'd be curious to understand in what situation the second hunk causes
failures without frame_pointer_required. But as I'm supposed to be on
holiday atm I can't spend any real time on it til I get back. ;-)
That said, the first hunk causes the CFA to get swapped back to the
stack pointer on the very insn that restores the frame pointer.
Which to me looks to do the right thing in all situations. Is there
a different window you are worried about?
r~
