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Date: Sat, 19 Dec 2009 09:47:52 -0800
From: Richard Henderson <rth@twiddle.net>
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Subject: Re: [Qemu-devel] [PATCH 5/7] tcg-sparc: Implement setcond, movcond,
	setcond2, brcond2.
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To: Blue Swirl <blauwirbel@gmail.com>
Cc: qemu-devel@nongnu.org

On 12/19/2009 02:31 AM, Blue Swirl wrote:
>>   static inline void tcg_out_movi_imm32(TCGContext *s, int ret, uint32_t arg)
>>   {
>> -    if (check_fit_tl(arg, 12))
>> +    if (check_fit_tl(arg, 13))
>>          tcg_out_movi_imm13(s, ret, arg);
>
> IIRC sign extension prevents this.

Pardon?  check_fit_tl checks a signed value, the OR opcode provides one. 
  Where's the conflict?

>> -    if (const_arg2&&  arg2 == 0)
>> -        /* orcc %g0, r, %g0 */
>> -        tcg_out_arith(s, TCG_REG_G0, TCG_REG_G0, arg1, ARITH_ORCC);
>> -    else
>> -        /* subcc r1, r2, %g0 */
>> -        tcg_out_arith(s, TCG_REG_G0, arg1, arg2, ARITH_SUBCC);
>> -    tcg_out_branch_i32(s, tcg_cond_to_bcond[cond], label_index);
>> +    tcg_out_cmp(s, arg1, arg2, const_arg2);
>
> What's wrong with 'orcc' (produces the synthetic instruction 'tst')?

What result does "orcc" give that isn't produced by "subcc"?  Unlike 
i386 where "test x,x" is one byte smaller than "cmp $0,x", it seems to 
me there's no reason to distingish the arg2 == constant zero case on sparc.


r~