On Sat, Dec 19, 2009 at 5:47 PM, Richard Henderson <r...@twiddle.net> wrote:
> 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?
Long time ago I tried the same change, but the generated code was not
correct. But now it seems to work.
>>> - 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.
Maybe it's faster on real CPUs. On my machine I don't see any
difference. I timed the following program:
#include <stdio.h>
#include <stdlib.h>
#define N 100000000
int main(int argc, char **argv)
{
unsigned int i;
if (atoi(argv[1])) {
for (i = 0; i < N; i++) {
asm volatile ("cmp %g1, 0");
}
} else {
for (i = 0; i < N; i++) {
asm volatile ("tst %g1");
}
}
return 0;
}
