On 05.04.2011, at 06:54, Aurelien Jarno wrote:
> On Mon, Apr 04, 2011 at 04:32:24PM +0200, Alexander Graf wrote:
>> With the s390x target we use the deposit instruction to store 32bit values
>> into 64bit registers without clobbering the upper 32 bits.
>>
>> This specific operation can be optimized slightly by using the ext operation
>> instead of an explicit and in the deposit instruction. This patch adds that
>> special case to the generic deposit implementation.
>>
>> Signed-off-by: Alexander Graf <ag...@suse.de>
>> ---
>> tcg/tcg-op.h | 6 +++++-
>> 1 files changed, 5 insertions(+), 1 deletions(-)
>
> Have you really measuring a difference here? This should already be
> handled, at least on x86, by this code:
>
> if (TCG_TARGET_REG_BITS == 64) {
> if (val == 0xffffffffu) {
> tcg_out_ext32u(s, r0, r0);
> return;
> }
> if (val == (uint32_t)val) {
> /* AND with no high bits set can use a 32-bit operation. */
> rexw = 0;
> }
> }
I've certainly looked at the -d op logs and seen that instead of creating a
const tcg variable plus an AND there was now an extu opcode issued, yes. No
idea why the case up there didn't trigger.
Alex
