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Hexagon (target/hexagon) Short-circuit packet predicate writes

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In certain cases, we can avoid the overhead of writing to hex_new_pred_value
and write directly to hex_pred.  We consider predicate reads/writes when
computing ctx->need_commit.  The get_result_pred() function uses this
field to decide between hex_new_pred_value and hex_pred.  Then, we can
early-exit from gen_pred_writes.

Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230427230012.3800327-13-tsimpson@quicinc.com>
This commit is contained in:
Taylor Simpson 2023-04-27 16:00:03 -07:00
parent d54c56156f
commit 455e169d7c
3 changed files with 24 additions and 6 deletions
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14
target/hexagon/translate.c
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@ -386,6 +386,14 @@ static bool need_commit(DisasContext *ctx)
}
}
/* Check for overlap between predicate reads and writes */
for (int i = 0; i < ctx->preg_log_idx; i++) {
int pnum = ctx->preg_log[i];
if (test_bit(pnum, ctx->pregs_read)) {
return true;
}
}
return false;
}
@ -503,7 +511,7 @@ static void gen_start_packet(DisasContext *ctx)
* Preload the predicated pred registers into hex_new_pred_value[pred_num]
* Only endloop instructions conditionally write to pred registers
*/
if (pkt->pkt_has_endloop) {
if (ctx->need_commit && pkt->pkt_has_endloop) {
for (int i = 0; i < ctx->preg_log_idx; i++) {
int pred_num = ctx->preg_log[i];
tcg_gen_mov_tl(hex_new_pred_value[pred_num], hex_pred[pred_num]);
@ -622,8 +630,8 @@ static void gen_reg_writes(DisasContext *ctx)
static void gen_pred_writes(DisasContext *ctx)
{
/* Early exit if the log is empty */
if (!ctx->preg_log_idx) {
/* Early exit if not needed or the log is empty */
if (!ctx->need_commit || !ctx->preg_log_idx) {
return;
}