From 250a87d5561a7212fe43357b084f69992eced75a Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Mon, 21 Nov 2016 12:06:26 +0100 Subject: [PATCH] target-s390x: Avoid a loop for popcnt Signed-off-by: Richard Henderson --- target/s390x/int_helper.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/target/s390x/int_helper.c b/target/s390x/int_helper.c index 5bc470bdc7..f26f36a904 100644 --- a/target/s390x/int_helper.c +++ b/target/s390x/int_helper.c @@ -137,14 +137,11 @@ uint64_t HELPER(cvd)(int32_t reg) return dec; } -uint64_t HELPER(popcnt)(uint64_t r2) +uint64_t HELPER(popcnt)(uint64_t val) { - uint64_t ret = 0; - int i; - - for (i = 0; i < 64; i += 8) { - uint64_t t = ctpop32((r2 >> i) & 0xff); - ret |= t << i; - } - return ret; + /* Note that we don't fold past bytes. */ + val = (val & 0x5555555555555555ULL) + ((val >> 1) & 0x5555555555555555ULL); + val = (val & 0x3333333333333333ULL) + ((val >> 2) & 0x3333333333333333ULL); + val = (val + (val >> 4)) & 0x0f0f0f0f0f0f0f0fULL; + return val; }