Because the three alternatives are monotonic, we don't
need to keep a couple of bitmasks, just identify the
strongest alternative at startup.
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
util/bufferiszero.c | 56 ++++++++++++++++++---------------------------
1 file changed, 22 insertions(+), 34 deletions(-)
diff --git a/util/bufferiszero.c b/util/bufferiszero.c
index 61ea59d2e0..9b338f7be5 100644
--- a/util/bufferiszero.c
+++ b/util/bufferiszero.c
@@ -180,51 +180,39 @@ buffer_zero_avx2(const void *buf, size_t len)
}
#endif /* CONFIG_AVX2_OPT */
-
-
-static unsigned __attribute__((noinline))
-select_accel_cpuinfo(unsigned info)
-{
- /* Array is sorted in order of algorithm preference. */
- static const struct {
- unsigned bit;
- biz_accel_fn fn;
- } all[] = {
+static biz_accel_fn const accel_table[] = {
+ buffer_is_zero_int_ge256,
+ buffer_zero_sse2,
#ifdef CONFIG_AVX2_OPT
- { CPUINFO_AVX2, buffer_zero_avx2 },
+ buffer_zero_avx2,
#endif
- { CPUINFO_SSE2, buffer_zero_sse2 },
- { CPUINFO_ALWAYS, buffer_is_zero_int_ge256 },
- };
-
- for (unsigned i = 0; i < ARRAY_SIZE(all); ++i) {
- if (info & all[i].bit) {
- buffer_is_zero_accel = all[i].fn;
- return all[i].bit;
- }
- }
- return 0;
-}
-
-static unsigned used_accel;
+};
+static unsigned accel_index;
static void __attribute__((constructor)) init_accel(void)
{
- used_accel = select_accel_cpuinfo(cpuinfo_init());
+ unsigned info = cpuinfo_init();
+ unsigned index = (info & CPUINFO_SSE2 ? 1 : 0);
+
+#ifdef CONFIG_AVX2_OPT
+ if (info & CPUINFO_AVX2) {
+ index = 2;
+ }
+#endif
+
+ accel_index = index;
+ buffer_is_zero_accel = accel_table[index];
}
#define INIT_ACCEL NULL
bool test_buffer_is_zero_next_accel(void)
{
- /*
- * Accumulate the accelerators that we've already tested, and
- * remove them from the set to test this round. We'll get back
- * a zero from select_accel_cpuinfo when there are no more.
- */
- unsigned used = select_accel_cpuinfo(cpuinfo & ~used_accel);
- used_accel |= used;
- return used;
+ if (accel_index != 0) {
+ buffer_is_zero_accel = accel_table[--accel_index];
+ return true;
+ }
+ return false;
}
#else
bool test_buffer_is_zero_next_accel(void)
--
2.34.1
