cpu: add support for sve2 detection

Fixes golang/go#66952

Change-Id: Idaf2ce3b09baf33cf29079677a83a51ea9c4b255
GitHub-Last-Rev: eac00886d1370e7a0fa7a6cb18299c5e7b6e21e4
GitHub-Pull-Request: golang/sys#193
Reviewed-on: https://go-review.googlesource.com/c/sys/+/580655
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>

cpu/cpu_linux_arm64.go

@@ -35,6 +35,8 @@ const (
 	hwcap_SHA512   = 1 << 21
 	hwcap_SVE      = 1 << 22
 	hwcap_ASIMDFHM = 1 << 23
+
+	hwcap2_SVE2 = 1 << 1
 )
 
 // linuxKernelCanEmulateCPUID reports whether we're running
@@ -104,6 +106,9 @@ func doinit() {
 	ARM64.HasSHA512 = isSet(hwCap, hwcap_SHA512)
 	ARM64.HasSVE = isSet(hwCap, hwcap_SVE)
 	ARM64.HasASIMDFHM = isSet(hwCap, hwcap_ASIMDFHM)
+
+	// HWCAP2 feature bits
+	ARM64.HasSVE2 = isSet(hwCap2, hwcap2_SVE2)
 }
 
 func isSet(hwc uint, value uint) bool {