From bb3bf5bb538df67d3939974854c99608be21e135 Mon Sep 17 00:00:00 2001 From: Akhil Indurti Date: Thu, 26 Jul 2018 23:46:38 -0400 Subject: [PATCH] internal/cpu: expose ARM feature flags for FMA MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This change exposes feature flags needed to implement an FMA intrinsic on ARM CPUs via auxv's HWCAP bits. Specifically, it exposes HasVFPv4 to detect if an ARM processor has the fourth version of the vector floating point unit. The relevant instruction for this CL is VFMA, emitted in Go as FMULAD. Updates #26630. Change-Id: Ibbc04fb24c2b4d994f93762360f1a37bc6d83ff7 Reviewed-on: https://go-review.googlesource.com/c/126315 Run-TryBot: Martin Möhrmann TryBot-Result: Gobot Gobot Reviewed-by: Martin Möhrmann --- src/internal/cpu/cpu.go | 1 + src/internal/cpu/cpu_arm.go | 3 +++ 2 files changed, 4 insertions(+) diff --git a/src/internal/cpu/cpu.go b/src/internal/cpu/cpu.go index fdda880af4..1f3411cc72 100644 --- a/src/internal/cpu/cpu.go +++ b/src/internal/cpu/cpu.go @@ -76,6 +76,7 @@ var ARM arm // The struct is padded to avoid false sharing. type arm struct { _ CacheLinePad + HasVFPv4 bool HasIDIVA bool _ CacheLinePad } diff --git a/src/internal/cpu/cpu_arm.go b/src/internal/cpu/cpu_arm.go index 6a5b30580c..1c3e529190 100644 --- a/src/internal/cpu/cpu_arm.go +++ b/src/internal/cpu/cpu_arm.go @@ -15,15 +15,18 @@ var HWCap2 uint // HWCAP/HWCAP2 bits. These are exposed by Linux and FreeBSD. const ( + hwcap_VFPv4 = 1 << 16 hwcap_IDIVA = 1 << 17 ) func doinit() { options = []option{ + {"vfpv4", &ARM.HasVFPv4}, {"idiva", &ARM.HasIDIVA}, } // HWCAP feature bits + ARM.HasVFPv4 = isSet(HWCap, hwcap_VFPv4) ARM.HasIDIVA = isSet(HWCap, hwcap_IDIVA) } -- 2.51.0