[v3][PATCH 2/2] goarch.bbclass: use MACHINEOVERRIDES and simplify go_map_arm()

[Mark Asselstine <mark.asselstine@windriver.com>]

Per https://github.com/golang/go/wiki/GoArm we need to set GOARM when
cross building for ARMv5, ARMv6 and ARMv7. The current approach of
using TUNE_FEATURES can be error prone, as we can see today when
attempting to build for Cortex-A7 which results in GOARM=''.

Since the value of MACHINEOVERRIDES already consolidates the values of
TUNE_FEATURES into something more consistent we can use the overrides
mechanism to set GOARM, leaving just a little bit of logic in
go_map_arm() to trigger off the arch (basically target vs host)
for the setting of GOARM.

Signed-off-by: Mark Asselstine <mark.asselstine@windriver.com>
---

V2
* Cover all ARMv7 Cortex* variants

V3
* Switch to using MACHINEOVERRIDES/overrides mechanism

 meta/classes/goarch.bbclass | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/meta/classes/goarch.bbclass b/meta/classes/goarch.bbclass
index 39fea5e..8fdb443 100644
--- a/meta/classes/goarch.bbclass
+++ b/meta/classes/goarch.bbclass
@@ -3,18 +3,26 @@ BUILD_GOARCH = "${@go_map_arch(d.getVar('BUILD_ARCH'), d)}"
 BUILD_GOTUPLE = "${BUILD_GOOS}_${BUILD_GOARCH}"
 HOST_GOOS = "${@go_map_os(d.getVar('HOST_OS'), d)}"
 HOST_GOARCH = "${@go_map_arch(d.getVar('HOST_ARCH'), d)}"
-HOST_GOARM = "${@go_map_arm(d.getVar('HOST_ARCH'), d.getVar('TUNE_FEATURES'), d)}"
+HOST_GOARM = "${@go_map_arm(d.getVar('HOST_ARCH'), d.getVar('BASE_GOARM'), d)}"
 HOST_GO386 = "${@go_map_386(d.getVar('HOST_ARCH'), d.getVar('TUNE_FEATURES'), d)}"
 HOST_GOMIPS = "${@go_map_mips(d.getVar('HOST_ARCH'), d.getVar('TUNE_FEATURES'), d)}"
 HOST_GOTUPLE = "${HOST_GOOS}_${HOST_GOARCH}"
 TARGET_GOOS = "${@go_map_os(d.getVar('TARGET_OS'), d)}"
 TARGET_GOARCH = "${@go_map_arch(d.getVar('TARGET_ARCH'), d)}"
-TARGET_GOARM = "${@go_map_arm(d.getVar('TARGET_ARCH'), d.getVar('TUNE_FEATURES'), d)}"
+TARGET_GOARM = "${@go_map_arm(d.getVar('TARGET_ARCH'), d.getVar('BASE_GOARM'), d)}"
 TARGET_GO386 = "${@go_map_386(d.getVar('TARGET_ARCH'), d.getVar('TUNE_FEATURES'), d)}"
 TARGET_GOMIPS = "${@go_map_mips(d.getVar('TARGET_ARCH'), d.getVar('TUNE_FEATURES'), d)}"
 TARGET_GOTUPLE = "${TARGET_GOOS}_${TARGET_GOARCH}"
 GO_BUILD_BINDIR = "${@['bin/${HOST_GOTUPLE}','bin'][d.getVar('BUILD_GOTUPLE') == d.getVar('HOST_GOTUPLE')]}"
 
+# Use the MACHINEOVERRIDES to map ARM CPU architecture passed to GO via GOARM.
+# This is combined with *_ARCH to set HOST_GOARM and TARGET_GOARM.
+BASE_GOARM = ''
+BASE_GOARM_armv7ve = '7'
+BASE_GOARM_armv7a = '7'
+BASE_GOARM_armv6 = '6'
+BASE_GOARM_armv5 = '5'
+
 # Go supports dynamic linking on a limited set of architectures.
 # See the supportsDynlink function in go/src/cmd/compile/internal/gc/main.go
 GO_DYNLINK = ""
@@ -74,12 +82,7 @@ def go_map_arch(a, d):
 def go_map_arm(a, f, d):
     import re
     if re.match('arm.*', a):
-        if 'armv7' in f:
-            return '7'
-        elif 'armv6' in f:
-            return '6'
-        elif 'armv5' in f:
-            return '5'
+        return f
     return ''
 
 def go_map_386(a, f, d):
-- 
2.7.4