<snip>

On Thu, May 13, 2021 at 6:41 PM Chengwen Feng
[off-list ref] wrote:

quoted

Currently, the soc_kunpeng930 declares '-march=armv8.2-a+crypto+sve',
but some compiler doesn't recognize the march because it doesn't
support sve.

To solve this bug we use the following scheme:
1. Define 'march_base' tuple which defines support march, it should
arrange from lower to higher.
e.g. 'march_base' : ['-march=armv8-a', '-march=armv8.2-a'] 2. Define
'march_feature' tuple which defines support feature.
e.g. 'march_feature' : ['crypto', 'sve'] 3. Select the most suitable
march+feature combination based on 'march_base' and 'march_feature'
tuples.
4. Use the selected march+feature combination as the default
machine_args.

Fixes: 7cf32a22b240 ("config/arm: add Hisilicon kunpeng")

Signed-off-by: Chengwen Feng <redacted>
---
 config/arm/meson.build | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/config/arm/meson.build b/config/arm/meson.build index

3f34ec9..8551a80 100644

--- a/config/arm/meson.build
+++ b/config/arm/meson.build

@@ -149,7 +149,9 @@ implementer_hisilicon = {
     ],
     'part_number_config': {
         '0xd01': {
-            'machine_args': ['-march=armv8.2-a+crypto', '-mtune=tsv110'],
+            'march_base' : ['-march=armv8-a', '-march=armv8.2-a'],

If the compiler supports armv8.1-a, you need to choose armv8.1-a.

Another target has the same issue. Could you fix that all together as it is
generic problem in the existing infrastructure.

I think this needs to be more generic solution. IMO, the requirement is as follows:

1) We need to pick the most closest march_base supported by the compiler. For ex: If the SoC support v8.2 and the compiler supports v8.1, we need to pick v8.1
2) SoCs are allowed to support a base march version + hand picked features from the next 1 base marchs. i.e. armv8.x compliant implementation can include any features from armv8.(x + 1). Please refer to  Arm-ARM section A2 for more details. So, it is possible that the compiler supports a base march and a bunch of optional features from the next version. We need to test all the features allowed by the architecture and pick the ones that are supported in the compiler.

quoted

+            'march_feature' : ['crypto'],
+            'machine_args': ['-mtune=tsv110'],
             'flags': [
                 ['RTE_MACHINE', '"Kunpeng 920"'],
                 ['RTE_ARM_FEATURE_ATOMICS', true], @@ -158,7 +160,9

@@ implementer_hisilicon = {
             ]
         },
         '0xd02': {
-            'machine_args': ['-march=armv8.2-a+crypto+sve'],
+            'march_base' : ['-march=armv8-a', '-march=armv8.2-a'],
+            'march_feature' : ['crypto', 'sve'],
+            'machine_args': [],
             'flags': [
                 ['RTE_MACHINE', '"Kunpeng 930"'],
                 ['RTE_ARM_FEATURE_ATOMICS', true], @@ -449,8 +453,27

@@ else
     # add/overwrite flags in the proper order
     dpdk_flags = flags_common + implementer_config['flags'] +

part_number_config.get('flags', []) + soc_flags

+    # select the most suitable march+feature combination
+    machine_march = []
+    if part_number_config.has_key('march_base')
+        foreach arch: part_number_config['march_base']
+            if cc.has_argument(arch)
+                machine_march = arch # Set the higher supported arch as

possible

quoted

+            endif
+        endforeach
+    endif
+    if part_number_config.has_key('march_feature')
+        foreach feature: part_number_config['march_feature']
+            tmp_machine_march = machine_march + '+' + feature
+            if cc.has_argument(tmp_machine_march)
+                machine_march = tmp_machine_march # Set the more supported

feature as possible

quoted

+            endif
+        endforeach
+    endif
+
     # apply supported machine args
     machine_args = [] # Clear previous machine args
+    machine_args += machine_march
     foreach flag: part_number_config['machine_args']
         if cc.has_argument(flag)
             machine_args += flag
--
2.8.1