From 562fd4d1886f04d21911c1e3305cfac1cb9f4d67 Mon Sep 17 00:00:00 2001
From: Kenneth Hoste <kenneth.hoste@ugent.be>
Date: Fri, 10 Jan 2025 13:24:57 +0100
Subject: [PATCH] fix logic for determining field to use to determine CPU flags

---
 init/arch_specs/eessi_arch_arm.spec |  2 ++
 init/eessi_archdetect.sh            | 17 +++++++++++++----
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/init/arch_specs/eessi_arch_arm.spec b/init/arch_specs/eessi_arch_arm.spec
index 595dddb800..c0d74bd4ad 100755
--- a/init/arch_specs/eessi_arch_arm.spec
+++ b/init/arch_specs/eessi_arch_arm.spec
@@ -1,4 +1,6 @@
 # ARM CPU architecture specifications (see https://gpages.juszkiewicz.com.pl/arm-socs-table/arm-socs.html for guidance)
+# CPU implementers: 0x41 (ARM), 0x46 (Fujitsu) - also see https://github.com/hrw/arm-socs-table/blob/main/data/socs.yml
+
 # Software path in EESSI 	| 'Vendor ID' or 'CPU implementer' 	| List of defining CPU features
 "aarch64/a64fx"		"0x46"		"asimdhp sve"		# Fujitsu A64FX
 "aarch64/neoverse_n1"	"ARM"		"asimddp"		# Ampere Altra
diff --git a/init/eessi_archdetect.sh b/init/eessi_archdetect.sh
index cca3764ee8..4fd979cea5 100755
--- a/init/eessi_archdetect.sh
+++ b/init/eessi_archdetect.sh
@@ -118,11 +118,20 @@ cpupath(){
     log "DEBUG" "cpupath: CPU vendor of host system: '$cpu_vendor'"
   
     # Identify the host CPU flags or features
-    local cpu_flag_tag='flags'
     # cpuinfo systems print different line identifiers, eg features, instead of flags
-    [ "${cpu_vendor}" == "ARM" ] && cpu_flag_tag='flags'
-    [ "${machine_type}" == "aarch64" ] && [ "${cpu_flag_tag}" == "flags" ] && cpu_flag_tag='features'
-    [ "${machine_type}" == "ppc64le" ] && cpu_flag_tag='cpu'
+    local cpu_flag_tag;
+    if [ "${cpu_vendor}" == "ARM" ]; then
+        # if CPU vendor field is ARM, then we should be able to determine CPU microarchitecture based on 'flags' field
+        cpu_flag_tag='flags'
+    # if 64-bit Arm CPU without "ARM" as vendor ID, we need to take into account 'features' field
+    elif [ "${machine_type}" == "aarch64" ]; then
+        cpu_flag_tag='features'
+    # on 64-bit POWER, we need to look at 'cpu' field
+    elif [ "${machine_type}" == "ppc64le" ]; then
+        cpu_flag_tag='cpu'
+    else
+        cpu_flag_tag='flags'
+    fi
   
     local cpu_flags=$(get_cpuinfo "$cpu_flag_tag")
     log "DEBUG" "cpupath: CPU flags of host system: '$cpu_flags'"