Add A32 support in CI

Add A32 support in CI.

Currently choose Cortex-A32 as test target because it only supports
AArch32. Moreover, Cortex-A32 has Armv8-A Cryptographic Extension,
which is an ideal target for testing Cryptographic Extension.

.github/workflows/github_actions.yml

@@ -55,7 +55,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        arch_with_features: [{arch: armv7, feature: none}, {arch: aarch64, feature: none}, {arch: aarch64, feature: crypto+crc}]
+        arch_with_features: [{arch: armv7, feature: none}, {arch: aarch64, feature: none}, {arch: aarch64, feature: crypto+crc}, {arch: armv7, feature: none, set_a32: 1}]
         cxx_compiler: [g++-10, clang++-11]
     steps:
       - name: checkout code
@@ -74,7 +74,7 @@ jobs:
             apt-get install -q -y "${{ matrix.cxx_compiler }}" make
             apt-get install -q -y gcc
           run: |
-            make FEATURE=${{ matrix.arch_with_features.feature }} check
+            make FEATURE=${{ matrix.arch_with_features.feature }} A32=${{ matrix.arch_with_features.set_a32 }} check
 
   host_win_msvc:
     runs-on: windows-2022

Makefile

@@ -34,7 +34,9 @@ ifeq ($(processor),$(filter $(processor),aarch64 arm64))
 else ifeq ($(processor),$(filter $(processor),i386 x86_64))
     ARCH_CFLAGS = -maes -mpclmul -mssse3 -msse4.2
 else ifeq ($(processor),$(filter $(processor),arm armv7 armv7l))
-    ARCH_CFLAGS = -mfpu=neon
+    ifndef ARCH_CFLAGS
+        ARCH_CFLAGS = -mfpu=neon
+    endif
 else
     $(error Unsupported architecture)
 endif

README.md

@@ -126,6 +126,13 @@ or
 ```shell
 $ make CROSS_COMPILE=arm-linux-gnueabihf- check # ARMv7-A
 ```
+or
+``` shell
+$ make \
+  CROSS_COMPILE=arm-linux-gnueabihf- \
+  ARCH_CFLAGS="-mcpu=cortex-a32 -mfpu=neon-fp-armv8" \
+  check # ARMv8-A running in 32-bit mode, i.e., A32 instruction set
+```
 
 Check the details via [Test Suite for SSE2NEON](tests/README.md).