tests/run-tests.py: Pass auto-detected architecture flags to mpy-cross.

This commit lets "run-tests.py" use the encoded architecture flags
provided by the interpreter when invoking "mpy-cross".

If architecture flags are detected, they're mapped into the necessary
strings needed by "mpy-cross"'s "-march-flags" argument, so that tests
will always use all available extensions reported by the target.

Currently this is limited to the RV32 platform, as it is the only one
that is making use of this facility as of now.  This also lets the QEMU
port remove forced arguments to "mpy-cross" when running the test suite.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

ports/qemu/Makefile

@@ -196,7 +196,7 @@ CFLAGS += $(SPECS_FRAGMENT)
 LDFLAGS += $(SPECS_FRAGMENT)
 endif
 
-RUN_TESTS_FULL_ARGS = -t execpty:"$(QEMU_SYSTEM) $(QEMU_ARGS) -serial pty -kernel ../ports/qemu/$<" --mpy-cross-flags='$(MPY_CROSS_FLAGS)' $(RUN_TESTS_ARGS)
+RUN_TESTS_FULL_ARGS = -t execpty:"$(QEMU_SYSTEM) $(QEMU_ARGS) -serial pty -kernel ../ports/qemu/$<" $(RUN_TESTS_ARGS)
 
 ################################################################################
 # Source files and libraries

tests/run-tests.py

@@ -22,6 +22,8 @@ TEST_TIMEOUT = float(os.environ.get("MICROPY_TEST_TIMEOUT", 30))
 # are guaranteed to always work, this one should though.
 BASEPATH = os.path.dirname(os.path.abspath(inspect.getsourcefile(lambda: None)))
 
+RV32_ARCH_FLAGS = {"zba": 1 << 0}
+
 
 def base_path(*p):
     return os.path.abspath(os.path.join(BASEPATH, *p)).replace("\\", "/")
@@ -382,6 +384,17 @@ def detect_inline_asm_arch(pyb, args):
     return None
 
 
+def map_rv32_arch_flags(flags):
+    mapped_flags = []
+    for extension, bit in RV32_ARCH_FLAGS.items():
+        if flags & bit:
+            mapped_flags.append(extension)
+        flags &= ~bit
+    if flags:
+        raise Exception("Unexpected flag bits set in value {}".format(flags))
+    return mapped_flags
+
+
 def detect_test_platform(pyb, args):
     # Run a script to detect various bits of information about the target test instance.
     output = run_feature_check(pyb, args, "target_info.py")
@@ -397,12 +410,18 @@ def detect_test_platform(pyb, args):
         thread = None
     float_prec = int(float_prec)
     unicode = unicode == "True"
+    if arch == "rv32imc":
+        arch_flags = map_rv32_arch_flags(int(arch_flags))
+    else:
+        arch_flags = None
 
     args.platform = platform
     args.arch = arch
+    args.arch_flags = arch_flags
     if arch and not args.mpy_cross_flags:
         args.mpy_cross_flags = "-march=" + arch
-    args.arch_flags = arch_flags
+        if arch_flags:
+            args.mpy_cross_flags += " -march-flags=" + ",".join(arch_flags)
     args.inlineasm_arch = inlineasm_arch
     args.build = build
     args.thread = thread
@@ -413,7 +432,8 @@ def detect_test_platform(pyb, args):
     print("platform={}".format(platform), end="")
     if arch:
         print(" arch={}".format(arch), end="")
-        print(" arch_flags={}".format(arch_flags), end="")
+        if arch_flags:
+            print(" arch_flags={}".format(",".join(arch_flags)), end="")
     if inlineasm_arch:
         print(" inlineasm={}".format(inlineasm_arch), end="")
     if thread: