1 files changed, 81 insertions, 0 deletions

diff --git a/meta/lib/oe/tune.py b/meta/lib/oe/tune.py
new file mode 100644
index 0000000000..7fda19430d
--- /dev/null
+++ b/meta/lib/oe/tune.py
@@ -0,0 +1,81 @@
+#
+# Copyright OpenEmbedded Contributors
+#
+# SPDX-License-Identifier: GPL-2.0-only
+#
+
+# riscv_isa_to_tune(isa)
+#
+# Automatically translate a RISC-V ISA string to TUNE_FEATURES
+#
+# Abbreviations, such as rv32g -> rv32imaffd_zicsr_zifencei are supported.
+#
+# Profiles, such as rva22u64, are NOT supported, you must use ISA strings.
+#
+def riscv_isa_to_tune(isa):
+    _isa = isa.lower()
+
+    feature = []
+    iter = 0
+
+    # rv or riscv
+    if _isa[iter:].startswith('rv'):
+        feature.append('rv')
+        iter = iter + 2
+    elif _isa[iter:].startswith('riscv'):
+        feature.append('rv')
+        iter = iter + 5
+    else:
+        # Not a risc-v ISA!
+        return _isa
+
+    while (_isa[iter:]):
+        # Skip _ and whitespace
+        if _isa[iter] == '_' or _isa[iter].isspace():
+            iter = iter + 1
+            continue
+
+        # Length, just capture numbers here
+        if _isa[iter].isdigit():
+            iter_end = iter
+            while iter_end < len(_isa) and _isa[iter_end].isdigit():
+                iter_end = iter_end + 1
+
+            feature.append(_isa[iter:iter_end])
+            iter = iter_end
+            continue
+
+        # Typically i, e or g is next, followed by extensions.
+        # Extensions are single character, except for Z, Ss, Sh, Sm, Sv, and X
+
+        # If the extension starts with 'Z', 'S' or 'X' use the name until the next _, whitespace or end
+        if _isa[iter] in ['z', 's', 'x']:
+            ext_type = _isa[iter]
+            iter_end = iter + 1
+
+            # Multicharacter extension, these are supposed to have a _ before the next multicharacter extension
+            # See 37.4 and 37.5:
+            # 37.4: Underscores "_" may be used to separate ISA extensions...
+            # 37.5: All multi-letter extensions ... must be separated from other multi-letter extensions by an underscore...
+            # Some extensions permit only alphabetic characters, while others allow alphanumeric chartacters
+            while iter_end < len(_isa) and _isa[iter_end] != "_" and not _isa[iter_end].isspace():
+                iter_end = iter_end + 1
+
+            feature.append(_isa[iter:iter_end])
+            iter = iter_end
+            continue
+
+        # 'g' is special, it's an abbreviation for imafd_zicsr_zifencei
+        # When expanding the abbreviation, any additional letters must appear before the _z* extensions
+        if _isa[iter] == 'g':
+            _isa = 'imafd' + _isa[iter+1:] + '_zicsr_zifencei'
+            iter = 0
+            continue
+
+        feature.append(_isa[iter])
+        iter = iter + 1
+        continue
+
+    # Eliminate duplicates, but preserve the order
+    feature = list(dict.fromkeys(feature))
+    return ' '.join(feature)