Add Zclsd extension YAML

Author: Shehrozkashif

arch/ext/Zclsd.yaml

@@ -0,0 +1,18 @@
+$schema: "ext_schema.json#"
+kind: extension
+name: Zclsd
+long_name: Compressed Load/Store Pair for RV32
+description: |
+  This specification adds load and store instructions using register pairs. It does so by reusing existing instruction encodings which are RV64-only. The specification defines 16-bit encodings.
+  Load and store instructions will use the same definition of even-odd pairs as defined by the Zdinx extension.
+  The extension improves static code density, by replacing two separate load or store instructions with a single one. In addition, it can provide a performance improvement for implementations that can make use of a wider than XLEN memory interface.
+  Zclsd depends on Zilsd and Zca. It has overlapping encodings with Zcf and is thus incompatible with Zcf.
+type: unprivileged
+versions:
+  - version: "1.0"
+    state: ratified
+    ratification_date: "2025-02"
+    requires:
+      allOf:
+      - Zilsd
+      - Zca