1 files changed, 10 insertions, 0 deletions
diff --git a/riscv/insns/cls.h b/riscv/insns/cls.h
new file mode 100644
index 00000000..3d80b618
--- /dev/null
+++ b/riscv/insns/cls.h
@@ -0,0 +1,10 @@
+require_extension('P');
+reg_t x = xlen - 1;
+reg_t msb = (RS1 >> (xlen - 1)) & 1;
+for (int i = 0; i < xlen - 1; i++) {
+  if (msb != ((RS1 >> (xlen - i - 2)) & 1)) {
+    x = i;
+    break;
+  }
+}
+WRITE_RD(sext_xlen(x));
+\ No newline at end of file