diff --git a/src/freedreno/isa/isa.py b/src/freedreno/isa/isa.py
index 6323812d600..87e0c6badaf 100644
--- a/src/freedreno/isa/isa.py
+++ b/src/freedreno/isa/isa.py
@@ -400,6 +400,9 @@ class ISA(object):
         # Table of all bitsets:
         self.bitsets = {}
 
+        # Max needed bitsize for one instruction
+        self.bitsize = 0
+
         root = ElementTree.parse(xmlpath).getroot()
         self.parse_file(root)
         self.validate_isa()
@@ -435,6 +438,7 @@ class ISA(object):
             if b.size is not None:
                 dbg("toplevel: " + b.name)
                 self.roots[b.name] = b
+                self.bitsize = max(self.bitsize, b.size)
             else:
                 dbg("derived: " + b.name)
             self.bitsets[b.name] = b
@@ -487,4 +491,4 @@ class ISA(object):
 
         # TODO we should probably be able to look at the contexts where
         # an expression is evaluated and verify that it doesn't have any
-        # {VARNAME} references that would be unresolved at evaluation time
\ No newline at end of file
+        # {VARNAME} references that would be unresolved at evaluation time