[compile] Parse compile range cache keys as Range during cache loading. (#30516)

Signed-off-by: zhxchen17 <zhxchen17@fb.com>

vllm/compilation/backends.py

@@ -141,7 +141,25 @@ class CompilerManager:
                 # we use ast.literal_eval to parse the data
                 # because it is a safe way to parse Python literals.
                 # do not use eval(), it is unsafe.
-                self.cache = ast.literal_eval(f.read())
+                cache = ast.literal_eval(f.read())
+
+            def check_type(value, ty):
+                if not isinstance(value, ty):
+                    raise TypeError(f"Expected {ty} but got {type(value)} for {value}")
+
+            def parse_key(key: Any) -> tuple[Range, int, str]:
+                range_tuple, graph_index, compiler_name = key
+                check_type(graph_index, int)
+                check_type(compiler_name, str)
+                if isinstance(range_tuple, tuple):
+                    start, end = range_tuple
+                    check_type(start, int)
+                    check_type(end, int)
+                    range_tuple = Range(start=start, end=end)
+                check_type(range_tuple, Range)
+                return range_tuple, graph_index, compiler_name
+
+            self.cache = {parse_key(key): value for key, value in cache.items()}
 
         self.compiler.initialize_cache(
             cache_dir=cache_dir, disable_cache=disable_cache, prefix=prefix