nak/calc_instr_deps: Set a delay of 13 for flow ops pre-Volta

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30381>

src/nouveau/compiler/nak/calc_instr_deps.rs

@@ -476,6 +476,10 @@ fn exec_latency(sm: u8, op: &Op) -> u32 {
             // CCTL.C needs 8, CCTL.I needs 11
             11
         }
+        _ if sm < 70 && (op.is_crs_push() || op.is_branch()) => {
+            // pre-Volta needs a delay for control-flow ops
+            13
+        }
         // Op::DepBar(_) => 4,
         _ => 1, // TODO: co-issue
     }

src/nouveau/compiler/nak/ir.rs

@@ -5961,6 +5961,26 @@ pub enum Op {
 }
 impl_display_for_op!(Op);
 
+impl Op {
+    pub fn is_crs_push(&self) -> bool {
+        match self {
+            Op::SSy(_) | Op::PBk(_) | Op::PCnt(_) => true,
+            _ => false,
+        }
+    }
+
+    pub fn is_branch(&self) -> bool {
+        match self {
+            Op::Bra(_)
+            | Op::Sync(_)
+            | Op::Brk(_)
+            | Op::Cont(_)
+            | Op::Exit(_) => true,
+            _ => false,
+        }
+    }
+}
+
 #[derive(Clone, Copy, Eq, Hash, PartialEq)]
 pub enum PredRef {
     None,
@@ -6254,14 +6274,7 @@ impl Instr {
     }
 
     pub fn is_branch(&self) -> bool {
-        match &self.op {
+        self.op.is_branch()
-            Op::Bra(_)
-            | Op::Sync(_)
-            | Op::Brk(_)
-            | Op::Cont(_)
-            | Op::Exit(_) => true,
-            _ => false,
-        }
     }
 
     pub fn uses_global_mem(&self) -> bool {