nak: Simplify shl64 lowering on Maxwell

Signed-off-by: Lorenzo Rossi <snowycoder@gmail.com>
Reviewed-by: Mel Henning <mhenning@darkrefraction.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34137>

src/nouveau/compiler/nak/builder.rs

@@ -161,21 +161,16 @@ pub trait SSABuilder: Builder {
             });
         } else {
             // On Maxwell and earlier, shf.l doesn't work without .high so we
-            // have to use a regular 32-bit shift here.  32-bit shift doesn't
-            // have the NIR wrap semantics so we need to wrap manually.
-            let shift = if let SrcRef::Imm32(imm) = shift.src_ref {
-                (imm & 0x3f).into()
-            } else {
-                self.lop2(LogicOp2::And, shift, 0x3f.into()).into()
-            };
+            // have to use only the high parts, hard-coding the lower parts
+            // to rZ
             self.push_op(OpShf {
                 dst: dst[0].into(),
                 low: 0.into(),
                 high: x[0].into(),
                 shift,
                 right: false,
-                wrap: false,
-                data_type: IntType::U32,
+                wrap: true,
+                data_type: IntType::U64,
                 dst_high: true,
             });
         }