nak/copy_prop: allow modified F16v2 and F16 sources

Seems to help a couple of shaders using MUFU.F16

Totals from 178 (0.01% of 1212873) affected shaders:
CodeSize: 5929856 -> 5925088 (-0.08%); split: -0.08%, +0.00%
Static cycle count: 8667151 -> 8665940 (-0.01%); split: -0.02%, +0.00%

Reviewed-by: Mel Henning <mhenning@darkrefraction.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/40897>

src/nouveau/compiler/nak/ir.rs

@@ -1315,6 +1315,16 @@ pub enum SrcType {
 
 impl SrcType {
     const DEFAULT: SrcType = SrcType::GPR;
+
+    pub fn is_fp16(&self) -> bool {
+        matches!(self, Self::F16 | Self::F16v2)
+    }
+
+    /// Checks if consuming a value has the same semantics in regards to ftz
+    /// and modifiers. E.g. F16v2 and F16 would return true here.
+    pub fn eq_ftz_mod(&self, other: Self) -> bool {
+        *self == other || (self.is_fp16() && other.is_fp16())
+    }
 }
 
 pub type SrcTypeList = AttrList<SrcType>;

src/nouveau/compiler/nak/opt_copy_prop.rs

@@ -301,7 +301,8 @@ impl<'a> CopyPropPass<'a> {
                     }
 
                     // If there are modifiers, the source types have to match
-                    if !entry.src.is_unmodified() && entry.src_type != src_type
+                    if !entry.src.is_unmodified()
+                        && !entry.src_type.eq_ftz_mod(src_type)
                     {
                         return;
                     }