nak: Fold Src::fold_imm() into the legalization pass

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34818>

src/nouveau/compiler/nak/ir.rs

@@ -1197,19 +1197,6 @@ impl Src {
         })
     }
 
-    pub fn fold_imm(&self, src_type: SrcType) -> Src {
-        // Don't fold Zero
-        if !matches!(self.src_ref, SrcRef::Imm32(_)) {
-            return *self;
-        }
-
-        if let Some(u) = self.as_u32(src_type) {
-            u.into()
-        } else {
-            *self
-        }
-    }
-
     pub fn as_ssa(&self) -> Option<&SSARef> {
         if self.src_mod.is_none() {
             self.src_ref.as_ssa()

src/nouveau/compiler/nak/legalize.rs

@@ -387,7 +387,15 @@ fn legalize_instr(
 
     let src_types = instr.src_types();
     for (i, src) in instr.srcs_mut().iter_mut().enumerate() {
-        *src = src.fold_imm(src_types[i]);
+        if matches!(src.src_ref, SrcRef::Imm32(_)) {
+            // Fold modifiers on Imm32 sources whenever possible.  Not all
+            // instructions suppport modifiers and immediates at the same time.
+            // But leave Zero sources alone as we don't want to make things
+            // immediates that could just be rZ.
+            if let Some(u) = src.as_u32(src_types[i]) {
+                *src = u.into();
+            }
+        }
         b.copy_src_if_not_same_file(src);
 
         if !block_uniform {