nak/legalize: Add a helper for lowering ineg

This is similar to the helper we have for lowering float modifiers.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34536>

src/nouveau/compiler/nak/legalize.rs

@@ -269,6 +269,29 @@ pub trait LegalizeBuildHelpers: SSABuilder {
         }
     }
 
+    fn copy_alu_src_and_lower_ineg(
+        &mut self,
+        src: &mut Src,
+        src_type: SrcType,
+    ) {
+        assert!(src_type == SrcType::I32);
+        let val = self.alloc_ssa(RegFile::GPR, 1);
+        if self.sm() >= 70 {
+            self.push_op(OpIAdd3 {
+                srcs: [Src::new_zero(), *src, Src::new_zero()],
+                overflow: [Dst::None; 2],
+                dst: val.into(),
+            });
+        } else {
+            self.push_op(OpIAdd2 {
+                dst: val.into(),
+                carry_out: Dst::None,
+                srcs: [Src::new_zero(), *src],
+            });
+        }
+        *src = val.into();
+    }
+
     fn copy_ssa_ref_if_uniform(&mut self, ssa_ref: &mut SSARef) {
         for ssa in &mut ssa_ref[..] {
             if ssa.is_uniform() {

src/nouveau/compiler/nak/sm50.rs

@@ -1265,13 +1265,7 @@ impl SM50Op for OpIAdd2 {
         swap_srcs_if_not_reg(src0, src1, GPR);
         if src0.src_mod.is_ineg() && src1.src_mod.is_ineg() {
             assert!(self.carry_out.is_none());
-            let val = b.alloc_ssa(GPR, 1);
+            b.copy_alu_src_and_lower_ineg(src0, SrcType::I32);
-            b.push_op(OpIAdd2 {
-                dst: val.into(),
-                carry_out: Dst::None,
-                srcs: [Src::new_zero(), *src0],
-            });
-            *src0 = val.into();
         }
         b.copy_alu_src_if_not_reg(src0, GPR, SrcType::I32);
         if !self.carry_out.is_none() {

src/nouveau/compiler/nak/sm70_encode.rs

@@ -1350,13 +1350,7 @@ impl SM70Op for OpIAdd3 {
         if !src0.src_mod.is_none() && !src1.src_mod.is_none() {
             assert!(self.overflow[0].is_none());
             assert!(self.overflow[1].is_none());
-            let val = b.alloc_ssa(gpr, 1);
+            b.copy_alu_src_and_lower_ineg(src0, SrcType::I32);
-            b.push_op(OpIAdd3 {
-                srcs: [Src::new_zero(), *src0, Src::new_zero()],
-                overflow: [Dst::None; 2],
-                dst: val.into(),
-            });
-            *src0 = val.into();
         }
         b.copy_alu_src_if_not_reg(src0, gpr, SrcType::I32);
         b.copy_alu_src_if_both_not_reg(src1, src2, gpr, SrcType::I32);