Improve wasmi_ir2 operators field layouts (#1670)

* change cmp+select operator fields

With this change all cmp+selector operators start with a common sequence of fields all of type `Slot`: result, val_true, val_false.

* change cmp+branch operator field layout

Now all cmp+branch operators start with their common offset: BranchOffset field.

Author: Robbepop

crates/ir2/build/op.rs

@@ -1336,7 +1336,7 @@ impl CmpBranchOp {
     }
 
     pub fn fields(&self) -> [Field; 3] {
-        [self.lhs_field(), self.rhs_field(), self.offset_field()]
+        [self.offset_field(), self.lhs_field(), self.rhs_field()]
     }
 }
 
@@ -1375,10 +1375,10 @@ impl CmpSelectOp {
     pub fn fields(&self) -> [Field; 5] {
         [
             self.result_field(),
-            self.lhs_field(),
-            self.rhs_field(),
             self.val_true_field(),
             self.val_false_field(),
+            self.lhs_field(),
+            self.rhs_field(),
         ]
     }
 }

crates/ir2/src/decode/op.rs

@@ -75,9 +75,9 @@ where
 
 #[derive(Copy, Clone)]
 pub struct CmpBranchOp<Lhs, Rhs> {
+    pub offset: BranchOffset,
     pub lhs: Lhs,
     pub rhs: Rhs,
-    pub offset: BranchOffset,
 }
 
 impl<Lhs, Rhs> Decode for CmpBranchOp<Lhs, Rhs>
@@ -97,10 +97,10 @@ where
 #[derive(Copy, Clone)]
 pub struct CmpSelectOp<Lhs, Rhs> {
     pub result: Slot,
-    pub lhs: Lhs,
-    pub rhs: Rhs,
     pub val_true: Slot,
     pub val_false: Slot,
+    pub lhs: Lhs,
+    pub rhs: Rhs,
 }
 
 impl<Lhs, Rhs> Decode for CmpSelectOp<Lhs, Rhs>
@@ -111,10 +111,10 @@ where
     fn decode<D: Decoder>(decoder: &mut D) -> Result<Self, DecodeError> {
         Ok(Self {
             result: Decode::decode(decoder)?,
-            lhs: Decode::decode(decoder)?,
-            rhs: Decode::decode(decoder)?,
             val_true: Decode::decode(decoder)?,
             val_false: Decode::decode(decoder)?,
+            lhs: Decode::decode(decoder)?,
+            rhs: Decode::decode(decoder)?,
         })
     }
 }