Refactor and turn on lowering for extend-add-pairwise

cranelift/codegen/meta/src/shared/instructions.rs

@@ -4114,8 +4114,9 @@ pub(crate) fn define(
         Inst::new(
             "uwiden_high",
             r#"
-        Lane-wise integer extended pairwise addition producing extended results
-        (twice wider results than the input)
+            Widen the high lanes of `x` using unsigned extension.
+
+            This will double the lane width and halve the number of lanes.
             "#,
             &formats.unary,
         )
@@ -4123,31 +4124,24 @@ pub(crate) fn define(
         .operands_out(vec![a]),
     );
 
-    ig.push(
-        Inst::new(
-            "extended_pairwise_add_signed",
-            r#"
-        Widen the high lanes of `x` using signed extension.
-
-        This will double the lane width and halve the number of lanes.
-            "#,
-            &formats.unary,
-        )
-        .operands_in(vec![x])
-        .operands_out(vec![a]),
-    );
+    let x = &Operand::new("x", I8or16or32xN);
+    let y = &Operand::new("y", I8or16or32xN);
+    let a = &Operand::new("a", I8or16or32xN);
 
     ig.push(
         Inst::new(
-            "extended_pairwise_add_unsigned",
+            "iadd_pairwise",
             r#"
-        Widen the high lanes of `x` extending with zeros.
-
-        This will double the lane width and halve the number of lanes.
+        Does lane-wise integer pairwise addition on two operands, putting the
+        combined results into a single vector result. Here a pair refers to adjacent
+        lanes in a vector, i.e. i*2 + (i*2+1) for i == num_lanes/2. The first operand
+        pairwise add results will make up the low half of the resulting vector while
+        the second operand pairwise add results will make up the upper half of the
+        resulting vector.
             "#,
-            &formats.unary,
+            &formats.binary,
         )
-        .operands_in(vec![x])
+        .operands_in(vec![x, y])
         .operands_out(vec![a]),
     );