Cranelift: implement redundant fill removal on tree-shaped CFG regions. Mozilla bug 1570584. (#906)

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

@@ -1194,6 +1194,22 @@ pub fn define(
         .can_load(true),
     );
 
+    ig.push(
+        Inst::new(
+            "fill_nop",
+            r#"
+        This is identical to `fill`, except it has no encoding, since it is a no-op.
+
+        This instruction is created only during late-stage redundant-reload removal, after all
+        registers and stack slots have been assigned.  It is used to replace `fill`s that have
+        been identified as redundant.
+        "#,
+        )
+        .operands_in(vec![x])
+        .operands_out(vec![a])
+        .can_load(true),
+    );
+
     let src = &operand("src", regunit);
     let dst = &operand("dst", regunit);
 
@@ -1233,6 +1249,23 @@ pub fn define(
         .other_side_effects(true),
     );
 
+    ig.push(
+        Inst::new(
+            "copy_to_ssa",
+            r#"
+        Copies the contents of ''src'' register to ''a'' SSA name.
+
+        This instruction copies the contents of one register, regardless of its SSA name, to
+        another register, creating a new SSA name.  In that sense it is a one-sided version
+        of ''copy_special''.  This instruction is internal and should not be created by
+        Cranelift users.
+        "#,
+        )
+        .operands_in(vec![src])
+        .operands_out(vec![a])
+        .other_side_effects(true),
+    );
+
     ig.push(
         Inst::new(
             "copy_nop",