Move second_result outside boxed storage.

In instruction formats that have multiple results AND boxed storage,
place the second_result field outside the boxed storage. The 16-byte
instruction format has room for opcode, type, second_result in the first
8 bytes, and the boxed pointer in the last 8 bytes.

This provides a simpler implementation of the second_result() and
second_result_mut() InstructionData methods.

cranelift/src/libcretonne/ir/instructions.rs

@@ -158,6 +158,7 @@ pub enum InstructionData {
     TernaryOverflow {
         opcode: Opcode,
         ty: Type,
+        second_result: Value,
         data: Box<TernaryOverflowData>,
     },
     InsertLane {
@@ -203,6 +204,7 @@ pub enum InstructionData {
     Call {
         opcode: Opcode,
         ty: Type,
+        second_result: Value,
         data: Box<CallData>,
     },
     Return {
@@ -284,7 +286,6 @@ impl Display for UnaryImmVectorData {
 /// Payload data for ternary instructions with multiple results, such as `iadd_carry`.
 #[derive(Clone, Debug)]
 pub struct TernaryOverflowData {
-    pub second_result: Value,
     pub args: [Value; 3],
 }
 
@@ -334,9 +335,6 @@ impl Display for BranchData {
 /// Payload of a call instruction.
 #[derive(Clone, Debug)]
 pub struct CallData {
-    /// Second result value for a call producing multiple return values.
-    second_result: Value,
-
     /// Callee function.
     pub func_ref: FuncRef,
 

cranelift/src/libreader/parser.rs

@@ -1089,10 +1089,8 @@ impl<'a> Parser<'a> {
                 InstructionData::TernaryOverflow {
                     opcode: opcode,
                     ty: VOID,
-                    data: Box::new(TernaryOverflowData {
-                        second_result: NO_VALUE,
-                        args: [lhs, rhs, cin],
-                    }),
+                    second_result: NO_VALUE,
+                    data: Box::new(TernaryOverflowData { args: [lhs, rhs, cin] }),
                 }
             }
             InstructionFormat::Jump => {