unique constants in the IR (#6896)

First step as part of #6351 .

---------

Co-authored-by: IGI-111 <igi-111@protonmail.com>

Author: vaivaswatha

sway-core/src/asm_generation/fuel/data_section.rs

@@ -1,5 +1,7 @@
 use rustc_hash::FxHashMap;
-use sway_ir::{size_bytes_round_up_to_word_alignment, Constant, ConstantValue, Context, Padding};
+use sway_ir::{
+    size_bytes_round_up_to_word_alignment, ConstantContent, ConstantValue, Context, Padding,
+};
 
 use std::{fmt, iter::repeat};
 
@@ -89,7 +91,7 @@ impl Entry {
 
     pub(crate) fn from_constant(
         context: &Context,
-        constant: &Constant,
+        constant: &ConstantContent,
         name: EntryName,
         padding: Option<Padding>,
     ) -> Entry {

sway-core/src/asm_generation/fuel/fuel_asm_builder.rs

@@ -102,7 +102,7 @@ impl AsmBuilder for FuelAsmBuilder<'_, '_> {
             ConfigContent::V0 { name, constant, .. } => {
                 let entry = Entry::from_constant(
                     self.context,
-                    constant,
+                    constant.get_content(self.context),
                     EntryName::Configurable(name.clone()),
                     None,
                 );
@@ -1130,7 +1130,7 @@ impl<'ir, 'eng> FuelAsmBuilder<'ir, 'eng> {
             idx_val
                 .get_constant(self.context)
                 .and_then(|idx_const| {
-                    if let ConstantValue::Uint(idx) = idx_const.value {
+                    if let ConstantValue::Uint(idx) = idx_const.get_content(self.context).value {
                         Some(idx as usize)
                     } else {
                         None
@@ -2072,7 +2072,7 @@ impl<'ir, 'eng> FuelAsmBuilder<'ir, 'eng> {
         config_name: Option<String>,
         span: Option<Span>,
     ) -> (VirtualRegister, Option<DataId>) {
-        match &constant.value {
+        match &constant.get_content(self.context).value {
             // Use cheaper $zero or $one registers if possible.
             ConstantValue::Unit | ConstantValue::Bool(false) | ConstantValue::Uint(0)
                 if config_name.is_none() =>
@@ -2091,7 +2091,12 @@ impl<'ir, 'eng> FuelAsmBuilder<'ir, 'eng> {
                 } else {
                     EntryName::NonConfigurable
                 };
-                let entry = Entry::from_constant(self.context, constant, config_name, None);
+                let entry = Entry::from_constant(
+                    self.context,
+                    constant.get_content(self.context),
+                    config_name,
+                    None,
+                );
                 let data_id = self.data_section.insert_data_value(entry);
 
                 // Allocate a register for it, and a load instruction.
@@ -2137,7 +2142,7 @@ impl<'ir, 'eng> FuelAsmBuilder<'ir, 'eng> {
             .or_else(|| {
                 value.get_constant(self.context).map(|constant| {
                     let span = self.md_mgr.val_to_span(self.context, *value);
-                    match constant.value {
+                    match constant.get_content(self.context).value {
                         // If it's a small enough constant, just initialize using an IMM value.
                         // (exceptions for zero and one as they have special registers).
                         ConstantValue::Uint(c)

sway-core/src/asm_generation/fuel/functions.rs

@@ -834,7 +834,7 @@ impl FuelAsmBuilder<'_, '_> {
                     ptr.is_mutable(self.context),
                     ptr.get_initializer(self.context),
                 ) {
-                    match constant.value {
+                    match constant.get_content(self.context).value {
                         ConstantValue::Uint(c) if c <= compiler_constants::EIGHTEEN_BITS => {
                             self.ptr_map.insert(
                                 *ptr,
@@ -848,7 +848,7 @@ impl FuelAsmBuilder<'_, '_> {
                             let data_id =
                                 self.data_section.insert_data_value(Entry::from_constant(
                                     self.context,
-                                    constant,
+                                    constant.get_content(self.context),
                                     EntryName::NonConfigurable,
                                     None,
                                 ));
@@ -863,7 +863,7 @@ impl FuelAsmBuilder<'_, '_> {
                     let var_size = ptr_ty.size(self.context);
 
                     if let Some(constant) = ptr.get_initializer(self.context) {
-                        match constant.value {
+                        match constant.get_content(self.context).value {
                             ConstantValue::Uint(c) if c <= compiler_constants::EIGHTEEN_BITS => {
                                 let imm = VirtualImmediate18::new_unchecked(
                                     c,
@@ -879,7 +879,7 @@ impl FuelAsmBuilder<'_, '_> {
                                 let data_id =
                                     self.data_section.insert_data_value(Entry::from_constant(
                                         self.context,
-                                        constant,
+                                        constant.get_content(self.context),
                                         EntryName::NonConfigurable,
                                         None,
                                     ));

sway-core/src/ir_generation/compile.rs

@@ -356,7 +356,7 @@ pub(crate) fn compile_configurables(
             let opt_metadata = md_mgr.span_to_md(context, &decl.span);
 
             if context.experimental.new_encoding {
-                let mut encoded_bytes = match constant.value {
+                let mut encoded_bytes = match constant.get_content(context).value.clone() {
                     ConstantValue::RawUntypedSlice(bytes) => bytes,
                     _ => unreachable!(),
                 };
@@ -651,11 +651,12 @@ fn compile_fn(
     // Special case: sometimes the returned value at the end of the function block is hacked
     // together and is invalid.  This can happen with diverging control flow or with implicit
     // returns.  We can double check here and make sure the return value type is correct.
+    let undef = Constant::unique(context, ConstantContent::get_undef(ret_type));
     ret_val = match ret_val.get_type(context) {
         Some(ret_val_type) if ret_type.eq(context, &ret_val_type) => ret_val,
 
         // Mismatched or unavailable type.  Set ret_val to a correctly typed Undef.
-        _otherwise => Value::new_constant(context, Constant::get_undef(ret_type)),
+        _otherwise => Value::new_constant(context, undef),
     };
 
     // Another special case: if the last expression in a function is a return then we don't want to
@@ -676,7 +677,7 @@ fn compile_fn(
             || compiler.current_block.num_predecessors(context) > 0)
     {
         if ret_type.is_unit(context) {
-            ret_val = Constant::get_unit(context);
+            ret_val = ConstantContent::get_unit(context);
         }
         compiler
             .current_block