Deterministic printing of IR values (#7490)

Closes #4517

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> IR printer now generates deterministic value IDs; tests and IR harness
updated to match new naming and ensure stable round-trips.
> 
> - **IR Printer**:
> - Deterministic value naming via stable keys (`v{:?}` from
`value.0.data()`); added `slotmap::Key` import.
> - **Tests/Fixtures**:
> - Switch FileCheck regex to `VAL=v\d+v\d+` and update expectations
across IR tests/snapshots to new value IDs.
> - Tweak const-folding tests to expect `const ...` lines without
temporary names.
> - **IR Test Harness**:
> - Update default regex definitions; verify determinism by
parsing/printing twice and comparing outputs.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
cfad08d. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: vaivaswatha

sway-ir/src/optimize/constants.rs

@@ -366,7 +366,7 @@ mod tests {
     use crate::{optimize::tests::*, CONST_FOLDING_NAME};
 
     fn assert_operator(t: &str, opcode: &str, l: &str, r: Option<&str>, result: Option<&str>) {
-        let expected = result.map(|result| format!("v0 = const {t} {result}"));
+        let expected = result.map(|result| format!("const {t} {result}"));
         let expected = expected.as_ref().map(|x| vec![x.as_str()]);
         let body = format!(
             "
@@ -495,9 +495,9 @@ mod tests {
                 ret u64 result6, !0
          }",
             Some([
-                "v0 = get_local __ptr u64, LOCAL",
-                "v1 = load v0",
-                "ret u64 v1",
+                "v3v1 = get_local __ptr u64, LOCAL",
+                "v4v1 = load v3v1",
+                "ret u64 v4v1",
             ]),
         );
     }

sway-ir/src/printer.rs

@@ -6,6 +6,7 @@
 
 use std::collections::{BTreeMap, HashMap};
 
+use slotmap::Key;
 use sway_types::SourceEngine;
 
 use crate::{
@@ -1401,7 +1402,7 @@ impl Namer {
 
     fn default_name(&mut self, value: &Value) -> String {
         self.names.get(value).cloned().unwrap_or_else(|| {
-            let new_name = format!("v{}", self.next_value_idx);
+            let new_name = format!("v{:?}", value.0.data());
             self.next_value_idx += 1;
             self.names.insert(*value, new_name.clone());
             new_name

sway-ir/tests/constants/u256_cmp.ir

@@ -1,11 +1,13 @@
+// regex: ID=[[:alpha:]_0-9]+
+
 script {
     fn main() -> bool {
         entry():
         v0 = const u256 0x0000000000000000000000000000000000000000000000000000000000000000
         v1 = const u256 0x0000000000000000000000000000000000000000000000000000000000000001
 
         v10 = cmp eq v0 v0
-//check: v0 = const bool true
+//check: $ID = const bool true
         ret bool v10
     }
 }

sway-ir/tests/constants/u256_ops.ir

@@ -1,3 +1,5 @@
+// regex: ID=[[:alpha:]_0-9]+
+
 script {
     fn main() -> u256 {
         entry():
@@ -22,7 +24,10 @@ script {
         v18 = not v17
         v19 = not v18
         v20 = xor v19, v6
-//check: v0 = const u256 0x0000000000000000000000000000000000000000000000000000000000000002
+// check: entry
+// nextln: $ID = const u256 0x0000000000000000000000000000000000000000000000000000000000000002
+// check-not: const
+// check: ret
         ret u256 v20
     }
 }

sway-ir/tests/cse/cse1.ir

@@ -1,5 +1,5 @@
 // regex: ID=[[:alpha:]0-9]+
-// regex: VAR=v\d+
+// regex: VAR=v\d+v\d+
 
 script {
     fn main() -> bool {

sway-ir/tests/cse/cse2.ir

@@ -1,5 +1,5 @@
 // regex: ID=[[:alpha:]0-9]+
-// regex: VAR=v\d+
+// regex: VAR=v\d+v\d+
 
 script {
     fn main() -> bool {

sway-ir/tests/cse/cse3.ir

@@ -1,5 +1,5 @@
 // regex: ID=[[:alpha:]0-9]+
-// regex: VAR=v\d+
+// regex: VAR=v\d+v\d+
 
 script {
     entry fn main(a: u64, b: u64) -> () {

sway-ir/tests/dce/copy_prop_1.ir

@@ -16,6 +16,6 @@ script {
     }
 }
 
-// regex: VAL=v\d+
+// regex: VAL=v\d+v\d+
 
 // not: mem_copy_val $VAL, $VAL

sway-ir/tests/dce/copy_prop_2.ir

@@ -16,6 +16,6 @@ script {
     }
 }
 
-// regex: VAL=v\d+
+// regex: VAL=v\d+v\d+
 
 // not: mem_copy_val $VAL, $VAL

sway-ir/tests/dce/copy_prop_3.ir

@@ -17,6 +17,6 @@ script {
     }
 }
 
-// regex: VAL=v\d+
+// regex: VAL=v\d+v\d+
 
 // not: mem_copy_val $VAL, $VAL