From d853070c6b7601eef95750963386ccf431435f10 Mon Sep 17 00:00:00 2001
From: Akosh Farkash <aakoshh@gmail.com>
Date: Fri, 15 Nov 2024 20:47:26 +0000
Subject: [PATCH] Add some tests with references

---
 .../hint_black_box/src/main.nr                | 36 +++++++++++++++++--
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/test_programs/execution_success/hint_black_box/src/main.nr b/test_programs/execution_success/hint_black_box/src/main.nr
index 635ac2b0b26..d944d4b75fb 100644
--- a/test_programs/execution_success/hint_black_box/src/main.nr
+++ b/test_programs/execution_success/hint_black_box/src/main.nr
@@ -27,6 +27,32 @@ fn main(a: u32, b: u32) {
         brillig_slice_sum(black_box(arr.as_slice()))
     };
     assert_eq(s, b);
+
+    let mut d = b;
+    // This gets completely eliminated:
+    let mut c = 0;
+    set_ref(&mut c, &mut d);
+    assert_eq(c, b);
+
+    // This way the constraint is preserved:
+    let mut c = 0;
+    set_ref(&mut c, &mut black_box(d));
+    assert_eq(c, b);
+
+    // A reference over the output of black box is not the original variable:
+    let mut c = 0;
+    set_ref(&mut black_box(c), &mut d);
+    assert_eq(c, 0);
+
+    // This would cause a causes a crash during SSA passes unless it's a Brillig runtime:
+    //  > Could not resolve some references to the array. All references must be resolved at compile time
+    // The SSA cannot have Allocate by the time we start generating ACIR, but `black_box` prevents them
+    // from being optimised away during SSA passes.
+    // If we use `--force-brillig` then the it doesn't crash but the assertion fails because `mem2reg`
+    // eliminates the storing to the reference.
+    //let mut c = 0;
+    //set_ref(black_box(&mut c), black_box(&mut d));
+    //assert_eq(c, b);
 }
 
 fn loop(n: u32, k: u32) -> u32 {
@@ -47,7 +73,7 @@ fn array_sum<let N: u32>(xs: [u32; N]) -> u32 {
 
 fn slice_sum(xs: [u32]) -> u32 {
     let mut sum = 0;
-    for x in xs{
+    for x in xs {
         sum = sum + x;
     }
     sum
@@ -55,8 +81,12 @@ fn slice_sum(xs: [u32]) -> u32 {
 
 unconstrained fn brillig_slice_sum(xs: [u32]) -> u32 {
     let mut sum = 0;
-    for x in xs{
+    for x in xs {
         sum = sum + x;
     }
     sum
-}
\ No newline at end of file
+}
+
+fn set_ref(c: &mut u32, b: &mut u32) {
+    *c = *b;
+}