fix(ssa): Only attempt to inline constant Brillig calls for entry points (#7260)

Author: vezenovm

compiler/noirc_evaluator/src/brillig/brillig_gen.rs

@@ -58,7 +58,11 @@ pub(crate) fn gen_brillig_for(
     brillig: &Brillig,
 ) -> Result<GeneratedBrillig<FieldElement>, InternalError> {
     // Create the entry point artifact
-    let globals_memory_size = brillig.globals_memory_size.get(&func.id()).copied().unwrap_or(0);
+    let globals_memory_size = brillig
+        .globals_memory_size
+        .get(&func.id())
+        .copied()
+        .expect("Should have the globals memory size specified for an entry point");
     let mut entry_point = BrilligContext::new_entry_point_artifact(
         arguments,
         FunctionContext::return_values(func),

compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs

@@ -119,7 +119,9 @@ impl Ssa {
                     let func_value = &function.dfg[*func_id];
                     let Value::Function(func_id) = func_value else { continue };
 
-                    brillig_functions.remove(func_id);
+                    if function.runtime().is_acir() {
+                        brillig_functions.remove(func_id);
+                    }
                 }
             }
         }
@@ -336,17 +338,22 @@ impl<'brillig> Context<'brillig> {
         };
 
         // First try to inline a call to a brillig function with all constant arguments.
-        let new_results = Self::try_inline_brillig_call_with_all_constants(
-            &instruction,
-            &old_results,
-            block,
-            dfg,
-            self.brillig_info,
-        )
-        // Otherwise, try inserting the instruction again to apply any optimizations using the newly resolved inputs.
-        .unwrap_or_else(|| {
+        let new_results = if runtime_is_brillig {
             Self::push_instruction(id, instruction.clone(), &old_results, block, dfg)
-        });
+        } else {
+            // We only want to try to inline Brillig calls for Brillig entry points (functions called from an ACIR runtime).
+            Self::try_inline_brillig_call_with_all_constants(
+                &instruction,
+                &old_results,
+                block,
+                dfg,
+                self.brillig_info,
+            )
+            // Otherwise, try inserting the instruction again to apply any optimizations using the newly resolved inputs.
+            .unwrap_or_else(|| {
+                Self::push_instruction(id, instruction.clone(), &old_results, block, dfg)
+            })
+        };
 
         Self::replace_result_ids(dfg, &old_results, &new_results);
 
@@ -1485,6 +1492,82 @@ mod test {
         assert_normalized_ssa_equals(ssa, expected);
     }
 
+    #[test]
+    fn inlines_brillig_call_with_entry_point_globals() {
+        let src = "
+        g0 = Field 2
+
+        acir(inline) fn main f0 {
+          b0():
+            v1 = call f1() -> Field
+            return v1
+        }
+
+        brillig(inline) fn one f1 {
+          b0():
+            v1 = add g0, Field 3
+            return v1
+        }
+        ";
+        let ssa = Ssa::from_str(src).unwrap();
+        let mut ssa = ssa.dead_instruction_elimination();
+        let used_globals_map = std::mem::take(&mut ssa.used_globals);
+        let brillig = ssa.to_brillig_with_globals(false, used_globals_map);
+
+        let expected = "
+        g0 = Field 2
+
+        acir(inline) fn main f0 {
+          b0():
+            return Field 5
+        }
+        ";
+
+        let ssa = ssa.fold_constants_with_brillig(&brillig);
+        assert_normalized_ssa_equals(ssa, expected);
+    }
+
+    #[test]
+    fn inlines_brillig_call_with_non_entry_point_globals() {
+        let src = "
+        g0 = Field 2
+
+        acir(inline) fn main f0 {
+          b0():
+            v1 = call f1() -> Field
+            return v1
+        }
+
+        brillig(inline) fn entry_point f1 {
+          b0():
+            v1 = call f2() -> Field
+            return v1
+        }
+
+        brillig(inline) fn one f2 {
+          b0():
+            v1 = add g0, Field 3
+            return v1
+        }
+        ";
+        let ssa = Ssa::from_str(src).unwrap();
+        let mut ssa = ssa.dead_instruction_elimination();
+        let used_globals_map = std::mem::take(&mut ssa.used_globals);
+        let brillig = ssa.to_brillig_with_globals(false, used_globals_map);
+
+        let expected = "
+        g0 = Field 2
+
+        acir(inline) fn main f0 {
+          b0():
+            return Field 5
+        }
+        ";
+
+        let ssa = ssa.fold_constants_with_brillig(&brillig);
+        assert_normalized_ssa_equals(ssa, expected);
+    }
+
     #[test]
     fn does_not_use_cached_constrain_in_block_that_is_not_dominated() {
         let src = "