From e8fc5aa7887e34fa7984ade8540cbde46575ed6c Mon Sep 17 00:00:00 2001
From: Sam Zhou <sam@developersam.com>
Date: Sat, 21 Oct 2023 10:00:52 -0700
Subject: [PATCH] [optimization] Optimize trivial if else returning bool
 literals

---
 .../conditional_constant_propagation.rs       | 14 ++++++++
 .../conditional_constant_propagation_tests.rs | 34 +++++++++++++++----
 2 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/crates/samlang-core/src/optimization/conditional_constant_propagation.rs b/crates/samlang-core/src/optimization/conditional_constant_propagation.rs
index 1a3dd40d..b4f12931 100644
--- a/crates/samlang-core/src/optimization/conditional_constant_propagation.rs
+++ b/crates/samlang-core/src/optimization/conditional_constant_propagation.rs
@@ -276,6 +276,20 @@ fn optimize_stmt(
         }
         return false;
       }
+      if s1.is_empty() && s2.is_empty() && final_assignments.len() == 1 {
+        let (n, _, e1, e2) = &final_assignments[0];
+        match (e1, e2) {
+          (Expression::IntLiteral(1), Expression::IntLiteral(0)) => {
+            value_cx.checked_bind(*n, condition);
+            return false;
+          }
+          (Expression::IntLiteral(0), Expression::IntLiteral(1)) => {
+            collector.push(Statement::binary(*n, Operator::XOR, condition, ONE));
+            return false;
+          }
+          _ => {}
+        }
+      }
       push_scope(value_cx, index_access_cx, binary_expr_cx);
       let mut s1_collector = vec![];
       optimize_stmts(s1, heap, value_cx, index_access_cx, binary_expr_cx, &mut s1_collector);
diff --git a/crates/samlang-core/src/optimization/conditional_constant_propagation_tests.rs b/crates/samlang-core/src/optimization/conditional_constant_propagation_tests.rs
index b22db57c..3595b9b5 100644
--- a/crates/samlang-core/src/optimization/conditional_constant_propagation_tests.rs
+++ b/crates/samlang-core/src/optimization/conditional_constant_propagation_tests.rs
@@ -769,30 +769,50 @@ return 0;"#,
             Expression::var_name(heap.alloc_str_for_test("a22"), INT_TYPE),
           )],
         },
+        Statement::IfElse {
+          condition: Expression::var_name(heap.alloc_str_for_test("ma2"), INT_TYPE),
+          s1: vec![],
+          s2: vec![],
+          final_assignments: vec![(heap.alloc_str_for_test("ma3"), INT_TYPE, ONE, ZERO)],
+        },
+        Statement::IfElse {
+          condition: Expression::var_name(heap.alloc_str_for_test("ma2"), INT_TYPE),
+          s1: vec![],
+          s2: vec![],
+          final_assignments: vec![(heap.alloc_str_for_test("ma4"), INT_TYPE, ZERO, ONE)],
+        },
         Statement::binary(
           heap.alloc_str_for_test("r1"),
           Operator::EQ,
           Expression::var_name(heap.alloc_str_for_test("ma1"), INT_TYPE),
           Expression::var_name(heap.alloc_str_for_test("ma2"), INT_TYPE),
         ),
-        Statement::binary(heap.alloc_str_for_test("r2"), Operator::NE, ONE, ZERO),
-        Statement::binary(heap.alloc_str_for_test("r3"), Operator::XOR, ONE, ZERO),
-        Statement::binary(heap.alloc_str_for_test("r4"), Operator::NE, ONE, ZERO),
         Statement::binary(
-          heap.alloc_str_for_test("r5"),
+          heap.alloc_str_for_test("r2"),
+          Operator::EQ,
+          Expression::var_name(heap.alloc_str_for_test("ma3"), INT_TYPE),
+          Expression::var_name(heap.alloc_str_for_test("ma4"), INT_TYPE),
+        ),
+        Statement::binary(heap.alloc_str_for_test("r3"), Operator::NE, ONE, ZERO),
+        Statement::binary(heap.alloc_str_for_test("r4"), Operator::XOR, ONE, ZERO),
+        Statement::binary(heap.alloc_str_for_test("r5"), Operator::NE, ONE, ZERO),
+        Statement::binary(
+          heap.alloc_str_for_test("r6"),
           Operator::EQ,
-          Expression::var_name(heap.alloc_str_for_test("r4"), INT_TYPE),
-          Expression::var_name(heap.alloc_str_for_test("r2"), INT_TYPE),
+          Expression::var_name(heap.alloc_str_for_test("r5"), INT_TYPE),
+          Expression::var_name(heap.alloc_str_for_test("r3"), INT_TYPE),
         ),
       ],
-      Expression::var_name(heap.alloc_str_for_test("r5"), INT_TYPE),
+      Expression::var_name(heap.alloc_str_for_test("r6"), INT_TYPE),
       heap,
       table,
       r#"__$foo();
 __$bar();
 let a1: int = __$foo();
 let a22: int = __$bar();
+let ma4 = (a22: int) ^ 1;
 let r1 = (a22: int) == (a1: int);
+let r2 = (ma4: int) == (a22: int);
 return 1;"#,
     );