feat(minifier): compress a = a + b to a += b

oxc-project · Jan 7, 2025 · e659142 · e659142
1 parent 9ea4e31
commit e659142
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Showing 3 changed files with 107 additions and 6 deletions.
diff --git a/crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs b/crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs
@@ -140,14 +140,19 @@ impl<'a> Traverse<'a> for PeepholeSubstituteAlternateSyntax {
                 Self::swap_binary_expressions(e);
                 self.try_compress_type_of_equal_string(e);
             }
+            Expression::AssignmentExpression(e) => {
+                self.try_compress_normal_assignment_to_combined_assignment(e, ctx);
+            }
             _ => {}
         }
 
         // Fold
         if let Some(folded_expr) = match expr {
             Expression::Identifier(ident) => self.try_compress_undefined(ident, ctx),
             Expression::BooleanLiteral(_) => self.try_compress_boolean(expr, ctx),
-            Expression::AssignmentExpression(e) => Self::try_compress_assignment_expression(e, ctx),
+            Expression::AssignmentExpression(e) => {
+                Self::try_compress_assignment_to_update_expression(e, ctx)
+            }
             Expression::LogicalExpression(e) => Self::try_compress_is_null_or_undefined(e, ctx),
             Expression::NewExpression(e) => Self::try_fold_new_expression(e, ctx),
             Expression::TemplateLiteral(t) => Self::try_fold_template_literal(t, ctx),
@@ -525,7 +530,32 @@ impl<'a, 'b> PeepholeSubstituteAlternateSyntax {
         }
     }
 
-    fn try_compress_assignment_expression(
+    /// Compress `a = a + b` to `a += b`
+    fn try_compress_normal_assignment_to_combined_assignment(
+        &mut self,
+        expr: &mut AssignmentExpression<'a>,
+        ctx: Ctx<'a, 'b>,
+    ) {
+        if !matches!(expr.operator, AssignmentOperator::Assign) {
+            return;
+        }
+        let AssignmentTarget::AssignmentTargetIdentifier(write_id_ref) = &mut expr.left else {
+            return;
+        };
+
+        let Expression::BinaryExpression(binary_expr) = &mut expr.right else { return };
+        let Some(new_op) = binary_expr.operator.to_assignment_operator() else { return };
+        let Expression::Identifier(read_id_ref) = &mut binary_expr.left else { return };
+        if write_id_ref.name != read_id_ref.name {
+            return;
+        }
+
+        expr.operator = new_op;
+        expr.right = ctx.ast.move_expression(&mut binary_expr.right);
+        self.changed = true;
+    }
+
+    fn try_compress_assignment_to_update_expression(
         expr: &mut AssignmentExpression<'a>,
         ctx: Ctx<'a, 'b>,
     ) -> Option<Expression<'a>> {
@@ -1020,6 +1050,58 @@ mod test {
         test("x !== false", "x !== !1");
     }
 
+    /// Based on https://github.com/terser/terser/blob/58ba5c163fa1684f2a63c7bc19b7ebcf85b74f73/test/compress/assignment.js
+    #[test]
+    fn test_fold_normal_assignment_to_combined_assignment() {
+        test("x = x + 3", "x += 3");
+        test("x = x - 3", "x -= 3");
+        test("x = x / 3", "x /= 3");
+        test("x = x * 3", "x *= 3");
+        test("x = x >> 3", "x >>= 3");
+        test("x = x << 3", "x <<= 3");
+        test("x = x >>> 3", "x >>>= 3");
+        test("x = x | 3", "x |= 3");
+        test("x = x ^ 3", "x ^= 3");
+        test("x = x % 3", "x %= 3");
+        test("x = x & 3", "x &= 3");
+        test("x = x + g()", "x += g()");
+        test("x = x - g()", "x -= g()");
+        test("x = x / g()", "x /= g()");
+        test("x = x * g()", "x *= g()");
+        test("x = x >> g()", "x >>= g()");
+        test("x = x << g()", "x <<= g()");
+        test("x = x >>> g()", "x >>>= g()");
+        test("x = x | g()", "x |= g()");
+        test("x = x ^ g()", "x ^= g()");
+        test("x = x % g()", "x %= g()");
+        test("x = x & g()", "x &= g()");
+
+        test_same("x = 3 + x");
+        test_same("x = 3 - x");
+        test_same("x = 3 / x");
+        test_same("x = 3 * x");
+        test_same("x = 3 >> x");
+        test_same("x = 3 << x");
+        test_same("x = 3 >>> x");
+        test_same("x = 3 | x");
+        test_same("x = 3 ^ x");
+        test_same("x = 3 % x");
+        test_same("x = 3 & x");
+        test_same("x = g() + x");
+        test_same("x = g() - x");
+        test_same("x = g() / x");
+        test_same("x = g() * x");
+        test_same("x = g() >> x");
+        test_same("x = g() << x");
+        test_same("x = g() >>> x");
+        test_same("x = g() | x");
+        test_same("x = g() ^ x");
+        test_same("x = g() % x");
+        test_same("x = g() & x");
+
+        test_same("x = (x -= 2) ^ x");
+    }
+
     #[test]
     fn test_fold_subtraction_assignment() {
         test("x -= 1", "--x");

diff --git a/crates/oxc_syntax/src/operator.rs b/crates/oxc_syntax/src/operator.rs
@@ -313,6 +313,25 @@ impl BinaryOperator {
         }
     }
 
+    /// Get [`AssignmentOperator`] corresponding to this [`BinaryOperator`].
+    pub fn to_assignment_operator(self) -> Option<AssignmentOperator> {
+        match self {
+            Self::Addition => Some(AssignmentOperator::Addition),
+            Self::Subtraction => Some(AssignmentOperator::Subtraction),
+            Self::Multiplication => Some(AssignmentOperator::Multiplication),
+            Self::Division => Some(AssignmentOperator::Division),
+            Self::Remainder => Some(AssignmentOperator::Remainder),
+            Self::Exponential => Some(AssignmentOperator::Exponential),
+            Self::ShiftLeft => Some(AssignmentOperator::ShiftLeft),
+            Self::ShiftRight => Some(AssignmentOperator::ShiftRight),
+            Self::ShiftRightZeroFill => Some(AssignmentOperator::ShiftRightZeroFill),
+            Self::BitwiseOR => Some(AssignmentOperator::BitwiseOR),
+            Self::BitwiseXOR => Some(AssignmentOperator::BitwiseXOR),
+            Self::BitwiseAnd => Some(AssignmentOperator::BitwiseAnd),
+            _ => None,
+        }
+    }
+
     /// The string representation of this operator as it appears in source code.
     pub fn as_str(&self) -> &'static str {
         match self {

diff --git a/tasks/minsize/minsize.snap b/tasks/minsize/minsize.snap
@@ -3,9 +3,9 @@ Original   | minified   | minified   | gzip       | gzip       | Fixture
 -------------------------------------------------------------------------------------
 72.14 kB   | 23.68 kB   | 23.70 kB   | 8.61 kB    | 8.54 kB    | react.development.js
 
-173.90 kB  | 59.79 kB   | 59.82 kB   | 19.42 kB   | 19.33 kB   | moment.js 
+173.90 kB  | 59.78 kB   | 59.82 kB   | 19.42 kB   | 19.33 kB   | moment.js 
 
-287.63 kB  | 90.06 kB   | 90.07 kB   | 32.07 kB   | 31.95 kB   | jquery.js 
+287.63 kB  | 90.05 kB   | 90.07 kB   | 32.07 kB   | 31.95 kB   | jquery.js 
 
 342.15 kB  | 118.16 kB  | 118.14 kB  | 44.52 kB   | 44.37 kB   | vue.js    
 
@@ -19,9 +19,9 @@ Original   | minified   | minified   | gzip       | gzip       | Fixture
 
 2.14 MB    | 726.02 kB  | 724.14 kB  | 180.14 kB  | 181.07 kB  | victory.js
 
-3.20 MB    | 1.01 MB    | 1.01 MB    | 331.84 kB  | 331.56 kB  | echarts.js
+3.20 MB    | 1.01 MB    | 1.01 MB    | 331.82 kB  | 331.56 kB  | echarts.js
 
 6.69 MB    | 2.32 MB    | 2.31 MB    | 492.75 kB  | 488.28 kB  | antd.js   
 
-10.95 MB   | 3.50 MB    | 3.49 MB    | 909.11 kB  | 915.50 kB  | typescript.js
+10.95 MB   | 3.50 MB    | 3.49 MB    | 909.10 kB  | 915.50 kB  | typescript.js