Keep Integer type for inc/dec of an integer (#2615)

Keep Integer type after running unary increment/decrement ops if possible. The integer type will be useful to take fast paths for accessing index properties. (e.g., `let a = 1; arr[++a]`)

boa_engine/src/tests.rs

@@ -541,6 +541,20 @@ fn unary_pre() {
         --a === 4;
     "#;
     assert_eq!(&exec(execs_before_dec), "true");
+
+    let i32_limit_inc = r#"
+        let a = 2147483647;
+        ++a;
+        a;
+    "#;
+    assert_eq!(&exec(i32_limit_inc), "2147483648");
+
+    let i32_limit_dec = r#"
+        let a = -2147483648;
+        --a;
+        a;
+    "#;
+    assert_eq!(&exec(i32_limit_dec), "-2147483649");
 }
 
 #[test]
@@ -683,6 +697,32 @@ fn unary_post() {
         a-- === 5;
     "#;
     assert_eq!(&exec(execs_after_dec), "true");
+
+    let i32_limit_inc = r#"
+        let a = 2147483647;
+        a++;
+        a;
+    "#;
+    assert_eq!(&exec(i32_limit_inc), "2147483648");
+
+    let i32_limit_dec = r#"
+        let a = -2147483648;
+        a--;
+        a;
+    "#;
+    assert_eq!(&exec(i32_limit_dec), "-2147483649");
+
+    let to_numeric_inc = r#"
+        let a = {[Symbol.toPrimitive]() { return 123; }};
+        a++
+    "#;
+    assert_eq!(&exec(to_numeric_inc), "123");
+
+    let to_numeric_dec = r#"
+        let a = {[Symbol.toPrimitive]() { return 123; }};
+        a--
+    "#;
+    assert_eq!(&exec(to_numeric_dec), "123");
 }
 
 #[test]

boa_engine/src/vm/opcode/unary_ops/decrement.rs

@@ -1,5 +1,5 @@
 use crate::{
-    value::Numeric,
+    value::{JsValue, Numeric},
     vm::{opcode::Operation, ShouldExit},
     Context, JsBigInt, JsResult,
 };
@@ -17,11 +17,16 @@ impl Operation for Dec {
 
     fn execute(context: &mut Context<'_>) -> JsResult<ShouldExit> {
         let value = context.vm.pop();
-        match value.to_numeric(context)? {
+        match value {
+            JsValue::Integer(number) if number > i32::MIN => {
+                context.vm.push(number - 1);
+            }
+            _ => match value.to_numeric(context)? {
                 Numeric::Number(number) => context.vm.push(number - 1f64),
                 Numeric::BigInt(bigint) => {
                     context.vm.push(JsBigInt::sub(&bigint, &JsBigInt::one()));
                 }
+            },
         }
         Ok(ShouldExit::False)
     }
@@ -40,6 +45,12 @@ impl Operation for DecPost {
 
     fn execute(context: &mut Context<'_>) -> JsResult<ShouldExit> {
         let value = context.vm.pop();
+        match value {
+            JsValue::Integer(number) if number > i32::MIN => {
+                context.vm.push(number - 1);
+                context.vm.push(value);
+            }
+            _ => {
                 let value = value.to_numeric(context)?;
                 match value {
                     Numeric::Number(number) => context.vm.push(number - 1f64),
@@ -48,6 +59,8 @@ impl Operation for DecPost {
                     }
                 }
                 context.vm.push(value);
+            }
+        }
         Ok(ShouldExit::False)
     }
 }

boa_engine/src/vm/opcode/unary_ops/increment.rs

@@ -1,5 +1,5 @@
 use crate::{
-    value::Numeric,
+    value::{JsValue, Numeric},
     vm::{opcode::Operation, ShouldExit},
     Context, JsBigInt, JsResult,
 };
@@ -17,11 +17,16 @@ impl Operation for Inc {
 
     fn execute(context: &mut Context<'_>) -> JsResult<ShouldExit> {
         let value = context.vm.pop();
-        match value.to_numeric(context)? {
+        match value {
+            JsValue::Integer(number) if number < i32::MAX => {
+                context.vm.push(number + 1);
+            }
+            _ => match value.to_numeric(context)? {
                 Numeric::Number(number) => context.vm.push(number + 1f64),
                 Numeric::BigInt(bigint) => {
                     context.vm.push(JsBigInt::add(&bigint, &JsBigInt::one()));
                 }
+            },
         }
         Ok(ShouldExit::False)
     }
@@ -40,6 +45,12 @@ impl Operation for IncPost {
 
     fn execute(context: &mut Context<'_>) -> JsResult<ShouldExit> {
         let value = context.vm.pop();
+        match value {
+            JsValue::Integer(number) if number < i32::MAX => {
+                context.vm.push(number + 1);
+                context.vm.push(value);
+            }
+            _ => {
                 let value = value.to_numeric(context)?;
                 match value {
                     Numeric::Number(number) => context.vm.push(number + 1f64),
@@ -48,6 +59,8 @@ impl Operation for IncPost {
                     }
                 }
                 context.vm.push(value);
+            }
+        }
         Ok(ShouldExit::False)
     }
 }