avm2: Fix edge cases in Math.pow

core/src/avm2/globals/math.rs

@@ -6,6 +6,7 @@ use crate::avm2::object::Object;
 use crate::avm2::parameters::ParametersExt;
 use crate::avm2::value::Value;
 use crate::avm2::{ClassObject, Error};
+use num_traits::ToPrimitive;
 use rand::Rng;
 
 macro_rules! wrap_std {
@@ -123,6 +124,30 @@ pub fn pow<'gc>(
     let n = args.get_f64(0);
     let p = args.get_f64(1);
 
+    // This condition is the simplest one that covers all special cases,
+    // so use it in order to create a fast path for finite n and p, which is
+    // the most common configuration.
+    if !n.is_finite() || !p.is_finite() {
+        match (n, p) {
+            // Special case: If p is NaN, the result is NaN.
+            (_, _) if p.is_nan() => return Ok(f64::NAN.into()),
+            // Special case: If p is ±Infinity and n is ±1, the result is NaN.
+            (1.0, _) | (-1.0, _) => {
+                // If (1) n or p is not finite, (2) p is not NaN, (3) n is finite,
+                // p has to be infinite.
+                debug_assert!(p.is_infinite());
+                return Ok(f64::NAN.into());
+            }
+            // Special case: If n is -Infinity and p < 0 and p is a negative even integer, Flash Player returns -0.
+            (f64::NEG_INFINITY, _) if p.to_i64().is_some_and(|i| i % 2 == 0 && i < 0) => {
+                return Ok(Value::Number(-0.0))
+            }
+            _ => {
+                // Fall back to regular powf
+            }
+        }
+    }
+
     Ok(f64::powf(n, p).into())
 }
 

tests/tests/swfs/from_avmplus/as3/Types/Number/pow/test.toml

@@ -1,2 +1 @@
 num_ticks = 1
-known_failure = true