1 files changed, 51 insertions, 0 deletions
diff --git a/js/src/tests/non262/Math/pow-approx-pow10.js b/js/src/tests/non262/Math/pow-approx-pow10.js
new file mode 100644
index 0000000000..c95eeab428
--- /dev/null
+++ b/js/src/tests/non262/Math/pow-approx-pow10.js
@@ -0,0 +1,51 @@
+if (typeof fdlibm === "undefined") {
+  var fdlibm = SpecialPowers.Cu.getJSTestingFunctions().fdlibm;
+}
+
+const f64 = new Float64Array(1);
+const ui64 = new BigUint64Array(f64.buffer);
+
+function toBits(n) {
+  f64[0] = n;
+  return ui64[0];
+}
+
+function errorInULP(actual, expected) {
+  // Handle NaN and +0/-0.
+  if (Object.is(actual, expected)) {
+    return 0;
+  }
+
+  let x = toBits(actual);
+  let y = toBits(expected);
+  return x <= y ? Number(y - x) : Number(x - y);
+}
+
+const maxExponent = Math.trunc(Math.log10(Number.MAX_VALUE));
+const minExponent = Math.trunc(Math.log10(Number.MIN_VALUE));
+
+assertEq(Math.pow(10, maxExponent + 1), Infinity);
+assertEq(Math.pow(10, minExponent - 1), 0);
+
+// Ensure the error is less than 2 ULP when compared to fdlibm.
+for (let i = minExponent; i <= maxExponent; ++i) {
+  let actual = Math.pow(10, i);
+  let expected = fdlibm.pow(10, i);
+  let error = errorInULP(actual, expected);
+
+  assertEq(error < 2, true,
+           `${10} ** ${i}: ${actual} (${toBits(actual).toString(16)}) != ${expected} (${toBits(expected).toString(16)})`);
+}
+
+// Ensure the error is less than 2 ULP when compared to parsed string |1ep|.
+for (let i = minExponent; i <= maxExponent; ++i) {
+  let actual = Math.pow(10, i);
+  let expected = Number("1e" + i);
+  let error = errorInULP(actual, expected);
+
+  assertEq(error < 2, true,
+           `${10} ** ${i}: ${actual} (${toBits(actual).toString(16)}) != ${expected} (${toBits(expected).toString(16)})`);
+}
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);