1 files changed, 85 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/ion/pow-base-power-of-two-bailouts.js b/js/src/jit-test/tests/ion/pow-base-power-of-two-bailouts.js
new file mode 100644
index 0000000000..34e7ed406f
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+++ b/js/src/jit-test/tests/ion/pow-base-power-of-two-bailouts.js
@@ -0,0 +1,85 @@
+// Lowering provides a specialisation when the base operand is a constant which
+// is a power of two.
+//
+// Test bailout conditions for this optimisation.
+
+function test(x) {
+    function pow(x, y) { return `Math.pow(${x}, ${y})` };
+    function exp(x, y) { return `((${x}) ** ${y})` };
+
+    function make(fn) {
+        return Function("y, z", `
+            // Load from array to prevent constant-folding.
+            // (Ion is currently not smart enough to realise that both array
+            // values are the same.)
+            var ys = [y, y];
+            var zs = [z, z];
+            for (var i = 0; i < 1000; ++i) {
+                assertEq(${fn(x, "ys[i & 1]")}, zs[i & 1]);
+            }
+        `);
+    }
+
+    function double(v) {
+        // NB: numberToDouble() always returns a double value.
+        return numberToDouble(v);
+    }
+
+    // Find the first power which will exceed the Int32 range by computing ⌈log_x(2 ^ 31)⌉.
+    var limit = Math.ceil(Math.log2(2 ** 31) / Math.log2(x));
+    assertEq(Math.pow(x, limit - 1) < 2 ** 31, true);
+    assertEq(Math.pow(x, limit) >= 2 ** 31, true);
+
+    function* args(first, last) {
+        // Run the test function a few times without a bailout.
+        for (var i = 0; i < 3; ++i) {
+            yield first;
+        }
+
+        // |last| should trigger a bailout.
+        yield last;
+    }
+
+    // Test precision loss when the result exceeds 2**31.
+    for (var fn of [make(pow), make(exp)]) {
+        for (var y of args(limit - 1, limit)) {
+            // Ensure the callee always sees a double to avoid an early Bailout_ArgumentCheck.
+            var z = double(Math.pow(x, y));
+            fn(y, z);
+        }
+    }
+
+    // Test precision loss when the result is a fractional number.
+    for (var fn of [make(pow), make(exp)]) {
+        for (var y of args(0, -1)) {
+            // Ensure the callee always sees a double to avoid an early Bailout_ArgumentCheck.
+            var z = double(Math.pow(x, y));
+            fn(y, z);
+        }
+    }
+
+    // Find the first negative power which can be represented as a double
+    var negLimit = -Math.floor(1074 / Math.log2(x));
+
+    // Test precision loss when the result is a non-zero, fractional number.
+    for (var fn of [make(pow), make(exp)]) {
+        for (var y of args(limit - 1, limit)) {
+            // Ensure the callee always sees a double to avoid an early Bailout_ArgumentCheck.
+            var z = double(Math.pow(x, y));
+            fn(y, z);
+        }
+    }
+}
+
+function* range(a, b, fn) {
+    for (var i = a; i <= b; ++i) {
+        yield fn(i);
+    }
+}
+
+// Only 2^i with |i| ∈ {1..8} currently triggers the optimisation, but also test
+// the next power-of-two values.
+
+for (var x of range(1, 10, i => 2 ** i)) {
+    test(x);
+}