Optimize left shift of a constant: compute max value of right that does not overflow into Mint/Bigi…

tests/standalone/constant_left_shift_test.dart

Index: tests/standalone/constant_left_shift_test.dart
===================================================================
--- tests/standalone/constant_left_shift_test.dart	(revision 0)
+++ tests/standalone/constant_left_shift_test.dart	(revision 0)
@@ -0,0 +1,74 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+//
+// Dart test program for testing left shifts of a constant.
+
+shiftLeft0(c) => 0 << c;
+shiftLeft1(c) => 1 << c;
+shiftLeft8448(c) => 8448 << c;
+
+shiftLeftNeg1(c) => -1 << c;
+shiftLeftNeg8448(c) => -8448 << c;
+
+main() {
+  // Optimize shifts.
+  for (int i = 0; i < 6000; i++) {
+    shiftLeft1(2);
+    shiftLeft0(2);
+    shiftLeft8448(2);
+    shiftLeftNeg1(2);
+    shiftLeftNeg8448(2);
+  }
+  for (int i = 0; i < 80; i++) {
+    Expect.equals(0, shiftLeft0(i));
+  }

[Florian Schneider, 2013/02/14 17:41:07]

Also add a test case for shiftLeft0(i) where i < 0.

[srdjan, 2013/02/27 18:27:25]

Done.

+  Expect.equals(1, shiftLeft1(0));
+  Expect.equals(128, shiftLeft1(7));
+  Expect.equals(536870912, shiftLeft1(29));
+  // Deoptimize on 32-bit.
+  Expect.equals(1073741824, shiftLeft1(30));
+  Expect.equals(2147483648, shiftLeft1(31));
+  Expect.equals(1152921504606846976, shiftLeft1(60));
+  Expect.equals(2305843009213693952, shiftLeft1(61));
+  // Deoptimize on 64 bits.
+  Expect.equals(4611686018427387904, shiftLeft1(62));
+  Expect.equals(9223372036854775808, shiftLeft1(63));
+
+  Expect.equals(8448, shiftLeft8448(0));
+  Expect.equals(1081344, shiftLeft8448(7));
+  Expect.equals(553648128, shiftLeft8448(16));
+  // Deoptimize on 32-bit.
+  Expect.equals(1107296256, shiftLeft8448(17));
+  Expect.equals(2214592512, shiftLeft8448(18));
+  Expect.equals(1188950301625810944, shiftLeft8448(47));
+  Expect.equals(2377900603251621888, shiftLeft8448(48));
+  // Deoptimize on 64 bits.
+  Expect.equals(4755801206503243776, shiftLeft8448(49));
+  Expect.equals(9511602413006487552, shiftLeft8448(50));
+
+  Expect.equals(-1, shiftLeftNeg1(0));
+  Expect.equals(-128, shiftLeftNeg1(7));
+  Expect.equals(-536870912, shiftLeftNeg1(29));
+  // Deoptimize on 32-bit.
+  Expect.equals(-1073741824, shiftLeftNeg1(30));
+  Expect.equals(-2147483648, shiftLeftNeg1(31));
+  Expect.equals(-1152921504606846976, shiftLeftNeg1(60));
+  Expect.equals(-2305843009213693952, shiftLeftNeg1(61));
+  // Deoptimize on 64 bits.
+  Expect.equals(-4611686018427387904, shiftLeftNeg1(62));
+  Expect.equals(-9223372036854775808, shiftLeftNeg1(63));
+
+  Expect.equals(-8448, shiftLeftNeg8448(0));
+  Expect.equals(-1081344, shiftLeftNeg8448(7));
+  Expect.equals(-553648128, shiftLeftNeg8448(16));
+  // Deoptimize on 32-bit.
+  Expect.equals(-1107296256, shiftLeftNeg8448(17));
+  Expect.equals(-2214592512, shiftLeftNeg8448(18));
+  Expect.equals(-1188950301625810944, shiftLeftNeg8448(47));
+  Expect.equals(-2377900603251621888, shiftLeftNeg8448(48));
+  // Deoptimize on 64 bits.
+  Expect.equals(-4755801206503243776, shiftLeftNeg8448(49));
+  Expect.equals(-9511602413006487552, shiftLeftNeg8448(50));
+}
+