optimized switch implementation

test/mjsunit/wasm/asm-wasm-switch.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --expose-wasm
+
+(function TestSwitch() {
+  function asmModule() {
+    "use asm"
+
+    function caller() {
+      var ret = 0;
+      var x = 7;
+      switch (x) {
+        case 1: return 0;
+        case 7: {
+          ret = 12;
+          break;
+        }
+        default: return 0;
+      }
+      switch (x) {
+        case 1: return 0;
+        case 8: return 0;
+        default: ret = (ret + 11)|0;
+      }
+      return ret|0;
+    }
+
+    return {caller:caller};
+  }
+  var wasm = Wasm.instantiateModuleFromAsm(asmModule.toString());
+  assertEquals(23, wasm.caller());
+})();
+
+(function TestSwitchFallthrough() {
+  function asmModule() {
+    "use asm"
+
+    function caller() {
+      var x = 17;
+      var ret = 0;
+      switch (x) {
+        case 17:
+        case 14: ret = 39;
+        case 1: ret = (ret + 3)|0;
+        case 4: break;
+        default: ret = (ret + 1)|0;
+      }
+      return ret|0;
+    }
+
+    return {caller:caller};
+  }
+  var wasm = Wasm.instantiateModuleFromAsm(asmModule.toString());
+  assertEquals(42, wasm.caller());
+})();
+
+(function TestNestedSwitch() {
+  function asmModule() {
+    "use asm"
+
+    function caller() {
+      var x = 3;
+      var y = -13;
+      switch (x) {
+        case 1: return 0;
+        case 3: {
+          switch (y) {
+            case 2: return 0;
+            case -13: return 43;
+            default: return 0;
+          }
+        }
+        default: return 0;
+      }
+      return 0;
+    }
+
+    return {caller:caller};
+  }
+  var wasm = Wasm.instantiateModuleFromAsm(asmModule.toString());
+  assertEquals(43, wasm.caller());
+})();
+
+(function TestSwitchWithDefaultOnly() {
+  function asmModule() {
+    "use asm";
+    function main(x) {
+      x = x|0;
+      switch(x|0) {
+        default: return -10;
+      }
+      return 0;
+    }
+    return {
+      main: main,
+    };
+  }
+  var wasm = Wasm.instantiateModuleFromAsm(asmModule.toString());
+  assertEquals(-10, wasm.main(2));
+  assertEquals(-10, wasm.main(54));
+})();
+
+(function TestEmptySwitch() {
+  function asmModule() {
+    "use asm";
+    function main(x) {
+      x = x|0;
+      switch(x|0) {
+      }
+      return 73;
+    }
+    return {
+      main: main,
+    };
+  }
+  var wasm = Wasm.instantiateModuleFromAsm(asmModule.toString());
+  assertEquals(73, wasm.main(7));
+})();
+
+(function TestSwitchWithBrTable() {
+  function asmModule() {
+    "use asm";
+    function main(x) {
+      x = x|0;
+      switch(x|0) {
+        case 14: return 14;
+        case 12: return 12;
+        case 15: return 15;
+        case 19: return 19;
+        case 18: return 18;
+        case 16: return 16;
+        default: return -1;
+      }
+      return 0;
+    }
+    return {
+      main: main,
+    };
+  }
+  var wasm = Wasm.instantiateModuleFromAsm(asmModule.toString());
+  assertEquals(12, wasm.main(12));
+  assertEquals(14, wasm.main(14));
+  assertEquals(15, wasm.main(15));
+  assertEquals(16, wasm.main(16));
+  assertEquals(18, wasm.main(18));
+  assertEquals(19, wasm.main(19));
+  assertEquals(-1, wasm.main(-1));
+})();
+
+(function TestSwitchWithBalancedTree() {
+  function asmModule() {
+    "use asm";
+    function main(x) {
+      x = x|0;
+      switch(x|0) {
+        case 5: return 5;
+        case 1: return 1;
+        case 6: return 6;
+        case 9: return 9;
+        case -4: return -4;
+      }
+      return 0;
+    }
+    return {
+      main: main,
+    };
+  }
+  var wasm = Wasm.instantiateModuleFromAsm(asmModule.toString());
+  assertEquals(-4, wasm.main(-4));
+  assertEquals(1, wasm.main(1));
+  assertEquals(5, wasm.main(5));
+  assertEquals(6, wasm.main(6));
+  assertEquals(9, wasm.main(9));
+  assertEquals(0, wasm.main(11));
+})();
+
+(function TestSwitchHybrid() {
+  function asmModule() {
+    "use asm";
+    function main(x) {
+      x = x|0;
+      switch(x|0) {
+        case 1: return 1;
+        case 2: return 2;
+        case 3: return 3;
+        case 4: return 4;
+        case 7: return 7;
+        case 10: return 10;
+        case 11: return 11;
+        case 12: return 12;
+        case 13: return 13;
+        case 16: return 16;
+        default: return -1;
+      }
+      return 0;
+    }
+    return {
+      main: main,
+    };
+  }
+  var wasm = Wasm.instantiateModuleFromAsm(asmModule.toString());
+  assertEquals(1, wasm.main(1));
+  assertEquals(2, wasm.main(2));
+  assertEquals(3, wasm.main(3));
+  assertEquals(4, wasm.main(4));
+  assertEquals(7, wasm.main(7));
+  assertEquals(10, wasm.main(10));
+  assertEquals(11, wasm.main(11));
+  assertEquals(12, wasm.main(12));
+  assertEquals(13, wasm.main(13));
+  assertEquals(16, wasm.main(16));
+  assertEquals(-1, wasm.main(20));
+})();
+
+(function TestSwitchFallthroughWithBrTable() {
+  function asmModule() {
+    "use asm";
+    function main(x) {
+      x = x|0;
+      var ret = 0;
+      switch(x|0) {
+        case 1: {
+          ret = 1;
+          break;
+        }
+        case 2: {
+          ret = 2;
+          break;
+        }
+        case 3: {
+          ret = 3;
+        }
+        case 4: {
+          ret = 4;
+          break;
+        }
+        default: {
+          ret = 10;
+          break;
+        }
+      }
+      return ret|0;
+    }
+    return {
+      main: main,
+    };
+  }
+  var wasm = Wasm.instantiateModuleFromAsm(asmModule.toString());
+  assertEquals(2, wasm.main(2));
+  assertEquals(10, wasm.main(10));
+  assertEquals(4, wasm.main(3));
+})();
+
+(function TestSwitchFallthroughHybrid() {
+  function asmModule() {
+    "use asm";
+    function main(x) {
+      x = x|0;
+      var ret = 0;
+      switch(x|0) {
+        case 1: {
+          ret = 1;
+          break;
+        }
+        case 2: {
+          ret = 2;
+          break;
+        }
+        case 3: {
+          ret = 3;
+          break;
+        }
+        case 4: {
+          ret = 4;
+        }
+        case 7: {
+          ret = 7;
+          break;
+        }
+        case 10: {
+          ret = 10;
+        }
+        case 16: {
+          ret = 16;
+          break;
+        }
+        case 17: {
+          ret = 17;
+          break;
+        }
+        case 18: {
+          ret = 18;
+          break;
+        }
+        case 19: {
+          ret = 19;
+        }
+        default: {
+          ret = -1;
+          break;
+        }
+      }
+      return ret|0;
+    }
+    return {
+      main: main,
+    };
+  }
+  var wasm = Wasm.instantiateModuleFromAsm(asmModule.toString());
+  assertEquals(7, wasm.main(4));
+  assertEquals(16, wasm.main(10));
+  assertEquals(-1, wasm.main(19));
+  assertEquals(-1, wasm.main(23));
+})();
+
+(function TestSwitchHybridWithNoDefault() {
+  function asmModule() {
+    "use asm";
+    function main(x) {
+      x = x|0;
+      var ret = 19;
+      switch(x|0) {
+        case 1: {
+          ret = 1;
+          break;
+        }
+        case 2: {
+          ret = 2;
+          break;
+        }
+        case 3: {
+          ret = 3;
+          break;
+        }
+        case 4: {
+          ret = 4;
+          break;
+        }
+        case 7: {
+          ret = 7;
+          break;
+        }
+      }
+      return ret|0;
+    }
+    return {
+      main: main,
+    };
+  }
+  var wasm = Wasm.instantiateModuleFromAsm(asmModule.toString());
+  assertEquals(2, wasm.main(2));
+  assertEquals(7, wasm.main(7));
+  assertEquals(19, wasm.main(-1));
+})();
+
+(function TestLargeSwitch() {
+  function LargeSwitchGenerator(size, gap, handle_case) {
+    var str = "function asmModule() {\
+      \"use asm\";\
+      function main(x) {\
+        x = x|0;\
+        switch(x|0) {";
+    for (var i = 0; i < size; i++) {
+      str = str.concat("case ", i*gap.toString(), ": ", handle_case(i*gap));
+    }
+    str = str.concat("default: return -1;\
+        }\
+        return -2;\
+      }\
+      return {main: main}; }");
+
+    var wasm = Wasm.instantiateModuleFromAsm(str);
+    return wasm;
+  }
+
+  var wasm = LargeSwitchGenerator(513, 1, function(k) {
+                  return "return ".concat(k, ";");

[bradn, 2016/04/12 20:36:10]

Tabbing is a little weird on this, I usually do just 2 for a nested function
(but consult the style guide to be sure).

[aseemgarg, 2016/04/12 22:20:17]

Changed to using variable. Much cleaner.

+                });
+  for (var i = 0; i < 513; i++) {
+    assertEquals(i, wasm.main(i));
+  }
+  assertEquals(-1, wasm.main(-1));
+
+  wasm = LargeSwitchGenerator(256, 3, function(k) {
+              return "return ".concat(k, ";");
+            });
+  for (var i = 0; i < 256; i++) {
+    assertEquals(i*3, wasm.main(i*3));
+  }
+  assertEquals(-1, wasm.main(-1));
+
+  wasm = LargeSwitchGenerator(212, 7, function(k) {
+              if (k != 7) return "return ".concat(k, ";");
+              else return "break;";
+            });
+  for (var i = 0; i < 212; i++) {
+    if (i == 1) assertEquals(-2, wasm.main(i*7));
+    else assertEquals(i*7, wasm.main(i*7));
+  }
+  assertEquals(-1, wasm.main(-1));
+
+  wasm = LargeSwitchGenerator(319, 2, function(k) {
+              if (k != 56) return "break;";
+              else return "return 23;";
+            });
+  for (var i = 0; i < 319; i++) {
+    if (i == 28) assertEquals(23, wasm.main(i*2));
+    else assertEquals(-2, wasm.main(i*2));
+  }
+  assertEquals(-1, wasm.main(-1));
+})();