optimized switch implementation

test/mjsunit/wasm/asm-wasm.js

Index: test/mjsunit/wasm/asm-wasm.js
diff --git a/test/mjsunit/wasm/asm-wasm.js b/test/mjsunit/wasm/asm-wasm.js
index 2efb006436a23333c7bf5bb48d92a46022a7d2d5..b7e866eeb8675a021ccc06633d3dfea4f362a176 100644
--- a/test/mjsunit/wasm/asm-wasm.js
+++ b/test/mjsunit/wasm/asm-wasm.js
@@ -1493,3 +1493,134 @@ assertWasm(1, TestXor);
   assertEquals(0x80000000, wasm.u0x80000000());
   assertEquals(0x87654321, wasm.u0x87654321());
 })();
+
+(function TestSwitchWithBrTable() {

[titzer, 2016/04/01 09:22:45]

Please pull these out into a new test file: test/mjsunit/wasm/asm-wasm-switch.js

[aseemgarg, 2016/04/07 23:32:36]

Done.

+  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(21));
+})();
+
+(function TestSwitchWithBalancedTree() {

[titzer, 2016/04/01 09:22:45]

There need to be a lot more tests, e.g. with break and fall through, the default
case in the middle, and many other permutations.

[aseemgarg, 2016/04/07 23:32:36]

Some of the tests were there before. Added some more.

+  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 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));
+})();

[bradn, 2016/04/04 22:31:12]

Yeah actually what would be really nice to vet tables larger than 256 don't blow
up.

How about an mjsunit test that:
Uses strings to build of the body of an asm module that does a large random
remapping with random fall-thrus like:
switch(x|0) {
  case 11:
  case 7:
    return 5;
  case 9:
  case 10:
    return 6;
  ...
}

And then check all the values in some range.

[aseemgarg, 2016/04/07 23:32:36]

Done.