pegjs#30: remove usage of BREAK opcode.

Mingun · Sep 20, 2013 · e14add5 · e14add5
1 parent 292a4bf
commit e14add5
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Showing 2 changed files with 30 additions and 38 deletions.
diff --git a/lib/compiler/passes/generate-bytecode.js b/lib/compiler/passes/generate-bytecode.js
@@ -197,10 +197,9 @@ var utils = require("../../utils"),
  *          interpret(ip + 3 + t, ip + 3 + t + f);
  *        }
  *
- * [29] BREAK x
+ * [29] BREAK offsetToBreakableInstruction - now instruction not used.
  *
  *        break;
- *        interpret(ip + 1 + x);
  */
 module.exports = function(ast, options) {
   var consts = [];
@@ -564,39 +563,33 @@ module.exports = function(ast, options) {
           });*/
       var minIndex = addConst(node.min);
       var maxIndex = addConst(node.max);
-      var loopCode = buildLoop(
-            [op.WHILE_NOT_ERROR],     // while (elem !== null) {
-            buildSequence(
-              [op.APPEND],            //   result.push(elem);     stack:[ [elem...] ]
-              [op.PUSH, maxIndex],    //                          stack:[ [elem...], min ]
-              buildCondition(         //   if (max !== undefined && result.length >= max)
-                [op.IF_ARRLEN_MAX],   //                          stack:[ [elem...] ]
-                [op.PUSH, nullIndex], //     elem = null;         stack:[ [elem...], null ]
-                expressionCode        //   else
-              )                       //     elem = expr();       stack:[ [elem...], elem ]
-            )
-          );                          // }                        stack:[ [elem...], elem ]
-      // var placeholderOffset = 2 + 1 + 2 + 3;
-          //                  ^   ^   ^   ^
-          //                  |   |   |   '- op.IF_ARRLEN_MAX + `then` len + `else` len
-          //                  |   |   '----- op.PUSH, maxIndex
-          //                  |   '--------- op.APPEND
-          //                  '------------- op.WHILE_NOT_ERROR + loop body len
-      // Replace placeholder after op.BREAK to offset to breakable instruction.
-      // loopCode[placeholderOffset+1] = -placeholderOffset;// Go to op.WHILE_NOT_ERROR
 
       return buildSequence(
         [op.PUSH, emptyArrayIndex], // var result = []          stack:[ [] ]
         expressionCode,             // var elem = expr();       stack:[ [], elem ]
-        loopCode,                   // while (elem !== null) {...}
+        buildLoop(
+          [op.WHILE_NOT_ERROR],     // while (elem !== null) {
+          buildSequence(
+            [op.APPEND],            //   result.push(elem);     stack:[ [elem...] ]
+            // Check high boundary.
+            [op.PUSH, maxIndex],    //                          stack:[ [elem...], min ]
+            buildCondition(         //   if (max !== undefined && result.length >= max) {
+              [op.IF_ARRLEN_MAX],   //                          stack:[ [elem...] ]
+              // push `null` - this break loop on next iteration.
+              [op.PUSH, nullIndex], //     elem = null;         stack:[ [elem...], null ]
+              expressionCode        //   } else {
+            )                       //     elem = expr();       stack:[ [elem...], elem ]
+          )                         //   }
+        ),                          // }                        stack:[ [elem...], elem ]
         [op.POP],                   //                          stack:[ [elem...] ] (pop elem=`null`)
-        [op.PUSH, minIndex],        //                          stack:[ [elem...], min ]
-
+
         // Check low boundary.
+        [op.PUSH, minIndex],        //                          stack:[ [elem...], min ]
         buildCondition(             // if (min !== undefined && result.length < min) 
           [op.IF_ARRLEN_MIN],       //                          stack:[ [elem...] ]
           buildSequence(            //   result = null;
-            [op.POP], [op.PUSH, nullIndex]//                    stack:[ null ]
+            [op.POP],
+            [op.PUSH, nullIndex]    //                          stack:[ null ]
           ),
           []
         )

diff --git a/lib/compiler/passes/generate-javascript.js b/lib/compiler/passes/generate-javascript.js
@@ -321,18 +321,17 @@ module.exports = function(ast, options) {
       '          i = stack.pop();',
                  indent10(generateCondition('typeof(i)!=="undefined" && stack[stack.length - 1].length >= i', 0)),
       '        }',
-      '        case ' + op.BREAK + ': {',            // BREAK offsetToBreakableInstruction
-      '          if (ips.length == 0) throw new Error("Illegal bytecode: BREAK instruction not in loop: "+ip);',
-      // <current ip> + <breakable instruction ip offset>
-      '          i = ip + bc[ip + 1];',// get breakable instruction ip
-      '          do {ip = ips.pop(); end = ends.pop();} while (ip !== i);',
-      // push element as `null`, that mean 'too many elements, this element match failed'.
-      '          stack.push(null);',
-      //'          ip = (ip + bc[ip + 1]) + 1;',
-      // <opcode + field for len> + <len of breakable instruction body>
-      '          ip += 2 + bc[ip + 1];',
-      '          break;',
-      '        }',
+      // '        case ' + op.BREAK + ': {',            // BREAK offsetToBreakableInstruction
+      // '          if (ips.length == 0) throw new Error("Illegal bytecode: BREAK instruction not in loop: "+ip);',
+      // // <current ip> + <breakable instruction ip offset>
+      // '          i = ip + bc[ip + 1];',// get breakable instruction ip
+      // '          do {ip = ips.pop(); end = ends.pop();} while (ip !== i);',
+      // // push element as `null`, that mean 'too many elements, this element match failed'.
+      // '          stack.push(null);',
+      // // <opcode + field for len> + <len of breakable instruction body>
+      // '          ip += 2 + bc[ip + 1];',
+      // '          break;',
+      // '        }',
       '        default:',
       '          throw new Error("Invalid opcode: " + bc[ip] + ".");',
       '      }',