diff options
Diffstat (limited to 'tools/js-optimizer.js')
| -rw-r--r-- | tools/js-optimizer.js | 142 |
1 files changed, 132 insertions, 10 deletions
diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js index bf971951..4d4ff1a9 100644 --- a/tools/js-optimizer.js +++ b/tools/js-optimizer.js @@ -357,6 +357,136 @@ function simplifyExpressionsPost(ast) { simplifyNotComps(ast); } +// Multiple blocks from the relooper are, in general, implemented by +// if (__label__ == x) { } else if .. +// and branching into them by +// if (condition) { __label__ == x } else .. +// We can hoist the multiple block into the condition, thus removing code and one 'if' check +function hoistMultiples(ast) { + ast[1].forEach(function(node, i) { + var type = node[0]; + if (type == 'defun') { + var statements = node[3]; + for (var i = 0; i < statements.length-1; i++) { + var modified = false; + var pre = statements[i]; + if (pre[0] != 'if') continue; + var post = statements[i+1]; + // Look into some block types. shell() will then recreate the shell that we looked into + var postInner = post; + var shell = function(x) { return x }; + while (true) { + /*if (postInner[0] == 'block') { + postInner = postInner[1][0]; + } else */if (postInner[0] == 'label') { + shell = (function(oldShell, oldPostInner) { + return function(x) { + return oldShell(['label', oldPostInner[1], x]); + }; + })(shell, postInner); + postInner = postInner[2]; + } else if (postInner[0] == 'do') { + shell = (function(oldShell, oldPostInner) { + return function(x) { + return oldShell(['do', copy(oldPostInner[1]), ['block', [x]]]); + } + })(shell, postInner);; + postInner = postInner[2][1][0]; + } else { + break; // give up + } + } + if (postInner[0] != 'if') continue; + // Look into this if, and its elseifs + while (postInner) { + assert(postInner[0] == 'if'); + var cond = postInner[1]; + if (cond[0] == 'binary' && cond[1] == '==' && cond[2][0] == 'name' && cond[2][1] == '__label__') { + assert(cond[3][0] == 'num'); + // We have a valid Multiple check here. Try to hoist it, look for the source in |pre| and its else's + var labelNum = cond[3][1]; + var labelBlock = postInner[2]; + assert(labelBlock[0] == 'block'); + var found = false; + traverse(pre, function(preNode, preType) { + if (!found && preType == 'assign' && preNode[2][0] == 'name' && preNode[2][1] == '__label__') { + assert(preNode[3][0] == 'num'); + if (preNode[3][1] == labelNum) { + // That's it! Hoist away + found = true; + modified = true; + postInner[2] = ['block', []]; + return ['block', [preNode].concat(labelBlock[1])]; + } + } + }); + } + postInner = postInner[3]; // Proceed to look in the else clause + } + if (modified) { + statements[i] = shell(pre); + } + } + } + }); + + // Clear out empty ifs and blocks, and redundant blocks/stats + var more = true; + while (more) { + more = false; + traverse(ast, function(node, type) { + if (type == 'if' && node[2][0] == 'block' && node[2][1].length == 0) { + more = true; + if (node[2][2]) { // if there is an else, return that + return node[2][2]; + } else { + return emptyNode(); + } + } else if (type == 'block' && !node[1]) { + return emptyNode(); + } else if (type == 'block' && (node[1].length == 0 || (node[1].length == 1 && jsonCompare(node[1][0], emptyNode())))) { + more = true; + return emptyNode(); + } else if (type == 'block' && node[1].length == 1 && node[1][0][0] == 'block') { + more = true; + return node[1][0]; + } else if (type == 'stat' && node[1][0] == 'block') { + more = true; + return node[1]; + } else if (type == 'block') { + var pre = node[1].length; + node[1] = node[1].filter(function(blockItem) { return !jsonCompare(blockItem, emptyNode()) }); + if (node[1].length < pre) { + more = true; + return node; + } + } else if (type == 'defun' && node[3].length == 1 && node[3][0][0] == 'block') { + more = true; + node[3] = node[3][0][1]; + return node; + } else if (type == 'defun') { + var pre = node[3].length; + node[3] = node[3].filter(function(blockItem) { return !jsonCompare(blockItem, emptyNode()) }); + if (node[3].length < pre) { + more = true; + return node; + } + } else if (type == 'do' && node[1][0] == 'num' && jsonCompare(node[2], emptyNode())) { + more = true; + return emptyNode(); + } else if (type == 'label' && jsonCompare(node[2], emptyNode())) { + more = true; + return emptyNode(); + } else if (type == 'if' && jsonCompare(node[3], emptyNode())) { // empty else clauses + node[3] = null; + return node; + } + }); + } +} + +// Simplifies loops +// WARNING: This assumes all loops and breaks/continues are labelled function loopOptimizer(ast) { // Remove unneeded labels and one-time (do while(0)) loops. It is convenient to do these both at once. function passTwo(ast) { @@ -442,6 +572,7 @@ var passes = { //removeUnneededLabelSettings: removeUnneededLabelSettings, simplifyExpressionsPre: simplifyExpressionsPre, simplifyExpressionsPost: simplifyExpressionsPost, + hoistMultiples: hoistMultiples, loopOptimizer: loopOptimizer }; @@ -457,16 +588,7 @@ if (metadata) setGeneratedFunctions(metadata); arguments.forEach(function(arg) { passes[arg](ast); }); -/* TODO: run only on generated functions (but, some passes look at globals...) -arguments.forEach(function(arg) { - ast[1].forEach(function(node, i) { - if (node[0] == 'defun' && isGenerated(node[1])) { - passes[arg](node); - } - }); -}); -*/ - +ast = srcToAst(astToSrc(ast)); // re-parse, to simplify a little print(astToSrc(ast)); if (metadata) print(metadata + '\n'); |