performance improvements and comments

sokra · sokra · commit 64c1e8a23ada · 2017-07-18T14:24:42.000+02:00
diff --git a/lib/optimize/AggressiveSplittingPlugin.js b/lib/optimize/AggressiveSplittingPlugin.js
@@ -39,6 +39,13 @@ class AggressiveSplittingPlugin {
 	apply(compiler) {
 		compiler.plugin("this-compilation", (compilation) => {
 			compilation.plugin("optimize-chunks-advanced", (chunks) => {
+				// Precompute stuff
+				const nameToModuleMap = new Map();
+				compilation.modules.forEach(m => {
+					const name = identifierUtils.makePathsRelative(compiler.context, m.identifier(), compilation.cache);
+					nameToModuleMap.set(name, m);
+				});
+
 				const savedSplits = compilation.records && compilation.records.aggressiveSplits || [];
 				const usedSplits = compilation._aggressiveSplittingSplits ?
 					savedSplits.concat(compilation._aggressiveSplittingSplits) : savedSplits;
@@ -48,45 +55,51 @@ class AggressiveSplittingPlugin {
 				// 1. try to restore to recorded splitting
 				for(let j = 0; j < usedSplits.length; j++) {
 					const splitData = usedSplits[j];
-					for(let i = 0; i < chunks.length; i++) {
-						const chunk = chunks[i];
+					const selectedModules = splitData.modules.map(name => nameToModuleMap.get(name));
 
-						if(chunk.getNumberOfModules() < splitData.modules.length)
-							continue;
+					// Does the modules exist at all?
+					if(selectedModules.every(Boolean)) {
 
-						const nameToModuleMap = new Map();
-						chunk.forEachModule(m => {
-							const name = identifierUtils.makePathsRelative(compiler.context, m.identifier(), compilation.cache);
-							nameToModuleMap.set(name, m);
-						});
+						// Find all chunks containing all modules in the split
+						for(let i = 0; i < chunks.length; i++) {
+							const chunk = chunks[i];
 
-						const selectedModules = splitData.modules.map(name => nameToModuleMap.get(name));
-						if(selectedModules.every(Boolean)) {
-							if(chunk.getNumberOfModules() > splitData.modules.length) {
-								const newChunk = compilation.addChunk();
-								selectedModules.forEach(moveModuleBetween(chunk, newChunk));
-								chunk.split(newChunk);
-								chunk.name = null;
-								newChunk._fromAggressiveSplitting = true;
-								if(j < savedSplits.length)
-									newChunk._fromAggressiveSplittingIndex = j;
-								if(splitData.id !== null && splitData.id !== undefined) {
-									newChunk.id = splitData.id;
-								}
-								newChunk.origins = chunk.origins.map(copyWithReason);
-								chunk.origins = chunk.origins.map(copyWithReason);
-								return true;
-							} else {
-								if(j < savedSplits.length)
-									chunk._fromAggressiveSplittingIndex = j;
-								chunk.name = null;
-								if(splitData.id !== null && splitData.id !== undefined) {
-									chunk.id = splitData.id;
+							// Cheap check if chunk is suitable at all
+							if(chunk.getNumberOfModules() < splitData.modules.length)
+								continue;
+
+							// Check if all modules are in the chunk
+							if(selectedModules.every(m => chunk.containsModule(m))) {
+
+								// Is chunk identical to the split or do we need to split it?
+								if(chunk.getNumberOfModules() > splitData.modules.length) {
+									// split the chunk into two parts
+									const newChunk = compilation.addChunk();
+									selectedModules.forEach(moveModuleBetween(chunk, newChunk));
+									chunk.split(newChunk);
+									chunk.name = null;
+									newChunk._fromAggressiveSplitting = true;
+									if(j < savedSplits.length)
+										newChunk._fromAggressiveSplittingIndex = j;
+									if(splitData.id !== null && splitData.id !== undefined) {
+										newChunk.id = splitData.id;
+									}
+									newChunk.origins = chunk.origins.map(copyWithReason);
+									chunk.origins = chunk.origins.map(copyWithReason);
+									return true;
+								} else { // chunk is identical to the split
+									if(j < savedSplits.length)
+										chunk._fromAggressiveSplittingIndex = j;
+									chunk.name = null;
+									if(splitData.id !== null && splitData.id !== undefined) {
+										chunk.id = splitData.id;
+									}
 								}
 							}
 						}
 					}
 				}
+
 				// 2. for any other chunk which isn't splitted yet, split it
 				for(let i = 0; i < chunks.length; i++) {
 					const chunk = chunks[i];
