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node_modules/webpack/lib/optimize/FlagIncludedChunksPlugin.js

@@ -5,30 +5,94 @@
 "use strict";
 
 class FlagIncludedChunksPlugin {
-
 	apply(compiler) {
-		compiler.plugin("compilation", (compilation) => {
-			compilation.plugin("optimize-chunk-ids", (chunks) => {
-				chunks.forEach((chunkA) => {
-					chunks.forEach((chunkB) => {
-						// as we iterate the same iterables twice
-						// skip if we find ourselves
-						if(chunkA === chunkB) return;
+		compiler.hooks.compilation.tap("FlagIncludedChunksPlugin", compilation => {
+			compilation.hooks.optimizeChunkIds.tap(
+				"FlagIncludedChunksPlugin",
+				chunks => {
+					// prepare two bit integers for each module
+					// 2^31 is the max number represented as SMI in v8
+					// we want the bits distributed this way:
+					// the bit 2^31 is pretty rar and only one module should get it
+					// so it has a probability of 1 / modulesCount
+					// the first bit (2^0) is the easiest and every module could get it
+					// if it doesn't get a better bit
+					// from bit 2^n to 2^(n+1) there is a probability of p
+					// so 1 / modulesCount == p^31
+					// <=> p = sqrt31(1 / modulesCount)
+					// so we use a modulo of 1 / sqrt31(1 / modulesCount)
+					const moduleBits = new WeakMap();
+					const modulesCount = compilation.modules.length;
 
-						// instead of swapping A and B just bail
-						// as we loop twice the current A will be B and B then A
-						if(chunkA.getNumberOfModules() < chunkB.getNumberOfModules()) return;
+					// precalculate the modulo values for each bit
+					const modulo = 1 / Math.pow(1 / modulesCount, 1 / 31);
+					const modulos = Array.from(
+						{ length: 31 },
+						(x, i) => Math.pow(modulo, i) | 0
+					);
 
-						if(chunkB.getNumberOfModules() === 0) return;
-
-						// is chunkB in chunkA?
-						for(const m of chunkB.modulesIterable) {
-							if(!chunkA.containsModule(m)) return;
+					// iterate all modules to generate bit values
+					let i = 0;
+					for (const module of compilation.modules) {
+						let bit = 30;
+						while (i % modulos[bit] !== 0) {
+							bit--;
 						}
-						chunkA.ids.push(chunkB.id);
-					});
-				});
-			});
+						moduleBits.set(module, 1 << bit);
+						i++;
+					}
+
+					// interate all chunks to generate bitmaps
+					const chunkModulesHash = new WeakMap();
+					for (const chunk of chunks) {
+						let hash = 0;
+						for (const module of chunk.modulesIterable) {
+							hash |= moduleBits.get(module);
+						}
+						chunkModulesHash.set(chunk, hash);
+					}
+
+					for (const chunkA of chunks) {
+						const chunkAHash = chunkModulesHash.get(chunkA);
+						const chunkAModulesCount = chunkA.getNumberOfModules();
+						if (chunkAModulesCount === 0) continue;
+						let bestModule = undefined;
+						for (const module of chunkA.modulesIterable) {
+							if (
+								bestModule === undefined ||
+								bestModule.getNumberOfChunks() > module.getNumberOfChunks()
+							)
+								bestModule = module;
+						}
+						loopB: for (const chunkB of bestModule.chunksIterable) {
+							// as we iterate the same iterables twice
+							// skip if we find ourselves
+							if (chunkA === chunkB) continue;
+
+							const chunkBModulesCount = chunkB.getNumberOfModules();
+
+							// ids for empty chunks are not included
+							if (chunkBModulesCount === 0) continue;
+
+							// instead of swapping A and B just bail
+							// as we loop twice the current A will be B and B then A
+							if (chunkAModulesCount > chunkBModulesCount) continue;
+
+							// is chunkA in chunkB?
+
+							// we do a cheap check for the hash value
+							const chunkBHash = chunkModulesHash.get(chunkB);
+							if ((chunkBHash & chunkAHash) !== chunkAHash) continue;
+
+							// compare all modules
+							for (const m of chunkA.modulesIterable) {
+								if (!chunkB.containsModule(m)) continue loopB;
+							}
+							chunkB.ids.push(chunkA.id);
+						}
+					}
+				}
+			);
 		});
 	}
 }