keep a cache of source location

remix-lib/src/sourceLocationTracker.js

@@ -11,6 +11,8 @@ function SourceLocationTracker (_codeManager) {
   this.codeManager = _codeManager
   this.event = new EventManager()
   this.sourceMappingDecoder = new SourceMappingDecoder()
+  this.sourceMapCacheOfInstructionIndex = {}
+  this.sourceMapCacheOfVMTraceIndex = {}
 }
 
 /**
@@ -23,10 +25,14 @@ function SourceLocationTracker (_codeManager) {
  */
 SourceLocationTracker.prototype.getSourceLocationFromInstructionIndex = function (address, index, contracts, cb) {
   var self = this
+  if (self.sourceMapCacheOfInstructionIndex[address]) {
+    return cb(null, self.sourceMappingDecoder.atIndex(index, self.sourceMapCacheOfInstructionIndex[address]))
+  }
   extractSourceMap(this.codeManager, address, contracts, function (error, sourceMap) {
     if (error) {
       cb(error)
     } else {
+      if (!helper.isContractCreation(address)) self.sourceMapCacheOfInstructionIndex[address] = sourceMap
       cb(null, self.sourceMappingDecoder.atIndex(index, sourceMap))
     }
   })
@@ -42,12 +48,16 @@ SourceLocationTracker.prototype.getSourceLocationFromInstructionIndex = function
  */
 SourceLocationTracker.prototype.getSourceLocationFromVMTraceIndex = function (address, vmtraceStepIndex, contracts, cb) {
   var self = this
+  if (self.sourceMapCacheOfVMTraceIndex[address]) {
+    return cb(null, self.sourceMappingDecoder.atIndex(vmtraceStepIndex, self.sourceMapCacheOfVMTraceIndex[address]))
+  }
   extractSourceMap(this.codeManager, address, contracts, function (error, sourceMap) {
     if (!error) {
       self.codeManager.getInstructionIndex(address, vmtraceStepIndex, function (error, index) {
         if (error) {
           cb(error)
         } else {
+          if (!helper.isContractCreation(address)) self.sourceMapCacheOfVMTraceIndex[address] = sourceMap
           cb(null, self.sourceMappingDecoder.atIndex(index, sourceMap))
         }
       })