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+//===---------------------------------------------------------------------===//
+// Random Notes
+//===---------------------------------------------------------------------===//
+
+C90/C99/C++ Comparisons:
+http://david.tribble.com/text/cdiffs.htm
+
+//===---------------------------------------------------------------------===//
+
+To time GCC preprocessing speed without output, use:
+   "time gcc -MM file"
+This is similar to -Eonly.
+
+//===---------------------------------------------------------------------===//
+
+Creating and using a PTH file for performance measurement (use a release-asserts
+build).
+
+$ clang -x objective-c-header INPUTS/Cocoa_h.m -o /tmp/tokencache
+$ clang -token-cache /tmp/tokencache INPUTS/Cocoa_h.m
+
+//===---------------------------------------------------------------------===//
+
+  C++ Template Instantiation benchmark:
+     http://users.rcn.com/abrahams/instantiation_speed/index.html
+
+//===---------------------------------------------------------------------===//
+
+TODO: File Manager Speedup:
+
+ We currently do a lot of stat'ing for files that don't exist, particularly
+ when lots of -I paths exist (e.g. see the <iostream> example, check for
+ failures in stat in FileManager::getFile).  It would be far better to make
+ the following changes:
+   1. FileEntry contains a sys::Path instead of a std::string for Name.
+   2. sys::Path contains timestamp and size, lazily computed.  Eliminate from
+      FileEntry.
+   3. File UIDs are created on request, not when files are opened.
+ These changes make it possible to efficiently have FileEntry objects for
+ files that exist on the file system, but have not been used yet.
+ 
+ Once this is done:
+   1. DirectoryEntry gets a boolean value "has read entries".  When false, not
+      all entries in the directory are in the file mgr, when true, they are.
+   2. Instead of stat'ing the file in FileManager::getFile, check to see if 
+      the dir has been read.  If so, fail immediately, if not, read the dir,
+      then retry.
+   3. Reading the dir uses the getdirentries syscall, creating an FileEntry
+      for all files found.
+
+//===---------------------------------------------------------------------===//
+// Specifying targets:  -triple and -arch
+===---------------------------------------------------------------------===//
+
+The clang supports "-triple" and "-arch" options. At most one -triple and one
+-arch option may be specified.  Both are optional.
+
+The "selection of target" behavior is defined as follows:
+
+(1) If the user does not specify -triple, we default to the host triple.
+(2) If the user specifies a -arch, that overrides the arch in the host or
+    specified triple. 
+
+//===---------------------------------------------------------------------===//
+
+
+verifyInputConstraint and verifyOutputConstraint should not return bool. 
+
+Instead we should return something like:
+
+enum VerifyConstraintResult {
+  Valid,
+  
+  // Output only
+  OutputOperandConstraintLacksEqualsCharacter,
+  MatchingConstraintNotValidInOutputOperand,
+
+  // Input only
+  InputOperandConstraintContainsEqualsCharacter,
+  MatchingConstraintReferencesInvalidOperandNumber,
+  
+  // Both
+  PercentConstraintUsedWithLastOperand
+};
+
+//===---------------------------------------------------------------------===//