1 //===---------------------------------------------------------------------===// 2 // Random Notes 3 //===---------------------------------------------------------------------===// 4 5 C90/C99/C++ Comparisons: 6 http://david.tribble.com/text/cdiffs.htm 7 8 //===---------------------------------------------------------------------===// 9 10 To time GCC preprocessing speed without output, use: 11 "time gcc -MM file" 12 This is similar to -Eonly. 13 14 //===---------------------------------------------------------------------===// 15 16 Creating and using a PTH file for performance measurement (use a release build). 17 18 $ clang -ccc-pch-is-pth -x objective-c-header INPUTS/Cocoa_h.m -o /tmp/tokencache 19 $ clang -cc1 -token-cache /tmp/tokencache INPUTS/Cocoa_h.m 20 21 //===---------------------------------------------------------------------===// 22 23 C++ Template Instantiation benchmark: 24 http://users.rcn.com/abrahams/instantiation_speed/index.html 25 26 //===---------------------------------------------------------------------===// 27 28 TODO: File Manager Speedup: 29 30 We currently do a lot of stat'ing for files that don't exist, particularly 31 when lots of -I paths exist (e.g. see the <iostream> example, check for 32 failures in stat in FileManager::getFile). It would be far better to make 33 the following changes: 34 1. FileEntry contains a sys::Path instead of a std::string for Name. 35 2. sys::Path contains timestamp and size, lazily computed. Eliminate from 36 FileEntry. 37 3. File UIDs are created on request, not when files are opened. 38 These changes make it possible to efficiently have FileEntry objects for 39 files that exist on the file system, but have not been used yet. 40 41 Once this is done: 42 1. DirectoryEntry gets a boolean value "has read entries". When false, not 43 all entries in the directory are in the file mgr, when true, they are. 44 2. Instead of stat'ing the file in FileManager::getFile, check to see if 45 the dir has been read. If so, fail immediately, if not, read the dir, 46 then retry. 47 3. Reading the dir uses the getdirentries syscall, creating an FileEntry 48 for all files found. 49 50 //===---------------------------------------------------------------------===// 51 // Specifying targets: -triple and -arch 52 //===---------------------------------------------------------------------===// 53 54 The clang supports "-triple" and "-arch" options. At most one -triple and one 55 -arch option may be specified. Both are optional. 56 57 The "selection of target" behavior is defined as follows: 58 59 (1) If the user does not specify -triple, we default to the host triple. 60 (2) If the user specifies a -arch, that overrides the arch in the host or 61 specified triple. 62 63 //===---------------------------------------------------------------------===// 64 65 66 verifyInputConstraint and verifyOutputConstraint should not return bool. 67 68 Instead we should return something like: 69 70 enum VerifyConstraintResult { 71 Valid, 72 73 // Output only 74 OutputOperandConstraintLacksEqualsCharacter, 75 MatchingConstraintNotValidInOutputOperand, 76 77 // Input only 78 InputOperandConstraintContainsEqualsCharacter, 79 MatchingConstraintReferencesInvalidOperandNumber, 80 81 // Both 82 PercentConstraintUsedWithLastOperand 83 }; 84 85 //===---------------------------------------------------------------------===// 86 87 Blocks should not capture variables that are only used in dead code. 88 89 The rule that we came up with is that blocks are required to capture 90 variables if they're referenced in evaluated code, even if that code 91 doesn't actually rely on the value of the captured variable. 92 93 For example, this requires a capture: 94 (void) var; 95 But this does not: 96 if (false) puts(var); 97 98 Summary of <rdar://problem/9851835>: if we implement this, we should 99 warn about non-POD variables that are referenced but not captured, but 100 only if the non-reachability is not due to macro or template 101 metaprogramming. 102 103 //===---------------------------------------------------------------------===// 104
