1 //===---------------------------------------------------------------------===// 2 // Random Notes 3 //===---------------------------------------------------------------------===// 4 5 //===---------------------------------------------------------------------===// 6 7 To time GCC preprocessing speed without output, use: 8 "time gcc -MM file" 9 This is similar to -Eonly. 10 11 //===---------------------------------------------------------------------===// 12 13 Creating and using a PTH file for performance measurement (use a release build). 14 15 $ clang -ccc-pch-is-pth -x objective-c-header INPUTS/Cocoa_h.m -o /tmp/tokencache 16 $ clang -cc1 -token-cache /tmp/tokencache INPUTS/Cocoa_h.m 17 18 //===---------------------------------------------------------------------===// 19 20 C++ Template Instantiation benchmark: 21 http://users.rcn.com/abrahams/instantiation_speed/index.html 22 23 //===---------------------------------------------------------------------===// 24 25 TODO: File Manager Speedup: 26 27 We currently do a lot of stat'ing for files that don't exist, particularly 28 when lots of -I paths exist (e.g. see the <iostream> example, check for 29 failures in stat in FileManager::getFile). It would be far better to make 30 the following changes: 31 1. FileEntry contains a sys::Path instead of a std::string for Name. 32 2. sys::Path contains timestamp and size, lazily computed. Eliminate from 33 FileEntry. 34 3. File UIDs are created on request, not when files are opened. 35 These changes make it possible to efficiently have FileEntry objects for 36 files that exist on the file system, but have not been used yet. 37 38 Once this is done: 39 1. DirectoryEntry gets a boolean value "has read entries". When false, not 40 all entries in the directory are in the file mgr, when true, they are. 41 2. Instead of stat'ing the file in FileManager::getFile, check to see if 42 the dir has been read. If so, fail immediately, if not, read the dir, 43 then retry. 44 3. Reading the dir uses the getdirentries syscall, creating a FileEntry 45 for all files found. 46 47 //===---------------------------------------------------------------------===// 48 // Specifying targets: -triple and -arch 49 //===---------------------------------------------------------------------===// 50 51 The clang supports "-triple" and "-arch" options. At most one -triple and one 52 -arch option may be specified. Both are optional. 53 54 The "selection of target" behavior is defined as follows: 55 56 (1) If the user does not specify -triple, we default to the host triple. 57 (2) If the user specifies a -arch, that overrides the arch in the host or 58 specified triple. 59 60 //===---------------------------------------------------------------------===// 61 62 63 verifyInputConstraint and verifyOutputConstraint should not return bool. 64 65 Instead we should return something like: 66 67 enum VerifyConstraintResult { 68 Valid, 69 70 // Output only 71 OutputOperandConstraintLacksEqualsCharacter, 72 MatchingConstraintNotValidInOutputOperand, 73 74 // Input only 75 InputOperandConstraintContainsEqualsCharacter, 76 MatchingConstraintReferencesInvalidOperandNumber, 77 78 // Both 79 PercentConstraintUsedWithLastOperand 80 }; 81 82 //===---------------------------------------------------------------------===// 83 84 Blocks should not capture variables that are only used in dead code. 85 86 The rule that we came up with is that blocks are required to capture 87 variables if they're referenced in evaluated code, even if that code 88 doesn't actually rely on the value of the captured variable. 89 90 For example, this requires a capture: 91 (void) var; 92 But this does not: 93 if (false) puts(var); 94 95 Summary of <rdar://problem/9851835>: if we implement this, we should 96 warn about non-POD variables that are referenced but not captured, but 97 only if the non-reachability is not due to macro or template 98 metaprogramming. 99 100 //===---------------------------------------------------------------------===// 101 102 We can still apply a modified version of the constructor/destructor 103 delegation optimization in cases of virtual inheritance where: 104 - there is no function-try-block, 105 - the constructor signature is not variadic, and 106 - the parameter variables can safely be copied and repassed 107 to the base constructor because either 108 - they have not had their addresses taken by the vbase initializers or 109 - they were passed indirectly. 110 111 //===---------------------------------------------------------------------===// 112
