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137 lines
6.1 KiB
Plaintext
137 lines
6.1 KiB
Plaintext
//===---------------------------------------------------------------------===//
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// Random Notes
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//===---------------------------------------------------------------------===//
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C90/C99/C++ Comparisons:
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http://david.tribble.com/text/cdiffs.htm
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//===---------------------------------------------------------------------===//
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To time GCC preprocessing speed without output, use:
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"time gcc -MM file"
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This is similar to -Eonly.
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//===---------------------------------------------------------------------===//
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C++ Template Instantiation benchmark:
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http://users.rcn.com/abrahams/instantiation_speed/index.html
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//===---------------------------------------------------------------------===//
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TODO: File Manager Speedup:
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We currently do a lot of stat'ing for files that don't exist, particularly
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when lots of -I paths exist (e.g. see the <iostream> example, check for
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failures in stat in FileManager::getFile). It would be far better to make
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the following changes:
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1. FileEntry contains a sys::Path instead of a std::string for Name.
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2. sys::Path contains timestamp and size, lazily computed. Eliminate from
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FileEntry.
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3. File UIDs are created on request, not when files are opened.
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These changes make it possible to efficiently have FileEntry objects for
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files that exist on the file system, but have not been used yet.
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Once this is done:
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1. DirectoryEntry gets a boolean value "has read entries". When false, not
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all entries in the directory are in the file mgr, when true, they are.
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2. Instead of stat'ing the file in FileManager::getFile, check to see if
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the dir has been read. If so, fail immediately, if not, read the dir,
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then retry.
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3. Reading the dir uses the getdirentries syscall, creating an FileEntry
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for all files found.
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//===---------------------------------------------------------------------===//
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TODO: Fast #Import:
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* Get frameworks that don't use #import to do so, e.g.
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DirectoryService, AudioToolbox, CoreFoundation, etc. Why not using #import?
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Because they work in C mode? C has #import.
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* Have the lexer return a token for #import instead of handling it itself.
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- Create a new preprocessor object with no external state (no -D/U options
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from the command line, etc). Alternatively, keep track of exactly which
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external state is used by a #import: declare it somehow.
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* When having reading a #import file, keep track of whether we have (and/or
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which) seen any "configuration" macros. Various cases:
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- Uses of target args (__POWERPC__, __i386): Header has to be parsed
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multiple times, per-target. What about #ifndef checks? How do we know?
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- "Configuration" preprocessor macros not defined: POWERPC, etc. What about
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things like __STDC__ etc? What is and what isn't allowed.
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* Special handling for "umbrella" headers, which just contain #import stmts:
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- Cocoa.h/AppKit.h - Contain pointers to digests instead of entire digests
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themselves? Foundation.h isn't pure umbrella!
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* Frameworks digests:
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- Can put "digest" of a framework-worth of headers into the framework
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itself. To open AppKit, just mmap
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/System/Library/Frameworks/AppKit.framework/"digest", which provides a
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symbol table in a well defined format. Lazily unstream stuff that is
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needed. Contains declarations, macros, and debug information.
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- System frameworks ship with digests. How do we handle configuration
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information? How do we handle stuff like:
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#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_2
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which guards a bunch of decls? Should there be a couple of default
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configs, then have the UI fall back to building/caching its own?
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- GUI automatically builds digests when UI is idle, both of system
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frameworks if they aren't not available in the right config, and of app
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frameworks.
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- GUI builds dependence graph of frameworks/digests based on #imports. If a
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digest is out date, dependent digests are automatically invalidated.
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* New constraints on #import for objc-v3:
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- #imported file must not define non-inline function bodies.
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- Alternatively, they can, and these bodies get compiled/linked *once*
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per app into a dylib. What about building user dylibs?
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- Restrictions on ObjC grammar: can't #import the body of a for stmt or fn.
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- Compiler must detect and reject these cases.
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- #defines defined within a #import have two behaviors:
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- By default, they escape the header. These macros *cannot* be #undef'd
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by other code: this is enforced by the front-end.
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- Optionally, user can specify what macros escape (whitelist) or can use
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#undef.
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//===---------------------------------------------------------------------===//
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TODO: New language feature: Configuration queries:
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- Instead of #ifdef __POWERPC__, use "if (strcmp(`cpu`, __POWERPC__))", or
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some other, better, syntax.
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- Use it to increase the number of "architecture-clean" #import'd files,
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allowing a single index to be used for all fat slices.
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//===---------------------------------------------------------------------===//
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// Specifying targets: -triple and -arch
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===---------------------------------------------------------------------===//
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The clang supports "-triple" and "-arch" options. At most one -triple and one
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-arch option may be specified. Both are optional.
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The "selection of target" behavior is defined as follows:
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(1) If the user does not specify -triple, we default to the host triple.
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(2) If the user specifies a -arch, that overrides the arch in the host or
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specified triple.
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//===---------------------------------------------------------------------===//
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verifyInputConstraint and verifyOutputConstraint should not return bool.
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Instead we should return something like:
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enum VerifyConstraintResult {
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Valid,
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// Output only
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OutputOperandConstraintLacksEqualsCharacter,
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MatchingConstraintNotValidInOutputOperand,
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// Input only
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InputOperandConstraintContainsEqualsCharacter,
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MatchingConstraintReferencesInvalidOperandNumber,
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// Both
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PercentConstraintUsedWithLastOperand
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};
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//===---------------------------------------------------------------------===//
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