112 lines
4.3 KiB
Text
112 lines
4.3 KiB
Text
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//===---------------------------------------------------------------------===//
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// Random Notes
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//===---------------------------------------------------------------------===//
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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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Creating and using a PTH file for performance measurement (use a release build).
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$ clang -ccc-pch-is-pth -x objective-c-header INPUTS/Cocoa_h.m -o /tmp/tokencache
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$ clang -cc1 -token-cache /tmp/tokencache INPUTS/Cocoa_h.m
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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 a FileEntry
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for all files found.
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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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Blocks should not capture variables that are only used in dead code.
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The rule that we came up with is that blocks are required to capture
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variables if they're referenced in evaluated code, even if that code
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doesn't actually rely on the value of the captured variable.
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For example, this requires a capture:
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(void) var;
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But this does not:
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if (false) puts(var);
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Summary of <rdar://problem/9851835>: if we implement this, we should
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warn about non-POD variables that are referenced but not captured, but
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only if the non-reachability is not due to macro or template
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metaprogramming.
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//===---------------------------------------------------------------------===//
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We can still apply a modified version of the constructor/destructor
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delegation optimization in cases of virtual inheritance where:
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- there is no function-try-block,
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- the constructor signature is not variadic, and
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- the parameter variables can safely be copied and repassed
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to the base constructor because either
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- they have not had their addresses taken by the vbase initializers or
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- they were passed indirectly.
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//===---------------------------------------------------------------------===//
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