0a6b5b653e
When debugging a boost build with a modified version of Clang, I discovered that the PTH implementation stores TokenKind in 8 bits. However, we currently have 368 TokenKinds. The result is that the value gets truncated and the wrong token gets picked up when including PTH files. It seems that this will go wrong every time someone uses a token that uses the 9th bit. Upon asking on IRC, it was brought up that this was a highly experimental features that was considered a failure. I discovered via googling that BoostBuild (mostly Boost.Math) is the only user of this feature, using the CC1 flag directly. I believe that this can be transferred over to normal PCH with minimal effort: https://github.com/boostorg/build/issues/367 Based on advice on IRC and research showing that this is a nearly completely unused feature, this patch removes it entirely. Note: I considered leaving the build-flags in place and making them emit an error/warning, however since I've basically identified and warned the only user, it seemed better to just remove them. Differential Revision: https://reviews.llvm.org/D54547 Change-Id: If32744275ef1f585357bd6c1c813d96973c4d8d9 llvm-svn: 348266
105 lines
4 KiB
Plaintext
105 lines
4 KiB
Plaintext
//===---------------------------------------------------------------------===//
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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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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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