[cxxmodules] Enable the semantic global module index to boost performance. #5884
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vgvassilev
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Axel-Naumann,
oshadura and
pcanal
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Environment variables can be set to 1, On, TRUE and 0, Off, FALSE to set a bool value. Implement a FoundationUtils facility to check for it.
…ance. The global module index (GMI) is an optimization which hides the introduced by clang overhead when pre-loading the C++ modules at startup. The GMI represents a mapping between an identifier and a set of modules which contain this indentifier. This mean that if we TH1 is undeclared the GMI will load all modules which contain this identifier which is usually suboptimal, too. The semantic GMI maps identifiers only to modules which contain a definition of the entity behind the identifier. For cases such as typedefs where the entity introduces a synonym (rather than declaration) we map the first module we encounter. For namespaces we add all modules which has a namespace partition. The namespace case is still suboptimal and further improved by inspecting what exactly is being looked up in the namespace by the qualified lookup facilities.
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Closing in favor of #5847 |
3 participants
The global module index (GMI) is an optimization which hides the introduced by clang overhead when pre-loading the C++ modules at startup.
The GMI represents a mapping between an identifier and a set of modules which contain this indentifier. This mean that if we TH1 is undeclared the GMI will load all modules which contain this identifier which is usually suboptimal, too.
The semantic GMI maps identifiers only to modules which contain a definition of the entity behind the identifier. For cases such as typedefs where the entity introduces a synonym (rather than declaration) we map the first module we encounter. For namespaces we add all modules which has a namespace partition. The namespace case is still suboptimal and further improved by inspecting what exactly is being looked up in the namespace by the qualified lookup facilities.