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Minor optimization in dependency checking. 

When reading the depend.internal file, check only once for every depender
whether it exists, instead of repeatedly in a loop for each dependee. Within
that function it can only change of the depender is removed. This is taken
care of.
This reduces the number of access() calls in kdelibs/khtml from 180000 to
90000 (i.e. 50%), and reduces the time for that (without the actual
scanning) from 0.3 s to 0.21 s on my system.

Alex
This commit is contained in:
Alexander Neundorf 2009-09-19 13:02:12 -04:00
parent d4cfb77ffe
commit 864e2670d6
1 changed files with 12 additions and 2 deletions
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14
Source/cmDepends.cxx
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@ -152,6 +152,7 @@ bool cmDepends::CheckDependencies(std::istream& internalDepends)
// or newer than the depender then dependencies should be // or newer than the depender then dependencies should be
// regenerated. // regenerated.
bool okay = true; bool okay = true;
bool dependerExists = false;
while(internalDepends.getline(this->Dependee, this->MaxPath)) while(internalDepends.getline(this->Dependee, this->MaxPath))
{ {
if ( this->Dependee[0] == 0 || this->Dependee[0] == '#' || if ( this->Dependee[0] == 0 || this->Dependee[0] == '#' ||
@ -168,6 +169,11 @@ bool cmDepends::CheckDependencies(std::istream& internalDepends)
if ( this->Dependee[0] != ' ' ) if ( this->Dependee[0] != ' ' )
{ {
memcpy(this->Depender, this->Dependee, len+1); memcpy(this->Depender, this->Dependee, len+1);
// Calling FileExists() for the depender here saves in many cases 50%
// of the calls to FileExists() further down in the loop. E.g. for
// kdelibs/khtml this reduces the number of calls from 184k down to 92k,
// or the time for cmake -E cmake_depends from 0.3 s down to 0.21 s.
dependerExists = cmSystemTools::FileExists(this->Depender);
continue; continue;
} }
/* /*
@ -198,7 +204,7 @@ bool cmDepends::CheckDependencies(std::istream& internalDepends)
cmSystemTools::Stdout(msg.str().c_str()); cmSystemTools::Stdout(msg.str().c_str());
} }
} }
else if(cmSystemTools::FileExists(depender)) else if(dependerExists)
{ {
// The dependee and depender both exist. Compare file times. // The dependee and depender both exist. Compare file times.
int result = 0; int result = 0;
@ -225,7 +231,11 @@ bool cmDepends::CheckDependencies(std::istream& internalDepends)
okay = false; okay = false;
// Remove the depender to be sure it is rebuilt. // Remove the depender to be sure it is rebuilt.
cmSystemTools::RemoveFile(depender); if (dependerExists)
{
cmSystemTools::RemoveFile(depender);
dependerExists = false;
}
} }
} }