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Optimize cmMakefile::ExpandVariablesInStringNew. 

We can remove the temporary allocations required for the
default-constructed t_lookup passed into the openstack by refactoring
the code slightly. Furthermore, we use a vector instead of a stack,
since the latter is based on a deque which is not required for a
heap / lifo structure.

This patch removes ~215k allocations.

This hotspot was found with heaptrack.
This commit is contained in:
Milian Wolff 2016-01-15 14:37:25 +01:00 committed by Stephen Kelly
parent ad9394f4fd
commit bd2384f593
1 changed files with 9 additions and 10 deletions
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19
Source/cmMakefile.cxx
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@ -2832,10 +2832,9 @@ cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
const char* last = in; const char* last = in;
std::string result; std::string result;
result.reserve(source.size()); result.reserve(source.size());
std::stack<t_lookup> openstack; std::vector<t_lookup> openstack;
bool error = false; bool error = false;
bool done = false; bool done = false;
openstack.push(t_lookup());
cmake::MessageType mtype = cmake::LOG; cmake::MessageType mtype = cmake::LOG;
cmState* state = this->GetCMakeInstance()->GetState(); cmState* state = this->GetCMakeInstance()->GetState();
@ -2846,10 +2845,10 @@ cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
switch(inc) switch(inc)
{ {
case '}': case '}':
if(openstack.size() > 1) if(!openstack.empty())
{ {
t_lookup var = openstack.top(); t_lookup var = openstack.back();
openstack.pop(); openstack.pop_back();
result.append(last, in - last); result.append(last, in - last);
std::string const& lookup = result.substr(var.loc); std::string const& lookup = result.substr(var.loc);
const char* value = NULL; const char* value = NULL;
@ -2970,7 +2969,7 @@ cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
last = start; last = start;
in = start - 1; in = start - 1;
lookup.loc = result.size(); lookup.loc = result.size();
openstack.push(lookup); openstack.push_back(lookup);
} }
break; break;
} }
@ -2997,7 +2996,7 @@ cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
result.append("\r"); result.append("\r");
last = next + 1; last = next + 1;
} }
else if(nextc == ';' && openstack.size() == 1) else if(nextc == ';' && openstack.empty())
{ {
// Handled in ExpandListArgument; pass the backslash literally. // Handled in ExpandListArgument; pass the backslash literally.
} }
@ -3065,7 +3064,7 @@ cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
/* FALLTHROUGH */ /* FALLTHROUGH */
default: default:
{ {
if(openstack.size() > 1 && if(!openstack.empty() &&
!(isalnum(inc) || inc == '_' || !(isalnum(inc) || inc == '_' ||
inc == '/' || inc == '.' || inc == '/' || inc == '.' ||
inc == '+' || inc == '-')) inc == '+' || inc == '-'))
@ -3074,7 +3073,7 @@ cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
errorstr += inc; errorstr += inc;
result.append(last, in - last); result.append(last, in - last);
errorstr += "\') in a variable name: " errorstr += "\') in a variable name: "
"'" + result.substr(openstack.top().loc) + "'"; "'" + result.substr(openstack.back().loc) + "'";
mtype = cmake::FATAL_ERROR; mtype = cmake::FATAL_ERROR;
error = true; error = true;
} }
@ -3085,7 +3084,7 @@ cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
} while(!error && !done && *++in); } while(!error && !done && *++in);
// Check for open variable references yet. // Check for open variable references yet.
if(!error && openstack.size() != 1) if(!error && !openstack.empty())
{ {
// There's an open variable reference waiting. Policy CMP0010 flags // There's an open variable reference waiting. Policy CMP0010 flags
// whether this is an error or not. The new parser now enforces // whether this is an error or not. The new parser now enforces