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Avoid constructing GlobalExtensions only to find out it is empty. 

Summary:
GlobalExtensions is dereferenced twice, once for iteration and then a check if it is empty.
As a ManagedStatic this dereference forces it's construction which is unnecessary.

Reviewers: efriedma, davide, mehdi_amini

Reviewed By: mehdi_amini

Subscribers: chapuni, llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D33381

llvm-svn: 307229
This commit is contained in:
Frederich Munch 2017-07-06 00:09:09 +00:00
parent 42a96a286c
commit 52dfcd18d1
1 changed files with 14 additions and 4 deletions
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18
llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
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@ -188,6 +188,13 @@ PassManagerBuilder::~PassManagerBuilder() {
static ManagedStatic<SmallVector<std::pair<PassManagerBuilder::ExtensionPointTy,
PassManagerBuilder::ExtensionFn>, 8> > GlobalExtensions;
/// Check if GlobalExtensions is constructed and not empty.
/// Since GlobalExtensions is a managed static, calling 'empty()' will trigger
/// the construction of the object.
static bool GlobalExtensionsNotEmpty() {
return GlobalExtensions.isConstructed() && !GlobalExtensions->empty();
}
void PassManagerBuilder::addGlobalExtension(
PassManagerBuilder::ExtensionPointTy Ty,
PassManagerBuilder::ExtensionFn Fn) {
@ -200,9 +207,12 @@ void PassManagerBuilder::addExtension(ExtensionPointTy Ty, ExtensionFn Fn) {
void PassManagerBuilder::addExtensionsToPM(ExtensionPointTy ETy,
legacy::PassManagerBase &PM) const {
for (unsigned i = 0, e = GlobalExtensions->size(); i != e; ++i)
if ((*GlobalExtensions)[i].first == ETy)
(*GlobalExtensions)[i].second(*this, PM);
if (GlobalExtensionsNotEmpty()) {
for (auto &Ext : *GlobalExtensions) {
if (Ext.first == ETy)
Ext.second(*this, PM);
}
}
for (unsigned i = 0, e = Extensions.size(); i != e; ++i)
if (Extensions[i].first == ETy)
Extensions[i].second(*this, PM);
@ -415,7 +425,7 @@ void PassManagerBuilder::populateModulePassManager(
// builds. The function merging pass is
if (MergeFunctions)
MPM.add(createMergeFunctionsPass());
else if (!GlobalExtensions->empty() || !Extensions.empty())
else if (GlobalExtensionsNotEmpty() || !Extensions.empty())
MPM.add(createBarrierNoopPass());
addExtensionsToPM(EP_EnabledOnOptLevel0, MPM);