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Drop references to globals who do exist in the globals graph, but are never

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read or written to.  Keep track of how many times this happens.  This should
be good for deleting things like references to type information in C++ classes


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6946 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2003-06-28 22:10:58 +00:00
parent 72d50a090f
commit 5e459dbc52
1 changed files with 16 additions and 1 deletions
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17
lib/Analysis/DataStructure/DataStructureOpt.cpp
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@ -14,6 +14,8 @@
namespace {
Statistic<>
NumGlobalsConstanted("ds-opt", "Number of globals marked constant");
Statistic<>
NumGlobalsIsolated("ds-opt", "Number of globals with references dropped");
class DSOpt : public Pass {
TDDataStructures *TD;
@ -60,8 +62,21 @@ bool DSOpt::OptimizeGlobals(Module &M) {
// can delete it. We don't ACTUALLY want to delete the global, just
// remove anything that references the global: later passes will take
// care of nuking it.
I->replaceAllUsesWith(Constant::getNullValue((Type*)I->getType()));
if (!I->use_empty()) {
I->replaceAllUsesWith(Constant::getNullValue((Type*)I->getType()));
++NumGlobalsIsolated;
}
} else if (GNode && GNode->isComplete()) {
// If the node has not been read or written, and it is not externally
// visible, kill any references to it so it can be DCE'd.
if (!GNode->isModified() && !GNode->isRead() &&I->hasInternalLinkage()){
if (!I->use_empty()) {
I->replaceAllUsesWith(Constant::getNullValue((Type*)I->getType()));
++NumGlobalsIsolated;
}
}
// We expect that there will almost always be a node for this global.
// If there is, and the node doesn't have the M bit set, we can set the
// 'constant' bit on the global.