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Fix conservative assumption, which was quite broken. Also, notice that

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functions known to not access memory (like sin/cos) don't access memory! :)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@15264 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-07-27 07:46:26 +00:00
parent eaa243039b
commit 105d26acb4
1 changed files with 22 additions and 2 deletions
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24
lib/Analysis/IPA/GlobalsModRef.cpp
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@ -64,6 +64,8 @@ namespace {
/// FunctionEffect - Capture whether or not this function reads or writes to
/// ANY memory. If not, we can do a lot of aggressive analysis on it.
unsigned FunctionEffect;
FunctionRecord() : FunctionEffect(0) {}
};
/// GlobalsModRef - The actual analysis pass.
@ -232,9 +234,27 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
// We do a bottom-up SCC traversal of the call graph. In other words, we
// visit all callees before callers (leaf-first).
for (scc_iterator<CallGraph*> I = scc_begin(&CG), E = scc_end(&CG); I!=E; ++I)
// Do not call AnalyzeSCC on the external function node.
if ((*I).size() != 1 || (*I)[0]->getFunction())
if ((*I).size() != 1) {
AnalyzeSCC(*I);
} else if (Function *F = (*I)[0]->getFunction()) {
if (!F->isExternal()) {
// Nonexternal function.
AnalyzeSCC(*I);
} else {
// Otherwise external function. Handle intrinsics and other special
// cases here.
if (getAnalysis<AliasAnalysis>().doesNotAccessMemory(F))
// If it does not access memory, process the function, causing us to
// realize it doesn't do anything (the body is empty).
AnalyzeSCC(*I);
else {
// Otherwise, don't process it. This will cause us to conservatively
// assume the worst.
}
}
} else {
// Do not process the external node, assume the worst.
}
}
void GlobalsModRef::AnalyzeSCC(std::vector<CallGraphNode *> &SCC) {