Fix conservative assumption, which was quite broken. Also, notice that
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
diff --git a/lib/Analysis/IPA/GlobalsModRef.cpp b/lib/Analysis/IPA/GlobalsModRef.cpp
index 162b11f..15d76bf 100644
--- a/lib/Analysis/IPA/GlobalsModRef.cpp
+++ b/lib/Analysis/IPA/GlobalsModRef.cpp
@@ -64,6 +64,8 @@
/// 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 @@
// 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) {