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authorHans Wennborg <hans@hanshq.net>2012-11-15 11:40:00 +0000
committerHans Wennborg <hans@hanshq.net>2012-11-15 11:40:00 +0000
commit1839858983dcbaf1808a6a37f5cd64d92981f27e (patch)
tree1dcce5725cc713d41175088b57f33a93a3f6e8b6 /lib/VMCore
parentac39a035351a20928e087617e412aa6ce510181f (diff)
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Make GlobalOpt be conservative with TLS variables (PR14309)
For global variables that get the same value stored into them everywhere, GlobalOpt will replace them with a constant. The problem is that a thread-local GlobalVariable looks like one value (the address of the TLS var), but is different between threads. This patch introduces Constant::isThreadDependent() which returns true for thread-local variables and constants which depend on them (e.g. a GEP into a thread-local array), and teaches GlobalOpt not to track such values. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168037 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/VMCore')
-rw-r--r--lib/VMCore/Constants.cpp25
1 files changed, 25 insertions, 0 deletions
diff --git a/lib/VMCore/Constants.cpp b/lib/VMCore/Constants.cpp
index f96fb1d..eae96ef 100644
--- a/lib/VMCore/Constants.cpp
+++ b/lib/VMCore/Constants.cpp
@@ -245,6 +245,31 @@ bool Constant::canTrap() const {
}
}
+/// isThreadDependent - Return true if the value can vary between threads.
+bool Constant::isThreadDependent() const {
+ SmallPtrSet<const Constant*, 64> Visited;
+ SmallVector<const Constant*, 64> WorkList;
+ WorkList.push_back(this);
+ Visited.insert(this);
+
+ while (!WorkList.empty()) {
+ const Constant *C = WorkList.pop_back_val();
+
+ if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
+ if (GV->isThreadLocal())
+ return true;
+ }
+
+ for (unsigned I = 0, E = C->getNumOperands(); I != E; ++I) {
+ const Constant *D = cast<Constant>(C->getOperand(I));
+ if (Visited.insert(D))
+ WorkList.push_back(D);
+ }
+ }
+
+ return false;
+}
+
/// isConstantUsed - Return true if the constant has users other than constant
/// exprs and other dangling things.
bool Constant::isConstantUsed() const {