From 1839858983dcbaf1808a6a37f5cd64d92981f27e Mon Sep 17 00:00:00 2001 From: Hans Wennborg Date: Thu, 15 Nov 2012 11:40:00 +0000 Subject: 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 --- lib/VMCore/Constants.cpp | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) (limited to 'lib/VMCore') diff --git a/lib/VMCore/Constants.cpp b/lib/VMCore/Constants.cpp index f96fb1d401..eae96ef86c 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 Visited; + SmallVector WorkList; + WorkList.push_back(this); + Visited.insert(this); + + while (!WorkList.empty()) { + const Constant *C = WorkList.pop_back_val(); + + if (const GlobalVariable *GV = dyn_cast(C)) { + if (GV->isThreadLocal()) + return true; + } + + for (unsigned I = 0, E = C->getNumOperands(); I != E; ++I) { + const Constant *D = cast(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 { -- cgit v1.2.3