From c66330504c3f433430a28cd7f7f981e555c51bce Mon Sep 17 00:00:00 2001 From: Eli Friedman Date: Thu, 20 Oct 2011 05:23:42 +0000 Subject: Refactor code from inlining and globalopt that checks whether a function definition is unused, and enhance it so it can tell that functions which are only used by a blockaddress are in fact dead. This probably doesn't happen much on most code, but the Linux kernel's _THIS_IP_ can trigger this issue with blockaddress. (GlobalDCE can also handle the given tescase, but we only run that at -O3.) Found while looking at PR11180. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142572 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/VMCore/Function.cpp | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'lib/VMCore') diff --git a/lib/VMCore/Function.cpp b/lib/VMCore/Function.cpp index be0f056..bb8f62a 100644 --- a/lib/VMCore/Function.cpp +++ b/lib/VMCore/Function.cpp @@ -402,6 +402,7 @@ Function *Intrinsic::getDeclaration(Module *M, ID id, ArrayRef Tys) { bool Function::hasAddressTaken(const User* *PutOffender) const { for (Value::const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) { const User *U = *I; + // FIXME: Check for blockaddress, which does not take the address. if (!isa(U) && !isa(U)) return PutOffender ? (*PutOffender = U, true) : true; ImmutableCallSite CS(cast(U)); @@ -411,6 +412,20 @@ bool Function::hasAddressTaken(const User* *PutOffender) const { return false; } +bool Function::isDefTriviallyDead() const { + // Check the linkage + if (!hasLinkOnceLinkage() && !hasLocalLinkage() && + !hasAvailableExternallyLinkage()) + return false; + + // Check if the function is used by anything other than a blockaddress. + for (Value::const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) + if (!isa(*I)) + return false; + + return true; +} + /// callsFunctionThatReturnsTwice - Return true if the function has a call to /// setjmp or other function that gcc recognizes as "returning twice". bool Function::callsFunctionThatReturnsTwice() const { -- cgit v1.1