diff --git a/llvm/include/llvm/IR/BasicBlock.h b/llvm/include/llvm/IR/BasicBlock.h --- a/llvm/include/llvm/IR/BasicBlock.h +++ b/llvm/include/llvm/IR/BasicBlock.h @@ -390,6 +390,12 @@ /// direct branches, switches, etc. to it. bool hasAddressTaken() const { return getSubclassDataFromValue() != 0; } + /// Returns true if there are any uses of the address of this basic block + /// that may escape the function. At the momement, this is a very + /// conservative approximation, and treats ANY use (except as a "noescape" + /// parameter to a call as potentially escaping. + bool addressPotentiallyEscapesFunction(); + /// Update all phi nodes in this basic block's successors to refer to basic /// block \p New instead of to it. void replaceSuccessorsPhiUsesWith(BasicBlock *New); diff --git a/llvm/lib/Analysis/InlineCost.cpp b/llvm/lib/Analysis/InlineCost.cpp --- a/llvm/lib/Analysis/InlineCost.cpp +++ b/llvm/lib/Analysis/InlineCost.cpp @@ -1832,7 +1832,7 @@ // see an indirect branch that ends up being dead code at a particular call // site. If the blockaddress escapes the function, e.g., via a global // variable, inlining may lead to an invalid cross-function reference. - if (BB->hasAddressTaken()) + if (BB->hasAddressTaken() && BB->addressPotentiallyEscapesFunction()) return "blockaddress"; // Analyze the cost of this block. If we blow through the threshold, this @@ -2082,7 +2082,7 @@ if (isa(BI->getTerminator())) return "contains indirect branches"; - if (BI->hasAddressTaken()) + if (BI->hasAddressTaken() && BI->addressPotentiallyEscapesFunction()) return "uses block address"; for (auto &II : *BI) { diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp --- a/llvm/lib/IR/BasicBlock.cpp +++ b/llvm/lib/IR/BasicBlock.cpp @@ -442,6 +442,33 @@ return New; } +bool BasicBlock::addressPotentiallyEscapesFunction() { + SmallVector Worklist; + for (auto &U : BlockAddress::get(this)->uses()) { + Worklist.push_back(&U); + } + while (!Worklist.empty()) { + const Use* U = Worklist.pop_back_val(); + // If the use is a Constant and not a GlobalValue, check their uses. + if (isa(U) && !isa(U)) { + for (auto &UU : U->getUser()->uses()) { + Worklist.push_back(&UU); + } + continue; + // If the use is a nocapture paramter, this is ok. + } else if (const CallInst* CI = dyn_cast(U)) { + if (CI->paramHasAttr(U->getOperandNo(), Attribute::NoCapture)) { + continue; + } + // Otherwise, conservatively return true. + } else { + return true; + } + } + // Use list was empty, or contained no faulty cases. + return false; +} + void BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *New) { Instruction *TI = getTerminator(); if (!TI)