From cc88595bce813464f4dc0c8351f7311bb233a3e2 Mon Sep 17 00:00:00 2001 From: Bill Wendling Date: Mon, 11 Apr 2011 21:32:34 +0000 Subject: [PATCH] The default of the dispatch switch statement was to branch to a BB that executed the 'unwind' instruction. However, later on that instruction was converted into a jump to the basic block it was located in, causing an infinite loop when we get there. It turns out, we get there if the _Unwind_Resume_or_Rethrow call returns (which it's not supposed to do). It returns if it cannot find a place to unwind to. Thus we would get what appears to be a "hang" when in reality it's just that the EH couldn't be propagated further along. Instead of infinitely looping (or calling `unwind', which none of our back-ends support (it's lowered into nothing...)), call the @llvm.trap() intrinsic instead. This may not conform to specific rules of a particular language, but it's rather better than infinitely looping. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129302 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/SjLjEHPrepare.cpp | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/lib/CodeGen/SjLjEHPrepare.cpp b/lib/CodeGen/SjLjEHPrepare.cpp index aaa8568c2f2..43904a76cf1 100644 --- a/lib/CodeGen/SjLjEHPrepare.cpp +++ b/lib/CodeGen/SjLjEHPrepare.cpp @@ -443,16 +443,17 @@ bool SjLjEHPass::insertSjLjEHSupport(Function &F) { BasicBlock::Create(F.getContext(), "eh.sjlj.setjmp.catch", &F); // Insert a load of the callsite in the dispatch block, and a switch on its - // value. By default, we go to a block that just does an unwind (which is the - // correct action for a standard call). - BasicBlock *UnwindBlock = - BasicBlock::Create(F.getContext(), "unwindbb", &F); - Unwinds.push_back(new UnwindInst(F.getContext(), UnwindBlock)); + // value. By default, we issue a trap statement. + BasicBlock *TrapBlock = + BasicBlock::Create(F.getContext(), "trapbb", &F); + CallInst::Create(Intrinsic::getDeclaration(F.getParent(), Intrinsic::trap), + "", TrapBlock); + new UnreachableInst(F.getContext(), TrapBlock); Value *DispatchLoad = new LoadInst(CallSite, "invoke.num", true, DispatchBlock); SwitchInst *DispatchSwitch = - SwitchInst::Create(DispatchLoad, UnwindBlock, Invokes.size(), + SwitchInst::Create(DispatchLoad, TrapBlock, Invokes.size(), DispatchBlock); // Split the entry block to insert the conditional branch for the setjmp. BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(), @@ -561,7 +562,7 @@ bool SjLjEHPass::insertSjLjEHSupport(Function &F) { // Replace all unwinds with a branch to the unwind handler. // ??? Should this ever happen with sjlj exceptions? for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) { - BranchInst::Create(UnwindBlock, Unwinds[i]); + BranchInst::Create(TrapBlock, Unwinds[i]); Unwinds[i]->eraseFromParent(); }