From 20b3e9a8355311aae1ca2f491b1eb2dd5ec44b84 Mon Sep 17 00:00:00 2001 From: Ahmed Bougacha Date: Wed, 1 Mar 2017 00:43:42 +0000 Subject: [CodeGen] Remove dead FastISel code after SDAG emitted a tailcall. When SDAGISel (top-down) selects a tail-call, it skips the remainder of the block. If, before that, FastISel (bottom-up) selected some of the (no-op) next few instructions, we can end up with dead instructions following the terminator (selected by SDAGISel). We need to erase them, as we know they aren't necessary (in addition to being incorrect). We already do this when FastISel falls back on the tail-call itself. Also remove the FastISel-emitted code if we fallback on the instructions between the tail-call and the return. llvm-svn: 296552 --- llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp') diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp index 645c9d2616a..7e876068525 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp @@ -1684,6 +1684,12 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) { // block. bool HadTailCall; SelectBasicBlock(Begin, BI, HadTailCall); + + // But if FastISel was run, we already selected some of the block. + // If we emitted a tail-call, we need to delete any previously emitted + // instruction that follows it. + if (HadTailCall && FuncInfo->InsertPt != FuncInfo->MBB->end()) + FastIS->removeDeadCode(FuncInfo->InsertPt, FuncInfo->MBB->end()); } FinishBasicBlock(); -- cgit v1.2.3