From 8848680ce0ab416cb646d0a03aa6f4f6f25e7623 Mon Sep 17 00:00:00 2001 From: Benjamin Kramer Date: Sat, 13 Apr 2013 12:53:18 +0000 Subject: Fix a scalability issue with complex ConstantExprs. This is basically the same fix in three different places. We use a set to avoid walking the whole tree of a big ConstantExprs multiple times. For example: (select cmp, (add big_expr 1), (add big_expr 2)) We don't want to visit big_expr twice here, it may consist of thousands of nodes. The testcase exercises this by creating an insanely large ConstantExprs out of a loop. It's questionable if the optimizer should ever create those, but this can be triggered with real C code. Fixes PR15714. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179458 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/IPO/GlobalDCE.cpp | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'lib/Transforms/IPO') diff --git a/lib/Transforms/IPO/GlobalDCE.cpp b/lib/Transforms/IPO/GlobalDCE.cpp index dc99492990..76d1287fb7 100644 --- a/lib/Transforms/IPO/GlobalDCE.cpp +++ b/lib/Transforms/IPO/GlobalDCE.cpp @@ -42,6 +42,7 @@ namespace { private: SmallPtrSet AliveGlobals; + SmallPtrSet SeenConstants; /// GlobalIsNeeded - mark the specific global value as needed, and /// recursively mark anything that it uses as also needed. @@ -151,6 +152,7 @@ bool GlobalDCE::runOnModule(Module &M) { // Make sure that all memory is released AliveGlobals.clear(); + SeenConstants.clear(); return Changed; } @@ -190,12 +192,15 @@ void GlobalDCE::GlobalIsNeeded(GlobalValue *G) { void GlobalDCE::MarkUsedGlobalsAsNeeded(Constant *C) { if (GlobalValue *GV = dyn_cast(C)) return GlobalIsNeeded(GV); - + // Loop over all of the operands of the constant, adding any globals they // use to the list of needed globals. - for (User::op_iterator I = C->op_begin(), E = C->op_end(); I != E; ++I) - if (Constant *OpC = dyn_cast(*I)) - MarkUsedGlobalsAsNeeded(OpC); + for (User::op_iterator I = C->op_begin(), E = C->op_end(); I != E; ++I) { + // If we've already processed this constant there's no need to do it again. + Constant *Op = cast(*I); + if (SeenConstants.insert(Op)) + MarkUsedGlobalsAsNeeded(Op); + } } // RemoveUnusedGlobalValue - Loop over all of the uses of the specified -- cgit v1.2.3