From 8379e298b31030b2731ec5c99ebbd7e05592f45d Mon Sep 17 00:00:00 2001 From: Oliver Stannard Date: Mon, 8 Jun 2015 16:55:31 +0000 Subject: [PATCH] Fix assertion failure in global-merge with unused ConstantExpr The global-merge pass was crashing because it assumes that all ConstantExprs (reached via the global variables that they use) have at least one user. I haven't worked out a way to test this, as an unused ConstantExpr cannot be represented by serialised IR, and global-merge can only be run in llc, which does not run any passes which can make a ConstantExpr dead. This (reduced to the point of silliness) C code triggers this bug when compiled for arm-none-eabi at -O1: static a = 7; static volatile b[10] = {&a}; c; main() { c = 0; for (; c < 10;) printf(b[c]); } Differential Revision: http://reviews.llvm.org/D10314 llvm-svn: 239308 --- llvm/lib/CodeGen/GlobalMerge.cpp | 2 ++ 1 file changed, 2 insertions(+) diff --git a/llvm/lib/CodeGen/GlobalMerge.cpp b/llvm/lib/CodeGen/GlobalMerge.cpp index df54a9c..37b3bf1 100644 --- a/llvm/lib/CodeGen/GlobalMerge.cpp +++ b/llvm/lib/CodeGen/GlobalMerge.cpp @@ -280,6 +280,8 @@ bool GlobalMerge::doMerge(SmallVectorImpl &Globals, // users, so look through ConstantExpr... Use *UI, *UE; if (ConstantExpr *CE = dyn_cast(U.getUser())) { + if (CE->use_empty()) + continue; UI = &*CE->use_begin(); UE = nullptr; } else if (isa(U.getUser())) { -- 2.7.4