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
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 @@
// users, so look through ConstantExpr...
Use *UI, *UE;
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U.getUser())) {
+ if (CE->use_empty())
+ continue;
UI = &*CE->use_begin();
UE = nullptr;
} else if (isa<Instruction>(U.getUser())) {