Fix a use-after-free error in GlobalOpt CleanupConstantGlobalUsers

GlobalOpt's CleanupConstantGlobalUsers function uses a worklist array to manage
constant users to be visited. The pointers in this array need to be weak
handles because when we delete a constant array, we may also be holding a
pointer to one of its elements (or an element of one of its elements if we're
dealing with an array of arrays) in the worklist.

Fixes PR17347.

llvm-svn: 197178

1 files changed, 32 insertions, 0 deletions

diff --git a/llvm/test/Transforms/GlobalOpt/array-elem-refs.ll b/llvm/test/Transforms/GlobalOpt/array-elem-refs.ll
new file mode 100644
index 00000000000..ec472b0e99f
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/array-elem-refs.ll
@@ -0,0 +1,32 @@
+; RUN: opt < %s -S -globalopt | FileCheck %s
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.S = type { i8, i8 }
+
+@c = internal global i8** bitcast (i8* getelementptr (i8* bitcast ([8 x i8*]* @b to i8*), i64 48) to i8**), align 8
+@b = internal global [8 x i8*] [i8* null, i8* null, i8* null, i8* null, i8* null, i8* null, i8* getelementptr inbounds (%struct.S* @a, i32 0, i32 0), i8* getelementptr (i8* getelementptr inbounds (%struct.S* @a, i32 0, i32 0), i64 1)], align 16
+@a = internal global %struct.S zeroinitializer, align 1
+
+; Function Attrs: nounwind uwtable
+define signext i8 @foo() #0 {
+entry:
+  %0 = load i8*** @c, align 8
+  %1 = load i8** %0, align 8
+  %2 = load i8* %1, align 1
+  ret i8 %2
+
+; CHECK-LABEL: @foo
+; CHECK: ret i8 0
+}
+
+; Function Attrs: nounwind uwtable
+define i32 @main() #0 {
+entry:
+  %retval = alloca i32, align 4
+  store i32 0, i32* %retval
+  ret i32 0
+}
+
+attributes #0 = { nounwind uwtable }
+