Internalize: internalize comdat members as a group, and drop comdat on such members.

Internalizing an individual comdat group member without also internalizing
the other members of the comdat can break comdat semantics. For example,
if a module contains a reference to an internalized comdat member, and the
linker chooses a comdat group from a different object file, this will break
the reference to the internalized member.

This change causes the internalizer to only internalize comdat members if all
other members of the comdat are not externally visible. Once a comdat group
has been fully internalized, there is no need to apply comdat rules to its
members; later optimization passes (e.g. globaldce) can legally drop individual
members of the comdat. So we drop the comdat attribute from all comdat members.

Differential Revision: http://reviews.llvm.org/D10679

llvm-svn: 242423

1 files changed, 52 insertions, 0 deletions

diff --git a/llvm/test/Transforms/Internalize/comdat.ll b/llvm/test/Transforms/Internalize/comdat.ll
new file mode 100644
index 00000000000..8217dd603a1
--- /dev/null
+++ b/llvm/test/Transforms/Internalize/comdat.ll
@@ -0,0 +1,52 @@
+; RUN: opt < %s -internalize -internalize-public-api-list c1 -internalize-public-api-list c2 -internalize-public-api-list c3 -internalize-public-api-list c4 -S | FileCheck %s
+
+$c1 = comdat any
+$c2 = comdat any
+$c3 = comdat any
+$c4 = comdat any
+
+; CHECK: @c1_c = global i32 0, comdat($c1)
+@c1_c = global i32 0, comdat($c1)
+
+; CHECK: @c2_b = internal global i32 0{{$}}
+@c2_b = global i32 0, comdat($c2)
+
+; CHECK: @c3 = global i32 0, comdat{{$}}
+@c3 = global i32 0, comdat
+
+; CHECK: @c4_a = internal global i32 0, comdat($c4)
+@c4_a = internal global i32 0, comdat($c4)
+
+; CHECK: @c1_d = alias i32* @c1_c
+@c1_d = alias i32* @c1_c
+
+; CHECK: @c2_c = internal alias i32* @c2_b
+@c2_c = alias i32* @c2_b
+
+; CHECK: @c4 = alias i32* @c4_a
+@c4 = alias i32* @c4_a
+
+; CHECK: define void @c1() comdat {
+define void @c1() comdat {
+  ret void
+}
+
+; CHECK: define void @c1_a() comdat($c1) {
+define void @c1_a() comdat($c1) {
+  ret void
+}
+
+; CHECK: define internal void @c2() {
+define internal void @c2() comdat {
+  ret void
+}
+
+; CHECK: define internal void @c2_a() {
+define void @c2_a() comdat($c2) {
+  ret void
+}
+
+; CHECK: define void @c3_a() comdat($c3) {
+define void @c3_a() comdat($c3) {
+  ret void
+}