Fix mergefunc infinite loop

Self-referential constants containing references to a merged function
no longer cause the MergeFunctions pass to infinite loop. Also adds a
reproduction IR which would otherwise fail, which was isolated from a similar
issue in Chromium.

Author: jrkoenig
Reviewers: nlewycky, jfb
Subscribers: llvm-commits, nlewycky, jfb

Differential Revision: http://reviews.llvm.org/D11208

llvm-svn: 242337

1 files changed, 40 insertions, 0 deletions

diff --git a/llvm/test/Transforms/MergeFunc/self-referential-global.ll b/llvm/test/Transforms/MergeFunc/self-referential-global.ll
new file mode 100644
index 00000000000..d3d1c62aa7f
--- /dev/null
+++ b/llvm/test/Transforms/MergeFunc/self-referential-global.ll
@@ -0,0 +1,40 @@
+; RUN: opt -mergefunc -disable-output < %s
+
+; A linked list type and simple payload
+%LL = type { %S, %LL* }
+%S = type { void (%S*, i32)* }
+
+; Table refers to itself via GEP
+@Table = internal global [3 x %LL] [%LL { %S { void (%S*, i32)* @B }, %LL* getelementptr inbounds ([3 x %LL], [3 x %LL]* @Table, i32 0, i32 0) }, %LL { %S { void (%S*, i32)* @A }, %LL* getelementptr inbounds ([3 x %LL], [3 x %LL]* @Table, i32 0, i32 0) }, %LL { %S { void (%S*, i32)* @A }, %LL* getelementptr inbounds ([3 x %LL], [3 x %LL]* @Table, i32 0, i32 0) }], align 16
+
+; The body of this is irrelevant; it is long so that mergefunc doesn't skip it as a small function.
+define internal void @A(%S* %self, i32 %a) {
+  %1 = add i32 %a, 32
+  %2 = add i32 %1, 32
+  %3 = add i32 %2, 32
+  %4 = add i32 %3, 32
+  %5 = add i32 %4, 32
+  %6 = add i32 %5, 32
+  %7 = add i32 %6, 32
+  %8 = add i32 %7, 32
+  %9 = add i32 %8, 32
+  %10 = add i32 %9, 32
+  %11 = add i32 %10, 32
+  ret void
+}
+
+define internal void @B(%S* %self, i32 %a) {
+  %1 = add i32 %a, 32
+  %2 = add i32 %1, 32
+  %3 = add i32 %2, 32
+  %4 = add i32 %3, 32
+  %5 = add i32 %4, 32
+  %6 = add i32 %5, 32
+  %7 = add i32 %6, 32
+  %8 = add i32 %7, 32
+  %9 = add i32 %8, 32
+  %10 = add i32 %9, 32
+  %11 = add i32 %10, 32
+  ret void
+}
+