[MemorySSAUpdater] Remove deleted trivial Phis from active workset

Bug fix for PR37808. The regression test is a reduced version of the
original reproducer attached to the bug report. As stated in the report,
the problem was that InsertedPHIs was keeping dangling pointers to
deleted Memory-Phis. MemoryPhis are created eagerly and sometimes get
zapped shortly afterwards. I've used WeakVH instead of an expensive
removal operation from the active workset.

Differential Revision: https://reviews.llvm.org/D48372

llvm-svn: 337149

1 files changed, 40 insertions, 0 deletions

diff --git a/llvm/test/Transforms/GVNHoist/pr37808.ll b/llvm/test/Transforms/GVNHoist/pr37808.ll
new file mode 100644
index 00000000000..5705c6b89a3
--- /dev/null
+++ b/llvm/test/Transforms/GVNHoist/pr37808.ll
@@ -0,0 +1,40 @@
+; RUN: opt < %s -gvn-hoist -S | FileCheck %s
+
+define void @func() {
+; CHECK-LABEL: @func()
+; CHECK:       bb6:
+; CHECK:         store i64 0, i64* undef, align 8
+; CHECK:       bb7:
+; CHECK-NOT:     store i64 0, i64* undef, align 8
+; CHECK:       bb8:
+; CHECK-NOT:     store i64 0, i64* undef, align 8
+
+entry:
+  br label %bb1
+
+bb1:
+  br label %bb2
+
+bb2:
+  br label %bb3
+
+bb3:
+  br i1 undef, label %bb4, label %bb2
+
+bb4:
+  br i1 undef, label %bb5, label %bb3
+
+bb5:
+  br label %bb6
+
+bb6:
+  br i1 undef, label %bb7, label %bb8
+
+bb7:
+  store i64 0, i64* undef, align 8
+  unreachable
+
+bb8:
+  store i64 0, i64* undef, align 8
+  ret void
+}