[Reassociate] Removing instructions mutates the IR.

Fixes PR 30784. Discussed with Justin, who pointed out that
in the new PassManager infrastructure we can have more fine-grained
control on which analyses we want to preserve, but this is the
best we can do with the current infrastructure.

llvm-svn: 285380

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/test/Transforms/Reassociate/reassociate-deadinst.ll b/llvm/test/Transforms/Reassociate/reassociate-deadinst.ll
new file mode 100644
index 00000000000..6a12c4723f2
--- /dev/null
+++ b/llvm/test/Transforms/Reassociate/reassociate-deadinst.ll
@@ -0,0 +1,16 @@
+; RUN: opt -inline -functionattrs -reassociate %s -S | FileCheck %s
+
+; CHECK-NOT: func1
+; CHECK-LABEL: main
+; CHECK-NEXT: ret void
+
+define internal i16 @func1() noinline #0 {
+  ret i16 0
+}
+
+define void @main(i16 %argc, i16** %argv) #0 {
+  %_tmp0 = call i16 @func1()
+  %_tmp2 = zext i16 %_tmp0 to i32
+  ret void
+}
+attributes #0 = { minsize nounwind optsize }