[dsymutil] Fix handling of empty CUs in LTO links.

r288399 introduced the DIEUnit class, and in the process broke
the corner case where dsymutil generates an empty CU during an
LTO link. This restores the logic and adds a test for the corner
case.

llvm-svn: 294618

1 files changed, 33 insertions, 0 deletions

diff --git a/llvm/test/tools/dsymutil/X86/generate-empty-CU.test b/llvm/test/tools/dsymutil/X86/generate-empty-CU.test
new file mode 100644
index 00000000000..233611460b6
--- /dev/null
+++ b/llvm/test/tools/dsymutil/X86/generate-empty-CU.test
@@ -0,0 +1,33 @@
+# RUN: llvm-dsymutil -f -o - -oso-prepend-path=%p/.. -y %s | llvm-dwarfdump - | FileCheck %s
+
+# This test on links the Dwarf for an LTO binary and on purpose doesn't retain
+# any symbol in the second CU out of 3. This is the only case where dsymutil
+# will generate an empty CU and it requires special handling.
+
+---
+triple:          'x86_64-apple-darwin'
+objects:
+  - filename:        /Inputs/basic-lto.macho.x86_64.o
+    timestamp:       1417654896
+    symbols:
+      - { sym: _main, objAddr: 0x0000000000000000, binAddr: 0x0000000100000F40, size: 0x00000010 }
+      - { sym: _bar, objAddr: 0x0000000000000050, binAddr: 0x0000000100000F90, size: 0x00000024 }
+...
+
+.debug_info contents:
+CHECK: Compile Unit: length = 0x0000007d version = 0x0002 abbr_offset = 0x0000 addr_size = 0x08 (next unit at 0x00000081)
+
+CHECK: DW_TAG_compile_unit
+CHECK:        DW_AT_name {{.*}} "basic1.c"
+CHECK:   DW_TAG_subprogram
+                DW_AT_name {{.*}} "main"
+
+CHECK: Compile Unit: length = 0x00000007 version = 0x0002 abbr_offset = 0x0000 addr_size = 0x08 (next unit at 0x0000008c)
+
+CHECK: Compile Unit: length = 0x00000089 version = 0x0002 abbr_offset = 0x0000 addr_size = 0x08 (next unit at 0x00000119)
+
+CHECK: DW_TAG_compile_unit
+CHECK:        DW_AT_name {{.*}} "basic3.c"
+
+CHECK:   DW_TAG_subprogram [7] *
+CHECK:          DW_AT_name {{.*}} = "bar"