DebugInfo: Consider global variables without locations to be valid

We were being a bit too aggresive here in classifying global variables
with no global reference or constant value to be invalid - this would
cause LLVM to not emit the DWARF description of the global variable if
it had been optimized away, which isn't helpful for users who might
benefit from the global variable's description even if there's no
location information.

This also fixes a crasher issue here that I was unable to reduce a test
case for - involving a using decl (& subsequent
DW_TAG_imported_declaration ) of such a global variable that, once
optimized away, would crash when an attempt to emit the imported
declaration was made.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185675 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 38 insertions, 0 deletions

diff --git a/test/DebugInfo/global.ll b/test/DebugInfo/global.ll
new file mode 100644
index 0000000..b438305
--- /dev/null
+++ b/test/DebugInfo/global.ll
@@ -0,0 +1,38 @@
+; REQUIRES: object-emission
+
+; RUN: llc -O0 -filetype=obj < %s > %t
+; RUN: llvm-dwarfdump %t | FileCheck %s
+
+; generated from the following source compiled to bitcode with clang -g -O1
+; static int i;
+; int main() {
+;   (void)&i;
+; }
+
+; CHECK: debug_info contents
+; CHECK: DW_TAG_variable
+
+; Function Attrs: nounwind readnone uwtable
+define i32 @main() #0 {
+entry:
+  ret i32 0, !dbg !12
+}
+
+attributes #0 = { nounwind readnone uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!11}
+
+!0 = metadata !{i32 786449, metadata !1, i32 4, metadata !"clang version 3.4 ", i1 true, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !9, metadata !2, metadata !""} ; [ DW_TAG_compile_unit ] [/tmp/global.cpp] [DW_LANG_C_plus_plus]
+!1 = metadata !{metadata !"global.cpp", metadata !"/tmp"}
+!2 = metadata !{i32 0}
+!3 = metadata !{metadata !4}
+!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"main", metadata !"main", metadata !"", i32 2, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 true, i32 ()* @main, null, null, metadata !2, i32 2} ; [ DW_TAG_subprogram ] [line 2] [def] [main]
+!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [/tmp/global.cpp]
+!6 = metadata !{i32 786453, i32 0, i32 0, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !7, i32 0, i32 0} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = metadata !{metadata !8}
+!8 = metadata !{i32 786468, null, null, metadata !"int", i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
+!9 = metadata !{metadata !10}
+!10 = metadata !{i32 786484, i32 0, null, metadata !"i", metadata !"i", metadata !"_ZL1i", metadata !5, i32 1, metadata !8, i32 1, i32 1, null, null}
+!11 = metadata !{i32 2, metadata !"Dwarf Version", i32 3}
+!12 = metadata !{i32 4, i32 0, metadata !4, null}