Fix a bug that prevents global variables from having a DW_OP_deref.

For local variables the first DW_OP_deref is consumed by turning the
location kind into a memeory location, but that only makes sense for
values that are in a register to begin with, which cannot happen for
global variables that are attached to a symbol.

rdar://problem/39741860

This reapplies r330970 after fixing an uncovered bug in r331086 and
working around the situation caused by it.

llvm-svn: 331090

1 files changed, 41 insertions, 0 deletions

diff --git a/llvm/test/DebugInfo/X86/global-expression.ll b/llvm/test/DebugInfo/X86/global-expression.ll
new file mode 100644
index 00000000000..fdae9bd5fa2
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/global-expression.ll
@@ -0,0 +1,41 @@
+; RUN: llc -mtriple=x86_64-apple-darwin %s -o - -filetype=obj | \
+; RUN:     llvm-dwarfdump --name i --name indirect - | FileCheck %s
+;
+; This is a hand-crafted testcase generated from:
+;   int i = 23;
+;   int *indirect = &i;
+
+; CHECK: DW_TAG_variable
+; CHECK:   DW_AT_name	("i")
+; CHECK:   DW_AT_location	(DW_OP_addr 0x8, DW_OP_deref)
+; CHECK: DW_TAG_variable
+; CHECK:   DW_AT_name	("indirect")
+; CHECK:   DW_AT_location	(DW_OP_addr 0x8
+
+source_filename = "global-deref.c"
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.13.0"
+
+@i = global i32 23, align 4
+@indirect = global i32* @i, align 8, !dbg !6, !dbg !0, !dbg !14, !dbg !15
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!10, !11, !12, !13}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_deref))
+!1 = distinct !DIGlobalVariable(name: "i", scope: !2, file: !3, line: 1, type: !9, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "global-deref.c", directory: "/")
+!4 = !{}
+!5 = !{!0, !6}
+!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
+!7 = distinct !DIGlobalVariable(name: "indirect", scope: !2, file: !3, line: 2, type: !8, isLocal: false, isDefinition: true)
+!8 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 64)
+!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!10 = !{i32 2, !"Dwarf Version", i32 4}
+!11 = !{i32 2, !"Debug Info Version", i32 3}
+!12 = !{i32 1, !"wchar_size", i32 4}
+!13 = !{i32 7, !"PIC Level", i32 2}
+; This is malformed, but too expensive to detect in the verifier.
+!14 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
+!15 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression(DW_OP_LLVM_fragment, 0, 1))