[IR] Remove the DIExpression field from DIGlobalVariable.

This patch implements PR31013 by introducing a
DIGlobalVariableExpression that holds a pair of DIGlobalVariable and
DIExpression.

Currently, DIGlobalVariables holds a DIExpression. This is not the
best way to model this:

(1) The DIGlobalVariable should describe the source level variable,
    not how to get to its location.

(2) It makes it unsafe/hard to update the expressions when we call
    replaceExpression on the DIGLobalVariable.

(3) It makes it impossible to represent a global variable that is in
    more than one location (e.g., a variable with multiple
    DW_OP_LLVM_fragment-s).  We also moved away from attaching the
    DIExpression to DILocalVariable for the same reasons.

This reapplies r289902 with additional testcase upgrades and a change
to the Bitcode record for DIGlobalVariable, that makes upgrading the
old format unambiguous also for variables without DIExpressions.

<rdar://problem/29250149>
https://llvm.org/bugs/show_bug.cgi?id=31013
Differential Revision: https://reviews.llvm.org/D26769

llvm-svn: 290153

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/test/DebugInfo/X86/inline-member-function.ll b/llvm/test/DebugInfo/X86/inline-member-function.ll
index f4c18bb3168..f4c190318c8 100644
--- a/llvm/test/DebugInfo/X86/inline-member-function.ll
+++ b/llvm/test/DebugInfo/X86/inline-member-function.ll
@@ -82,7 +82,7 @@ attributes #1 = { nounwind readnone }
 !16 = !{!9}
 !17 = distinct !DISubprogram(name: "func", linkageName: "_ZN3foo4funcEi", line: 2, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 2, file: !1, scope: !4, type: !7, declaration: !6, variables: !2)
 !18 = !{!19}
-!19 = !DIGlobalVariable(name: "i", line: 5, isLocal: false, isDefinition: true, scope: null, file: !14, type: !9)
+!19 = !DIGlobalVariableExpression(var: !DIGlobalVariable(name: "i", line: 5, isLocal: false, isDefinition: true, scope: null, file: !14, type: !9))
 !20 = !{i32 2, !"Dwarf Version", i32 4}
 !21 = !{i32 1, !"Debug Info Version", i32 3}
 !22 = !{!"clang version 3.5.0 "}