[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.

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

llvm-svn: 289920

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/test/DebugInfo/COFF/anonymous-struct.ll b/llvm/test/DebugInfo/COFF/anonymous-struct.ll
index 2cce0343521..767e6797e55 100644
--- a/llvm/test/DebugInfo/COFF/anonymous-struct.ll
+++ b/llvm/test/DebugInfo/COFF/anonymous-struct.ll
@@ -46,7 +46,7 @@ target triple = "i686-pc-windows-msvc18.0.0"
 !1 = !DIFile(filename: "-", directory: "/usr/local/google/home/majnemer/llvm/src")
 !2 = !{}
 !3 = !{!4}
-!4 = distinct !DIGlobalVariable(name: "s", scope: !0, file: !5, line: 5, type: !6, isLocal: false, isDefinition: true)
+!4 = !DIGlobalVariableExpression(var: !DIGlobalVariable(name: "s", scope: !0, file: !5, line: 5, type: !6, isLocal: false, isDefinition: true))
 !5 = !DIFile(filename: "<stdin>", directory: "/usr/local/google/home/majnemer/llvm/src")
 !6 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "S", file: !5, line: 2, size: 64, align: 32, elements: !7)
 !7 = !{!8, !10}