[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, 6 insertions, 10 deletions

diff --git a/llvm/test/Assembler/diglobalvariable.ll b/llvm/test/Assembler/diglobalvariable.ll
index 33c2ec3a762..02dd6289c0a 100644
--- a/llvm/test/Assembler/diglobalvariable.ll
+++ b/llvm/test/Assembler/diglobalvariable.ll
@@ -3,8 +3,8 @@
 
 @foo = global i32 0
 
-; CHECK: !named = !{!0, !1, !2, !3, !4, !5, !6, !8, !9, !10}
-!named = !{!0, !1, !2, !3, !4, !5, !6, !7, !8, !9}
+; CHECK: !named = !{!0, !1, !2, !3, !4, !5, !6, !7, !8}
+!named = !{!0, !1, !2, !3, !4, !5, !6, !7, !8}
 
 !0 = !DIFile(filename: "scope.h", directory: "/path/to/dir")
 !1 = distinct !{}
@@ -17,12 +17,8 @@
                        file: !2, line: 7, type: !3, isLocal: true,
                        isDefinition: false, align: 32)
 
-; CHECK: !6 = !DIGlobalVariable(name: "foo", scope: !0, isLocal: false, isDefinition: true, expr: !7)
-; CHECK: !7 = !DIExpression(DW_OP_constu, 42, DW_OP_stack_value)
-!6 = !DIGlobalVariable(name: "foo", scope: !0, expr: !DIExpression(DW_OP_constu, 42, DW_OP_stack_value))
+!6 = !DICompositeType(tag: DW_TAG_structure_type, name: "Class", size: 8, align: 8)
+!7 = !DIDerivedType(tag: DW_TAG_member, name: "mem", flags: DIFlagStaticMember, scope: !6, baseType: !3)
 
-!7 = !DICompositeType(tag: DW_TAG_structure_type, name: "Class", size: 8, align: 8)
-!8 = !DIDerivedType(tag: DW_TAG_member, name: "mem", flags: DIFlagStaticMember, scope: !7, baseType: !3)
-
-; CHECK: !10 = !DIGlobalVariable(name: "mem", scope: !0, isLocal: false, isDefinition: true, declaration: !9)
-!9 = !DIGlobalVariable(name: "mem", scope: !0, declaration: !8)
+; CHECK: !8 = !DIGlobalVariable(name: "mem", scope: !0, isLocal: false, isDefinition: true, declaration: !7)
+!8 = !DIGlobalVariable(name: "mem", scope: !0, declaration: !7)