[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, 2 insertions, 2 deletions

diff --git a/llvm/test/DebugInfo/X86/isel-cse-line.ll b/llvm/test/DebugInfo/X86/isel-cse-line.ll
index 7140a4ddf42..94502fc9a21 100644
--- a/llvm/test/DebugInfo/X86/isel-cse-line.ll
+++ b/llvm/test/DebugInfo/X86/isel-cse-line.ll
@@ -73,10 +73,10 @@ declare void @llvm.dbg.declare(metadata, metadata, metadata)
 !4 = !DIDerivedType(tag: DW_TAG_typedef, name: "fp_t", file: !1, line: 1, baseType: !5)
 !5 = !DIBasicType(name: "double", size: 64, align: 64, encoding: DW_ATE_float)
 !6 = !{!7, !10}
-!7 = distinct !DIGlobalVariable(name: "glb_start", scope: !0, file: !1, line: 4, type: !8, isLocal: false, isDefinition: true)
+!7 = distinct !DIGlobalVariableExpression(var: !DIGlobalVariable(name: "glb_start", scope: !0, file: !1, line: 4, type: !8, isLocal: false, isDefinition: true))
 !8 = !DIDerivedType(tag: DW_TAG_typedef, name: "int_t", file: !1, line: 2, baseType: !9)
 !9 = !DIBasicType(name: "long unsigned int", size: 64, align: 64, encoding: DW_ATE_unsigned)
-!10 = distinct !DIGlobalVariable(name: "glb_end", scope: !0, file: !1, line: 5, type: !8, isLocal: false, isDefinition: true)
+!10 = distinct !DIGlobalVariableExpression(var: !DIGlobalVariable(name: "glb_end", scope: !0, file: !1, line: 5, type: !8, isLocal: false, isDefinition: true))
 !11 = !{i32 2, !"Dwarf Version", i32 4}
 !12 = !{i32 2, !"Debug Info Version", i32 3}
 !13 = !{!"clang version 3.9.0 (trunk 268246)"}