[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/CodeGen/X86/fpstack-debuginstr-kill.ll b/llvm/test/CodeGen/X86/fpstack-debuginstr-kill.ll
index 60d335dd48d..208a893c82c 100644
--- a/llvm/test/CodeGen/X86/fpstack-debuginstr-kill.ll
+++ b/llvm/test/CodeGen/X86/fpstack-debuginstr-kill.ll
@@ -64,7 +64,7 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
 !19 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
 !20 = !DILocalVariable(name: "value", line: 16, scope: !4, file: !6, type: !14)
 !21 = !{!22, !23}
-!22 = !DIGlobalVariable(name: "g1", line: 5, isLocal: false, isDefinition: true, scope: null, file: !6, type: !14)
-!23 = !DIGlobalVariable(name: "g2", line: 6, isLocal: false, isDefinition: true, scope: null, file: !6, type: !19)
+!22 = !DIGlobalVariableExpression(var: !DIGlobalVariable(name: "g1", line: 5, isLocal: false, isDefinition: true, scope: null, file: !6, type: !14))
+!23 = !DIGlobalVariableExpression(var: !DIGlobalVariable(name: "g2", line: 6, isLocal: false, isDefinition: true, scope: null, file: !6, type: !19))
 !24 = !{i32 2, !"Dwarf Version", i32 2}
 !25 = !{i32 2, !"Debug Info Version", i32 3}