[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.

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

llvm-svn: 289902

1 files changed, 6 insertions, 4 deletions

diff --git a/llvm/test/Transforms/GlobalMerge/debug-info.ll b/llvm/test/Transforms/GlobalMerge/debug-info.ll
index 04f81b54877..2ec7b117313 100644
--- a/llvm/test/Transforms/GlobalMerge/debug-info.ll
+++ b/llvm/test/Transforms/GlobalMerge/debug-info.ll
@@ -14,12 +14,14 @@ define void @use1() {
   ret void
 }
 
-; CHECK: [[A]] = distinct !DIGlobalVariable(name: "a", scope: null, isLocal: false, isDefinition: true)
-; CHECK: [[B]] = distinct !DIGlobalVariable(name: "b", scope: null, isLocal: false, isDefinition: true, expr: [[EXPR:![0-9]+]])
+; CHECK: [[A]] = !DIGlobalVariableExpression(var: [[AVAR:![0-9]+]])
+; CHECK: [[AVAR]] = !DIGlobalVariable(name: "a", scope: null, isLocal: false, isDefinition: true)
+; CHECK: [[B]] = !DIGlobalVariableExpression(var: [[BVAR:![0-9]+]], expr: [[EXPR:![0-9]+]])
+; CHECK: [[BVAR]] = !DIGlobalVariable(name: "b", scope: null, isLocal: false, isDefinition: true)
 ; CHECK: [[EXPR]] = !DIExpression(DW_OP_plus, 4)
 
 !llvm.module.flags = !{!2, !3}
-!0 = distinct !DIGlobalVariable(name: "a")
-!1 = distinct !DIGlobalVariable(name: "b")
+!0 = !DIGlobalVariableExpression(var: !DIGlobalVariable(name: "a"))
+!1 = !DIGlobalVariableExpression(var: !DIGlobalVariable(name: "b"))
 !2 = !{i32 2, !"Debug Info Version", i32 3}
 !3 = !{i32 2, !"Dwarf Version", i32 4}