[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, 23 insertions, 0 deletions

diff --git a/llvm/test/Assembler/diglobalvariableexpression.ll b/llvm/test/Assembler/diglobalvariableexpression.ll
new file mode 100644
index 00000000000..19f3d1443bf
--- /dev/null
+++ b/llvm/test/Assembler/diglobalvariableexpression.ll
@@ -0,0 +1,23 @@
+; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
+; RUN: verify-uselistorder %s
+
+@foo = global i32 0
+
+; CHECK: !named = !{!0, !1, !2, !3, !4, !5, !6, !7}
+!named = !{!0, !1, !2, !3, !4, !5, !6, !7}
+
+!0 = !DIFile(filename: "scope.h", directory: "/path/to/dir")
+!1 = distinct !{}
+!2 = !DIFile(filename: "path/to/file", directory: "/path/to/dir")
+!3 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!4 = distinct !{}
+
+; CHECK: !5 = !DIGlobalVariable(name: "foo", linkageName: "foo", scope: !0, file: !2, line: 7, type: !3, isLocal: true, isDefinition: false, align: 32)
+!5 = !DIGlobalVariable(name: "foo", linkageName: "foo", scope: !0,
+                       file: !2, line: 7, type: !3, isLocal: true,
+                       isDefinition: false, align: 32)
+
+; CHECK: !6 = !DIGlobalVariableExpression(var: !5, expr: !7)
+!6 = !DIGlobalVariableExpression(var: !5, expr: !7)
+; CHECK: !7 = !DIExpression(DW_OP_constu, 42, DW_OP_stack_value)
+!7 = !DIExpression(DW_OP_constu, 42, DW_OP_stack_value)