[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, 1 insertions, 1 deletions

diff --git a/llvm/test/Transforms/SampleProfile/cov-zero-samples.ll b/llvm/test/Transforms/SampleProfile/cov-zero-samples.ll
index 9ffa8ca36ee..9ec87ef1eb7 100644
--- a/llvm/test/Transforms/SampleProfile/cov-zero-samples.ll
+++ b/llvm/test/Transforms/SampleProfile/cov-zero-samples.ll
@@ -98,7 +98,7 @@ declare i32 @printf(i8*, ...)
 !9 = !DISubroutineType(types: !10)
 !10 = !{!7}
 !11 = !{!12}
-!12 = !DIGlobalVariable(name: "N", scope: !0, file: !1, line: 3, type: !13, isLocal: false, isDefinition: true)
+!12 = !DIGlobalVariableExpression(var: !DIGlobalVariable(name: "N", scope: !0, file: !1, line: 3, type: !13, isLocal: false, isDefinition: true))
 !13 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !14)
 !14 = !DIBasicType(name: "long long int", size: 64, align: 64, encoding: DW_ATE_signed)
 !15 = !{i32 2, !"Dwarf Version", i32 4}