[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, 17 insertions, 5 deletions

diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index d4de28e2c1f..712a2c6762d 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -4197,8 +4197,7 @@ bool LLParser::ParseDITemplateValueParameter(MDNode *&Result, bool IsDistinct) {
 /// ParseDIGlobalVariable:
 ///   ::= !DIGlobalVariable(scope: !0, name: "foo", linkageName: "foo",
 ///                         file: !1, line: 7, type: !2, isLocal: false,
-///                         isDefinition: true, variable: i32* @foo,
-///                         declaration: !3, align: 8)
+///                         isDefinition: true, declaration: !3, align: 8)
 bool LLParser::ParseDIGlobalVariable(MDNode *&Result, bool IsDistinct) {
 #define VISIT_MD_FIELDS(OPTIONAL, REQUIRED)                                    \
   REQUIRED(name, MDStringField, (/* AllowEmpty */ false));                     \
@@ -4209,7 +4208,6 @@ bool LLParser::ParseDIGlobalVariable(MDNode *&Result, bool IsDistinct) {
   OPTIONAL(type, MDField, );                                                   \
   OPTIONAL(isLocal, MDBoolField, );                                            \
   OPTIONAL(isDefinition, MDBoolField, (true));                                 \
-  OPTIONAL(expr, MDField, );                                                   \
   OPTIONAL(declaration, MDField, );                                            \
   OPTIONAL(align, MDUnsignedField, (0, UINT32_MAX));
   PARSE_MD_FIELDS();
@@ -4218,8 +4216,7 @@ bool LLParser::ParseDIGlobalVariable(MDNode *&Result, bool IsDistinct) {
   Result = GET_OR_DISTINCT(DIGlobalVariable,
                            (Context, scope.Val, name.Val, linkageName.Val,
                             file.Val, line.Val, type.Val, isLocal.Val,
-                            isDefinition.Val, expr.Val, declaration.Val,
-                            align.Val));
+                            isDefinition.Val, declaration.Val, align.Val));
   return false;
 }
 
@@ -4287,6 +4284,21 @@ bool LLParser::ParseDIExpression(MDNode *&Result, bool IsDistinct) {
   return false;
 }
 
+/// ParseDIGlobalVariableExpression:
+///   ::= !DIGlobalVariableExpression(var: !0, expr: !1)
+bool LLParser::ParseDIGlobalVariableExpression(MDNode *&Result,
+                                               bool IsDistinct) {
+#define VISIT_MD_FIELDS(OPTIONAL, REQUIRED)                                    \
+  REQUIRED(var, MDField, );                                                    \
+  OPTIONAL(expr, MDField, );
+  PARSE_MD_FIELDS();
+#undef VISIT_MD_FIELDS
+
+  Result =
+      GET_OR_DISTINCT(DIGlobalVariableExpression, (Context, var.Val, expr.Val));
+  return false;
+}
+
 /// ParseDIObjCProperty:
 ///   ::= !DIObjCProperty(name: "foo", file: !1, line: 7, setter: "setFoo",
 ///                       getter: "getFoo", attributes: 7, type: !2)