[llvm] r331090 - Fix a bug that prevents global variables from having a DW_OP_deref.

[Adrian Prantl via llvm-commits]

Author: adrian
Date: Fri Apr 27 15:05:31 2018
New Revision: 331090

URL: http://llvm.org/viewvc/llvm-project?rev=331090&view=rev
Log:
Fix a bug that prevents global variables from having a DW_OP_deref.

For local variables the first DW_OP_deref is consumed by turning the
location kind into a memeory location, but that only makes sense for
values that are in a register to begin with, which cannot happen for
global variables that are attached to a symbol.

rdar://problem/39741860

This reapplies r330970 after fixing an uncovered bug in r331086 and
working around the situation caused by it.

Added:
    llvm/trunk/test/DebugInfo/X86/global-expression.ll
Modified:
    llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
    llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
    llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.h

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp?rev=331090&r1=331089&r2=331090&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp Fri Apr 27 15:05:31 2018
@@ -230,8 +230,13 @@ DIE *DwarfCompileUnit::getOrCreateGlobal
         addOpAddress(*Loc, Sym);
       }
     }
-    if (Expr)
-      DwarfExpr->addExpression(Expr);
+    // Global variables attached to symbols are memory locations.
+    // It would be better if this were unconditional, but malformed input that
+    // mixes non-fragments and fragments for the same variable is too expensive
+    // to detect in the verifier.
+    if (!DwarfExpr->isMemoryLocation())
+      DwarfExpr->setMemoryLocationKind();
+    DwarfExpr->addExpression(Expr);
   }
   if (Loc)
     addBlock(*VariableDIE, dwarf::DW_AT_location, DwarfExpr->finalize());

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp?rev=331090&r1=331089&r2=331090&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp Fri Apr 27 15:05:31 2018
@@ -361,7 +361,7 @@ void DwarfExpression::addExpression(DIEx
       break;
     case dwarf::DW_OP_deref:
       assert(LocationKind != Register);
-      if (LocationKind != Memory && isMemoryLocation(ExprCursor))
+      if (LocationKind != Memory && ::isMemoryLocation(ExprCursor))
         // Turning this into a memory location description makes the deref
         // implicit.
         LocationKind = Memory;

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.h?rev=331090&r1=331089&r2=331090&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.h (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.h Fri Apr 27 15:05:31 2018
@@ -211,6 +211,8 @@ public:
   /// Emit an unsigned constant.
   void addUnsignedConstant(const APInt &Value);
 
+  bool isMemoryLocation() const { return LocationKind == Memory; }
+
   /// Lock this down to become a memory location description.
   void setMemoryLocationKind() {
     assert(LocationKind == Unknown);

Added: llvm/trunk/test/DebugInfo/X86/global-expression.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/global-expression.ll?rev=331090&view=auto
==============================================================================
--- llvm/trunk/test/DebugInfo/X86/global-expression.ll (added)
+++ llvm/trunk/test/DebugInfo/X86/global-expression.ll Fri Apr 27 15:05:31 2018
@@ -0,0 +1,41 @@
+; RUN: llc -mtriple=x86_64-apple-darwin %s -o - -filetype=obj | \
+; RUN:     llvm-dwarfdump --name i --name indirect - | FileCheck %s
+;
+; This is a hand-crafted testcase generated from:
+;   int i = 23;
+;   int *indirect = &i;
+
+; CHECK: DW_TAG_variable
+; CHECK:   DW_AT_name	("i")
+; CHECK:   DW_AT_location	(DW_OP_addr 0x8, DW_OP_deref)
+; CHECK: DW_TAG_variable
+; CHECK:   DW_AT_name	("indirect")
+; CHECK:   DW_AT_location	(DW_OP_addr 0x8
+
+source_filename = "global-deref.c"
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.13.0"
+
+ at i = global i32 23, align 4
+ at indirect = global i32* @i, align 8, !dbg !6, !dbg !0, !dbg !14, !dbg !15
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!10, !11, !12, !13}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_deref))
+!1 = distinct !DIGlobalVariable(name: "i", scope: !2, file: !3, line: 1, type: !9, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "global-deref.c", directory: "/")
+!4 = !{}
+!5 = !{!0, !6}
+!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
+!7 = distinct !DIGlobalVariable(name: "indirect", scope: !2, file: !3, line: 2, type: !8, isLocal: false, isDefinition: true)
+!8 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 64)
+!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!10 = !{i32 2, !"Dwarf Version", i32 4}
+!11 = !{i32 2, !"Debug Info Version", i32 3}
+!12 = !{i32 1, !"wchar_size", i32 4}
+!13 = !{i32 7, !"PIC Level", i32 2}
+; This is malformed, but too expensive to detect in the verifier.
+!14 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
+!15 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression(DW_OP_LLVM_fragment, 0, 1))