DWARF: Add some support for non-native directory separators

Summary:
If we opened a file which was produced on system with different path
syntax, we would parse the paths from the debug info incorrectly.

The reason for that is that we would parse the paths as they were
native. For example this meant that on linux we would treat the entire
windows path as a single file name with no directory component, and then
we would concatenate that with the single directory component from the
DW_AT_comp_dir attribute. When parsing posix paths on windows, we would
at least get the directory separators right, but we still would treat
the posix paths as relative, and concatenate them where we shouldn't.

This patch attempts to remedy this by guessing the path syntax used in
each compile unit. (Unfortunately, there is no info in DWARF which would
give the definitive path style used by the produces, so guessing is all
we can do.) Currently, this guessing is based on the DW_AT_comp_dir
attribute of the compile unit, but this can be refined later if needed
(for example, the DW_AT_name of the compile unit may also contain some
useful info). This style is then used when parsing the line table of
that compile unit.

This patch is sufficient to make the line tables come out right, and
enable breakpoint setting by file name work correctly. Setting a
breakpoint by full path still has some kinks (specifically, using a
windows-style full path will not work on linux because the path will be
parsed as a linux path), but this will require larger changes in how
breakpoint setting works.

Reviewers: clayborg, zturner, JDevlieghere

Subscribers: aprantl, lldb-commits

Differential Revision: https://reviews.llvm.org/D56543

15 files changed, 382 insertions, 77 deletions

diff --git a/lldb/include/lldb/Utility/FileSpec.h b/lldb/include/lldb/Utility/FileSpec.h
index 0699ab7b5c9..03c2fa1d156 100644
--- a/lldb/include/lldb/Utility/FileSpec.h
+++ b/lldb/include/lldb/Utility/FileSpec.h
@@ -326,6 +326,10 @@ public:
   //------------------------------------------------------------------
   bool IsAbsolute() const;
 
+  /// Make the FileSpec absolute by treating it relative to \a dir. Absolute
+  /// FileSpecs are never changed by this function.
+  void MakeAbsolute(const FileSpec &dir);
+
   /// Temporary helper for FileSystem change.
   void SetPath(llvm::StringRef p) { SetFile(p); }
 
diff --git a/lldb/lit/SymbolFile/DWARF/Inputs/dir-separator-no-comp-dir-relative-name.lldbinit b/lldb/lit/SymbolFile/DWARF/Inputs/dir-separator-no-comp-dir-relative-name.lldbinit
new file mode 100644
index 00000000000..390408ec8cc
--- /dev/null
+++ b/lldb/lit/SymbolFile/DWARF/Inputs/dir-separator-no-comp-dir-relative-name.lldbinit
@@ -0,0 +1,3 @@
+image dump line-table a.c
+breakpoint set -f a.c -l 1
+breakpoint set -f foo/b.c -l 1
diff --git a/lldb/lit/SymbolFile/DWARF/Inputs/dir-separator-posix.lldbinit b/lldb/lit/SymbolFile/DWARF/Inputs/dir-separator-posix.lldbinit
new file mode 100644
index 00000000000..73a8a491bb2
--- /dev/null
+++ b/lldb/lit/SymbolFile/DWARF/Inputs/dir-separator-posix.lldbinit
@@ -0,0 +1,3 @@
+image dump line-table a.c
+breakpoint set -f a.c -l 1
+breakpoint set -f /tmp/b.c -l 1
diff --git a/lldb/lit/SymbolFile/DWARF/Inputs/dir-separator-windows.lldbinit b/lldb/lit/SymbolFile/DWARF/Inputs/dir-separator-windows.lldbinit
new file mode 100644
index 00000000000..8737aafc8a2
--- /dev/null
+++ b/lldb/lit/SymbolFile/DWARF/Inputs/dir-separator-windows.lldbinit
@@ -0,0 +1,7 @@
+image dump line-table a.c
+breakpoint set -f a.c -l 1
+breakpoint set -f C:/tmp/b.c -l 1
+
+# This will fail on non-windows systems because the path will by parsed
+# according to posix rules
+# breakpoint set -f 'C:\tmp\b.c' -l 1
diff --git a/lldb/lit/SymbolFile/DWARF/dir-separator-no-comp-dir-relative-name.s b/lldb/lit/SymbolFile/DWARF/dir-separator-no-comp-dir-relative-name.s
new file mode 100644
index 00000000000..6df3a3d3e48
--- /dev/null
+++ b/lldb/lit/SymbolFile/DWARF/dir-separator-no-comp-dir-relative-name.s
@@ -0,0 +1,62 @@
+# Test that parsing of line tables works reasonably, even if the host directory
+# separator does not match the separator of the compile unit.
+
+# REQUIRES: lld
+
+# RUN: llvm-mc -triple x86_64-pc-linux %s -filetype=obj > %t.o
+# RUN: ld.lld %t.o -o %t
+# RUN: %lldb %t -s %S/Inputs/dir-separator-no-comp-dir-relative-name.lldbinit -o exit | FileCheck %s
+
+# CHECK-LABEL: image dump line-table a.c
+# CHECK: Line table for foo/a.c
+# CHECK-NEXT: 0x0000000000201000: foo/a.c:1
+# CHECK-NEXT: 0x0000000000201001: foo/b.c:1
+# CHECK-NEXT: 0x0000000000201002: foo/b.c:1
+# CHECK-EMPTY:
+
+# CHECK-LABEL: breakpoint set -f a.c -l 1
+# CHECK: Breakpoint 1: {{.*}}`_start,
+
+# CHECK-LABEL: breakpoint set -f foo/b.c -l 1
+# CHECK: Breakpoint 2: {{.*}}`_start + 1,
+
+	.text
+	.globl	_start
+_start:
+	.file	1 "foo/a.c"
+	.loc	1 1 0
+        nop
+	.file	2 "foo/b.c"
+	.loc	2 1 0
+        nop
+
+	.section	.debug_str,"MS",@progbits,1
+.Linfo_string1:
+	.asciz	"foo/a.c"
+	.section	.debug_abbrev,"",@progbits
+	.byte	1                       # Abbreviation Code
+	.byte	17                      # DW_TAG_compile_unit
+	.byte	0                       # DW_CHILDREN_no
+	.byte	19                      # DW_AT_language
+	.byte	5                       # DW_FORM_data2
+	.byte	3                       # DW_AT_name
+	.byte	14                      # DW_FORM_strp
+	.byte	16                      # DW_AT_stmt_list
+	.byte	23                      # DW_FORM_sec_offset
+	.byte	0                       # EOM(1)
+	.byte	0                       # EOM(2)
+	.byte	0                       # EOM(3)
+	.section	.debug_info,"",@progbits
+.Lcu_begin0:
+	.long	.Lcu_end0-.Lcu_start0   # Length of Unit
+.Lcu_start0:
+	.short	4                       # DWARF version number
+	.long	.debug_abbrev           # Offset Into Abbrev. Section
+	.byte	8                       # Address Size (in bytes)
+	.byte	1                       # Abbrev [1] 0xb:0x1f DW_TAG_compile_unit
+	.short	12                      # DW_AT_language
+	.long	.Linfo_string1          # DW_AT_name
+	.long	.Lline_table_start0     # DW_AT_stmt_list
+.Lcu_end0:
+	.section	.debug_line,"",@progbits
+.Lline_table_start0:
diff --git a/lldb/lit/SymbolFile/DWARF/dir-separator-no-comp-dir.s b/lldb/lit/SymbolFile/DWARF/dir-separator-no-comp-dir.s
new file mode 100644
index 00000000000..9e3281a334f
--- /dev/null
+++ b/lldb/lit/SymbolFile/DWARF/dir-separator-no-comp-dir.s
@@ -0,0 +1,62 @@
+# Test that we properly determine the path syntax of a compile unit even if the
+# compile unit does not have a DW_AT_comp_dir attribute.
+
+# REQUIRES: lld
+
+# RUN: llvm-mc -triple x86_64-pc-linux %s -filetype=obj > %t.o
+# RUN: ld.lld %t.o -o %t
+# RUN: %lldb %t -s %S/Inputs/dir-separator-windows.lldbinit -o exit | FileCheck %s
+
+# CHECK-LABEL: image dump line-table a.c
+# CHECK: Line table for C:\tmp\a.c
+# CHECK-NEXT: 0x0000000000201000: C:\tmp\a.c:1
+# CHECK-NEXT: 0x0000000000201001: C:\tmp\b.c:1
+# CHECK-NEXT: 0x0000000000201002: C:\tmp\b.c:1
+# CHECK-EMPTY:
+
+# CHECK-LABEL: breakpoint set -f a.c -l 1
+# CHECK: Breakpoint 1: {{.*}}`_start,
+
+# CHECK-LABEL: breakpoint set -f C:/tmp/b.c -l 1
+# CHECK: Breakpoint 2: {{.*}}`_start + 1,
+
+	.text
+	.globl	_start
+_start:
+	.file	1 "C:\\tmp\\a.c"
+	.loc	1 1 0
+        nop
+	.file	2 "C:\\tmp\\b.c"
+	.loc	2 1 0
+        nop
+
+	.section	.debug_str,"MS",@progbits,1
+.Linfo_string1:
+	.asciz	"C:\\tmp\\a.c"
+	.section	.debug_abbrev,"",@progbits
+	.byte	1                       # Abbreviation Code
+	.byte	17                      # DW_TAG_compile_unit
+	.byte	0                       # DW_CHILDREN_no
+	.byte	19                      # DW_AT_language
+	.byte	5                       # DW_FORM_data2
+	.byte	3                       # DW_AT_name
+	.byte	14                      # DW_FORM_strp
+	.byte	16                      # DW_AT_stmt_list
+	.byte	23                      # DW_FORM_sec_offset
+	.byte	0                       # EOM(1)
+	.byte	0                       # EOM(2)
+	.byte	0                       # EOM(3)
+	.section	.debug_info,"",@progbits
+.Lcu_begin0:
+	.long	.Lcu_end0-.Lcu_start0   # Length of Unit
+.Lcu_start0:
+	.short	4                       # DWARF version number
+	.long	.debug_abbrev           # Offset Into Abbrev. Section
+	.byte	8                       # Address Size (in bytes)
+	.byte	1                       # Abbrev [1] 0xb:0x1f DW_TAG_compile_unit
+	.short	12                      # DW_AT_language
+	.long	.Linfo_string1          # DW_AT_name
+	.long	.Lline_table_start0     # DW_AT_stmt_list
+.Lcu_end0:
+	.section	.debug_line,"",@progbits
+.Lline_table_start0:
diff --git a/lldb/lit/SymbolFile/DWARF/dir-separator-posix.s b/lldb/lit/SymbolFile/DWARF/dir-separator-posix.s
new file mode 100644
index 00000000000..976038a9f8b
--- /dev/null
+++ b/lldb/lit/SymbolFile/DWARF/dir-separator-posix.s
@@ -0,0 +1,67 @@
+# Test that parsing of line tables works reasonably, even if the host directory
+# separator does not match the separator of the compile unit.
+
+# REQUIRES: lld
+
+# RUN: llvm-mc -triple x86_64-pc-linux %s -filetype=obj > %t.o
+# RUN: ld.lld %t.o -o %t
+# RUN: %lldb %t -s %S/Inputs/dir-separator-posix.lldbinit -o exit | FileCheck %s
+
+# CHECK-LABEL: image dump line-table a.c
+# CHECK: Line table for /tmp/a.c
+# CHECK-NEXT: 0x0000000000201000: /tmp/a.c:1
+# CHECK-NEXT: 0x0000000000201001: /tmp/b.c:1
+# CHECK-NEXT: 0x0000000000201002: /tmp/b.c:1
+# CHECK-EMPTY:
+
+# CHECK-LABEL: breakpoint set -f a.c -l 1
+# CHECK: Breakpoint 1: {{.*}}`_start,
+
+# CHECK-LABEL: breakpoint set -f /tmp/b.c -l 1
+# CHECK: Breakpoint 2: {{.*}}`_start + 1,
+
+	.text
+	.globl	_start
+_start:
+	.file	1 "/tmp/a.c"
+	.loc	1 1 0
+        nop
+	.file	2 "/tmp/b.c"
+	.loc	2 1 0
+        nop
+
+	.section	.debug_str,"MS",@progbits,1
+.Linfo_string1:
+	.asciz	"a.c"
+.Linfo_string2:
+	.asciz	"/tmp"
+	.section	.debug_abbrev,"",@progbits
+	.byte	1                       # Abbreviation Code
+	.byte	17                      # DW_TAG_compile_unit
+	.byte	0                       # DW_CHILDREN_no
+	.byte	19                      # DW_AT_language
+	.byte	5                       # DW_FORM_data2
+	.byte	3                       # DW_AT_name
+	.byte	14                      # DW_FORM_strp
+	.byte	16                      # DW_AT_stmt_list
+	.byte	23                      # DW_FORM_sec_offset
+	.byte	27                      # DW_AT_comp_dir
+	.byte	14                      # DW_FORM_strp
+	.byte	0                       # EOM(1)
+	.byte	0                       # EOM(2)
+	.byte	0                       # EOM(3)
+	.section	.debug_info,"",@progbits
+.Lcu_begin0:
+	.long	.Lcu_end0-.Lcu_start0   # Length of Unit
+.Lcu_start0:
+	.short	4                       # DWARF version number
+	.long	.debug_abbrev           # Offset Into Abbrev. Section
+	.byte	8                       # Address Size (in bytes)
+	.byte	1                       # Abbrev [1] 0xb:0x1f DW_TAG_compile_unit
+	.short	12                      # DW_AT_language
+	.long	.Linfo_string1          # DW_AT_name
+	.long	.Lline_table_start0     # DW_AT_stmt_list
+	.long	.Linfo_string2          # DW_AT_comp_dir
+.Lcu_end0:
+	.section	.debug_line,"",@progbits
+.Lline_table_start0:
diff --git a/lldb/lit/SymbolFile/DWARF/dir-separator-windows.s b/lldb/lit/SymbolFile/DWARF/dir-separator-windows.s
new file mode 100644
index 00000000000..30308ab9dfb
--- /dev/null
+++ b/lldb/lit/SymbolFile/DWARF/dir-separator-windows.s
@@ -0,0 +1,67 @@
+# Test that parsing of line tables works reasonably, even if the host directory
+# separator does not match the separator of the compile unit.
+
+# REQUIRES: lld
+
+# RUN: llvm-mc -triple x86_64-pc-linux %s -filetype=obj > %t.o
+# RUN: ld.lld %t.o -o %t
+# RUN: %lldb %t -s %S/Inputs/dir-separator-windows.lldbinit -o exit | FileCheck %s
+
+# CHECK-LABEL: image dump line-table a.c
+# CHECK: Line table for C:\tmp\a.c
+# CHECK-NEXT: 0x0000000000201000: C:\tmp\a.c:1
+# CHECK-NEXT: 0x0000000000201001: C:\tmp\b.c:1
+# CHECK-NEXT: 0x0000000000201002: C:\tmp\b.c:1
+# CHECK-EMPTY:
+
+# CHECK-LABEL: breakpoint set -f a.c -l 1
+# CHECK: Breakpoint 1: {{.*}}`_start,
+
+# CHECK-LABEL: breakpoint set -f C:/tmp/b.c -l 1
+# CHECK: Breakpoint 2: {{.*}}`_start + 1,
+
+	.text
+	.globl	_start
+_start:
+	.file	1 "C:\\tmp\\a.c"
+	.loc	1 1 0
+        nop
+	.file	2 "C:\\tmp\\b.c"
+	.loc	2 1 0
+        nop
+
+	.section	.debug_str,"MS",@progbits,1
+.Linfo_string1:
+	.asciz	"a.c"
+.Linfo_string2:
+	.asciz	"C:\\tmp"
+	.section	.debug_abbrev,"",@progbits
+	.byte	1                       # Abbreviation Code
+	.byte	17                      # DW_TAG_compile_unit
+	.byte	0                       # DW_CHILDREN_no
+	.byte	19                      # DW_AT_language
+	.byte	5                       # DW_FORM_data2
+	.byte	3                       # DW_AT_name
+	.byte	14                      # DW_FORM_strp
+	.byte	16                      # DW_AT_stmt_list
+	.byte	23                      # DW_FORM_sec_offset
+	.byte	27                      # DW_AT_comp_dir
+	.byte	14                      # DW_FORM_strp
+	.byte	0                       # EOM(1)
+	.byte	0                       # EOM(2)
+	.byte	0                       # EOM(3)
+	.section	.debug_info,"",@progbits
+.Lcu_begin0:
+	.long	.Lcu_end0-.Lcu_start0   # Length of Unit
+.Lcu_start0:
+	.short	4                       # DWARF version number
+	.long	.debug_abbrev           # Offset Into Abbrev. Section
+	.byte	8                       # Address Size (in bytes)
+	.byte	1                       # Abbrev [1] 0xb:0x1f DW_TAG_compile_unit
+	.short	12                      # DW_AT_language
+	.long	.Linfo_string1          # DW_AT_name
+	.long	.Lline_table_start0     # DW_AT_stmt_list
+	.long	.Linfo_string2          # DW_AT_comp_dir
+.Lcu_end0:
+	.section	.debug_line,"",@progbits
+.Lline_table_start0:
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugLine.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugLine.cpp
index d9f50122bd6..cd50d40887e 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugLine.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugLine.cpp
@@ -18,6 +18,7 @@
 #include "lldb/Utility/Log.h"
 #include "lldb/Utility/Timer.h"
 
+#include "DWARFUnit.h"
 #include "LogChannelDWARF.h"
 #include "SymbolFileDWARF.h"
 
@@ -528,8 +529,7 @@ bool DWARFDebugLine::ParsePrologue(const DWARFDataExtractor &debug_line_data,
 
 bool DWARFDebugLine::ParseSupportFiles(
     const lldb::ModuleSP &module_sp, const DWARFDataExtractor &debug_line_data,
-    const lldb_private::FileSpec &cu_comp_dir, dw_offset_t stmt_list,
-    FileSpecList &support_files, DWARFUnit *dwarf_cu) {
+    dw_offset_t stmt_list, FileSpecList &support_files, DWARFUnit *dwarf_cu) {
   lldb::offset_t offset = stmt_list;
 
   Prologue prologue;
@@ -545,7 +545,9 @@ bool DWARFDebugLine::ParseSupportFiles(
   std::string remapped_file;
 
   for (uint32_t file_idx = 1;
-       prologue.GetFile(file_idx, cu_comp_dir, file_spec); ++file_idx) {
+       prologue.GetFile(file_idx, dwarf_cu->GetCompilationDirectory(),
+                        dwarf_cu->GetPathStyle(), file_spec);
+       ++file_idx) {
     if (module_sp->RemapSourceFile(file_spec.GetPath(), remapped_file))
       file_spec.SetFile(remapped_file, FileSpec::Style::native);
     support_files.Append(file_spec);
@@ -947,10 +949,12 @@ void DWARFDebugLine::Prologue::Dump(Log *log) {
 //}
 
 bool DWARFDebugLine::Prologue::GetFile(uint32_t file_idx,
-    const lldb_private::FileSpec &comp_dir, FileSpec &file) const {
+                                       const FileSpec &comp_dir,
+                                       FileSpec::Style style,
+                                       FileSpec &file) const {
   uint32_t idx = file_idx - 1; // File indexes are 1 based...
   if (idx < file_names.size()) {
-    file.SetFile(file_names[idx].name, FileSpec::Style::native);
+    file.SetFile(file_names[idx].name, style);
     if (file.IsRelative()) {
       if (file_names[idx].dir_idx > 0) {
         const uint32_t dir_idx = file_names[idx].dir_idx - 1;
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugLine.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugLine.h
index 04f72e03a2d..976e4038c6f 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugLine.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugLine.h
@@ -14,6 +14,7 @@
 #include <string>
 #include <vector>
 
+#include "lldb/Utility/FileSpec.h"
 #include "lldb/lldb-private.h"
 
 #include "DWARFDataExtractor.h"
@@ -99,6 +100,7 @@ public:
       file_names.clear();
     }
     bool GetFile(uint32_t file_idx, const lldb_private::FileSpec &cu_comp_dir,
+                 lldb_private::FileSpec::Style style,
                  lldb_private::FileSpec &file) const;
   };
 
@@ -207,9 +209,9 @@ public:
   static bool
   ParseSupportFiles(const lldb::ModuleSP &module_sp,
                     const lldb_private::DWARFDataExtractor &debug_line_data,
-                    const lldb_private::FileSpec &cu_comp_dir,
                     dw_offset_t stmt_list,
-                    lldb_private::FileSpecList &support_files, DWARFUnit *dwarf_cu);
+                    lldb_private::FileSpecList &support_files,
+                    DWARFUnit *dwarf_cu);
   static bool
   ParsePrologue(const lldb_private::DWARFDataExtractor &debug_line_data,
                 lldb::offset_t *offset_ptr, Prologue *prologue,
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp
index 7afc71bc24f..f794a77587f 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp
@@ -766,6 +766,80 @@ bool DWARFUnit::GetIsOptimized() {
   return m_is_optimized == eLazyBoolYes;
 }
 
+FileSpec::Style DWARFUnit::GetPathStyle() {
+  if (!m_comp_dir)
+    ComputeCompDirAndGuessPathStyle();
+  return m_comp_dir->GetPathStyle();
+}
+
+const FileSpec &DWARFUnit::GetCompilationDirectory() {
+  if (!m_comp_dir)
+    ComputeCompDirAndGuessPathStyle();
+  return *m_comp_dir;
+}
+
+// DWARF2/3 suggests the form hostname:pathname for compilation directory.
+// Remove the host part if present.
+static llvm::StringRef
+removeHostnameFromPathname(llvm::StringRef path_from_dwarf) {
+  llvm::StringRef host, path;
+  std::tie(host, path) = path_from_dwarf.split(':');
+
+  if (host.contains('/'))
+    return path_from_dwarf;
+
+  // check whether we have a windows path, and so the first character is a
+  // drive-letter not a hostname.
+  if (host.size() == 1 && llvm::isAlpha(host[0]) && path.startswith("\\"))
+    return path_from_dwarf;
+
+  return path;
+}
+
+static FileSpec resolveCompDir(const FileSpec &path) {
+  bool is_symlink = SymbolFileDWARF::GetSymlinkPaths().FindFileIndex(
+                        0, path, /*full*/ true) != UINT32_MAX;
+
+  if (!is_symlink)
+    return path;
+
+  namespace fs = llvm::sys::fs;
+  if (fs::get_file_type(path.GetPath(), false) != fs::file_type::symlink_file)
+    return path;
+
+  FileSpec resolved_symlink;
+  const auto error = FileSystem::Instance().Readlink(path, resolved_symlink);
+  if (error.Success())
+    return resolved_symlink;
+
+  return path;
+}
+
+void DWARFUnit::ComputeCompDirAndGuessPathStyle() {
+  m_comp_dir = FileSpec();
+  const DWARFDebugInfoEntry *die = GetUnitDIEPtrOnly();
+  if (!die)
+    return;
+
+  auto guess = [](llvm::StringRef str) {
+    if (str.startswith("/"))
+      return FileSpec::Style::posix;
+    if (str.size() > 3 && llvm::isAlpha(str[0]) && str.substr(1, 2) == ":\\")
+      return FileSpec::Style::windows;
+    return FileSpec::Style::native;
+  };
+  llvm::StringRef comp_dir = removeHostnameFromPathname(
+      die->GetAttributeValueAsString(m_dwarf, this, DW_AT_comp_dir, NULL));
+  if (!comp_dir.empty()) {
+    m_comp_dir = resolveCompDir(FileSpec(comp_dir, guess(comp_dir)));
+  } else {
+    // Try to detect the style based on the DW_AT_name attribute, but just store
+    // the detected style in the m_comp_dir field.
+    m_comp_dir = FileSpec("", guess(die->GetAttributeValueAsString(
+                                  m_dwarf, this, DW_AT_name, NULL)));
+  }
+}
+
 SymbolFileDWARFDwo *DWARFUnit::GetDwoSymbolFile() const {
   return m_dwo_symbol_file.get();
 }
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h
index 178c894686e..c6cff7ac5c6 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h
@@ -169,6 +169,9 @@ public:
 
   bool GetIsOptimized();
 
+  const lldb_private::FileSpec &GetCompilationDirectory();
+  lldb_private::FileSpec::Style GetPathStyle();
+
   SymbolFileDWARFDwo *GetDwoSymbolFile() const;
 
   dw_offset_t GetBaseObjOffset() const;
@@ -214,6 +217,7 @@ protected:
   lldb::LanguageType m_language_type = lldb::eLanguageTypeUnknown;
   bool m_is_dwarf64 = false;
   lldb_private::LazyBool m_is_optimized = lldb_private::eLazyBoolCalculate;
+  llvm::Optional<lldb_private::FileSpec> m_comp_dir;
   dw_addr_t m_addr_base = 0;   // Value of DW_AT_addr_base
   dw_addr_t m_ranges_base = 0; // Value of DW_AT_ranges_base
   // If this is a dwo compile unit this is the offset of the base compile unit
@@ -249,6 +253,8 @@ private:
   void AddUnitDIE(const DWARFDebugInfoEntry &cu_die);
   void ExtractDIEsEndCheck(lldb::offset_t offset) const;
 
+  void ComputeCompDirAndGuessPathStyle();
+
   DISALLOW_COPY_AND_ASSIGN(DWARFUnit);
 };
 
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
index 2a0a89f0b25..33cd2aba496 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -158,64 +158,8 @@ static const SymbolFileDWARFPropertiesSP &GetGlobalPluginProperties() {
 
 } // anonymous namespace end
 
-static const char *removeHostnameFromPathname(const char *path_from_dwarf) {
-  if (!path_from_dwarf || !path_from_dwarf[0]) {
-    return path_from_dwarf;
-  }
-
-  const char *colon_pos = strchr(path_from_dwarf, ':');
-  if (nullptr == colon_pos) {
-    return path_from_dwarf;
-  }
-
-  const char *slash_pos = strchr(path_from_dwarf, '/');
-  if (slash_pos && (slash_pos < colon_pos)) {
-    return path_from_dwarf;
-  }
-
-  // check whether we have a windows path, and so the first character is a
-  // drive-letter not a hostname.
-  if (colon_pos == path_from_dwarf + 1 && isalpha(*path_from_dwarf) &&
-      strlen(path_from_dwarf) > 2 && '\\' == path_from_dwarf[2]) {
-    return path_from_dwarf;
-  }
-
-  return colon_pos + 1;
-}
-
-static FileSpec resolveCompDir(const char *path_from_dwarf) {
-  if (!path_from_dwarf)
-    return FileSpec();
-
-  // DWARF2/3 suggests the form hostname:pathname for compilation directory.
-  // Remove the host part if present.
-  const char *local_path = removeHostnameFromPathname(path_from_dwarf);
-  if (!local_path)
-    return FileSpec();
-
-  bool is_symlink = false;
-  // Always normalize our compile unit directory to get rid of redundant
-  // slashes and other path anomalies before we use it for path prepending
-  FileSpec local_spec(local_path);
-  const auto &file_specs = GetGlobalPluginProperties()->GetSymLinkPaths();
-  for (size_t i = 0; i < file_specs.GetSize() && !is_symlink; ++i)
-    is_symlink = FileSpec::Equal(file_specs.GetFileSpecAtIndex(i),
-                                 local_spec, true);
-
-  if (!is_symlink)
-    return local_spec;
-
-  namespace fs = llvm::sys::fs;
-  if (fs::get_file_type(local_spec.GetPath(), false) !=
-      fs::file_type::symlink_file)
-    return local_spec;
-
-  FileSpec resolved_symlink;
-  const auto error = FileSystem::Instance().Readlink(local_spec, resolved_symlink);
-  if (error.Success())
-    return resolved_symlink;
-
-  return local_spec;
+const FileSpecList &SymbolFileDWARF::GetSymlinkPaths() {
+  return GetGlobalPluginProperties()->GetSymLinkPaths();
 }
 
 DWARFUnit *SymbolFileDWARF::GetBaseCompileUnit() {
@@ -810,17 +754,12 @@ lldb::CompUnitSP SymbolFileDWARF::ParseCompileUnit(DWARFUnit *dwarf_cu,
         if (module_sp) {
           const DWARFDIE cu_die = dwarf_cu->DIE();
           if (cu_die) {
-            FileSpec cu_file_spec(cu_die.GetName());
+            FileSpec cu_file_spec(cu_die.GetName(), dwarf_cu->GetPathStyle());
             if (cu_file_spec) {
               // If we have a full path to the compile unit, we don't need to
               // resolve the file.  This can be expensive e.g. when the source
-              // files are
-              // NFS mounted.
-              if (cu_file_spec.IsRelative()) {
-                const char *cu_comp_dir{
-                    cu_die.GetAttributeValueAsString(DW_AT_comp_dir, nullptr)};
-                cu_file_spec.PrependPathComponent(resolveCompDir(cu_comp_dir));
-              }
+              // files are NFS mounted.
+              cu_file_spec.MakeAbsolute(dwarf_cu->GetCompilationDirectory());
 
               std::string remapped_file;
               if (module_sp->RemapSourceFile(cu_file_spec.GetPath(),
@@ -947,8 +886,6 @@ bool SymbolFileDWARF::ParseSupportFiles(CompileUnit &comp_unit,
     const DWARFBaseDIE cu_die = dwarf_cu->GetUnitDIEOnly();
 
     if (cu_die) {
-      FileSpec cu_comp_dir = resolveCompDir(
-          cu_die.GetAttributeValueAsString(DW_AT_comp_dir, nullptr));
       const dw_offset_t stmt_list = cu_die.GetAttributeValueAsUnsigned(
           DW_AT_stmt_list, DW_INVALID_OFFSET);
       if (stmt_list != DW_INVALID_OFFSET) {
@@ -956,8 +893,8 @@ bool SymbolFileDWARF::ParseSupportFiles(CompileUnit &comp_unit,
         // supposed to be the compile unit itself.
         support_files.Append(comp_unit);
         return DWARFDebugLine::ParseSupportFiles(
-            comp_unit.GetModule(), get_debug_line_data(), cu_comp_dir,
-            stmt_list, support_files, dwarf_cu);
+            comp_unit.GetModule(), get_debug_line_data(), stmt_list,
+            support_files, dwarf_cu);
       }
     }
   }
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
index d351289f8b5..e6fe19e75c1 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
@@ -86,6 +86,8 @@ public:
   static lldb_private::SymbolFile *
   CreateInstance(lldb_private::ObjectFile *obj_file);
 
+  static const lldb_private::FileSpecList &GetSymlinkPaths();
+
   //------------------------------------------------------------------
   // Constructors and Destructors
   //------------------------------------------------------------------
diff --git a/lldb/source/Utility/FileSpec.cpp b/lldb/source/Utility/FileSpec.cpp
index 954968b7a8a..e621ada794e 100644
--- a/lldb/source/Utility/FileSpec.cpp
+++ b/lldb/source/Utility/FileSpec.cpp
@@ -557,6 +557,11 @@ bool FileSpec::IsAbsolute() const {
   return llvm::sys::path::is_absolute(current_path, m_style);
 }
 
+void FileSpec::MakeAbsolute(const FileSpec &dir) {
+  if (IsRelative())
+    PrependPathComponent(dir);
+}
+
 void llvm::format_provider<FileSpec>::format(const FileSpec &F,
                                              raw_ostream &Stream,
                                              StringRef Style) {