Debug Info: Store the SDK in the DICompileUnit.

[aprantl]

Summary

This is another intermediate step for PR44213 (https://bugs.llvm.org/show_bug.cgi?id=44213).

This stores the SDK *name* in the debug info, to make it possible to -fdebug-prefix-map-replace the sysroot with a recognizable string and allowing the debugger to find a fitting SDK relative to itself, not the machine the executable was compiled on.

rdar://problem/51645582

[JDevlieghere]

Looks good to me.

[davide]

LGTM

[aprantl]

842ea709e4ed881c2bc59155af5df910eccda9c6

clang/lib/CodeGen/CGDebugInfo.cpp

void CGDebugInfo::CreateCompileUnit() {
   // DW_AT_comp_dir (the compilation directory), even if the source
   // file was specified with an absolute path.
   if (CSKind)
     CSInfo.emplace(*CSKind, Checksum);
   llvm::DIFile *CUFile = DBuilder.createFile(
       remapDIPath(MainFileName), remapDIPath(getCurrentDirname()), CSInfo,
       getSource(SM, SM.getMainFileID()));
 
-  StringRef Sysroot;
-  if (CGM.getCodeGenOpts().getDebuggerTuning() == llvm::DebuggerKind::LLDB)
+  StringRef Sysroot, SDK;
+  if (CGM.getCodeGenOpts().getDebuggerTuning() == llvm::DebuggerKind::LLDB) {
     Sysroot = CGM.getHeaderSearchOpts().Sysroot;
+    auto B = llvm::sys::path::rbegin(Sysroot);
+    auto E = llvm::sys::path::rend(Sysroot);
+    auto It = std::find_if(B, E, [](auto SDK) { return SDK.endswith(".sdk"); });
+    if (It != E)
+      SDK = *It;
+  }
 
   // Create new compile unit.
   TheCU = DBuilder.createCompileUnit(
       LangTag, CUFile, CGOpts.EmitVersionIdentMetadata ? Producer : "",
       LO.Optimize || CGOpts.PrepareForLTO || CGOpts.PrepareForThinLTO,
       CGOpts.DwarfDebugFlags, RuntimeVers, CGOpts.SplitDwarfFile, EmissionKind,
       DwoId, CGOpts.SplitDwarfInlining, CGOpts.DebugInfoForProfiling,
       CGM.getTarget().getTriple().isNVPTX()
           ? llvm::DICompileUnit::DebugNameTableKind::None
           : static_cast<llvm::DICompileUnit::DebugNameTableKind>(
                 CGOpts.DebugNameTable),
-      CGOpts.DebugRangesBaseAddress, Sysroot);
+      CGOpts.DebugRangesBaseAddress, Sysroot, SDK);
 }
 
 llvm::DIType *CGDebugInfo::CreateType(const BuiltinType *BT) {
   llvm::dwarf::TypeKind Encoding;
   StringRef BTName;
   switch (BT->getKind()) {
 #define BUILTIN_TYPE(Id, SingletonId)
 #define PLACEHOLDER_TYPE(Id, SingletonId) case BuiltinType::Id:

clang/test/CodeGen/debug-info-sysroot-sdk.c

+// RUN: %clang_cc1 -debug-info-kind=limited -triple %itanium_abi_triple \
+// RUN:   %s -isysroot /CLANG_SYSROOT/MacOSX.sdk -emit-llvm -o - \
+// RUN:   -debugger-tuning=lldb | FileCheck %s --check-prefix=LLDB
+// RUN: %clang_cc1 -debug-info-kind=limited -triple %itanium_abi_triple \
+// RUN:   %s -isysroot /CLANG_SYSROOT/MacOSX.sdk -emit-llvm -o - \
+// RUN:   -debugger-tuning=gdb | FileCheck %s --check-prefix=GDB
+
+void foo() {}
+
+// The sysroot and sdk are a LLDB-tuning-specific attributes.
+
+// LLDB: distinct !DICompileUnit({{.*}}sysroot: "/CLANG_SYSROOT/MacOSX.sdk",
+// LLDB-SAME:                          sdk: "MacOSX.sdk"
+// GDB: distinct !DICompileUnit(
+// GDB-NOT: sysroot: "/CLANG_SYSROOT/MacOSX.sdk"
+// GDB-NOT: sdk: "MacOSX.sdk"

clang/test/CodeGen/debug-info-sysroot.c

-// RUN: %clang_cc1 -debug-info-kind=limited -triple %itanium_abi_triple \
-// RUN:   %s -isysroot /CLANG_SYSROOT -emit-llvm -o - \
-// RUN:   -debugger-tuning=lldb | FileCheck %s --check-prefix=LLDB
-// RUN: %clang_cc1 -debug-info-kind=limited -triple %itanium_abi_triple \
-// RUN:   %s -isysroot /CLANG_SYSROOT -emit-llvm -o - \
-// RUN:   -debugger-tuning=gdb | FileCheck %s --check-prefix=GDB
-
-void foo() {}
-
-// The sysroot is an LLDB-tuning-specific attribute.
-
-// LLDB: distinct !DICompileUnit({{.*}}sysroot: "/CLANG_SYSROOT"
-// GDB: distinct !DICompileUnit(
-// GDB-NOT: sysroot: "/CLANG_SYSROOT"
-