[WebAssembly] Support debug info for TLS + global in PIC mode

[aheejin]

Summary

This adds debug info support for

• thread_local global variables, both in non-PIC and PIC modes
• (non-thread_local) Global variables in PIC mode

The former needs to read the value from an offset relative to
__tls_base and the latter an offset from __memory_base. The code for
doing this overlaps with some of the existing code to add
__stack_pointer global, so this adds a new member function to add a
a global in TI_GLOBAL_RELOC mode and use it in all three places.

Split DWARF support is currently patchy at best, because the index for
__tls_base is not fixed after dynamic linking. The preexisting split
DWARF support for __stack_pointer relies on that in practice it is
always index 0. This does similar hardcoding for __tls_base and
__memory_base, but __tls_base's index in dynamic linking is not
fixed now (See
https://github.com/llvm/llvm-project/blob/19afbfe33156d211fa959dadeea46cd17b9c723c/lld/wasm/Driver.cpp#L786-L823
for details), TLS + dynamic linking will not work at the moment.

Fixes https://bugs.chromium.org/p/chromium/issues/detail?id=1416702.

[aheejin]

Remove TODO

[sbc100]

When you say ", TLS + dynamic linking will not work at the moment." do you mean just the debug info won't work? Or it won't work at all?

[aheejin]

Only debug info won't work. So the devtools DWARF extension (https://chrome.google.com/webstore/detail/cc%20%20-devtools-support-dwa/pdcpmagijalfljmkmjngeonclgbbannb) will display undefined or some garbage value for TLS variables in dynamic linking. But that's the status quo for them anyway.

[aheejin]

Test tidying up

[aheejin]

fix

[aheejin]

sed fix

[aheejin]

Add split DWARF tests

[aheejin]

Revert unnecessary changes

[dschuff]

In D145626#4179867, @aheejin wrote:

Only debug info won't work. So the devtools DWARF extension (https://chrome.google.com/webstore/detail/cc%20%20-devtools-support-dwa/pdcpmagijalfljmkmjngeonclgbbannb) will display undefined or some garbage value for TLS variables in dynamic linking. But that's the status quo for them anyway.

Just so I'm clear, this is TLS + dynamic linking + split-dwarf, right?

Since the test does actually run that case, maybe it makes sense to put a comment in there about what the output should look like once that case is fixed?

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

496

[aheejin]

In D145626#4181966, @dschuff wrote:

In D145626#4179867, @aheejin wrote:

Only debug info won't work. So the devtools DWARF extension (https://chrome.google.com/webstore/detail/cc%20%20-devtools-support-dwa/pdcpmagijalfljmkmjngeonclgbbannb) will display undefined or some garbage value for TLS variables in dynamic linking. But that's the status quo for them anyway.

Just so I'm clear, this is TLS + dynamic linking + split-dwarf, right?

Yes.

Since the test does actually run that case, maybe it makes sense to put a comment in there about what the output should look like once that case is fixed?

That was tricky part when adding the test case. You can see that I put {{[0-9]+}} in place of all global indices. Internally they would contain a relocation symbol that's to be resolved in linker, but at this object file stage they don't mean much; I think they just mean the order of symbols added. So, when you don't use split dwarf, when you use dylink + TLS, because source code adds TLS first, __tls_base is shown as 0 and __memory_base is shown as 1. And if you use dylink witout TLS, __memory_base is shown as 0 instead. So these are not final indices. On the other hand, in case of split dwarf, the indices are fixed, because we hardcoded them, which can be incorrect in the case of dylink + TLS + split dwarf.

If we want to test final indices, we should move this test to lld. I actually considered that, but didn't end up doing it because the change itself doesn't involve anything in the linker. Do you think it's better? Or we leave this as is and only test indices in case of split dwarf? This is not really easy either because we don't know what the real values of those indices in split dwarf should be at this point in the object file.

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

496

lol

[aheejin]

stack_overflow -> stack_pointer

[dschuff]

Ah right. With regular codegen tests we don't have this kind of problem because the assembly output is symbolic; also some tests that test disassembly use objdump -dr which prints relocation info next to instructions that need relocations. But I don't think dwarfdump will do that.
I agree that moving this test to lld doesn't seem great either.

We could test explicitly for relocation information using llvm-readobj (many MC tests do this). I guess for the static linking cases we could assert that there's a relocation against __stack_pointer and in the split dwarf case we could check that there are no relocations. Not sure whether that would be worth it though.

[dschuff]

One other question about the test. Did you generate it from a C file? When I've made tests like this in the past I've usually included the C source as a comment at the top to make it easier to regenerate if needed.
Maybe we can land this as-is and see how it works in the debugger, and work on the test more if we improve the code.

[aheejin]

In D145626#4185463, @dschuff wrote:

We could test explicitly for relocation information using llvm-readobj (many MC tests do this). I guess for the static linking cases we could assert that there's a relocation against __stack_pointer and in the split dwarf case we could check that there are no relocations. Not sure whether that would be worth it though.

I guess you mean not __stack_pointer but __tls_base and __memory_base, right? This CL doesn't change anything related to __stack_pointer handling. (It refactors the code that handles it, but NFC on that part.)

Yes, I can do that, but AFAIK llvm-readobj doesn't provide any specific info on which global indices contain which reloc. All I can test is that in non-split objects there are relocations referring to __tls_base/__memory_base in .debug_info section, and there are no relocations in dwo files. I guess the latter should be ensured, like, by definition of split DWARF though.

In D145626#4185501, @dschuff wrote:

One other question about the test. Did you generate it from a C file?

I originally used a C file, but edited the generated .ll file in several places. Also I removed unrelated debug info a lot; for example, we don't need any line debug info / local variable debug info in this test so I removed all of them to make the test simpler.

When I've made tests like this in the past I've usually included the C source as a comment at the top to make it easier to regenerate if needed.

I used to do that for some tests too, especially the ones that involve control flow (e.g. comments in https://github.com/llvm/llvm-project/blob/main/llvm/test/CodeGen/WebAssembly/exception.ll). For this code, I removed unnecessary parts from the generated code so it wouldn't be exactly the same, but I can come up with C code more or less matches the structure.

[aheejin]

Add reloc test + original C source comment

[aheejin]

Comment fix

[dschuff]

I guess you mean not stack_pointer but tls_base and __memory_base, right?

Yes, sorry.

Yes, I can do that, but AFAIK llvm-readobj doesn't provide any specific info on which global indices contain which reloc. All I can test is that in non-split objects there are relocations referring to tls_base/memory_base in .debug_info section, and there are no relocations in dwo files.

Yes, exactly. We can test part of the behavior we want this way, but not all of it. Hence me not being sure whether it's worth it. But I do like what you've come up with here, it seems pretty straightforward.

I guess the latter should be ensured, like, by definition of split DWARF though.

I'm not actually sure what would happen if we accidentally did something wrong here. e.g. I'm not sure whether the dwo file is created via the same MC mechanism that creates object files (in which case it might be possible or even easy to accidentally create a relocation) or some other mechanism, which case it might not be likely.

I used to do that for some tests too, especially the ones that involve control flow (e.g. comments in https://github.com/llvm/llvm-project/blob/main/llvm/test/CodeGen/WebAssembly/exception.ll). For this code, I removed unnecessary parts from the generated code so it wouldn't be exactly the same, but I can come up with C code more or less matches the structure.

Makes sense, thanks.

This looks good now overall.

[aheejin]

Fix typo in comment

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h

class DwarfCompileUnit final : public DwarfUnit {
   DenseMap<const DINode *, std::unique_ptr<DbgEntity>> &getAbstractEntities() {
     if (isDwoUnit() && !DD->shareAcrossDWOCUs())
       return AbstractEntities;
     return DU->getAbstractEntities();
   }
 
   void finishNonUnitTypeDIE(DIE& D, const DICompositeType *CTy) override;
 
+  /// Add info for Wasm-global-based relocation.
+  void addWasmRelocBaseGlobal(DIELoc *Loc, StringRef GlobalName,
+                              uint64_t GlobalIndex);
+
 public:
   DwarfCompileUnit(unsigned UID, const DICompileUnit *Node, AsmPrinter *A,
                    DwarfDebug *DW, DwarfFile *DWU,
                    UnitKind Kind = UnitKind::Full);
 
   bool hasRangeLists() const { return HasRangeLists; }
   unsigned getUniqueID() const { return UniqueID; }
 

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

if (Global) {
           dwarf::Form Form;
           dwarf::LocationAtom Op;
         };
         return PointerSize == 4
                    ? FormAndOp{dwarf::DW_FORM_data4, dwarf::DW_OP_const4u}
                    : FormAndOp{dwarf::DW_FORM_data8, dwarf::DW_OP_const8u};
       };
       if (Global->isThreadLocal()) {
-        if (Asm->TM.useEmulatedTLS()) {
+        if (Asm->TM.getTargetTriple().isWasm()) {
+          // FIXME This is not guaranteed, but in practice, in static linking,
+          // if present, __tls_base's index is 1. This doesn't hold for dynamic
+          // linking, so TLS variables used in dynamic linking won't have
+          // correct debug info for now. See
+          // https://github.com/llvm/llvm-project/blob/19afbfe33156d211fa959dadeea46cd17b9c723c/lld/wasm/Driver.cpp#L786-L823
+          addWasmRelocBaseGlobal(Loc, "__tls_base", 1);
+          addOpAddress(*Loc, Sym);
+          addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_plus);
+        } else if (Asm->TM.useEmulatedTLS()) {
           // TODO: add debug info for emulated thread local mode.
         } else {
           // FIXME: Make this work with -gsplit-dwarf.
           // Based on GCC's support for TLS:
           if (!DD->useSplitDwarf()) {
             auto FormAndOp = GetPointerSizedFormAndOp();
             // 1) Start with a constNu of the appropriate pointer size
             addUInt(*Loc, dwarf::DW_FORM_data1, FormAndOp.Op);
             // 2) containing the (relocated) offset of the TLS variable
             //    within the module's TLS block.
             addExpr(*Loc, FormAndOp.Form,
                     Asm->getObjFileLowering().getDebugThreadLocalSymbol(Sym));
           } else {
             addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_GNU_const_index);
             addUInt(*Loc, dwarf::DW_FORM_udata,
                     DD->getAddressPool().getIndex(Sym, /* TLS */ true));
           }
           // 3) followed by an OP to make the debugger do a TLS lookup.
           addUInt(*Loc, dwarf::DW_FORM_data1,
                   DD->useGNUTLSOpcode() ? dwarf::DW_OP_GNU_push_tls_address
                                         : dwarf::DW_OP_form_tls_address);
         }
+      } else if (Asm->TM.getTargetTriple().isWasm() &&
+                 Asm->TM.getRelocationModel() == Reloc::PIC_) {
+        // FIXME This is not guaranteed, but in practice, if present,
+        // __memory_base's index is 1. See
+        // https://github.com/llvm/llvm-project/blob/19afbfe33156d211fa959dadeea46cd17b9c723c/lld/wasm/Driver.cpp#L786-L823
+        addWasmRelocBaseGlobal(Loc, "__memory_base", 1);
+        addOpAddress(*Loc, Sym);
+        addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_plus);
       } else if ((Asm->TM.getRelocationModel() == Reloc::RWPI ||
                   Asm->TM.getRelocationModel() == Reloc::ROPI_RWPI) &&
                  !Asm->getObjFileLowering()
                       .getKindForGlobal(Global, Asm->TM)
                       .isReadOnly()) {
         auto FormAndOp = GetPointerSizedFormAndOp();
         // Constant
         addUInt(*Loc, dwarf::DW_FORM_data1, FormAndOp.Op);

 // and DW_AT_high_pc attributes. If there are global variables in this
 // scope then create and insert DIEs for these variables.
 DIE &DwarfCompileUnit::updateSubprogramScopeDIE(const DISubprogram *SP) {
   DIE *SPDie = getOrCreateSubprogramDIE(SP, includeMinimalInlineScopes());
   auto *ContextCU = static_cast<DwarfCompileUnit *>(SPDie->getUnit());
   return ContextCU->updateSubprogramScopeDIEImpl(SP, SPDie);
 }
 
+// Add info for Wasm-global-based relocation.
+// 'GlobalIndex' is used for split dwarf, which currently relies on a few
+// assumptions that are not guaranteed in a formal way but work in practice.
+void DwarfCompileUnit::addWasmRelocBaseGlobal(DIELoc *Loc, StringRef GlobalName,
+                                              uint64_t GlobalIndex) {
+  // FIXME: duplicated from Target/WebAssembly/WebAssembly.h
+  // don't want to depend on target specific headers in this code?
+  const unsigned TI_GLOBAL_RELOC = 3;
+  unsigned PointerSize = Asm->getDataLayout().getPointerSize();
+  auto *Sym = cast<MCSymbolWasm>(Asm->GetExternalSymbolSymbol(GlobalName));
+  // FIXME: this repeats what WebAssemblyMCInstLower::
+  // GetExternalSymbolSymbol does, since if there's no code that
+  // refers to this symbol, we have to set it here.
+  Sym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
+  Sym->setGlobalType(wasm::WasmGlobalType{
+      static_cast<uint8_t>(PointerSize == 4 ? wasm::WASM_TYPE_I32
+                                            : wasm::WASM_TYPE_I64),
+      true});
+  addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_WASM_location);
+  addSInt(*Loc, dwarf::DW_FORM_sdata, TI_GLOBAL_RELOC);
+  if (!isDwoUnit()) {
+    addLabel(*Loc, dwarf::DW_FORM_data4, Sym);
+  } else {
+    // FIXME: when writing dwo, we need to avoid relocations. Probably
+    // the "right" solution is to treat globals the way func and data
+    // symbols are (with entries in .debug_addr).
+    // For now we hardcode the indices in the callsites. Global indices are not
+    // fixed, but in practice a few are fixed; for example, __stack_pointer is
+    // always index 0.
+    addUInt(*Loc, dwarf::DW_FORM_data4, GlobalIndex);
+  }
+}
+
 DIE &DwarfCompileUnit::updateSubprogramScopeDIEImpl(const DISubprogram *SP,
                                                     DIE *SPDie) {
   SmallVector<RangeSpan, 2> BB_List;
   // If basic block sections are on, ranges for each basic block section has
   // to be emitted separately.
   for (const auto &R : Asm->MBBSectionRanges)
     BB_List.push_back({R.second.BeginLabel, R.second.EndLabel});
 
if (!includeMinimalInlineScopes()) {
     case TargetFrameLowering::DwarfFrameBase::CFA: {
       DIELoc *Loc = new (DIEValueAllocator) DIELoc;
       addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_call_frame_cfa);
       addBlock(*SPDie, dwarf::DW_AT_frame_base, Loc);
       break;
     }
     case TargetFrameLowering::DwarfFrameBase::WasmFrameBase: {
       // FIXME: duplicated from Target/WebAssembly/WebAssembly.h
-      // don't want to depend on target specific headers in this code?
       const unsigned TI_GLOBAL_RELOC = 3;
       if (FrameBase.Location.WasmLoc.Kind == TI_GLOBAL_RELOC) {
         // These need to be relocatable.
-        assert(FrameBase.Location.WasmLoc.Index == 0);  // Only SP so far.
-        auto SPSym = cast<MCSymbolWasm>(
-          Asm->GetExternalSymbolSymbol("__stack_pointer"));
-        // FIXME: this repeats what WebAssemblyMCInstLower::
-        // GetExternalSymbolSymbol does, since if there's no code that
-        // refers to this symbol, we have to set it here.
-        SPSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
-        SPSym->setGlobalType(wasm::WasmGlobalType{
-            uint8_t(Asm->getSubtargetInfo().getTargetTriple().getArch() ==
-                            Triple::wasm64
-                        ? wasm::WASM_TYPE_I64
-                        : wasm::WASM_TYPE_I32),
-            true});
         DIELoc *Loc = new (DIEValueAllocator) DIELoc;
-        addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_WASM_location);
-        addSInt(*Loc, dwarf::DW_FORM_sdata, TI_GLOBAL_RELOC);
-        if (!isDwoUnit()) {
-          addLabel(*Loc, dwarf::DW_FORM_data4, SPSym);
-        } else {
-          // FIXME: when writing dwo, we need to avoid relocations. Probably
-          // the "right" solution is to treat globals the way func and data
-          // symbols are (with entries in .debug_addr).
-          // For now, since we only ever use index 0, this should work as-is.
-          addUInt(*Loc, dwarf::DW_FORM_data4, FrameBase.Location.WasmLoc.Index);
-        }
+        assert(FrameBase.Location.WasmLoc.Index == 0); // Only SP so far.
+        addWasmRelocBaseGlobal(Loc, "__stack_pointer",
+                               FrameBase.Location.WasmLoc.Index);
         addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_stack_value);
         addBlock(*SPDie, dwarf::DW_AT_frame_base, Loc);
       } else {
         DIELoc *Loc = new (DIEValueAllocator) DIELoc;
         DIEDwarfExpression DwarfExpr(*Asm, *this, *Loc);
         DIExpressionCursor Cursor({});
         DwarfExpr.addWasmLocation(FrameBase.Location.WasmLoc.Kind,
             FrameBase.Location.WasmLoc.Index);

llvm/test/DebugInfo/WebAssembly/tls_pic_globals.ll

+; Non-PIC tests
+; RUN: sed -e 's/\[\[TLS_MODE\]\]/(localexec)/' %s | llc -filetype=obj -mattr=+bulk-memory,atomics - -o %t.localexec.o
+; RUN: sed -e 's/\[\[TLS_MODE\]\]//' %s | llc -filetype=obj -mattr=+bulk-memory,atomics - -o %t.generaldynamic.o
+; RUN: llvm-dwarfdump %t.localexec.o | FileCheck %s --check-prefixes=CHECK,NOPIC
+; RUN: llvm-dwarfdump %t.generaldynamic.o | FileCheck %s --check-prefixes=CHECK,NOPIC
+; RUN: llvm-readobj -r %t.localexec.o | FileCheck %s --check-prefixes=RELOCS-NOSPLIT
+; RUN: llvm-readobj -r %t.generaldynamic.o | FileCheck %s --check-prefixes=RELOCS-NOSPLIT
+
+; PIC tests
+; RUN: sed -e 's/\[\[TLS_MODE\]\]/(localexec)/' %s | llc -filetype=obj -mattr=+bulk-memory,atomics -relocation-model=pic - -o %t.localexec.pic.o
+; RUN: sed -e 's/\[\[TLS_MODE\]\]//' %s | llc -filetype=obj -mattr=+bulk-memory,atomics -relocation-model=pic - -o %t.generaldynamic.pic.o
+; RUN: llvm-dwarfdump %t.localexec.pic.o | FileCheck %s --check-prefixes=CHECK,PIC
+; RUN: llvm-dwarfdump %t.generaldynamic.pic.o | FileCheck %s --check-prefixes=CHECK,PIC
+; RUN: llvm-readobj -r %t.localexec.pic.o | FileCheck %s --check-prefixes=RELOCS-NOSPLIT,RELOCS-PIC-NOSPLIT
+; RUN: llvm-readobj -r %t.generaldynamic.pic.o | FileCheck %s --check-prefixes=RELOCS-NOSPLIT,RELOCS-PIC-NOSPLIT
+
+; Non-PIC + split DWARF tests
+; RUN: sed -e 's/\[\[TLS_MODE\]\]/(localexec)/' %s | llc -filetype=obj -mattr=+bulk-memory,atomics -split-dwarf-file=%t.localexec.split.dwo -split-dwarf-output=%t.localexec.split.dwo - -o %t.localexec.split.o
+; RUN: sed -e 's/\[\[TLS_MODE\]\]//' %s | llc -filetype=obj -mattr=+bulk-memory,atomics -split-dwarf-file=%t.generaldynamic.split.dwo -split-dwarf-output=%t.generaldynamic.split.dwo - -o %t.generaldynamic.split.o
+; RUN: llvm-dwarfdump %t.localexec.split.dwo | FileCheck %s --check-prefixes=CHECK,NOPIC
+; RUN: llvm-dwarfdump %t.generaldynamic.split.dwo | FileCheck %s --check-prefixes=CHECK,NOPIC
+; RUN: llvm-readobj -r %t.localexec.split.dwo | FileCheck %s --check-prefixes=RELOCS-SPLIT
+; RUN: llvm-readobj -r %t.generaldynamic.split.dwo | FileCheck %s --check-prefixes=RELOCS-SPLIT
+
+; PIC + split DWARF tests
+; RUN: sed -e 's/\[\[TLS_MODE\]\]/(localexec)/' %s | llc -filetype=obj -mattr=+bulk-memory,atomics -relocation-model=pic -split-dwarf-file=%t.localexec.pic.split.dwo -split-dwarf-output=%t.localexec.pic.split.dwo - -o %t.localexec.pic.split.o
+; RUN: sed -e 's/\[\[TLS_MODE\]\]//' %s | llc -filetype=obj -mattr=+bulk-memory,atomics -relocation-model=pic -split-dwarf-file=%t.generaldynamic.pic.split.dwo -split-dwarf-output=%t.generaldynamic.pic.split.dwo - -o %t.generaldynamic.pic.split.o
+; RUN: llvm-dwarfdump %t.localexec.pic.split.dwo | FileCheck %s --check-prefixes=CHECK,PIC
+; RUN: llvm-dwarfdump %t.generaldynamic.pic.split.dwo | FileCheck %s --check-prefixes=CHECK,PIC
+; RUN: llvm-readobj -r %t.localexec.pic.split.dwo | FileCheck %s --check-prefixes=RELOCS-SPLIT
+; RUN: llvm-readobj -r %t.generaldynamic.pic.split.dwo | FileCheck %s --check-prefixes=RELOCS-SPLIT
+
+; This test is generated and from the following C code, after which some
+; unnecessary debug info is removed.
+
+; int external_var0 = 111;
+; int external_var1 = 222;
+; static int internal_var0 = 333;
+; static int internal_var1 = 444;
+; _Thread_local int external_tls_var0 = 555;
+; _Thread_local int external_tls_var1 = 666;
+; _Thread_local int internal_tls_var0 = 777;
+; _Thread_local int internal_tls_var1 = 888;
+;
+; void foo(int, int, int, int, int, int, int, int);
+;
+; void test_tls_pic_globals() {
+;   foo(external_var0, external_var1, internal_var0, internal_var1,
+;       external_tls_var0, external_tls_var1, internal_tls_var0,
+;       internal_tls_var1);
+; }
+
+target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-f128:64-n32:64-S128-ni:1:10:20"
+target triple = "wasm32-unknown-emscripten"
+
+@external_var0 = global i32 111, align 4, !dbg !0
+@external_var1 = global i32 222, align 4, !dbg !5
+@internal_var0 = internal global i32 333, align 4, !dbg !8
+@internal_var1 = internal global i32 444, align 4, !dbg !10
+@external_tls_var0 = thread_local[[TLS_MODE]] global i32 555, align 4, !dbg !12
+@external_tls_var1 = thread_local[[TLS_MODE]] global i32 666, align 4, !dbg !14
+@internal_tls_var0 = internal thread_local[[TLS_MODE]] global i32 777, align 4, !dbg !16
+@internal_tls_var1 = internal thread_local[[TLS_MODE]] global i32 888, align 4, !dbg !18
+
+define void @foo(i32, i32, i32, i32, i32, i32, i32, i32) {
+  ret void
+}
+
+define void @test_tls_pic_globals() !dbg !24 {
+entry:
+  %0 = load i32, ptr @external_var0, align 4
+  %1 = load i32, ptr @external_var1, align 4
+  %2 = load i32, ptr @internal_var0, align 4
+  %3 = load i32, ptr @internal_var1, align 4
+  %4 = call align 4 ptr @llvm.threadlocal.address.p0(ptr align 4 @external_tls_var0)
+  %5 = load i32, ptr %4, align 4
+  %6 = call align 4 ptr @llvm.threadlocal.address.p0(ptr align 4 @external_tls_var1)
+  %7 = load i32, ptr %6, align 4
+  %8 = call align 4 ptr @llvm.threadlocal.address.p0(ptr align 4 @internal_tls_var0)
+  %9 = load i32, ptr %8, align 4
+  %10 = call align 4 ptr @llvm.threadlocal.address.p0(ptr align 4 @internal_tls_var1)
+  %11 = load i32, ptr %10, align 4
+  call void @foo(i32 %0, i32 %1, i32 %2, i32 %3, i32 %5, i32 %7, i32 %9, i32 %11)
+  ret void
+}
+
+; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
+declare nonnull ptr @llvm.threadlocal.address.p0(ptr nonnull) #0
+
+attributes #0 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!20, !21, !22, !23}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "external_var0", scope: !2, file: !3, line: 4, type: !7, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C11, file: !3, isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, globals: !4)
+!3 = !DIFile(filename: "test.c", directory: "")
+!4 = !{!0, !5, !8, !10, !12, !14, !16, !18}
+!5 = !DIGlobalVariableExpression(var: !6, expr: !DIExpression())
+!6 = distinct !DIGlobalVariable(name: "external_var1", scope: !2, file: !3, line: 4, type: !7, isLocal: false, isDefinition: true)
+!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!8 = !DIGlobalVariableExpression(var: !9, expr: !DIExpression())
+!9 = distinct !DIGlobalVariable(name: "internal_var0", scope: !2, file: !3, line: 6, type: !7, isLocal: true, isDefinition: true)
+!10 = !DIGlobalVariableExpression(var: !11, expr: !DIExpression())
+!11 = distinct !DIGlobalVariable(name: "internal_var1", scope: !2, file: !3, line: 7, type: !7, isLocal: true, isDefinition: true)
+!12 = !DIGlobalVariableExpression(var: !13, expr: !DIExpression())
+!13 = distinct !DIGlobalVariable(name: "external_tls_var0", scope: !2, file: !3, line: 8, type: !7, isLocal: false, isDefinition: true)
+!14 = !DIGlobalVariableExpression(var: !15, expr: !DIExpression())
+!15 = distinct !DIGlobalVariable(name: "external_tls_var1", scope: !2, file: !3, line: 9, type: !7, isLocal: false, isDefinition: true)
+!16 = !DIGlobalVariableExpression(var: !17, expr: !DIExpression())
+!17 = distinct !DIGlobalVariable(name: "internal_tls_var0", scope: !2, file: !3, line: 9, type: !7, isLocal: true, isDefinition: true)
+!18 = !DIGlobalVariableExpression(var: !19, expr: !DIExpression())
+!19 = distinct !DIGlobalVariable(name: "internal_tls_var1", scope: !2, file: !3, line: 9, type: !7, isLocal: true, isDefinition: true)
+!20 = !{i32 7, !"Dwarf Version", i32 5}
+!21 = !{i32 2, !"Debug Info Version", i32 3}
+!22 = !{i32 1, !"wchar_size", i32 4}
+!23 = !{i32 8, !"PIC Level", i32 2}
+!24 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 16, type: !25, spFlags: DISPFlagDefinition, unit: !2)
+!25 = !DISubroutineType(types: !26)
+!26 = !{null}
+
+; Tests if TLS variables and global variables in PIC mode have a correct debug
+; info location. TLS variables should have their location relative to __tls_base
+; global, and global variables in PIC objects should have their location
+; relative to __memory_base global.
+
+; CHECK:      DW_TAG_variable
+; CHECK-NEXT:   DW_AT_name  ("external_var0")
+; CHECK:        DW_AT_external  (true)
+; NOPIC:        DW_AT_location  (DW_OP_addrx 0x0)
+; PIC:          DW_AT_location  (DW_OP_WASM_location 0x3 0x{{[0-9]+}}, DW_OP_addrx 0x0, DW_OP_plus)
+
+; CHECK:      DW_TAG_variable
+; CHECK-NEXT:   DW_AT_name  ("external_var1")
+; CHECK:        DW_AT_external  (true)
+; NOPIC:        DW_AT_location  (DW_OP_addrx 0x1)
+; PIC:          DW_AT_location  (DW_OP_WASM_location 0x3 0x{{[0-9]+}}, DW_OP_addrx 0x1, DW_OP_plus)
+
+; CHECK:      DW_TAG_variable
+; CHECK-NEXT:   DW_AT_name  ("internal_var0")
+; NOPIC:        DW_AT_location  (DW_OP_addrx 0x2)
+; PIC:          DW_AT_location  (DW_OP_WASM_location 0x3 0x{{[0-9]+}}, DW_OP_addrx 0x2, DW_OP_plus)
+
+; CHECK:      DW_TAG_variable
+; CHECK-NEXT:   DW_AT_name  ("internal_var1")
+; NOPIC:        DW_AT_location  (DW_OP_addrx 0x3)
+; PIC:          DW_AT_location  (DW_OP_WASM_location 0x3 0x{{[0-9]+}}, DW_OP_addrx 0x3, DW_OP_plus)
+
+; CHECK:      DW_TAG_variable
+; CHECK-NEXT:   DW_AT_name  ("external_tls_var0")
+; CHECK:        DW_AT_external  (true)
+; CHECK:        DW_AT_location  (DW_OP_WASM_location 0x3 0x{{[0-9]+}}, DW_OP_addrx 0x4, DW_OP_plus)
+
+; CHECK:      DW_TAG_variable
+; CHECK-NEXT:   DW_AT_name  ("external_tls_var1")
+; CHECK:        DW_AT_external  (true)
+; CHECK:        DW_AT_location  (DW_OP_WASM_location 0x3 0x{{[0-9]+}}, DW_OP_addrx 0x5, DW_OP_plus)
+
+; CHECK:      DW_TAG_variable
+; CHECK-NEXT:   DW_AT_name  ("internal_tls_var0")
+; CHECK:        DW_AT_location  (DW_OP_WASM_location 0x3 0x{{[0-9]+}}, DW_OP_addrx 0x6, DW_OP_plus)
+
+; CHECK:      DW_TAG_variable
+; CHECK-NEXT:   DW_AT_name  ("internal_tls_var1")
+; CHECK:        DW_AT_location  (DW_OP_WASM_location 0x3 0x{{[0-9]+}}, DW_OP_addrx 0x7, DW_OP_plus)
+
+; In non-split DWARF, .debug_info section contains relocations referring to
+; __stack_pointer, __tls_base, and __memory_base (if they use them)
+
+; RELOCS-NOSPLIT:         Relocations [
+; RELOCS-NOSPLIT:           Section (8) .debug_info {
+; RELOCS-NOSPLIT-DAG:         0x{{.*}} R_WASM_GLOBAL_INDEX_I32 __tls_base
+; RELOCS-NOSPLIT-DAG:         0x{{.*}} R_WASM_GLOBAL_INDEX_I32 __stack_pointer
+; RELOCS-PIC-NOSPLIT-DAG:     0x{{.*}} R_WASM_GLOBAL_INDEX_I32 __memory_base
+; RELOCS-NOSPLIT:           }
+; RELOCS-NOSPLIT:           Section (9) .debug_str_offsets {
+
+; In split DWARF, there should be no relocations in .dwo files.
+
+; RELOCS-SPLIT:           Relocations [
+; RELOCS-SPLIT-NEXT:      ]