[PATCH] D43860: [AArch64] DWARF: do not generate AT_location for thread local
Lei Liu via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Feb 27 23:14:47 PST 2018
lliu0 created this revision.
Herald added subscribers: llvm-commits, JDevlieghere, kristof.beyls, javed.absar, rengolin.
AArch64 ELF ABI does not define a static relocation type for TLS offset within a module, which makes it impossible for compiler to generate a valid DW_AT_location content for thread local variables. Currently LLVM generates an invalid R_AARCH64_ABS64 relocation at the DW_AT_location field for a TLS variable. That causes trouble for linker because thread local variable does not have an absolute address at link time. AArch64 GCC solves the problem by not generating DW_AT_location for thread local variables. We should do the same in LLVM.
Repository:
rL LLVM
https://reviews.llvm.org/D43860
Files:
include/llvm/CodeGen/TargetLoweringObjectFile.h
lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
lib/Target/AArch64/AArch64TargetObjectFile.cpp
test/DebugInfo/AArch64/tls-at-location.ll
Index: test/DebugInfo/AArch64/tls-at-location.ll
===================================================================
--- /dev/null
+++ test/DebugInfo/AArch64/tls-at-location.ll
@@ -0,0 +1,42 @@
+; RUN: llc -filetype=obj -o - %s | llvm-dwarfdump -v - | FileCheck %s
+;
+; CHECK: .debug_info contents:
+; CHECK: DW_TAG_variable
+; CHECK-NOT: DW_AT_location
+
+; ModuleID = 'tls-at-location.c'
+source_filename = "tls-at-location.c"
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "arm64"
+
+ at var = thread_local global i32 0, align 4, !dbg !0
+
+; Function Attrs: noinline nounwind optnone
+define i32 @foo() #0 !dbg !11 {
+entry:
+ %0 = load i32, i32* @var, align 4, !dbg !14
+ ret i32 %0, !dbg !15
+}
+
+attributes #0 = { noinline nounwind optnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="generic" "target-features"="+neon" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8, !9}
+!llvm.ident = !{!10}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "var", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 7.0.0 (https://github.com/llvm-mirror/clang.git 43eac1f9d7d2c985831b485d9ccc807416d1cf29) (https://github.com/llvm-mirror/llvm.git d53cdbf4cc5414ea540174a036202c555ce8fc4b)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "tls-at-location.c", directory: "/home/lliu0/llvm/tls-at-location/DebugInfo/AArch64")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!7 = !{i32 2, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 1, !"wchar_size", i32 4}
+!10 = !{!"clang version 7.0.0 (https://github.com/llvm-mirror/clang.git 43eac1f9d7d2c985831b485d9ccc807416d1cf29) (https://github.com/llvm-mirror/llvm.git d53cdbf4cc5414ea540174a036202c555ce8fc4b)"}
+!11 = distinct !DISubprogram(name: "foo", scope: !3, file: !3, line: 3, type: !12, isLocal: false, isDefinition: true, scopeLine: 3, isOptimized: false, unit: !2, variables: !4)
+!12 = !DISubroutineType(types: !13)
+!13 = !{!6}
+!14 = !DILocation(line: 4, column: 10, scope: !11)
+!15 = !DILocation(line: 4, column: 3, scope: !11)
Index: lib/Target/AArch64/AArch64TargetObjectFile.cpp
===================================================================
--- lib/Target/AArch64/AArch64TargetObjectFile.cpp
+++ lib/Target/AArch64/AArch64TargetObjectFile.cpp
@@ -22,6 +22,9 @@
const TargetMachine &TM) {
TargetLoweringObjectFileELF::Initialize(Ctx, TM);
InitializeELF(TM.Options.UseInitArray);
+ // AARCH64 ELF ABI does not define static relocation type for TLS offset
+ // within a module. Do not generate AT_location for TLS variables.
+ SupportDebugThreadLocalLocation = false;
}
AArch64_MachoTargetObjectFile::AArch64_MachoTargetObjectFile()
Index: lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -186,6 +186,10 @@
if (!Global && (!Expr || !Expr->isConstant()))
continue;
+ if (Global && Global->isThreadLocal() &&
+ !Asm->getObjFileLowering().supportDebugThreadLocalLocation())
+ continue;
+
if (!Loc) {
addToAccelTable = true;
Loc = new (DIEValueAllocator) DIELoc;
Index: include/llvm/CodeGen/TargetLoweringObjectFile.h
===================================================================
--- include/llvm/CodeGen/TargetLoweringObjectFile.h
+++ include/llvm/CodeGen/TargetLoweringObjectFile.h
@@ -45,6 +45,7 @@
protected:
bool SupportIndirectSymViaGOTPCRel = false;
bool SupportGOTPCRelWithOffset = true;
+ bool SupportDebugThreadLocalLocation = true;
/// This section contains the static constructor pointer list.
MCSection *StaticCtorSection = nullptr;
@@ -171,6 +172,11 @@
return SupportGOTPCRelWithOffset;
}
+ /// \brief Target supports TLS offset relocation in debug section?
+ bool supportDebugThreadLocalLocation() const {
+ return SupportDebugThreadLocalLocation;
+ }
+
/// \brief Get the target specific PC relative GOT entry relocation
virtual const MCExpr *getIndirectSymViaGOTPCRel(const MCSymbol *Sym,
const MCValue &MV,
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