[dwarf] make dwarf fission compatible with RISCV relaxations 1/2 #166597
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@llvm/pr-subscribers-debuginfo Author: None (dlav-sc) ChangesCurrently, -gsplit-dwarf and -mrelax are incompatible options in Clang. The issue is that .dwo files should not contain any relocations, as they are not processed by the linker. However, relaxable code emits relocations in DWARF for debug ranges that reside in the .dwo file when DWARF fission is enabled. This patch makes DWARF fission compatible with RISC-V relaxations. It uses the StartxEndx DWARF forms in .debug_rnglists.dwo, which allow referencing addresses from .debug_addr instead of using absolute addresses. This approach eliminates relocations from .dwo files. Full diff: https://github.com/llvm/llvm-project/pull/166597.diff 4 Files Affected:
diff --git a/llvm/include/llvm/MC/MCSymbol.h b/llvm/include/llvm/MC/MCSymbol.h
index e31d0374baf4a..eef248354b70f 100644
--- a/llvm/include/llvm/MC/MCSymbol.h
+++ b/llvm/include/llvm/MC/MCSymbol.h
@@ -383,6 +383,8 @@ inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
return OS;
}
+bool isRangeRelaxable(const MCSymbol *Begin, const MCSymbol *End);
+
} // end namespace llvm
#endif // LLVM_MC_MCSYMBOL_H
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 567acf75d1b8d..46895a3ccb027 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -3291,14 +3291,12 @@ static MCSymbol *emitLoclistsTableHeader(AsmPrinter *Asm,
}
template <typename Ranges, typename PayloadEmitter>
-static void emitRangeList(
- DwarfDebug &DD, AsmPrinter *Asm, MCSymbol *Sym, const Ranges &R,
- const DwarfCompileUnit &CU, unsigned BaseAddressx, unsigned OffsetPair,
- unsigned StartxLength, unsigned EndOfList,
- StringRef (*StringifyEnum)(unsigned),
- bool ShouldUseBaseAddress,
- PayloadEmitter EmitPayload) {
-
+static void
+emitRangeList(DwarfDebug &DD, AsmPrinter *Asm, MCSymbol *Sym, const Ranges &R,
+ const DwarfCompileUnit &CU, unsigned BaseAddressx,
+ unsigned OffsetPair, unsigned StartxLength, unsigned StartxEndx,
+ unsigned EndOfList, StringRef (*StringifyEnum)(unsigned),
+ bool ShouldUseBaseAddress, PayloadEmitter EmitPayload) {
auto Size = Asm->MAI->getCodePointerSize();
bool UseDwarf5 = DD.getDwarfVersion() >= 5;
@@ -3317,7 +3315,8 @@ static void emitRangeList(
bool BaseIsSet = false;
for (const auto &P : SectionRanges) {
auto *Base = CUBase;
- if ((Asm->TM.getTargetTriple().isNVPTX() && DD.tuneForGDB())) {
+ if ((Asm->TM.getTargetTriple().isNVPTX() && DD.tuneForGDB()) ||
+ (DD.useSplitDwarf() && UseDwarf5 && P.first->isLinkerRelaxable())) {
// PTX does not support subtracting labels from the code section in the
// debug_loc section. To work around this, the NVPTX backend needs the
// compile unit to have no low_pc in order to have a zero base_address
@@ -3373,12 +3372,21 @@ static void emitRangeList(
Asm->emitLabelDifference(End, Base, Size);
}
} else if (UseDwarf5) {
- Asm->OutStreamer->AddComment(StringifyEnum(StartxLength));
- Asm->emitInt8(StartxLength);
- Asm->OutStreamer->AddComment(" start index");
- Asm->emitULEB128(DD.getAddressPool().getIndex(Begin));
- Asm->OutStreamer->AddComment(" length");
- Asm->emitLabelDifferenceAsULEB128(End, Begin);
+ if (DD.useSplitDwarf() && llvm::isRangeRelaxable(Begin, End)) {
+ Asm->OutStreamer->AddComment(StringifyEnum(StartxEndx));
+ Asm->emitInt8(StartxEndx);
+ Asm->OutStreamer->AddComment(" start index");
+ Asm->emitULEB128(DD.getAddressPool().getIndex(Begin));
+ Asm->OutStreamer->AddComment(" end index");
+ Asm->emitULEB128(DD.getAddressPool().getIndex(End));
+ } else {
+ Asm->OutStreamer->AddComment(StringifyEnum(StartxLength));
+ Asm->emitInt8(StartxLength);
+ Asm->OutStreamer->AddComment(" start index");
+ Asm->emitULEB128(DD.getAddressPool().getIndex(Begin));
+ Asm->OutStreamer->AddComment(" length");
+ Asm->emitLabelDifferenceAsULEB128(End, Begin);
+ }
} else {
Asm->OutStreamer->emitSymbolValue(Begin, Size);
Asm->OutStreamer->emitSymbolValue(End, Size);
@@ -3399,14 +3407,14 @@ static void emitRangeList(
// Handles emission of both debug_loclist / debug_loclist.dwo
static void emitLocList(DwarfDebug &DD, AsmPrinter *Asm, const DebugLocStream::List &List) {
- emitRangeList(DD, Asm, List.Label, DD.getDebugLocs().getEntries(List),
- *List.CU, dwarf::DW_LLE_base_addressx,
- dwarf::DW_LLE_offset_pair, dwarf::DW_LLE_startx_length,
- dwarf::DW_LLE_end_of_list, llvm::dwarf::LocListEncodingString,
- /* ShouldUseBaseAddress */ true,
- [&](const DebugLocStream::Entry &E) {
- DD.emitDebugLocEntryLocation(E, List.CU);
- });
+ emitRangeList(
+ DD, Asm, List.Label, DD.getDebugLocs().getEntries(List), *List.CU,
+ dwarf::DW_LLE_base_addressx, dwarf::DW_LLE_offset_pair,
+ dwarf::DW_LLE_startx_length, dwarf::DW_LLE_startx_endx,
+ dwarf::DW_LLE_end_of_list, llvm::dwarf::LocListEncodingString,
+ /* ShouldUseBaseAddress */ true, [&](const DebugLocStream::Entry &E) {
+ DD.emitDebugLocEntryLocation(E, List.CU);
+ });
}
void DwarfDebug::emitDebugLocImpl(MCSection *Sec) {
@@ -3628,8 +3636,8 @@ static void emitRangeList(DwarfDebug &DD, AsmPrinter *Asm,
const RangeSpanList &List) {
emitRangeList(DD, Asm, List.Label, List.Ranges, *List.CU,
dwarf::DW_RLE_base_addressx, dwarf::DW_RLE_offset_pair,
- dwarf::DW_RLE_startx_length, dwarf::DW_RLE_end_of_list,
- llvm::dwarf::RangeListEncodingString,
+ dwarf::DW_RLE_startx_length, dwarf::DW_RLE_startx_endx,
+ dwarf::DW_RLE_end_of_list, llvm::dwarf::RangeListEncodingString,
List.CU->getCUNode()->getRangesBaseAddress() ||
DD.getDwarfVersion() >= 5,
[](auto) {});
diff --git a/llvm/lib/MC/MCSymbol.cpp b/llvm/lib/MC/MCSymbol.cpp
index b86873824cb00..7440fd8687b4d 100644
--- a/llvm/lib/MC/MCSymbol.cpp
+++ b/llvm/lib/MC/MCSymbol.cpp
@@ -84,7 +84,22 @@ void MCSymbol::print(raw_ostream &OS, const MCAsmInfo *MAI) const {
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
-LLVM_DUMP_METHOD void MCSymbol::dump() const {
- dbgs() << *this;
-}
+LLVM_DUMP_METHOD void MCSymbol::dump() const { dbgs() << *this; }
#endif
+
+bool llvm::isRangeRelaxable(const MCSymbol *Begin, const MCSymbol *End) {
+ assert(Begin && "Range without a begin symbol?");
+ assert(End && "Range without an end symbol?");
+ llvm::SmallVector<const MCFragment *> RangeFragments{};
+ for (const auto *Fragment = Begin->getFragment();
+ Fragment != End->getFragment(); Fragment = Fragment->getNext()) {
+ RangeFragments.push_back(Fragment);
+ }
+ RangeFragments.push_back(End->getFragment());
+
+ bool IsRelaxableRange = llvm::any_of(RangeFragments, [](auto &&Fragment) {
+ assert(Fragment);
+ return Fragment->isLinkerRelaxable();
+ });
+ return IsRelaxableRange;
+}
diff --git a/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll b/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll
new file mode 100644
index 0000000000000..f8ab7fc5ad900
--- /dev/null
+++ b/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll
@@ -0,0 +1,187 @@
+; RUN: llc -dwarf-version=5 -split-dwarf-file=foo.dwo -O0 %s -mtriple=riscv64-unknown-linux-gnu -filetype=obj -o %t
+; RUN: llvm-dwarfdump -v %t | FileCheck --check-prefix=DWARF5 %s
+; RUN: llvm-dwarfdump --debug-info %t 2> %t.txt
+; RUN: FileCheck --input-file=%t.txt %s --check-prefix=RELOCS --implicit-check-not=warning:
+
+; RUN: llc -dwarf-version=4 -split-dwarf-file=foo.dwo -O0 %s -mtriple=riscv64-unknown-linux-gnu -filetype=obj -o %t
+; RUN: llvm-dwarfdump -v %t | FileCheck --check-prefix=DWARF4 %s
+; RUN: llvm-dwarfdump --debug-info %t 2> %t.txt
+; RUN: FileCheck --input-file=%t.txt %s --check-prefix=RELOCS --implicit-check-not=warning:
+
+; In the RISC-V architecture, the .text section is subject to
+; relaxation, meaning the start address of each function can change
+; during the linking process. Therefore, the .debug_rnglists.dwo
+; section must obtain function's start addresses from the .debug_addr
+; section.
+
+; Generally, a function's body can be relaxed (for example, the
+; square() and main() functions in this test, which contain call
+; instructions). For such code ranges, the linker must place the
+; start and end addresses into the .debug_addr section and use
+; the DW_RLE_startx_endx entry form in the .debug_rnglists.dwo
+; section within the .dwo file.
+
+; However, some functions may not contain any relaxable instructions
+; (for example, the boo() function in this test). In these cases,
+; it is possible to use the more space-efficient DW_RLE_startx_length
+; range entry form.
+
+; From the code:
+
+; __attribute__((noinline)) int boo();
+
+; int square(int num) {
+; int num1 = boo();
+; return num1 * num;
+; }
+
+; __attribute__((noinline)) int boo() {
+; return 8;
+; }
+
+; int main() {
+; int a = 10;
+; int squared = square(a);
+; return squared;
+; }
+
+; compiled with
+
+; clang -g -S -gsplit-dwarf --target=riscv64 -march=rv64gc -O0 relax_dwo_ranges.cpp
+
+; Currently, square() still uses an offset to represent the function's end address,
+; which requires a relocation here.
+; RELOCS: warning: unexpected relocations for dwo section '.debug_info.dwo'
+
+; DWARF5: .debug_info.dwo contents:
+; DWARF5: DW_TAG_subprogram
+; DWARF5-NEXT: DW_AT_low_pc [DW_FORM_addrx] (indexed (00000000) address = 0x0000000000000000 ".text")
+; DWARF5-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000000)
+; DWARF5: DW_AT_name {{.*}} "square")
+; DWARF5: DW_TAG_formal_parameter
+
+; Ensure there is no unnecessary addresses in .o file
+; DWARF5: .debug_addr contents:
+; DWARF5: Addrs: [
+; DWARF5-NEXT: 0x0000000000000000
+; DWARF5-NEXT: 0x0000000000000046
+; DWARF5-NEXT: 0x000000000000006c
+; DWARF5-NEXT: 0x00000000000000b0
+; DWARF5-NEXT: ]
+
+; Ensure that 'boo()' and 'main()' use DW_RLE_startx_length and DW_RLE_startx_endx
+; entries respectively
+; DWARF5: .debug_rnglists.dwo contents:
+; DWARF5: ranges:
+; DWARF5-NEXT: 0x00000014: [DW_RLE_startx_length]: 0x0000000000000001, 0x0000000000000024 => [0x0000000000000046, 0x000000000000006a)
+; DWARF5-NEXT: 0x00000017: [DW_RLE_end_of_list ]
+; DWARF5-NEXT: 0x00000018: [DW_RLE_startx_endx ]: 0x0000000000000002, 0x0000000000000003 => [0x000000000000006c, 0x00000000000000b0)
+; DWARF5-NEXT: 0x0000001b: [DW_RLE_end_of_list ]
+; DWARF5-EMPTY:
+
+; DWARF4: .debug_info.dwo contents:
+; DWARF4: DW_TAG_subprogram
+; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000000) address = 0x0000000000000000 ".text")
+; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000000)
+; DWARF4: DW_AT_name {{.*}} "square")
+
+; DWARF4: DW_TAG_subprogram
+; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000001) address = 0x0000000000000046 ".text")
+; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000024)
+; DWARF4: DW_AT_name {{.*}} "boo")
+
+; DWARF4: DW_TAG_subprogram
+; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000002) address = 0x000000000000006c ".text")
+; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000000)
+; DWARF4: DW_AT_name {{.*}} "main")
+
+; Ensure there is no unnecessary addresses in .o file
+; DWARF4: .debug_addr contents:
+; DWARF4: Addrs: [
+; DWARF4-NEXT: 0x0000000000000000
+; DWARF4-NEXT: 0x0000000000000046
+; DWARF4-NEXT: 0x000000000000006c
+; DWARF4-NEXT: ]
+
+; Function Attrs: mustprogress noinline optnone
+define dso_local noundef signext i32 @_Z6squarei(i32 noundef signext %0) #0 !dbg !11 {
+ %2 = alloca i32, align 4
+ %3 = alloca i32, align 4
+ store i32 %0, ptr %2, align 4
+ #dbg_declare(ptr %2, !16, !DIExpression(), !17)
+ #dbg_declare(ptr %3, !18, !DIExpression(), !19)
+ %4 = call noundef signext i32 @_Z3boov(), !dbg !20
+ store i32 %4, ptr %3, align 4, !dbg !19
+ %5 = load i32, ptr %3, align 4, !dbg !21
+ %6 = load i32, ptr %2, align 4, !dbg !22
+ %7 = mul nsw i32 %5, %6, !dbg !23
+ ret i32 %7, !dbg !24
+}
+
+; Function Attrs: mustprogress noinline nounwind optnone
+define dso_local noundef signext i32 @_Z3boov() #1 !dbg !25 {
+ ret i32 8, !dbg !28
+}
+
+; Function Attrs: mustprogress noinline norecurse optnone
+define dso_local noundef signext i32 @main() #2 !dbg !29 {
+ %1 = alloca i32, align 4
+ %2 = alloca i32, align 4
+ %3 = alloca i32, align 4
+ store i32 0, ptr %1, align 4
+ #dbg_declare(ptr %2, !30, !DIExpression(), !31)
+ store i32 10, ptr %2, align 4, !dbg !31
+ #dbg_declare(ptr %3, !32, !DIExpression(), !33)
+ %4 = load i32, ptr %2, align 4, !dbg !34
+ %5 = call noundef signext i32 @_Z6squarei(i32 noundef signext %4), !dbg !35
+ store i32 %5, ptr %3, align 4, !dbg !33
+ %6 = load i32, ptr %3, align 4, !dbg !36
+ ret i32 %6, !dbg !37
+}
+
+attributes #0 = { mustprogress noinline optnone "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic-rv64" "target-features"="+64bit,+relax,+f,+d" }
+attributes #1 = { mustprogress noinline nounwind optnone "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic-rv64" "target-features"="+64bit,+relax,+f,+d" }
+attributes #2 = { mustprogress noinline norecurse optnone "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic-rv64" "target-features"="+64bit,+relax,+f,+d" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5, !6, !8, !9}
+!llvm.ident = !{!10}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 22.0.0git ([email protected]:dlav-sc/llvm-project.git 972928c7a5fecec79f36c6899f1df779d0a17202)", isOptimized: false, runtimeVersion: 0, splitDebugFilename: "riscv_relax_dwo_ranges.dwo", emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: GNU)
+!1 = !DIFile(filename: "riscv_relax_dwo_ranges.cpp", directory: "/root/test/dwarf/generate", checksumkind: CSK_MD5, checksum: "ea48d4b4acc770ff327714eaf1348b92")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 4}
+!5 = !{i32 1, !"target-abi", !"lp64d"}
+!6 = !{i32 6, !"riscv-isa", !7}
+!7 = !{!"rv64i2p1_m2p0_a2p1_f2p2_d2p2_c2p0_zicsr2p0_zifencei2p0_zmmul1p0_zaamo1p0_zalrsc1p0_zca1p0_zcd1p0"}
+!8 = !{i32 7, !"frame-pointer", i32 2}
+!9 = !{i32 8, !"SmallDataLimit", i32 0}
+!10 = !{!"clang version 22.0.0git ([email protected]:dlav-sc/llvm-project.git 972928c7a5fecec79f36c6899f1df779d0a17202)"}
+!11 = distinct !DISubprogram(name: "square", linkageName: "_Z6squarei", scope: !1, file: !1, line: 3, type: !12, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !15)
+!12 = !DISubroutineType(types: !13)
+!13 = !{!14, !14}
+!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!15 = !{}
+!16 = !DILocalVariable(name: "num", arg: 1, scope: !11, file: !1, line: 3, type: !14)
+!17 = !DILocation(line: 3, column: 16, scope: !11)
+!18 = !DILocalVariable(name: "num1", scope: !11, file: !1, line: 4, type: !14)
+!19 = !DILocation(line: 4, column: 7, scope: !11)
+!20 = !DILocation(line: 4, column: 14, scope: !11)
+!21 = !DILocation(line: 5, column: 10, scope: !11)
+!22 = !DILocation(line: 5, column: 17, scope: !11)
+!23 = !DILocation(line: 5, column: 15, scope: !11)
+!24 = !DILocation(line: 5, column: 3, scope: !11)
+!25 = distinct !DISubprogram(name: "boo", linkageName: "_Z3boov", scope: !1, file: !1, line: 8, type: !26, scopeLine: 8, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0)
+!26 = !DISubroutineType(types: !27)
+!27 = !{!14}
+!28 = !DILocation(line: 9, column: 3, scope: !25)
+!29 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 12, type: !26, scopeLine: 12, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !15)
+!30 = !DILocalVariable(name: "a", scope: !29, file: !1, line: 13, type: !14)
+!31 = !DILocation(line: 13, column: 7, scope: !29)
+!32 = !DILocalVariable(name: "squared", scope: !29, file: !1, line: 14, type: !14)
+!33 = !DILocation(line: 14, column: 7, scope: !29)
+!34 = !DILocation(line: 14, column: 24, scope: !29)
+!35 = !DILocation(line: 14, column: 17, scope: !29)
+!36 = !DILocation(line: 15, column: 10, scope: !29)
+!37 = !DILocation(line: 15, column: 3, scope: !29)
|
Member
|
@llvm/pr-subscribers-backend-risc-v Author: None (dlav-sc) ChangesCurrently, -gsplit-dwarf and -mrelax are incompatible options in Clang. The issue is that .dwo files should not contain any relocations, as they are not processed by the linker. However, relaxable code emits relocations in DWARF for debug ranges that reside in the .dwo file when DWARF fission is enabled. This patch makes DWARF fission compatible with RISC-V relaxations. It uses the StartxEndx DWARF forms in .debug_rnglists.dwo, which allow referencing addresses from .debug_addr instead of using absolute addresses. This approach eliminates relocations from .dwo files. Full diff: https://github.com/llvm/llvm-project/pull/166597.diff 4 Files Affected:
diff --git a/llvm/include/llvm/MC/MCSymbol.h b/llvm/include/llvm/MC/MCSymbol.h
index e31d0374baf4a..eef248354b70f 100644
--- a/llvm/include/llvm/MC/MCSymbol.h
+++ b/llvm/include/llvm/MC/MCSymbol.h
@@ -383,6 +383,8 @@ inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
return OS;
}
+bool isRangeRelaxable(const MCSymbol *Begin, const MCSymbol *End);
+
} // end namespace llvm
#endif // LLVM_MC_MCSYMBOL_H
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 567acf75d1b8d..46895a3ccb027 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -3291,14 +3291,12 @@ static MCSymbol *emitLoclistsTableHeader(AsmPrinter *Asm,
}
template <typename Ranges, typename PayloadEmitter>
-static void emitRangeList(
- DwarfDebug &DD, AsmPrinter *Asm, MCSymbol *Sym, const Ranges &R,
- const DwarfCompileUnit &CU, unsigned BaseAddressx, unsigned OffsetPair,
- unsigned StartxLength, unsigned EndOfList,
- StringRef (*StringifyEnum)(unsigned),
- bool ShouldUseBaseAddress,
- PayloadEmitter EmitPayload) {
-
+static void
+emitRangeList(DwarfDebug &DD, AsmPrinter *Asm, MCSymbol *Sym, const Ranges &R,
+ const DwarfCompileUnit &CU, unsigned BaseAddressx,
+ unsigned OffsetPair, unsigned StartxLength, unsigned StartxEndx,
+ unsigned EndOfList, StringRef (*StringifyEnum)(unsigned),
+ bool ShouldUseBaseAddress, PayloadEmitter EmitPayload) {
auto Size = Asm->MAI->getCodePointerSize();
bool UseDwarf5 = DD.getDwarfVersion() >= 5;
@@ -3317,7 +3315,8 @@ static void emitRangeList(
bool BaseIsSet = false;
for (const auto &P : SectionRanges) {
auto *Base = CUBase;
- if ((Asm->TM.getTargetTriple().isNVPTX() && DD.tuneForGDB())) {
+ if ((Asm->TM.getTargetTriple().isNVPTX() && DD.tuneForGDB()) ||
+ (DD.useSplitDwarf() && UseDwarf5 && P.first->isLinkerRelaxable())) {
// PTX does not support subtracting labels from the code section in the
// debug_loc section. To work around this, the NVPTX backend needs the
// compile unit to have no low_pc in order to have a zero base_address
@@ -3373,12 +3372,21 @@ static void emitRangeList(
Asm->emitLabelDifference(End, Base, Size);
}
} else if (UseDwarf5) {
- Asm->OutStreamer->AddComment(StringifyEnum(StartxLength));
- Asm->emitInt8(StartxLength);
- Asm->OutStreamer->AddComment(" start index");
- Asm->emitULEB128(DD.getAddressPool().getIndex(Begin));
- Asm->OutStreamer->AddComment(" length");
- Asm->emitLabelDifferenceAsULEB128(End, Begin);
+ if (DD.useSplitDwarf() && llvm::isRangeRelaxable(Begin, End)) {
+ Asm->OutStreamer->AddComment(StringifyEnum(StartxEndx));
+ Asm->emitInt8(StartxEndx);
+ Asm->OutStreamer->AddComment(" start index");
+ Asm->emitULEB128(DD.getAddressPool().getIndex(Begin));
+ Asm->OutStreamer->AddComment(" end index");
+ Asm->emitULEB128(DD.getAddressPool().getIndex(End));
+ } else {
+ Asm->OutStreamer->AddComment(StringifyEnum(StartxLength));
+ Asm->emitInt8(StartxLength);
+ Asm->OutStreamer->AddComment(" start index");
+ Asm->emitULEB128(DD.getAddressPool().getIndex(Begin));
+ Asm->OutStreamer->AddComment(" length");
+ Asm->emitLabelDifferenceAsULEB128(End, Begin);
+ }
} else {
Asm->OutStreamer->emitSymbolValue(Begin, Size);
Asm->OutStreamer->emitSymbolValue(End, Size);
@@ -3399,14 +3407,14 @@ static void emitRangeList(
// Handles emission of both debug_loclist / debug_loclist.dwo
static void emitLocList(DwarfDebug &DD, AsmPrinter *Asm, const DebugLocStream::List &List) {
- emitRangeList(DD, Asm, List.Label, DD.getDebugLocs().getEntries(List),
- *List.CU, dwarf::DW_LLE_base_addressx,
- dwarf::DW_LLE_offset_pair, dwarf::DW_LLE_startx_length,
- dwarf::DW_LLE_end_of_list, llvm::dwarf::LocListEncodingString,
- /* ShouldUseBaseAddress */ true,
- [&](const DebugLocStream::Entry &E) {
- DD.emitDebugLocEntryLocation(E, List.CU);
- });
+ emitRangeList(
+ DD, Asm, List.Label, DD.getDebugLocs().getEntries(List), *List.CU,
+ dwarf::DW_LLE_base_addressx, dwarf::DW_LLE_offset_pair,
+ dwarf::DW_LLE_startx_length, dwarf::DW_LLE_startx_endx,
+ dwarf::DW_LLE_end_of_list, llvm::dwarf::LocListEncodingString,
+ /* ShouldUseBaseAddress */ true, [&](const DebugLocStream::Entry &E) {
+ DD.emitDebugLocEntryLocation(E, List.CU);
+ });
}
void DwarfDebug::emitDebugLocImpl(MCSection *Sec) {
@@ -3628,8 +3636,8 @@ static void emitRangeList(DwarfDebug &DD, AsmPrinter *Asm,
const RangeSpanList &List) {
emitRangeList(DD, Asm, List.Label, List.Ranges, *List.CU,
dwarf::DW_RLE_base_addressx, dwarf::DW_RLE_offset_pair,
- dwarf::DW_RLE_startx_length, dwarf::DW_RLE_end_of_list,
- llvm::dwarf::RangeListEncodingString,
+ dwarf::DW_RLE_startx_length, dwarf::DW_RLE_startx_endx,
+ dwarf::DW_RLE_end_of_list, llvm::dwarf::RangeListEncodingString,
List.CU->getCUNode()->getRangesBaseAddress() ||
DD.getDwarfVersion() >= 5,
[](auto) {});
diff --git a/llvm/lib/MC/MCSymbol.cpp b/llvm/lib/MC/MCSymbol.cpp
index b86873824cb00..7440fd8687b4d 100644
--- a/llvm/lib/MC/MCSymbol.cpp
+++ b/llvm/lib/MC/MCSymbol.cpp
@@ -84,7 +84,22 @@ void MCSymbol::print(raw_ostream &OS, const MCAsmInfo *MAI) const {
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
-LLVM_DUMP_METHOD void MCSymbol::dump() const {
- dbgs() << *this;
-}
+LLVM_DUMP_METHOD void MCSymbol::dump() const { dbgs() << *this; }
#endif
+
+bool llvm::isRangeRelaxable(const MCSymbol *Begin, const MCSymbol *End) {
+ assert(Begin && "Range without a begin symbol?");
+ assert(End && "Range without an end symbol?");
+ llvm::SmallVector<const MCFragment *> RangeFragments{};
+ for (const auto *Fragment = Begin->getFragment();
+ Fragment != End->getFragment(); Fragment = Fragment->getNext()) {
+ RangeFragments.push_back(Fragment);
+ }
+ RangeFragments.push_back(End->getFragment());
+
+ bool IsRelaxableRange = llvm::any_of(RangeFragments, [](auto &&Fragment) {
+ assert(Fragment);
+ return Fragment->isLinkerRelaxable();
+ });
+ return IsRelaxableRange;
+}
diff --git a/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll b/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll
new file mode 100644
index 0000000000000..f8ab7fc5ad900
--- /dev/null
+++ b/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll
@@ -0,0 +1,187 @@
+; RUN: llc -dwarf-version=5 -split-dwarf-file=foo.dwo -O0 %s -mtriple=riscv64-unknown-linux-gnu -filetype=obj -o %t
+; RUN: llvm-dwarfdump -v %t | FileCheck --check-prefix=DWARF5 %s
+; RUN: llvm-dwarfdump --debug-info %t 2> %t.txt
+; RUN: FileCheck --input-file=%t.txt %s --check-prefix=RELOCS --implicit-check-not=warning:
+
+; RUN: llc -dwarf-version=4 -split-dwarf-file=foo.dwo -O0 %s -mtriple=riscv64-unknown-linux-gnu -filetype=obj -o %t
+; RUN: llvm-dwarfdump -v %t | FileCheck --check-prefix=DWARF4 %s
+; RUN: llvm-dwarfdump --debug-info %t 2> %t.txt
+; RUN: FileCheck --input-file=%t.txt %s --check-prefix=RELOCS --implicit-check-not=warning:
+
+; In the RISC-V architecture, the .text section is subject to
+; relaxation, meaning the start address of each function can change
+; during the linking process. Therefore, the .debug_rnglists.dwo
+; section must obtain function's start addresses from the .debug_addr
+; section.
+
+; Generally, a function's body can be relaxed (for example, the
+; square() and main() functions in this test, which contain call
+; instructions). For such code ranges, the linker must place the
+; start and end addresses into the .debug_addr section and use
+; the DW_RLE_startx_endx entry form in the .debug_rnglists.dwo
+; section within the .dwo file.
+
+; However, some functions may not contain any relaxable instructions
+; (for example, the boo() function in this test). In these cases,
+; it is possible to use the more space-efficient DW_RLE_startx_length
+; range entry form.
+
+; From the code:
+
+; __attribute__((noinline)) int boo();
+
+; int square(int num) {
+; int num1 = boo();
+; return num1 * num;
+; }
+
+; __attribute__((noinline)) int boo() {
+; return 8;
+; }
+
+; int main() {
+; int a = 10;
+; int squared = square(a);
+; return squared;
+; }
+
+; compiled with
+
+; clang -g -S -gsplit-dwarf --target=riscv64 -march=rv64gc -O0 relax_dwo_ranges.cpp
+
+; Currently, square() still uses an offset to represent the function's end address,
+; which requires a relocation here.
+; RELOCS: warning: unexpected relocations for dwo section '.debug_info.dwo'
+
+; DWARF5: .debug_info.dwo contents:
+; DWARF5: DW_TAG_subprogram
+; DWARF5-NEXT: DW_AT_low_pc [DW_FORM_addrx] (indexed (00000000) address = 0x0000000000000000 ".text")
+; DWARF5-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000000)
+; DWARF5: DW_AT_name {{.*}} "square")
+; DWARF5: DW_TAG_formal_parameter
+
+; Ensure there is no unnecessary addresses in .o file
+; DWARF5: .debug_addr contents:
+; DWARF5: Addrs: [
+; DWARF5-NEXT: 0x0000000000000000
+; DWARF5-NEXT: 0x0000000000000046
+; DWARF5-NEXT: 0x000000000000006c
+; DWARF5-NEXT: 0x00000000000000b0
+; DWARF5-NEXT: ]
+
+; Ensure that 'boo()' and 'main()' use DW_RLE_startx_length and DW_RLE_startx_endx
+; entries respectively
+; DWARF5: .debug_rnglists.dwo contents:
+; DWARF5: ranges:
+; DWARF5-NEXT: 0x00000014: [DW_RLE_startx_length]: 0x0000000000000001, 0x0000000000000024 => [0x0000000000000046, 0x000000000000006a)
+; DWARF5-NEXT: 0x00000017: [DW_RLE_end_of_list ]
+; DWARF5-NEXT: 0x00000018: [DW_RLE_startx_endx ]: 0x0000000000000002, 0x0000000000000003 => [0x000000000000006c, 0x00000000000000b0)
+; DWARF5-NEXT: 0x0000001b: [DW_RLE_end_of_list ]
+; DWARF5-EMPTY:
+
+; DWARF4: .debug_info.dwo contents:
+; DWARF4: DW_TAG_subprogram
+; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000000) address = 0x0000000000000000 ".text")
+; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000000)
+; DWARF4: DW_AT_name {{.*}} "square")
+
+; DWARF4: DW_TAG_subprogram
+; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000001) address = 0x0000000000000046 ".text")
+; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000024)
+; DWARF4: DW_AT_name {{.*}} "boo")
+
+; DWARF4: DW_TAG_subprogram
+; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000002) address = 0x000000000000006c ".text")
+; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000000)
+; DWARF4: DW_AT_name {{.*}} "main")
+
+; Ensure there is no unnecessary addresses in .o file
+; DWARF4: .debug_addr contents:
+; DWARF4: Addrs: [
+; DWARF4-NEXT: 0x0000000000000000
+; DWARF4-NEXT: 0x0000000000000046
+; DWARF4-NEXT: 0x000000000000006c
+; DWARF4-NEXT: ]
+
+; Function Attrs: mustprogress noinline optnone
+define dso_local noundef signext i32 @_Z6squarei(i32 noundef signext %0) #0 !dbg !11 {
+ %2 = alloca i32, align 4
+ %3 = alloca i32, align 4
+ store i32 %0, ptr %2, align 4
+ #dbg_declare(ptr %2, !16, !DIExpression(), !17)
+ #dbg_declare(ptr %3, !18, !DIExpression(), !19)
+ %4 = call noundef signext i32 @_Z3boov(), !dbg !20
+ store i32 %4, ptr %3, align 4, !dbg !19
+ %5 = load i32, ptr %3, align 4, !dbg !21
+ %6 = load i32, ptr %2, align 4, !dbg !22
+ %7 = mul nsw i32 %5, %6, !dbg !23
+ ret i32 %7, !dbg !24
+}
+
+; Function Attrs: mustprogress noinline nounwind optnone
+define dso_local noundef signext i32 @_Z3boov() #1 !dbg !25 {
+ ret i32 8, !dbg !28
+}
+
+; Function Attrs: mustprogress noinline norecurse optnone
+define dso_local noundef signext i32 @main() #2 !dbg !29 {
+ %1 = alloca i32, align 4
+ %2 = alloca i32, align 4
+ %3 = alloca i32, align 4
+ store i32 0, ptr %1, align 4
+ #dbg_declare(ptr %2, !30, !DIExpression(), !31)
+ store i32 10, ptr %2, align 4, !dbg !31
+ #dbg_declare(ptr %3, !32, !DIExpression(), !33)
+ %4 = load i32, ptr %2, align 4, !dbg !34
+ %5 = call noundef signext i32 @_Z6squarei(i32 noundef signext %4), !dbg !35
+ store i32 %5, ptr %3, align 4, !dbg !33
+ %6 = load i32, ptr %3, align 4, !dbg !36
+ ret i32 %6, !dbg !37
+}
+
+attributes #0 = { mustprogress noinline optnone "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic-rv64" "target-features"="+64bit,+relax,+f,+d" }
+attributes #1 = { mustprogress noinline nounwind optnone "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic-rv64" "target-features"="+64bit,+relax,+f,+d" }
+attributes #2 = { mustprogress noinline norecurse optnone "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic-rv64" "target-features"="+64bit,+relax,+f,+d" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5, !6, !8, !9}
+!llvm.ident = !{!10}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 22.0.0git ([email protected]:dlav-sc/llvm-project.git 972928c7a5fecec79f36c6899f1df779d0a17202)", isOptimized: false, runtimeVersion: 0, splitDebugFilename: "riscv_relax_dwo_ranges.dwo", emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: GNU)
+!1 = !DIFile(filename: "riscv_relax_dwo_ranges.cpp", directory: "/root/test/dwarf/generate", checksumkind: CSK_MD5, checksum: "ea48d4b4acc770ff327714eaf1348b92")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 4}
+!5 = !{i32 1, !"target-abi", !"lp64d"}
+!6 = !{i32 6, !"riscv-isa", !7}
+!7 = !{!"rv64i2p1_m2p0_a2p1_f2p2_d2p2_c2p0_zicsr2p0_zifencei2p0_zmmul1p0_zaamo1p0_zalrsc1p0_zca1p0_zcd1p0"}
+!8 = !{i32 7, !"frame-pointer", i32 2}
+!9 = !{i32 8, !"SmallDataLimit", i32 0}
+!10 = !{!"clang version 22.0.0git ([email protected]:dlav-sc/llvm-project.git 972928c7a5fecec79f36c6899f1df779d0a17202)"}
+!11 = distinct !DISubprogram(name: "square", linkageName: "_Z6squarei", scope: !1, file: !1, line: 3, type: !12, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !15)
+!12 = !DISubroutineType(types: !13)
+!13 = !{!14, !14}
+!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!15 = !{}
+!16 = !DILocalVariable(name: "num", arg: 1, scope: !11, file: !1, line: 3, type: !14)
+!17 = !DILocation(line: 3, column: 16, scope: !11)
+!18 = !DILocalVariable(name: "num1", scope: !11, file: !1, line: 4, type: !14)
+!19 = !DILocation(line: 4, column: 7, scope: !11)
+!20 = !DILocation(line: 4, column: 14, scope: !11)
+!21 = !DILocation(line: 5, column: 10, scope: !11)
+!22 = !DILocation(line: 5, column: 17, scope: !11)
+!23 = !DILocation(line: 5, column: 15, scope: !11)
+!24 = !DILocation(line: 5, column: 3, scope: !11)
+!25 = distinct !DISubprogram(name: "boo", linkageName: "_Z3boov", scope: !1, file: !1, line: 8, type: !26, scopeLine: 8, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0)
+!26 = !DISubroutineType(types: !27)
+!27 = !{!14}
+!28 = !DILocation(line: 9, column: 3, scope: !25)
+!29 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 12, type: !26, scopeLine: 12, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !15)
+!30 = !DILocalVariable(name: "a", scope: !29, file: !1, line: 13, type: !14)
+!31 = !DILocation(line: 13, column: 7, scope: !29)
+!32 = !DILocalVariable(name: "squared", scope: !29, file: !1, line: 14, type: !14)
+!33 = !DILocation(line: 14, column: 7, scope: !29)
+!34 = !DILocation(line: 14, column: 24, scope: !29)
+!35 = !DILocation(line: 14, column: 17, scope: !29)
+!36 = !DILocation(line: 15, column: 10, scope: !29)
+!37 = !DILocation(line: 15, column: 3, scope: !29)
|
Member
|
@llvm/pr-subscribers-llvm-mc Author: None (dlav-sc) ChangesCurrently, -gsplit-dwarf and -mrelax are incompatible options in Clang. The issue is that .dwo files should not contain any relocations, as they are not processed by the linker. However, relaxable code emits relocations in DWARF for debug ranges that reside in the .dwo file when DWARF fission is enabled. This patch makes DWARF fission compatible with RISC-V relaxations. It uses the StartxEndx DWARF forms in .debug_rnglists.dwo, which allow referencing addresses from .debug_addr instead of using absolute addresses. This approach eliminates relocations from .dwo files. Full diff: https://github.com/llvm/llvm-project/pull/166597.diff 4 Files Affected:
diff --git a/llvm/include/llvm/MC/MCSymbol.h b/llvm/include/llvm/MC/MCSymbol.h
index e31d0374baf4a..eef248354b70f 100644
--- a/llvm/include/llvm/MC/MCSymbol.h
+++ b/llvm/include/llvm/MC/MCSymbol.h
@@ -383,6 +383,8 @@ inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
return OS;
}
+bool isRangeRelaxable(const MCSymbol *Begin, const MCSymbol *End);
+
} // end namespace llvm
#endif // LLVM_MC_MCSYMBOL_H
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 567acf75d1b8d..46895a3ccb027 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -3291,14 +3291,12 @@ static MCSymbol *emitLoclistsTableHeader(AsmPrinter *Asm,
}
template <typename Ranges, typename PayloadEmitter>
-static void emitRangeList(
- DwarfDebug &DD, AsmPrinter *Asm, MCSymbol *Sym, const Ranges &R,
- const DwarfCompileUnit &CU, unsigned BaseAddressx, unsigned OffsetPair,
- unsigned StartxLength, unsigned EndOfList,
- StringRef (*StringifyEnum)(unsigned),
- bool ShouldUseBaseAddress,
- PayloadEmitter EmitPayload) {
-
+static void
+emitRangeList(DwarfDebug &DD, AsmPrinter *Asm, MCSymbol *Sym, const Ranges &R,
+ const DwarfCompileUnit &CU, unsigned BaseAddressx,
+ unsigned OffsetPair, unsigned StartxLength, unsigned StartxEndx,
+ unsigned EndOfList, StringRef (*StringifyEnum)(unsigned),
+ bool ShouldUseBaseAddress, PayloadEmitter EmitPayload) {
auto Size = Asm->MAI->getCodePointerSize();
bool UseDwarf5 = DD.getDwarfVersion() >= 5;
@@ -3317,7 +3315,8 @@ static void emitRangeList(
bool BaseIsSet = false;
for (const auto &P : SectionRanges) {
auto *Base = CUBase;
- if ((Asm->TM.getTargetTriple().isNVPTX() && DD.tuneForGDB())) {
+ if ((Asm->TM.getTargetTriple().isNVPTX() && DD.tuneForGDB()) ||
+ (DD.useSplitDwarf() && UseDwarf5 && P.first->isLinkerRelaxable())) {
// PTX does not support subtracting labels from the code section in the
// debug_loc section. To work around this, the NVPTX backend needs the
// compile unit to have no low_pc in order to have a zero base_address
@@ -3373,12 +3372,21 @@ static void emitRangeList(
Asm->emitLabelDifference(End, Base, Size);
}
} else if (UseDwarf5) {
- Asm->OutStreamer->AddComment(StringifyEnum(StartxLength));
- Asm->emitInt8(StartxLength);
- Asm->OutStreamer->AddComment(" start index");
- Asm->emitULEB128(DD.getAddressPool().getIndex(Begin));
- Asm->OutStreamer->AddComment(" length");
- Asm->emitLabelDifferenceAsULEB128(End, Begin);
+ if (DD.useSplitDwarf() && llvm::isRangeRelaxable(Begin, End)) {
+ Asm->OutStreamer->AddComment(StringifyEnum(StartxEndx));
+ Asm->emitInt8(StartxEndx);
+ Asm->OutStreamer->AddComment(" start index");
+ Asm->emitULEB128(DD.getAddressPool().getIndex(Begin));
+ Asm->OutStreamer->AddComment(" end index");
+ Asm->emitULEB128(DD.getAddressPool().getIndex(End));
+ } else {
+ Asm->OutStreamer->AddComment(StringifyEnum(StartxLength));
+ Asm->emitInt8(StartxLength);
+ Asm->OutStreamer->AddComment(" start index");
+ Asm->emitULEB128(DD.getAddressPool().getIndex(Begin));
+ Asm->OutStreamer->AddComment(" length");
+ Asm->emitLabelDifferenceAsULEB128(End, Begin);
+ }
} else {
Asm->OutStreamer->emitSymbolValue(Begin, Size);
Asm->OutStreamer->emitSymbolValue(End, Size);
@@ -3399,14 +3407,14 @@ static void emitRangeList(
// Handles emission of both debug_loclist / debug_loclist.dwo
static void emitLocList(DwarfDebug &DD, AsmPrinter *Asm, const DebugLocStream::List &List) {
- emitRangeList(DD, Asm, List.Label, DD.getDebugLocs().getEntries(List),
- *List.CU, dwarf::DW_LLE_base_addressx,
- dwarf::DW_LLE_offset_pair, dwarf::DW_LLE_startx_length,
- dwarf::DW_LLE_end_of_list, llvm::dwarf::LocListEncodingString,
- /* ShouldUseBaseAddress */ true,
- [&](const DebugLocStream::Entry &E) {
- DD.emitDebugLocEntryLocation(E, List.CU);
- });
+ emitRangeList(
+ DD, Asm, List.Label, DD.getDebugLocs().getEntries(List), *List.CU,
+ dwarf::DW_LLE_base_addressx, dwarf::DW_LLE_offset_pair,
+ dwarf::DW_LLE_startx_length, dwarf::DW_LLE_startx_endx,
+ dwarf::DW_LLE_end_of_list, llvm::dwarf::LocListEncodingString,
+ /* ShouldUseBaseAddress */ true, [&](const DebugLocStream::Entry &E) {
+ DD.emitDebugLocEntryLocation(E, List.CU);
+ });
}
void DwarfDebug::emitDebugLocImpl(MCSection *Sec) {
@@ -3628,8 +3636,8 @@ static void emitRangeList(DwarfDebug &DD, AsmPrinter *Asm,
const RangeSpanList &List) {
emitRangeList(DD, Asm, List.Label, List.Ranges, *List.CU,
dwarf::DW_RLE_base_addressx, dwarf::DW_RLE_offset_pair,
- dwarf::DW_RLE_startx_length, dwarf::DW_RLE_end_of_list,
- llvm::dwarf::RangeListEncodingString,
+ dwarf::DW_RLE_startx_length, dwarf::DW_RLE_startx_endx,
+ dwarf::DW_RLE_end_of_list, llvm::dwarf::RangeListEncodingString,
List.CU->getCUNode()->getRangesBaseAddress() ||
DD.getDwarfVersion() >= 5,
[](auto) {});
diff --git a/llvm/lib/MC/MCSymbol.cpp b/llvm/lib/MC/MCSymbol.cpp
index b86873824cb00..7440fd8687b4d 100644
--- a/llvm/lib/MC/MCSymbol.cpp
+++ b/llvm/lib/MC/MCSymbol.cpp
@@ -84,7 +84,22 @@ void MCSymbol::print(raw_ostream &OS, const MCAsmInfo *MAI) const {
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
-LLVM_DUMP_METHOD void MCSymbol::dump() const {
- dbgs() << *this;
-}
+LLVM_DUMP_METHOD void MCSymbol::dump() const { dbgs() << *this; }
#endif
+
+bool llvm::isRangeRelaxable(const MCSymbol *Begin, const MCSymbol *End) {
+ assert(Begin && "Range without a begin symbol?");
+ assert(End && "Range without an end symbol?");
+ llvm::SmallVector<const MCFragment *> RangeFragments{};
+ for (const auto *Fragment = Begin->getFragment();
+ Fragment != End->getFragment(); Fragment = Fragment->getNext()) {
+ RangeFragments.push_back(Fragment);
+ }
+ RangeFragments.push_back(End->getFragment());
+
+ bool IsRelaxableRange = llvm::any_of(RangeFragments, [](auto &&Fragment) {
+ assert(Fragment);
+ return Fragment->isLinkerRelaxable();
+ });
+ return IsRelaxableRange;
+}
diff --git a/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll b/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll
new file mode 100644
index 0000000000000..f8ab7fc5ad900
--- /dev/null
+++ b/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll
@@ -0,0 +1,187 @@
+; RUN: llc -dwarf-version=5 -split-dwarf-file=foo.dwo -O0 %s -mtriple=riscv64-unknown-linux-gnu -filetype=obj -o %t
+; RUN: llvm-dwarfdump -v %t | FileCheck --check-prefix=DWARF5 %s
+; RUN: llvm-dwarfdump --debug-info %t 2> %t.txt
+; RUN: FileCheck --input-file=%t.txt %s --check-prefix=RELOCS --implicit-check-not=warning:
+
+; RUN: llc -dwarf-version=4 -split-dwarf-file=foo.dwo -O0 %s -mtriple=riscv64-unknown-linux-gnu -filetype=obj -o %t
+; RUN: llvm-dwarfdump -v %t | FileCheck --check-prefix=DWARF4 %s
+; RUN: llvm-dwarfdump --debug-info %t 2> %t.txt
+; RUN: FileCheck --input-file=%t.txt %s --check-prefix=RELOCS --implicit-check-not=warning:
+
+; In the RISC-V architecture, the .text section is subject to
+; relaxation, meaning the start address of each function can change
+; during the linking process. Therefore, the .debug_rnglists.dwo
+; section must obtain function's start addresses from the .debug_addr
+; section.
+
+; Generally, a function's body can be relaxed (for example, the
+; square() and main() functions in this test, which contain call
+; instructions). For such code ranges, the linker must place the
+; start and end addresses into the .debug_addr section and use
+; the DW_RLE_startx_endx entry form in the .debug_rnglists.dwo
+; section within the .dwo file.
+
+; However, some functions may not contain any relaxable instructions
+; (for example, the boo() function in this test). In these cases,
+; it is possible to use the more space-efficient DW_RLE_startx_length
+; range entry form.
+
+; From the code:
+
+; __attribute__((noinline)) int boo();
+
+; int square(int num) {
+; int num1 = boo();
+; return num1 * num;
+; }
+
+; __attribute__((noinline)) int boo() {
+; return 8;
+; }
+
+; int main() {
+; int a = 10;
+; int squared = square(a);
+; return squared;
+; }
+
+; compiled with
+
+; clang -g -S -gsplit-dwarf --target=riscv64 -march=rv64gc -O0 relax_dwo_ranges.cpp
+
+; Currently, square() still uses an offset to represent the function's end address,
+; which requires a relocation here.
+; RELOCS: warning: unexpected relocations for dwo section '.debug_info.dwo'
+
+; DWARF5: .debug_info.dwo contents:
+; DWARF5: DW_TAG_subprogram
+; DWARF5-NEXT: DW_AT_low_pc [DW_FORM_addrx] (indexed (00000000) address = 0x0000000000000000 ".text")
+; DWARF5-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000000)
+; DWARF5: DW_AT_name {{.*}} "square")
+; DWARF5: DW_TAG_formal_parameter
+
+; Ensure there is no unnecessary addresses in .o file
+; DWARF5: .debug_addr contents:
+; DWARF5: Addrs: [
+; DWARF5-NEXT: 0x0000000000000000
+; DWARF5-NEXT: 0x0000000000000046
+; DWARF5-NEXT: 0x000000000000006c
+; DWARF5-NEXT: 0x00000000000000b0
+; DWARF5-NEXT: ]
+
+; Ensure that 'boo()' and 'main()' use DW_RLE_startx_length and DW_RLE_startx_endx
+; entries respectively
+; DWARF5: .debug_rnglists.dwo contents:
+; DWARF5: ranges:
+; DWARF5-NEXT: 0x00000014: [DW_RLE_startx_length]: 0x0000000000000001, 0x0000000000000024 => [0x0000000000000046, 0x000000000000006a)
+; DWARF5-NEXT: 0x00000017: [DW_RLE_end_of_list ]
+; DWARF5-NEXT: 0x00000018: [DW_RLE_startx_endx ]: 0x0000000000000002, 0x0000000000000003 => [0x000000000000006c, 0x00000000000000b0)
+; DWARF5-NEXT: 0x0000001b: [DW_RLE_end_of_list ]
+; DWARF5-EMPTY:
+
+; DWARF4: .debug_info.dwo contents:
+; DWARF4: DW_TAG_subprogram
+; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000000) address = 0x0000000000000000 ".text")
+; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000000)
+; DWARF4: DW_AT_name {{.*}} "square")
+
+; DWARF4: DW_TAG_subprogram
+; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000001) address = 0x0000000000000046 ".text")
+; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000024)
+; DWARF4: DW_AT_name {{.*}} "boo")
+
+; DWARF4: DW_TAG_subprogram
+; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000002) address = 0x000000000000006c ".text")
+; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000000)
+; DWARF4: DW_AT_name {{.*}} "main")
+
+; Ensure there is no unnecessary addresses in .o file
+; DWARF4: .debug_addr contents:
+; DWARF4: Addrs: [
+; DWARF4-NEXT: 0x0000000000000000
+; DWARF4-NEXT: 0x0000000000000046
+; DWARF4-NEXT: 0x000000000000006c
+; DWARF4-NEXT: ]
+
+; Function Attrs: mustprogress noinline optnone
+define dso_local noundef signext i32 @_Z6squarei(i32 noundef signext %0) #0 !dbg !11 {
+ %2 = alloca i32, align 4
+ %3 = alloca i32, align 4
+ store i32 %0, ptr %2, align 4
+ #dbg_declare(ptr %2, !16, !DIExpression(), !17)
+ #dbg_declare(ptr %3, !18, !DIExpression(), !19)
+ %4 = call noundef signext i32 @_Z3boov(), !dbg !20
+ store i32 %4, ptr %3, align 4, !dbg !19
+ %5 = load i32, ptr %3, align 4, !dbg !21
+ %6 = load i32, ptr %2, align 4, !dbg !22
+ %7 = mul nsw i32 %5, %6, !dbg !23
+ ret i32 %7, !dbg !24
+}
+
+; Function Attrs: mustprogress noinline nounwind optnone
+define dso_local noundef signext i32 @_Z3boov() #1 !dbg !25 {
+ ret i32 8, !dbg !28
+}
+
+; Function Attrs: mustprogress noinline norecurse optnone
+define dso_local noundef signext i32 @main() #2 !dbg !29 {
+ %1 = alloca i32, align 4
+ %2 = alloca i32, align 4
+ %3 = alloca i32, align 4
+ store i32 0, ptr %1, align 4
+ #dbg_declare(ptr %2, !30, !DIExpression(), !31)
+ store i32 10, ptr %2, align 4, !dbg !31
+ #dbg_declare(ptr %3, !32, !DIExpression(), !33)
+ %4 = load i32, ptr %2, align 4, !dbg !34
+ %5 = call noundef signext i32 @_Z6squarei(i32 noundef signext %4), !dbg !35
+ store i32 %5, ptr %3, align 4, !dbg !33
+ %6 = load i32, ptr %3, align 4, !dbg !36
+ ret i32 %6, !dbg !37
+}
+
+attributes #0 = { mustprogress noinline optnone "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic-rv64" "target-features"="+64bit,+relax,+f,+d" }
+attributes #1 = { mustprogress noinline nounwind optnone "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic-rv64" "target-features"="+64bit,+relax,+f,+d" }
+attributes #2 = { mustprogress noinline norecurse optnone "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic-rv64" "target-features"="+64bit,+relax,+f,+d" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5, !6, !8, !9}
+!llvm.ident = !{!10}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 22.0.0git ([email protected]:dlav-sc/llvm-project.git 972928c7a5fecec79f36c6899f1df779d0a17202)", isOptimized: false, runtimeVersion: 0, splitDebugFilename: "riscv_relax_dwo_ranges.dwo", emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: GNU)
+!1 = !DIFile(filename: "riscv_relax_dwo_ranges.cpp", directory: "/root/test/dwarf/generate", checksumkind: CSK_MD5, checksum: "ea48d4b4acc770ff327714eaf1348b92")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 4}
+!5 = !{i32 1, !"target-abi", !"lp64d"}
+!6 = !{i32 6, !"riscv-isa", !7}
+!7 = !{!"rv64i2p1_m2p0_a2p1_f2p2_d2p2_c2p0_zicsr2p0_zifencei2p0_zmmul1p0_zaamo1p0_zalrsc1p0_zca1p0_zcd1p0"}
+!8 = !{i32 7, !"frame-pointer", i32 2}
+!9 = !{i32 8, !"SmallDataLimit", i32 0}
+!10 = !{!"clang version 22.0.0git ([email protected]:dlav-sc/llvm-project.git 972928c7a5fecec79f36c6899f1df779d0a17202)"}
+!11 = distinct !DISubprogram(name: "square", linkageName: "_Z6squarei", scope: !1, file: !1, line: 3, type: !12, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !15)
+!12 = !DISubroutineType(types: !13)
+!13 = !{!14, !14}
+!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!15 = !{}
+!16 = !DILocalVariable(name: "num", arg: 1, scope: !11, file: !1, line: 3, type: !14)
+!17 = !DILocation(line: 3, column: 16, scope: !11)
+!18 = !DILocalVariable(name: "num1", scope: !11, file: !1, line: 4, type: !14)
+!19 = !DILocation(line: 4, column: 7, scope: !11)
+!20 = !DILocation(line: 4, column: 14, scope: !11)
+!21 = !DILocation(line: 5, column: 10, scope: !11)
+!22 = !DILocation(line: 5, column: 17, scope: !11)
+!23 = !DILocation(line: 5, column: 15, scope: !11)
+!24 = !DILocation(line: 5, column: 3, scope: !11)
+!25 = distinct !DISubprogram(name: "boo", linkageName: "_Z3boov", scope: !1, file: !1, line: 8, type: !26, scopeLine: 8, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0)
+!26 = !DISubroutineType(types: !27)
+!27 = !{!14}
+!28 = !DILocation(line: 9, column: 3, scope: !25)
+!29 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 12, type: !26, scopeLine: 12, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !15)
+!30 = !DILocalVariable(name: "a", scope: !29, file: !1, line: 13, type: !14)
+!31 = !DILocation(line: 13, column: 7, scope: !29)
+!32 = !DILocalVariable(name: "squared", scope: !29, file: !1, line: 14, type: !14)
+!33 = !DILocation(line: 14, column: 7, scope: !29)
+!34 = !DILocation(line: 14, column: 24, scope: !29)
+!35 = !DILocation(line: 14, column: 17, scope: !29)
+!36 = !DILocation(line: 15, column: 10, scope: !29)
+!37 = !DILocation(line: 15, column: 3, scope: !29)
|
Contributor
Author
|
@dwblaikie, I've addressed your comments from #164812:
I just wanted to separate consernse here, but yeah, we can make everything in a single loop.
I've moved this logic into the existing loop as well. |
Collaborator
Yeah, please make that change. |
Contributor
Author
Done |
Contributor
Author
I'm not sure |
Collaborator
Doesn't seem so different? It computes the difference between two labels if it can be known at compile time - so... if there is no compile-time answer, that means it's relaxable & so can't use a label difference range encoding. @lenary thanks for pointing to the existing functionality |
|
✅ With the latest revision this PR passed the C/C++ code formatter. |
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Well, perhaps not entirely different, but as I understand, one of the conditions for Therefore, I attempted to use |
Collaborator
Fair point - might be a minor performance/optimality bug?
I don't think that's acceptable - could you look into why that happens? Perhaps it provides a concrete example of the multi-fragment case you outlined above. Perhaps the |
Contributor
Author
I attempted to handle multiple fragment cases in Moreover even if it were possible, I don't think If we can't compute the label difference with
Therefore, I believe I might be mistaken about something, so please feel free to share any concerns you have. |
Member
|
Drive by comment -- I believe your assessment @dlav-sc is totally correct, about the purposes of absoluteSymbolDiff and isRangeRelaxable. I've run into similar issues in #134677 . AFAIUI the RISC-V linetable is emitted slightly inefficiently because of this distinction. (I don't have anything to say about this PR, but figured I'd confirm the understanding in the comment above). |
Collaborator
|
fair enough - thanks for the write up (& thanks for the prior experience/validation, @jmorse) - let's go with the isRangeRelaxable, then. |
Member
|
Thank you for investigating this more deeply. I learned from your analysis. I now understand from your explanation that It would be good if you could summarise your analysis above into comments on the functions themselves, to help anyone that comes afterwards :) |
Currently, -gsplit-dwarf and -mrelax are incompatible options in Clang. The issue is that .dwo files should not contain any relocations, as they are not processed by the linker. However, relaxable code emits relocations in DWARF for debug ranges that reside in the .dwo file when DWARF fission is enabled. This patch makes DWARF fission compatible with RISC-V relaxations. It uses the StartxEndx DWARF forms in .debug_rnglists.dwo, which allow referencing addresses from .debug_addr instead of using absolute addresses. This approach eliminates relocations from .dwo files.
daniilavdeev
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I've rolled back to
Yep, I've added an appropriate comment on the One thing I'm not sure about is where to place |
🐧 Linux x64 Test Results
|
Member
Probably on MCStreamer, if you think it should be on any object. I don't think it's a problem that it's a free function right now though. We can always move it somewhere else later. |
MaskRay
reviewed
Nov 21, 2025
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| ; From the code: | ||
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| ; __attribute__((noinline)) int boo(); |
Member
There was a problem hiding this comment.
https://llvm.org/docs/TestingGuide.html#elaborated-tests for tests requiring elaborate IR or assembly files where cleanup is less practical (e.g., a large amount of debug information output from Clang), you can include generation instructions within split-file part called gen. Then, run llvm/utils/update_test_body.py on the test file to generate the needed content.
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Currently, -gsplit-dwarf and -mrelax are incompatible options in Clang. The issue is that .dwo files should not contain any relocations, as they are not processed by the linker. However, relaxable code emits relocations in DWARF for debug ranges that reside in the .dwo file when DWARF fission is enabled.
This patch makes DWARF fission compatible with RISC-V relaxations. It uses the StartxEndx DWARF forms in .debug_rnglists.dwo, which allow referencing addresses from .debug_addr instead of using absolute addresses. This approach eliminates relocations from .dwo files.