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Add CodeView S_LABEL32 symbols for jump table targets (for Windows debugging) #146121

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Merged
dpaoliello merged 1 commit into from
Jul 7, 2025
Merged

Add CodeView S_LABEL32 symbols for jump table targets (for Windows debugging) #146121

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29 changes: 24 additions & 5 deletions llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3566,15 +3566,34 @@ void CodeViewDebug::collectDebugInfoForJumpTables(const MachineFunction *MF,
break;
}

CurFn->JumpTables.push_back(
{EntrySize, Base, BaseOffset, Branch,
MF->getJTISymbol(JumpTableIndex, MMI->getContext()),
JTI.getJumpTables()[JumpTableIndex].MBBs.size()});
const MachineJumpTableEntry &JTE = JTI.getJumpTables()[JumpTableIndex];
JumpTableInfo CVJTI{EntrySize,
Base,
BaseOffset,
Branch,
MF->getJTISymbol(JumpTableIndex, MMI->getContext()),
JTE.MBBs.size()};
for (const auto &MBB : JTE.MBBs)
CVJTI.Cases.push_back(MBB->getSymbol());
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@MaskRay MaskRay Jul 1, 2025

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omit braces for singe-line simple body https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements

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@sivadeilra sivadeilra Jul 1, 2025

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Thanks; updated.

CurFn->JumpTables.push_back(std::move(CVJTI));
});
}

void CodeViewDebug::emitDebugInfoForJumpTables(const FunctionInfo &FI) {
for (auto JumpTable : FI.JumpTables) {
// Emit S_LABEL32 records for each jump target
for (const auto &JumpTable : FI.JumpTables) {
for (const auto &CaseSym : JumpTable.Cases) {
MCSymbol *LabelEnd = beginSymbolRecord(SymbolKind::S_LABEL32);
OS.AddComment("Offset and segment");
OS.emitCOFFSecRel32(CaseSym, 0);
OS.AddComment("Flags");
OS.emitInt8(0);
emitNullTerminatedSymbolName(OS, CaseSym->getName());
endSymbolRecord(LabelEnd);
}
}

for (const auto &JumpTable : FI.JumpTables) {
MCSymbol *JumpTableEnd = beginSymbolRecord(SymbolKind::S_ARMSWITCHTABLE);
if (JumpTable.Base) {
OS.AddComment("Base offset");
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1 change: 1 addition & 0 deletions llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,7 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
const MCSymbol *Branch;
const MCSymbol *Table;
size_t TableSize;
std::vector<const MCSymbol *> Cases;
};

// For each function, store a vector of labels to its instructions, as well as
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9 changes: 9 additions & 0 deletions llvm/test/DebugInfo/COFF/jump-table.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -118,6 +118,15 @@
; CV: GlobalProcIdSym {
; CV: DisplayName: func
; CV-NOT: GlobalProcIdSym
; CV: LabelSym {
; CV-NEXT: Kind: S_LABEL32 (0x1105)
; CV-NEXT: CodeOffset: 0xC0
; CV-NEXT: Segment: 0x0
; CV-NEXT: Flags: 0x0
; CV-NEXT: Flags [ (0x0)
; CV-NEXT: ]
; CV-NEXT: DisplayName:
; CV-NEXT: }
; CV: JumpTableSym {
; CV-NEXT: Kind: S_ARMSWITCHTABLE (0x1159)
; CV-NEXT: BaseOffset: 0x0
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