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[BPF] Avoid relocation for jumptable entries #166301

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Merged
merged 1 commit into from
Nov 4, 2025
Merged

[BPF] Avoid relocation for jumptable entries #166301

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10 changes: 8 additions & 2 deletions llvm/lib/Target/BPF/BPFAsmPrinter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -219,6 +219,10 @@ void BPFAsmPrinter::emitJumpTableInfo() {

const TargetLoweringObjectFile &TLOF = getObjFileLowering();
const Function &F = MF->getFunction();

MCSection *Sec = OutStreamer->getCurrentSectionOnly();
MCSymbol *SecStart = Sec->getBeginSymbol();

MCSection *JTS = TLOF.getSectionForJumpTable(F, TM);
assert(MJTI->getEntryKind() == MachineJumpTableInfo::EK_BlockAddress);
unsigned EntrySize = MJTI->getEntrySize(getDataLayout());
Expand All @@ -231,8 +235,10 @@ void BPFAsmPrinter::emitJumpTableInfo() {
MCSymbol *JTStart = getJTPublicSymbol(JTI);
OutStreamer->emitLabel(JTStart);
for (const MachineBasicBlock *MBB : JTBBs) {
const MCExpr *LHS = MCSymbolRefExpr::create(MBB->getSymbol(), OutContext);
OutStreamer->emitValue(LHS, EntrySize);
const MCExpr *Diff = MCBinaryExpr::createSub(
MCSymbolRefExpr::create(MBB->getSymbol(), OutContext),
MCSymbolRefExpr::create(SecStart, OutContext), OutContext);
OutStreamer->emitValue(Diff, EntrySize);
}
const MCExpr *JTSize =
MCConstantExpr::create(JTBBs.size() * EntrySize, OutContext);
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4 changes: 2 additions & 2 deletions llvm/test/CodeGen/BPF/jump_table_blockaddr.ll
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Expand Up @@ -84,8 +84,8 @@ llc -march=bpf -mcpu=v4 < test.ll \
; CHECK: .cfi_endproc
; CHECK: .section .jumptables,"",@progbits
; CHECK: BPF.JT.0.0:
; CHECK: .quad LBB0_3
; CHECK: .quad LBB0_3-.text
; CHECK: .size BPF.JT.0.0, 8
; CHECK: BPF.JT.0.1:
; CHECK: .quad LBB0_4
; CHECK: .quad LBB0_4-.text
; CHECK: .size BPF.JT.0.1, 8
4 changes: 2 additions & 2 deletions llvm/test/CodeGen/BPF/jump_table_global_var.ll
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Expand Up @@ -78,6 +78,6 @@ llc -march=bpf -mcpu=v4 < test.ll \
; CHECK: .cfi_endproc
; CHECK: .section .jumptables,"",@progbits
; CHECK: BPF.JT.0.0:
; CHECK: .quad LBB0_1
; CHECK: .quad LBB0_2
; CHECK: .quad LBB0_1-.text
; CHECK: .quad LBB0_2-.text
; CHECK: .size BPF.JT.0.0, 16
60 changes: 30 additions & 30 deletions llvm/test/CodeGen/BPF/jump_table_switch_stmt.ll
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Expand Up @@ -93,34 +93,34 @@ llc -march=bpf -mcpu=v4 -bpf-min-jump-table-entries=3 < test.ll \
; CHECK: .cfi_endproc
; CHECK: .section .jumptables,"",@progbits
; CHECK: BPF.JT.0.0:
; CHECK: .quad LBB0_4
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_2
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_5
; CHECK: .quad LBB0_3
; CHECK: .quad LBB0_4-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_2-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_5-.text
; CHECK: .quad LBB0_3-.text
; CHECK: .size BPF.JT.0.0, 240
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