[llvm] [RISCV] Add big-endian support to RISC-V backend (PR #146534)
Djordje Todorovic via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 30 04:08:29 PDT 2025
https://github.com/djtodoro updated https://github.com/llvm/llvm-project/pull/146534
>From 2d6aa04463f79bbcfeef7f4d5c4d941430aa3e9f Mon Sep 17 00:00:00 2001
From: Djordje Todorovic <djordje.todorovic at htecgroup.com>
Date: Mon, 2 Jun 2025 14:07:16 +0200
Subject: [PATCH] [RISCV] Add initial assembler/MC layer support for big-endian
This patch adds basic assembler and MC layer infrastructure for
RISC-V big-endian targets (riscv32be/riscv64be):
- Register big-endian targets in RISCVTargetMachine
- Add big-endian data layout strings
- Implement endianness-aware fixup application in assembler
backend
- Add byte swapping for data fixups on BE cores
- Update MC layer components (AsmInfo, MCTargetDesc, Disassembler,
AsmParser)
- Handle BE targets in AddressSanitizer
This provides the foundation for BE support but does not yet include:
- Codegen patterns for BE
- Load/store instruction handling
- BE-specific subtarget features
---
llvm/cmake/config.guess | 2 +-
.../CodeGen/TargetLoweringObjectFileImpl.cpp | 2 +
.../Target/RISCV/AsmParser/RISCVAsmParser.cpp | 2 +
.../RISCV/Disassembler/RISCVDisassembler.cpp | 4 ++
.../RISCV/MCTargetDesc/RISCVAsmBackend.cpp | 52 +++++++++++++++----
.../RISCV/MCTargetDesc/RISCVAsmBackend.h | 2 +-
.../RISCV/MCTargetDesc/RISCVMCAsmInfo.cpp | 1 +
.../RISCV/MCTargetDesc/RISCVMCTargetDesc.cpp | 3 +-
llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp | 2 +
llvm/lib/Target/RISCV/RISCVTargetMachine.cpp | 30 ++++++-----
.../RISCV/TargetInfo/RISCVTargetInfo.cpp | 14 +++++
.../Target/RISCV/TargetInfo/RISCVTargetInfo.h | 2 +
.../Instrumentation/AddressSanitizer.cpp | 3 +-
13 files changed, 93 insertions(+), 26 deletions(-)
diff --git a/llvm/cmake/config.guess b/llvm/cmake/config.guess
index 96cc554f181ab..27b55bd166edc 100644
--- a/llvm/cmake/config.guess
+++ b/llvm/cmake/config.guess
@@ -1003,7 +1003,7 @@ EOF
ppcle:Linux:*:*)
echo powerpcle-unknown-linux-gnu
exit ;;
- riscv32:Linux:*:* | riscv64:Linux:*:*)
+ riscv32:Linux:*:* | riscv64:Linux:*:* | riscv32be:Linux:*:* | riscv64be:Linux:*:*)
LIBC=gnu
eval $set_cc_for_build
# Do not check for __GLIBC__ because uclibc defines it too
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index e9172f4acb0cb..94d39ad403d17 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -247,6 +247,8 @@ void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
break;
case Triple::riscv32:
case Triple::riscv64:
+ case Triple::riscv32be:
+ case Triple::riscv64be:
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
diff --git a/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp b/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
index d71c42c0a5fc1..c87362a1b4e87 100644
--- a/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
+++ b/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
@@ -4053,4 +4053,6 @@ extern "C" LLVM_ABI LLVM_EXTERNAL_VISIBILITY void
LLVMInitializeRISCVAsmParser() {
RegisterMCAsmParser<RISCVAsmParser> X(getTheRISCV32Target());
RegisterMCAsmParser<RISCVAsmParser> Y(getTheRISCV64Target());
+ RegisterMCAsmParser<RISCVAsmParser> A(getTheRISCV32beTarget());
+ RegisterMCAsmParser<RISCVAsmParser> B(getTheRISCV64beTarget());
}
diff --git a/llvm/lib/Target/RISCV/Disassembler/RISCVDisassembler.cpp b/llvm/lib/Target/RISCV/Disassembler/RISCVDisassembler.cpp
index 67cc01e647a04..c535dc0891f9c 100644
--- a/llvm/lib/Target/RISCV/Disassembler/RISCVDisassembler.cpp
+++ b/llvm/lib/Target/RISCV/Disassembler/RISCVDisassembler.cpp
@@ -72,6 +72,10 @@ LLVMInitializeRISCVDisassembler() {
createRISCVDisassembler);
TargetRegistry::RegisterMCDisassembler(getTheRISCV64Target(),
createRISCVDisassembler);
+ TargetRegistry::RegisterMCDisassembler(getTheRISCV32beTarget(),
+ createRISCVDisassembler);
+ TargetRegistry::RegisterMCDisassembler(getTheRISCV64beTarget(),
+ createRISCVDisassembler);
}
static DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, uint32_t RegNo,
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
index 82e3b5ceb4ef6..f2126ea02c6eb 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
@@ -33,9 +33,11 @@ static cl::opt<bool> ULEB128Reloc(
cl::desc("Emit R_RISCV_SET_ULEB128/E_RISCV_SUB_ULEB128 if appropriate"));
RISCVAsmBackend::RISCVAsmBackend(const MCSubtargetInfo &STI, uint8_t OSABI,
- bool Is64Bit, const MCTargetOptions &Options)
- : MCAsmBackend(llvm::endianness::little), STI(STI), OSABI(OSABI),
- Is64Bit(Is64Bit), TargetOptions(Options) {
+ bool Is64Bit, bool IsLittleEndian,
+ const MCTargetOptions &Options)
+ : MCAsmBackend(IsLittleEndian ? llvm::endianness::little
+ : llvm::endianness::big),
+ STI(STI), OSABI(OSABI), Is64Bit(Is64Bit), TargetOptions(Options) {
RISCVFeatures::validate(STI.getTargetTriple(), STI.getFeatureBits());
}
@@ -370,7 +372,7 @@ bool RISCVAsmBackend::relaxDwarfLineAddr(MCFragment &F,
OS << uint8_t(dwarf::DW_LNS_fixed_advance_pc);
Offset = OS.tell();
Fixup = RISCV::getRelocPairForSize(2);
- support::endian::write<uint16_t>(OS, 0, llvm::endianness::little);
+ support::endian::write<uint16_t>(OS, 0, Endian);
}
const MCBinaryExpr &MBE = cast<MCBinaryExpr>(AddrDelta);
@@ -426,15 +428,15 @@ bool RISCVAsmBackend::relaxDwarfCFA(MCFragment &F, bool &WasRelaxed) const {
AddFixups(0, {ELF::R_RISCV_SET6, ELF::R_RISCV_SUB6});
} else if (isUInt<8>(Value)) {
OS << uint8_t(dwarf::DW_CFA_advance_loc1);
- support::endian::write<uint8_t>(OS, 0, llvm::endianness::little);
+ support::endian::write<uint8_t>(OS, 0, Endian);
AddFixups(1, {ELF::R_RISCV_SET8, ELF::R_RISCV_SUB8});
} else if (isUInt<16>(Value)) {
OS << uint8_t(dwarf::DW_CFA_advance_loc2);
- support::endian::write<uint16_t>(OS, 0, llvm::endianness::little);
+ support::endian::write<uint16_t>(OS, 0, Endian);
AddFixups(1, {ELF::R_RISCV_SET16, ELF::R_RISCV_SUB16});
} else if (isUInt<32>(Value)) {
OS << uint8_t(dwarf::DW_CFA_advance_loc4);
- support::endian::write<uint32_t>(OS, 0, llvm::endianness::little);
+ support::endian::write<uint32_t>(OS, 0, Endian);
AddFixups(1, {ELF::R_RISCV_SET32, ELF::R_RISCV_SUB32});
} else {
llvm_unreachable("unsupported CFA encoding");
@@ -880,6 +882,34 @@ bool RISCVAsmBackend::addReloc(const MCFragment &F, const MCFixup &Fixup,
return false;
}
+// Data should be swapped for big endian cores.
+static bool isDataFixup(unsigned Kind) {
+ switch (Kind) {
+ default:
+ llvm_unreachable("Unknown fixup kind!");
+
+ case FK_Data_1:
+ case FK_Data_2:
+ case FK_Data_4:
+ case FK_Data_8:
+ return true;
+
+ case RISCV::fixup_riscv_hi20:
+ case RISCV::fixup_riscv_lo12_i:
+ case RISCV::fixup_riscv_lo12_s:
+ case RISCV::fixup_riscv_pcrel_hi20:
+ case RISCV::fixup_riscv_pcrel_lo12_i:
+ case RISCV::fixup_riscv_pcrel_lo12_s:
+ case RISCV::fixup_riscv_jal:
+ case RISCV::fixup_riscv_branch:
+ case RISCV::fixup_riscv_call:
+ case RISCV::fixup_riscv_call_plt:
+ case RISCV::fixup_riscv_rvc_jump:
+ case RISCV::fixup_riscv_rvc_branch:
+ return false;
+ }
+}
+
void RISCVAsmBackend::applyFixup(const MCFragment &F, const MCFixup &Fixup,
const MCValue &Target,
MutableArrayRef<char> Data, uint64_t Value,
@@ -905,8 +935,11 @@ void RISCVAsmBackend::applyFixup(const MCFragment &F, const MCFixup &Fixup,
// For each byte of the fragment that the fixup touches, mask in the
// bits from the fixup value.
+ // For big endian cores, data fixup should be swapped.
+ bool SwapValue = (Endian == llvm::endianness::big) && isDataFixup(Kind);
for (unsigned i = 0; i != NumBytes; ++i) {
- Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff);
+ unsigned Idx = SwapValue ? (NumBytes - 1 - i) : i;
+ Data[Offset + Idx] |= uint8_t((Value >> (i * 8)) & 0xff);
}
}
@@ -921,5 +954,6 @@ MCAsmBackend *llvm::createRISCVAsmBackend(const Target &T,
const MCTargetOptions &Options) {
const Triple &TT = STI.getTargetTriple();
uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TT.getOS());
- return new RISCVAsmBackend(STI, OSABI, TT.isArch64Bit(), Options);
+ return new RISCVAsmBackend(STI, OSABI, TT.isArch64Bit(), TT.isLittleEndian(),
+ Options);
}
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.h b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.h
index d97d63204e7e4..80c1f200b09af 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.h
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.h
@@ -35,7 +35,7 @@ class RISCVAsmBackend : public MCAsmBackend {
public:
RISCVAsmBackend(const MCSubtargetInfo &STI, uint8_t OSABI, bool Is64Bit,
- const MCTargetOptions &Options);
+ bool IsLittleEndian, const MCTargetOptions &Options);
~RISCVAsmBackend() override = default;
std::optional<bool> evaluateFixup(const MCFragment &, MCFixup &, MCValue &,
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCAsmInfo.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCAsmInfo.cpp
index 090d331d99cab..77f65d814ce7a 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCAsmInfo.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCAsmInfo.cpp
@@ -21,6 +21,7 @@ using namespace llvm;
void RISCVMCAsmInfo::anchor() {}
RISCVMCAsmInfo::RISCVMCAsmInfo(const Triple &TT) {
+ IsLittleEndian = TT.isLittleEndian();
CodePointerSize = CalleeSaveStackSlotSize = TT.isArch64Bit() ? 8 : 4;
CommentString = "#";
AlignmentIsInBytes = false;
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCTargetDesc.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCTargetDesc.cpp
index 61ecfb278a7d3..d917ef4129791 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCTargetDesc.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCTargetDesc.cpp
@@ -376,7 +376,8 @@ static MCInstrAnalysis *createRISCVInstrAnalysis(const MCInstrInfo *Info) {
extern "C" LLVM_ABI LLVM_EXTERNAL_VISIBILITY void
LLVMInitializeRISCVTargetMC() {
- for (Target *T : {&getTheRISCV32Target(), &getTheRISCV64Target()}) {
+ for (Target *T : {&getTheRISCV32Target(), &getTheRISCV64Target(),
+ &getTheRISCV32beTarget(), &getTheRISCV64beTarget()}) {
TargetRegistry::RegisterMCAsmInfo(*T, createRISCVMCAsmInfo);
TargetRegistry::RegisterMCObjectFileInfo(*T, createRISCVMCObjectFileInfo);
TargetRegistry::RegisterMCInstrInfo(*T, createRISCVMCInstrInfo);
diff --git a/llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp b/llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp
index 2f32e2ac3eba3..83566b1c57782 100644
--- a/llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp
+++ b/llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp
@@ -611,6 +611,8 @@ extern "C" LLVM_ABI LLVM_EXTERNAL_VISIBILITY void
LLVMInitializeRISCVAsmPrinter() {
RegisterAsmPrinter<RISCVAsmPrinter> X(getTheRISCV32Target());
RegisterAsmPrinter<RISCVAsmPrinter> Y(getTheRISCV64Target());
+ RegisterAsmPrinter<RISCVAsmPrinter> A(getTheRISCV32beTarget());
+ RegisterAsmPrinter<RISCVAsmPrinter> B(getTheRISCV64beTarget());
}
void RISCVAsmPrinter::LowerHWASAN_CHECK_MEMACCESS(const MachineInstr &MI) {
diff --git a/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp b/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
index da6ac2f6f31e9..3a16256aed462 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
@@ -117,6 +117,8 @@ static cl::opt<bool>
extern "C" LLVM_ABI LLVM_EXTERNAL_VISIBILITY void LLVMInitializeRISCVTarget() {
RegisterTargetMachine<RISCVTargetMachine> X(getTheRISCV32Target());
RegisterTargetMachine<RISCVTargetMachine> Y(getTheRISCV64Target());
+ RegisterTargetMachine<RISCVTargetMachine> A(getTheRISCV32beTarget());
+ RegisterTargetMachine<RISCVTargetMachine> B(getTheRISCV64beTarget());
auto *PR = PassRegistry::getPassRegistry();
initializeGlobalISel(*PR);
initializeRISCVO0PreLegalizerCombinerPass(*PR);
@@ -150,21 +152,23 @@ extern "C" LLVM_ABI LLVM_EXTERNAL_VISIBILITY void LLVMInitializeRISCVTarget() {
initializeRISCVAsmPrinterPass(*PR);
}
-static StringRef computeDataLayout(const Triple &TT,
- const TargetOptions &Options) {
- StringRef ABIName = Options.MCOptions.getABIName();
- if (TT.isArch64Bit()) {
- if (ABIName == "lp64e")
- return "e-m:e-p:64:64-i64:64-i128:128-n32:64-S64";
+static std::string computeDataLayout(const Triple &TT,
+ const TargetOptions &Opts) {
+ const bool IsLittle = TT.isLittleEndian();
+ StringRef ABI = Opts.MCOptions.getABIName();
+ std::string DL;
- return "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128";
+ if (TT.isArch64Bit()) {
+ DL = (Twine(IsLittle ? "e" : "E") + "-m:e-p:64:64-i64:64-i128:128-n32:64-" +
+ (ABI == "lp64e" ? "S64" : "S128"))
+ .str();
+ } else {
+ assert(TT.isArch32Bit() && "only RV32 and RV64 are currently supported");
+ DL = (Twine(IsLittle ? "e" : "E") + "-m:e-p:32:32-i64:64-n32-" +
+ (ABI == "ilp32e" ? "S32" : "S128"))
+ .str();
}
- assert(TT.isArch32Bit() && "only RV32 and RV64 are currently supported");
-
- if (ABIName == "ilp32e")
- return "e-m:e-p:32:32-i64:64-n32-S32";
-
- return "e-m:e-p:32:32-i64:64-n32-S128";
+ return DL;
}
static Reloc::Model getEffectiveRelocModel(const Triple &TT,
diff --git a/llvm/lib/Target/RISCV/TargetInfo/RISCVTargetInfo.cpp b/llvm/lib/Target/RISCV/TargetInfo/RISCVTargetInfo.cpp
index fc0965d263a8a..7b0afe46971a3 100644
--- a/llvm/lib/Target/RISCV/TargetInfo/RISCVTargetInfo.cpp
+++ b/llvm/lib/Target/RISCV/TargetInfo/RISCVTargetInfo.cpp
@@ -21,10 +21,24 @@ Target &llvm::getTheRISCV64Target() {
return TheRISCV64Target;
}
+Target &llvm::getTheRISCV32beTarget() {
+ static Target TheRISCV32beTarget;
+ return TheRISCV32beTarget;
+}
+
+Target &llvm::getTheRISCV64beTarget() {
+ static Target TheRISCV64beTarget;
+ return TheRISCV64beTarget;
+}
+
extern "C" LLVM_ABI LLVM_EXTERNAL_VISIBILITY void
LLVMInitializeRISCVTargetInfo() {
RegisterTarget<Triple::riscv32, /*HasJIT=*/true> X(
getTheRISCV32Target(), "riscv32", "32-bit RISC-V", "RISCV");
RegisterTarget<Triple::riscv64, /*HasJIT=*/true> Y(
getTheRISCV64Target(), "riscv64", "64-bit RISC-V", "RISCV");
+ RegisterTarget<Triple::riscv32be> A(getTheRISCV32beTarget(), "riscv32be",
+ "32-bit big endian RISC-V", "RISCV");
+ RegisterTarget<Triple::riscv64be> B(getTheRISCV64beTarget(), "riscv64be",
+ "64-bit big endian RISC-V", "RISCV");
}
diff --git a/llvm/lib/Target/RISCV/TargetInfo/RISCVTargetInfo.h b/llvm/lib/Target/RISCV/TargetInfo/RISCVTargetInfo.h
index ed00a01fa1a2a..9b9fd2cca2fd0 100644
--- a/llvm/lib/Target/RISCV/TargetInfo/RISCVTargetInfo.h
+++ b/llvm/lib/Target/RISCV/TargetInfo/RISCVTargetInfo.h
@@ -15,6 +15,8 @@ class Target;
Target &getTheRISCV32Target();
Target &getTheRISCV64Target();
+Target &getTheRISCV32beTarget();
+Target &getTheRISCV64beTarget();
} // namespace llvm
diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index e87bee79a6a69..2eb727fc2a596 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -496,7 +496,8 @@ static ShadowMapping getShadowMapping(const Triple &TargetTriple, int LongSize,
bool IsAArch64 = TargetTriple.getArch() == Triple::aarch64 ||
TargetTriple.getArch() == Triple::aarch64_be;
bool IsLoongArch64 = TargetTriple.isLoongArch64();
- bool IsRISCV64 = TargetTriple.getArch() == Triple::riscv64;
+ bool IsRISCV64 = TargetTriple.getArch() == Triple::riscv64 ||
+ TargetTriple.getArch() == Triple::riscv64be;
bool IsWindows = TargetTriple.isOSWindows();
bool IsFuchsia = TargetTriple.isOSFuchsia();
bool IsAMDGPU = TargetTriple.isAMDGPU();
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