[RISCV] Add support for Zihintpause extention

[mundaym]

Summary

Add support for the 'pause' hint instruction as an alias for
'fence w, 0'. To do this allow the 'fence' operands pred and succ
to be set to 0 (the empty set). This will also allow future hints
to be encoded as 'fence 0, <x>' and 'fence <x>, 0'.

[lenary]

LGTM! Let's wait for the spec to be merged before merging this though.

[luojia]

Hello! I noticed that the pause hint instruction is merged into spec (https://github.com/riscv/riscv-isa-manual/pull/398) and got ratified (https://github.com/riscv/riscv-isa-manual/commit/7a58119dad5bd43e2171a26b56ef60f9591a1c9c).

Should this patch be merged? :) This patch LGTM.

[asb]

In D93019#3166382, @luojia wrote:

Hello! I noticed that the pause hint instruction is merged into spec (https://github.com/riscv/riscv-isa-manual/pull/398) and got ratified (https://github.com/riscv/riscv-isa-manual/commit/7a58119dad5bd43e2171a26b56ef60f9591a1c9c).

Should this patch be merged? :) This patch LGTM.

It just needs to be appropriately gated by a zihintpause attribute.

[achieveartificialintelligence]

Add support for Zihintpause extention

[achieveartificialintelligence]

Since this commit hasn't been updated for a year, I updated it. @mundaym

[achieveartificialintelligence]

Can we land now?@asb @luismarques @lenary

[achieveartificialintelligence]

This patch is accepted a year ago. Could this patch land now?

[asb]

This LGTM.

[mundaym]

@achieveartificialintelligence would you mind creating your revised change as a new patch? I'm going to abandon this. Feel free to include any of my original code.

Once you have done that ping @asb and he can do a quick check and approve again.

llvm/lib/Support/RISCVISAInfo.cpp

static const RISCVSupportedExtension SupportedExtensions[] = {
     {"i", RISCVExtensionVersion{2, 0}},
     {"e", RISCVExtensionVersion{1, 9}},
     {"m", RISCVExtensionVersion{2, 0}},
     {"a", RISCVExtensionVersion{2, 0}},
     {"f", RISCVExtensionVersion{2, 0}},
     {"d", RISCVExtensionVersion{2, 0}},
     {"c", RISCVExtensionVersion{2, 0}},
 
+    {"zihintpause", RISCVExtensionVersion{2, 0}},
+
     {"zfhmin", RISCVExtensionVersion{1, 0}},
     {"zfh", RISCVExtensionVersion{1, 0}},
 
     {"zba", RISCVExtensionVersion{1, 0}},
     {"zbb", RISCVExtensionVersion{1, 0}},
     {"zbc", RISCVExtensionVersion{1, 0}},
     {"zbs", RISCVExtensionVersion{1, 0}},
 };

llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp

bool isVTypeI11() const {
     return Kind == KindTy::VType;
   }
 
   /// Return true if the operand is a valid for the fence instruction e.g.
   /// ('iorw').
   bool isFenceArg() const {
     if (!isImm())
       return false;
-    const MCExpr *Val = getImm();
-    auto *SVal = dyn_cast<MCSymbolRefExpr>(Val);
+
+    int64_t Imm;
+    RISCVMCExpr::VariantKind VK = RISCVMCExpr::VK_RISCV_None;
+    if (evaluateConstantImm(getImm(), Imm, VK)) {
+      // Only accept 0 as a constant immediate.
+      return VK == RISCVMCExpr::VK_RISCV_None && Imm == 0;
+    }
+
+    auto *SVal = dyn_cast<MCSymbolRefExpr>(getImm());
+
     if (!SVal || SVal->getKind() != MCSymbolRefExpr::VK_None)
       return false;
 
     StringRef Str = SVal->getSymbol().getName();
     // Letters must be unique, taken from 'iorw', and in ascending order. This
     // holds as long as each individual character is one of 'iorw' and is
     // greater than the previous character.
     char Prev = '\0';
public:
 
   void addImmOperands(MCInst &Inst, unsigned N) const {
     assert(N == 1 && "Invalid number of operands!");
     addExpr(Inst, getImm());
   }
 
   void addFenceArgOperands(MCInst &Inst, unsigned N) const {
     assert(N == 1 && "Invalid number of operands!");
+
+    int64_t Constant = 0;
+    RISCVMCExpr::VariantKind VK = RISCVMCExpr::VK_RISCV_None;
+    if (evaluateConstantImm(getImm(), Constant, VK)) {
+      if (Constant == 0) {
+        Inst.addOperand(MCOperand::createImm(Constant));
+        return;
+      }
+      llvm_unreachable("FenceArg must contain only [iorw] or be 0");
+    }
+
     // isFenceArg has validated the operand, meaning this cast is safe
     auto SE = cast<MCSymbolRefExpr>(getImm());
 
     unsigned Imm = 0;
     for (char c : SE->getSymbol().getName()) {
       switch (c) {
       default:
-        llvm_unreachable("FenceArg must contain only [iorw]");
+        llvm_unreachable("FenceArg must contain only [iorw] or be 0");
       case 'i':
         Imm |= RISCVFenceField::I;
         break;
       case 'o':
         Imm |= RISCVFenceField::O;
         break;
       case 'r':
         Imm |= RISCVFenceField::R;
return generateImmOutOfRangeError(
         "immediate must be a multiple of 2 bytes in the range");
   case Match_InvalidCSRSystemRegister: {
     return generateImmOutOfRangeError(Operands, ErrorInfo, 0, (1 << 12) - 1,
                                       "operand must be a valid system register "
                                       "name or an integer in the range");
   }
   case Match_InvalidFenceArg: {
     SMLoc ErrorLoc = ((RISCVOperand &)*Operands[ErrorInfo]).getStartLoc();
-    return Error(
-        ErrorLoc,
-        "operand must be formed of letters selected in-order from 'iorw'");
+    return Error(ErrorLoc, "operand must be formed of letters selected "
+                           "in-order from 'iorw' or be 0");
   }
   case Match_InvalidFRMArg: {
     SMLoc ErrorLoc = ((RISCVOperand &)*Operands[ErrorInfo]).getStartLoc();
     return Error(
         ErrorLoc,
         "operand must be a valid floating point rounding mode mnemonic");
   }
   case Match_InvalidBareSymbol: {

llvm/lib/Target/RISCV/MCTargetDesc/RISCVInstPrinter.cpp

if ((FenceArg & RISCVFenceField::I) != 0)
     O << 'i';
   if ((FenceArg & RISCVFenceField::O) != 0)
     O << 'o';
   if ((FenceArg & RISCVFenceField::R) != 0)
     O << 'r';
   if ((FenceArg & RISCVFenceField::W) != 0)
     O << 'w';
   if (FenceArg == 0)
-    O << "unknown";
+    O << "0";
 }
 
 void RISCVInstPrinter::printFRMArg(const MCInst *MI, unsigned OpNo,
                                    const MCSubtargetInfo &STI, raw_ostream &O) {
   auto FRMArg =
       static_cast<RISCVFPRndMode::RoundingMode>(MI->getOperand(OpNo).getImm());
   O << RISCVFPRndMode::roundingModeToString(FRMArg);
 }

llvm/lib/Target/RISCV/RISCV.td

 def FeatureStdExtD
     : SubtargetFeature<"d", "HasStdExtD", "true",
                        "'D' (Double-Precision Floating-Point)",
                        [FeatureStdExtF]>;
 def HasStdExtD : Predicate<"Subtarget->hasStdExtD()">,
                            AssemblerPredicate<(all_of FeatureStdExtD),
                            "'D' (Double-Precision Floating-Point)">;
 
+def FeatureStdExtZihintpause
+    : SubtargetFeature<"zihintpause", "HasStdExtZihintpause", "true",
+                       "'zihintpause' (Pause Hint)">;
+def HasStdExtZihintpause : Predicate<"Subtarget->hasStdExtZihintpause()">,
+                                     AssemblerPredicate<(all_of FeatureStdExtZihintpause),
+                                     "'Zihintpause' (Pause Hint)">;
+
 def FeatureStdExtZfhmin
     : SubtargetFeature<"zfhmin", "HasStdExtZfhmin", "true",
                        "'Zfhmin' (Half-Precision Floating-Point Minimal)",
                        [FeatureStdExtF]>;
 def HasStdExtZfhmin : Predicate<"Subtarget->hasStdExtZfhmin()">,
                              AssemblerPredicate<(all_of FeatureStdExtZfhmin),
                              "'Zfhmin' (Half-Precision Floating-Point Minimal)">;
 

llvm/lib/Target/RISCV/RISCVInstrInfo.td

 
 // Non-canonical forms for jump targets also accepted by the assembler.
 def : InstAlias<"jr $rs, $offset",        (JALR      X0, GPR:$rs, simm12:$offset), 0>;
 def : InstAlias<"jalr $rs, $offset",      (JALR      X1, GPR:$rs, simm12:$offset), 0>;
 def : InstAlias<"jalr $rd, $rs, $offset", (JALR GPR:$rd, GPR:$rs, simm12:$offset), 0>;
 
 def : InstAlias<"fence", (FENCE 0xF, 0xF)>; // 0xF == iorw
 
+let Predicates = [HasStdExtZihintpause] in
+def : InstAlias<"pause", (FENCE 0x1, 0x0)>; // 0x1 == w
+
 def : InstAlias<"rdinstret $rd", (CSRRS GPR:$rd, INSTRET.Encoding, X0)>;
 def : InstAlias<"rdcycle $rd",   (CSRRS GPR:$rd, CYCLE.Encoding, X0)>;
 def : InstAlias<"rdtime $rd",    (CSRRS GPR:$rd, TIME.Encoding, X0)>;
 
 let Predicates = [IsRV32] in {
 def : InstAlias<"rdinstreth $rd", (CSRRS GPR:$rd, INSTRETH.Encoding, X0)>;
 def : InstAlias<"rdcycleh $rd",   (CSRRS GPR:$rd, CYCLEH.Encoding, X0)>;
 def : InstAlias<"rdtimeh $rd",    (CSRRS GPR:$rd, TIMEH.Encoding, X0)>;

llvm/lib/Target/RISCV/RISCVSubtarget.h

private:
   bool HasStdExtZbe = false;
   bool HasStdExtZbf = false;
   bool HasStdExtZbm = false;
   bool HasStdExtZbp = false;
   bool HasStdExtZbr = false;
   bool HasStdExtZbs = false;
   bool HasStdExtZbt = false;
   bool HasStdExtV = false;
+  bool HasStdExtZihintpause = false;
   bool HasStdExtZvlsseg = false;
   bool HasStdExtZfhmin = false;
   bool HasStdExtZfh = false;
   bool HasRV64 = false;
   bool IsRV32E = false;
   bool EnableLinkerRelax = false;
   bool EnableRVCHintInstrs = true;
   bool EnableSaveRestore = false;
public:
   bool hasStdExtZbe() const { return HasStdExtZbe; }
   bool hasStdExtZbf() const { return HasStdExtZbf; }
   bool hasStdExtZbm() const { return HasStdExtZbm; }
   bool hasStdExtZbp() const { return HasStdExtZbp; }
   bool hasStdExtZbr() const { return HasStdExtZbr; }
   bool hasStdExtZbs() const { return HasStdExtZbs; }
   bool hasStdExtZbt() const { return HasStdExtZbt; }
   bool hasStdExtV() const { return HasStdExtV; }
+  bool hasStdExtZihintpause() const { return HasStdExtZihintpause; }
   bool hasStdExtZvlsseg() const { return HasStdExtZvlsseg; }
   bool hasStdExtZvl() const { return ZvlLen != ExtZvl::NotSet; }
   bool hasStdExtZfhmin() const { return HasStdExtZfhmin; }
   bool hasStdExtZfh() const { return HasStdExtZfh; }
   bool is64Bit() const { return HasRV64; }
   bool isRV32E() const { return IsRV32E; }
   bool enableLinkerRelax() const { return EnableLinkerRelax; }
   bool enableRVCHintInstrs() const { return EnableRVCHintInstrs; }

llvm/test/CodeGen/RISCV/attributes.ll

 ;; Generate ELF attributes from llc.
 
 ; RUN: llc -mtriple=riscv32 -mattr=+m %s -o - | FileCheck --check-prefix=RV32M %s
 ; RUN: llc -mtriple=riscv32 -mattr=+a %s -o - | FileCheck --check-prefix=RV32A %s
 ; RUN: llc -mtriple=riscv32 -mattr=+f %s -o - | FileCheck --check-prefix=RV32F %s
 ; RUN: llc -mtriple=riscv32 -mattr=+d %s -o - | FileCheck --check-prefix=RV32D %s
 ; RUN: llc -mtriple=riscv32 -mattr=+c %s -o - | FileCheck --check-prefix=RV32C %s
+; RUN: llc -mtriple=riscv32 -mattr=+zihintpause %s -o - | FileCheck --check-prefix=RV32ZIHINTPAUSE %s
 ; RUN: llc -mtriple=riscv32 -mattr=+zfhmin %s -o - | FileCheck --check-prefix=RV32ZFHMIN %s
 ; RUN: llc -mtriple=riscv32 -mattr=+zfh %s -o - | FileCheck --check-prefix=RV32ZFH %s
 ; RUN: llc -mtriple=riscv32 -mattr=+zba %s -o - | FileCheck --check-prefix=RV32ZBA %s
 ; RUN: llc -mtriple=riscv32 -mattr=+zbb %s -o - | FileCheck --check-prefix=RV32ZBB %s
 ; RUN: llc -mtriple=riscv32 -mattr=+zbc %s -o - | FileCheck --check-prefix=RV32ZBC %s
 ; RUN: llc -mtriple=riscv32 -mattr=+experimental-zbe %s -o - | FileCheck --check-prefix=RV32ZBE %s
 ; RUN: llc -mtriple=riscv32 -mattr=+experimental-zbf %s -o - | FileCheck --check-prefix=RV32ZBF %s
 ; RUN: llc -mtriple=riscv32 -mattr=+experimental-zbm %s -o - | FileCheck --check-prefix=RV32ZBM %s
 ; RUN: llc -mtriple=riscv32 -mattr=+experimental-zbp %s -o - | FileCheck --check-prefix=RV32ZBP %s
 ; RUN: llc -mtriple=riscv32 -mattr=+experimental-zbr %s -o - | FileCheck --check-prefix=RV32ZBR %s
 ; RUN: llc -mtriple=riscv32 -mattr=+zbs %s -o - | FileCheck --check-prefix=RV32ZBS %s
 ; RUN: llc -mtriple=riscv32 -mattr=+experimental-zbt %s -o - | FileCheck --check-prefix=RV32ZBT %s
 ; RUN: llc -mtriple=riscv32 -mattr=+experimental-v %s -o - | FileCheck --check-prefix=RV32V %s
 ; RUN: llc -mtriple=riscv32 -mattr=+zbb,+zfh,+experimental-v,+f,+experimental-zvlsseg %s -o - | FileCheck --check-prefix=RV32COMBINED %s
 ; RUN: llc -mtriple=riscv64 -mattr=+m %s -o - | FileCheck --check-prefix=RV64M %s
 ; RUN: llc -mtriple=riscv64 -mattr=+a %s -o - | FileCheck --check-prefix=RV64A %s
 ; RUN: llc -mtriple=riscv64 -mattr=+f %s -o - | FileCheck --check-prefix=RV64F %s
 ; RUN: llc -mtriple=riscv64 -mattr=+d %s -o - | FileCheck --check-prefix=RV64D %s
 ; RUN: llc -mtriple=riscv64 -mattr=+c %s -o - | FileCheck --check-prefix=RV64C %s
+; RUN: llc -mtriple=riscv64 -mattr=+zihintpause %s -o - | FileCheck --check-prefix=RV64ZIHINTPAUSE %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zfhmin %s -o - | FileCheck --check-prefix=RV64ZFHMIN %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zfh %s -o - | FileCheck --check-prefix=RV64ZFH %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zba %s -o - | FileCheck --check-prefix=RV64ZBA %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zbb %s -o - | FileCheck --check-prefix=RV64ZBB %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zbc %s -o - | FileCheck --check-prefix=RV64ZBC %s
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-zbe %s -o - | FileCheck --check-prefix=RV64ZBE %s
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-zbf %s -o - | FileCheck --check-prefix=RV64ZBF %s
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-zbm %s -o - | FileCheck --check-prefix=RV64ZBM %s
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-zbp %s -o - | FileCheck --check-prefix=RV64ZBP %s
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-zbr %s -o - | FileCheck --check-prefix=RV64ZBR %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zbs %s -o - | FileCheck --check-prefix=RV64ZBS %s
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-zbt %s -o - | FileCheck --check-prefix=RV64ZBT %s
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-v %s -o - | FileCheck --check-prefix=RV64V %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zbb,+zfh,+experimental-v,+f,+experimental-zvlsseg %s -o - | FileCheck --check-prefix=RV64COMBINED %s
 
 
 ; RV32M: .attribute 5, "rv32i2p0_m2p0"
 ; RV32A: .attribute 5, "rv32i2p0_a2p0"
 ; RV32F: .attribute 5, "rv32i2p0_f2p0"
 ; RV32D: .attribute 5, "rv32i2p0_f2p0_d2p0"
 ; RV32C: .attribute 5, "rv32i2p0_c2p0"
+; RV32ZIHINTPAUSE: .attribute 5, "rv32i2p0_zihintpause2p0"
 ; RV32ZFHMIN: .attribute 5, "rv32i2p0_f2p0_zfhmin1p0"
 ; RV32ZFH: .attribute 5, "rv32i2p0_f2p0_zfh1p0_zfhmin1p0"
 ; RV32ZBA: .attribute 5, "rv32i2p0_zba1p0"
 ; RV32ZBB: .attribute 5, "rv32i2p0_zbb1p0"
 ; RV32ZBC: .attribute 5, "rv32i2p0_zbc1p0"
 ; RV32ZBE: .attribute 5, "rv32i2p0_zbe0p93"
 ; RV32ZBF: .attribute 5, "rv32i2p0_zbf0p93"
 ; RV32ZBM: .attribute 5, "rv32i2p0_zbm0p93"
 ; RV32ZBP: .attribute 5, "rv32i2p0_zbp0p93"
 ; RV32ZBR: .attribute 5, "rv32i2p0_zbr0p93"
 ; RV32ZBS: .attribute 5, "rv32i2p0_zbs1p0"
 ; RV32ZBT: .attribute 5, "rv32i2p0_zbt0p93"
 ; RV32V: .attribute 5, "rv32i2p0_v0p10_zvl128b0p10_zvl32b0p10_zvl64b0p10_zvlsseg0p10"
 ; RV32COMBINED: .attribute 5, "rv32i2p0_f2p0_v0p10_zfh1p0_zfhmin1p0_zbb1p0_zvl128b0p10_zvl32b0p10_zvl64b0p10_zvlsseg0p10"
 
 ; RV64M: .attribute 5, "rv64i2p0_m2p0"
 ; RV64A: .attribute 5, "rv64i2p0_a2p0"
 ; RV64F: .attribute 5, "rv64i2p0_f2p0"
 ; RV64D: .attribute 5, "rv64i2p0_f2p0_d2p0"
 ; RV64C: .attribute 5, "rv64i2p0_c2p0"
+; RV64ZIHINTPAUSE: .attribute 5, "rv64i2p0_zihintpause2p0"
 ; RV64ZFHMIN: .attribute 5, "rv64i2p0_f2p0_zfhmin1p0"
 ; RV64ZFH: .attribute 5, "rv64i2p0_f2p0_zfh1p0_zfhmin1p0"
 ; RV64ZBA: .attribute 5, "rv64i2p0_zba1p0"
 ; RV64ZBB: .attribute 5, "rv64i2p0_zbb1p0"
 ; RV64ZBC: .attribute 5, "rv64i2p0_zbc1p0"
 ; RV64ZBE: .attribute 5, "rv64i2p0_zbe0p93"
 ; RV64ZBF: .attribute 5, "rv64i2p0_zbf0p93"
 ; RV64ZBM: .attribute 5, "rv64i2p0_zbm0p93"

llvm/test/MC/Disassembler/RISCV/unknown-fence-field.txt

-# RUN: llvm-mc -disassemble -triple=riscv32 < %s 2>&1 | FileCheck %s
-# RUN: llvm-mc -disassemble -triple=riscv64 < %s 2>&1 | FileCheck %s
-#
-# Test generated by a LLVM MC Disassembler Protocol Buffer Fuzzer
-# for the RISC-V assembly language.
-
-# This decodes as fence , iorw with invalid fence field as 0.
-[0x0f 0x00 0xf0 0x00]
-# CHECK: fence unknown, iorw

llvm/test/MC/RISCV/rv32i-invalid.s

 # RUN: not llvm-mc -triple riscv32 < %s 2>&1 | FileCheck %s
 
 # Out of range immediates
 ## fencearg
-fence iorw, iore # CHECK: :[[@LINE]]:13: error: operand must be formed of letters selected in-order from 'iorw'
-fence wr, wr # CHECK: :[[@LINE]]:7: error: operand must be formed of letters selected in-order from 'iorw'
-fence rw, rr # CHECK: :[[@LINE]]:11: error: operand must be formed of letters selected in-order from 'iorw'
-fence 1, rw # CHECK: :[[@LINE]]:7: error: operand must be formed of letters selected in-order from 'iorw'
-fence unknown, unknown # CHECK: :[[@LINE]]:7: error: operand must be formed of letters selected in-order from 'iorw'
+fence iorw, iore # CHECK: :[[@LINE]]:13: error: operand must be formed of letters selected in-order from 'iorw' or be 0
+fence wr, wr # CHECK: :[[@LINE]]:7: error: operand must be formed of letters selected in-order from 'iorw' or be 0
+fence rw, rr # CHECK: :[[@LINE]]:11: error: operand must be formed of letters selected in-order from 'iorw' or be 0
+fence 1, rw # CHECK: :[[@LINE]]:7: error: operand must be formed of letters selected in-order from 'iorw' or be 0
+fence unknown, unknown # CHECK: :[[@LINE]]:7: error: operand must be formed of letters selected in-order from 'iorw' or be 0
 
 ## uimm5
 slli a0, a0, 32 # CHECK: :[[@LINE]]:14: error: immediate must be an integer in the range [0, 31]
 srli a0, a0, -1 # CHECK: :[[@LINE]]:14: error: immediate must be an integer in the range [0, 31]
 srai a0, a0, -19 # CHECK: :[[@LINE]]:14: error: immediate must be an integer in the range [0, 31]
 csrrwi a1, 0x1, -1 # CHECK: :[[@LINE]]:17: error: immediate must be an integer in the range [0, 31]
 csrrsi t1, 999, 32 # CHECK: :[[@LINE]]:17: error: immediate must be an integer in the range [0, 31]
 csrrci x0, 43, -90 # CHECK: :[[@LINE]]:16: error: immediate must be an integer in the range [0, 31]

 ori a0, a1 # CHECK: :[[@LINE]]:1: error: too few operands for instruction
 xor s2, s2 # CHECK: :[[@LINE]]:1: error: too few operands for instruction
 
 # Instruction not in the base ISA
 mul a4, ra, s0 # CHECK: :[[@LINE]]:1: error: instruction requires the following: 'M' (Integer Multiplication and Division)
 amomaxu.w s5, s4, (s3) # CHECK: :[[@LINE]]:1: error: instruction requires the following: 'A' (Atomic Instructions)
 fadd.s ft0, ft1, ft2 # CHECK: :[[@LINE]]:1: error: instruction requires the following: 'F' (Single-Precision Floating-Point)
 fadd.h ft0, ft1, ft2 # CHECK: :[[@LINE]]:1: error: instruction requires the following: 'Zfh' (Half-Precision Floating-Point)
+pause # CHECK: :[[@LINE]]:1: error: instruction requires the following: 'Zihintpause' (Pause Hint)
 
 # Using floating point registers when integer registers are expected
 addi a2, ft0, 24 # CHECK: :[[@LINE]]:10: error: invalid operand for instruction
 
 # fence.tso accepts no operands
 fence.tso rw, rw # CHECK: :[[@LINE]]:11: error: invalid operand for instruction

llvm/test/MC/RISCV/rv32zihintpause-valid.s

+# RUN: llvm-mc %s -triple=riscv32 -mattr=+zihintpause -riscv-no-aliases -show-encoding \
+# RUN:     | FileCheck -check-prefixes=CHECK-ASM,CHECK-ASM-AND-OBJ %s
+# RUN: llvm-mc %s -triple=riscv64 -mattr=+zihintpause -riscv-no-aliases -show-encoding \
+# RUN:     | FileCheck -check-prefixes=CHECK-ASM,CHECK-ASM-AND-OBJ %s
+# RUN: llvm-mc -filetype=obj -triple=riscv32 -mattr=+zihintpause < %s \
+# RUN:     | llvm-objdump --mattr=+zihintpause -M no-aliases -d -r - \
+# RUN:     | FileCheck --check-prefix=CHECK-ASM-AND-OBJ %s
+# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+zihintpause < %s \
+# RUN:     | llvm-objdump --mattr=+zihintpause -M no-aliases -d -r - \
+# RUN:     | FileCheck --check-prefix=CHECK-ASM-AND-OBJ %s
+
+# CHECK-ASM-AND-OBJ: fence w, 0
+# CHECK-ASM: encoding: [0x0f,0x00,0x00,0x01]
+fence w,0
+# CHECK-ASM-AND-OBJ: fence 0, w
+# CHECK-ASM: encoding: [0x0f,0x00,0x10,0x00]
+fence 0,w
+# CHECK-ASM-AND-OBJ: fence 0, 0
+# CHECK-ASM: encoding: [0x0f,0x00,0x00,0x00]
+fence 0,0

llvm/test/MC/RISCV/rvzihintpause-aliases-valid.s

+# RUN: llvm-mc %s -triple=riscv32 -mattr=+zihintpause -M no-aliases \
+# RUN:     | FileCheck -check-prefixes=CHECK-S-OBJ-NOALIAS %s
+# RUN: llvm-mc %s -triple=riscv32 -mattr=+zihintpause \
+# RUN:     | FileCheck -check-prefixes=CHECK-S-OBJ %s
+# RUN: llvm-mc %s -triple=riscv64 -mattr=+zihintpause -M no-aliases \
+# RUN:     | FileCheck -check-prefixes=CHECK-S-OBJ-NOALIAS %s
+# RUN: llvm-mc %s -triple=riscv64 -mattr=+zihintpause \
+# RUN:     | FileCheck -check-prefixes=CHECK-S-OBJ %s
+# RUN: llvm-mc -filetype=obj -triple riscv32 -mattr=+zihintpause < %s \
+# RUN:     | llvm-objdump --mattr=+zihintpause -d -r -M no-aliases - \
+# RUN:     | FileCheck -check-prefixes=CHECK-S-OBJ-NOALIAS %s
+# RUN: llvm-mc -filetype=obj -triple riscv32 -mattr=+zihintpause < %s \
+# RUN:     | llvm-objdump --mattr=+zihintpause -d -r - \
+# RUN:     | FileCheck -check-prefixes=CHECK-S-OBJ %s
+# RUN: llvm-mc -filetype=obj -triple riscv64 -mattr=+zihintpause < %s \
+# RUN:     | llvm-objdump --mattr=+zihintpause -d -r -M no-aliases - \
+# RUN:     | FileCheck -check-prefixes=CHECK-S-OBJ-NOALIAS %s
+# RUN: llvm-mc -filetype=obj -triple riscv64 -mattr=+zihintpause < %s \
+# RUN:     | llvm-objdump --mattr=+zihintpause -d -r - \
+# RUN:     | FileCheck -check-prefixes=CHECK-S-OBJ %s
+
+# CHECK-S-OBJ-NOALIAS: fence w, 0
+# CHECK-S-OBJ: pause
+pause