[RISCV] Add support for -ffixed-xX flags

This adds support for reserving GPRs such that the compiler will not
choose a register for register allocation. The implementation follows
the same design as for AArch64; each reserved register becomes a target
feature and used for getting the reserved registers for a given
MachineFunction. The backend checks that it does not need to write to
any reserved register; if it does a relevant error is generated.

Differential Revision: https://reviews.llvm.org/D67185
diff --git a/llvm/lib/Target/RISCV/RISCV.td b/llvm/lib/Target/RISCV/RISCV.td
index 46530a8f..70d87d6 100644
--- a/llvm/lib/Target/RISCV/RISCV.td
+++ b/llvm/lib/Target/RISCV/RISCV.td
@@ -69,6 +69,11 @@
     : SubtargetFeature<"relax", "EnableLinkerRelax", "true",
                        "Enable Linker relaxation.">;
 
+foreach i = {1-31} in
+    def FeatureReserveX#i :
+        SubtargetFeature<"reserve-x"#i, "UserReservedRegister[RISCV::X"#i#"]",
+                         "true", "Reserve X"#i>;
+
 //===----------------------------------------------------------------------===//
 // Named operands for CSR instructions.
 //===----------------------------------------------------------------------===//
diff --git a/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp b/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
index 6b6f62e..daa7b7a 100644
--- a/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
@@ -18,6 +18,7 @@
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/RegisterScavenging.h"
+#include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/MC/MCDwarf.h"
 
 using namespace llvm;
@@ -131,6 +132,12 @@
   if (StackSize == 0 && !MFI.adjustsStack())
     return;
 
+  // If the stack pointer has been marked as reserved, then produce an error if
+  // the frame requires stack allocation
+  if (STI.isRegisterReservedByUser(SPReg))
+    MF.getFunction().getContext().diagnose(DiagnosticInfoUnsupported{
+        MF.getFunction(), "Stack pointer required, but has been reserved."});
+
   uint64_t FirstSPAdjustAmount = getFirstSPAdjustAmount(MF);
   // Split the SP adjustment to reduce the offsets of callee saved spill.
   if (FirstSPAdjustAmount)
@@ -167,6 +174,10 @@
 
   // Generate new FP.
   if (hasFP(MF)) {
+    if (STI.isRegisterReservedByUser(FPReg))
+      MF.getFunction().getContext().diagnose(DiagnosticInfoUnsupported{
+          MF.getFunction(), "Frame pointer required, but has been reserved."});
+
     adjustReg(MBB, MBBI, DL, FPReg, SPReg,
               StackSize - RVFI->getVarArgsSaveSize(), MachineInstr::FrameSetup);
 
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index dc829fc..b56d951 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -2247,6 +2247,16 @@
     Glue = Chain.getValue(1);
   }
 
+  // Validate that none of the argument registers have been marked as
+  // reserved, if so report an error. Do the same for the return address if this
+  // is not a tailcall.
+  validateCCReservedRegs(RegsToPass, MF);
+  if (!IsTailCall &&
+      MF.getSubtarget<RISCVSubtarget>().isRegisterReservedByUser(RISCV::X1))
+    MF.getFunction().getContext().diagnose(DiagnosticInfoUnsupported{
+        MF.getFunction(),
+        "Return address register required, but has been reserved."});
+
   // If the callee is a GlobalAddress/ExternalSymbol node, turn it into a
   // TargetGlobalAddress/TargetExternalSymbol node so that legalize won't
   // split it and then direct call can be matched by PseudoCALL.
@@ -2362,6 +2372,9 @@
                                  const SmallVectorImpl<ISD::OutputArg> &Outs,
                                  const SmallVectorImpl<SDValue> &OutVals,
                                  const SDLoc &DL, SelectionDAG &DAG) const {
+  const MachineFunction &MF = DAG.getMachineFunction();
+  const RISCVSubtarget &STI = MF.getSubtarget<RISCVSubtarget>();
+
   // Stores the assignment of the return value to a location.
   SmallVector<CCValAssign, 16> RVLocs;
 
@@ -2391,6 +2404,13 @@
       Register RegLo = VA.getLocReg();
       assert(RegLo < RISCV::X31 && "Invalid register pair");
       Register RegHi = RegLo + 1;
+
+      if (STI.isRegisterReservedByUser(RegLo) ||
+          STI.isRegisterReservedByUser(RegHi))
+        MF.getFunction().getContext().diagnose(DiagnosticInfoUnsupported{
+            MF.getFunction(),
+            "Return value register required, but has been reserved."});
+
       Chain = DAG.getCopyToReg(Chain, DL, RegLo, Lo, Glue);
       Glue = Chain.getValue(1);
       RetOps.push_back(DAG.getRegister(RegLo, MVT::i32));
@@ -2402,6 +2422,11 @@
       Val = convertValVTToLocVT(DAG, Val, VA, DL);
       Chain = DAG.getCopyToReg(Chain, DL, VA.getLocReg(), Val, Glue);
 
+      if (STI.isRegisterReservedByUser(VA.getLocReg()))
+        MF.getFunction().getContext().diagnose(DiagnosticInfoUnsupported{
+            MF.getFunction(),
+            "Return value register required, but has been reserved."});
+
       // Guarantee that all emitted copies are stuck together.
       Glue = Chain.getValue(1);
       RetOps.push_back(DAG.getRegister(VA.getLocReg(), VA.getLocVT()));
@@ -2440,6 +2465,19 @@
   return DAG.getNode(RISCVISD::RET_FLAG, DL, MVT::Other, RetOps);
 }
 
+void RISCVTargetLowering::validateCCReservedRegs(
+    const SmallVectorImpl<std::pair<llvm::Register, llvm::SDValue>> &Regs,
+    MachineFunction &MF) const {
+  const Function &F = MF.getFunction();
+  const RISCVSubtarget &STI = MF.getSubtarget<RISCVSubtarget>();
+
+  if (std::any_of(std::begin(Regs), std::end(Regs), [&STI](auto Reg) {
+        return STI.isRegisterReservedByUser(Reg.first);
+      }))
+    F.getContext().diagnose(DiagnosticInfoUnsupported{
+        F, "Argument register required, but has been reserved."});
+}
+
 const char *RISCVTargetLowering::getTargetNodeName(unsigned Opcode) const {
   switch ((RISCVISD::NodeType)Opcode) {
   case RISCVISD::FIRST_NUMBER:
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.h b/llvm/lib/Target/RISCV/RISCVISelLowering.h
index 18fc735..0d2d14e 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.h
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.h
@@ -210,6 +210,12 @@
                                    Value *AlignedAddr, Value *CmpVal,
                                    Value *NewVal, Value *Mask,
                                    AtomicOrdering Ord) const override;
+
+  /// Generate error diagnostics if any register used by CC has been marked
+  /// reserved.
+  void validateCCReservedRegs(
+      const SmallVectorImpl<std::pair<llvm::Register, llvm::SDValue>> &Regs,
+      MachineFunction &MF) const;
 };
 }
 
diff --git a/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp b/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
index 6655768..65a7e41 100644
--- a/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
@@ -69,6 +69,12 @@
   const TargetFrameLowering *TFI = getFrameLowering(MF);
   BitVector Reserved(getNumRegs());
 
+  // Mark any registers requested to be reserved as such
+  for (size_t Reg = 0; Reg < getNumRegs(); Reg++) {
+    if (MF.getSubtarget<RISCVSubtarget>().isRegisterReservedByUser(Reg))
+      markSuperRegs(Reserved, Reg);
+  }
+
   // Use markSuperRegs to ensure any register aliases are also reserved
   markSuperRegs(Reserved, RISCV::X0); // zero
   markSuperRegs(Reserved, RISCV::X1); // ra
@@ -81,6 +87,11 @@
   return Reserved;
 }
 
+bool RISCVRegisterInfo::isAsmClobberable(const MachineFunction &MF,
+                                         unsigned PhysReg) const {
+  return !MF.getSubtarget<RISCVSubtarget>().isRegisterReservedByUser(PhysReg);
+}
+
 bool RISCVRegisterInfo::isConstantPhysReg(unsigned PhysReg) const {
   return PhysReg == RISCV::X0;
 }
diff --git a/llvm/lib/Target/RISCV/RISCVRegisterInfo.h b/llvm/lib/Target/RISCV/RISCVRegisterInfo.h
index 56a50fe..30b6395 100644
--- a/llvm/lib/Target/RISCV/RISCVRegisterInfo.h
+++ b/llvm/lib/Target/RISCV/RISCVRegisterInfo.h
@@ -30,6 +30,8 @@
   const MCPhysReg *getCalleeSavedRegs(const MachineFunction *MF) const override;
 
   BitVector getReservedRegs(const MachineFunction &MF) const override;
+  bool isAsmClobberable(const MachineFunction &MF,
+                        unsigned PhysReg) const override;
 
   bool isConstantPhysReg(unsigned PhysReg) const override;
 
diff --git a/llvm/lib/Target/RISCV/RISCVSubtarget.cpp b/llvm/lib/Target/RISCV/RISCVSubtarget.cpp
index f114c6a..83e7e2d 100644
--- a/llvm/lib/Target/RISCV/RISCVSubtarget.cpp
+++ b/llvm/lib/Target/RISCV/RISCVSubtarget.cpp
@@ -50,6 +50,7 @@
 RISCVSubtarget::RISCVSubtarget(const Triple &TT, StringRef CPU, StringRef FS,
                                StringRef ABIName, const TargetMachine &TM)
     : RISCVGenSubtargetInfo(TT, CPU, FS),
+      UserReservedRegister(RISCV::NUM_TARGET_REGS),
       FrameLowering(initializeSubtargetDependencies(TT, CPU, FS, ABIName)),
       InstrInfo(*this), RegInfo(getHwMode()), TLInfo(TM, *this) {
   CallLoweringInfo.reset(new RISCVCallLowering(*getTargetLowering()));
diff --git a/llvm/lib/Target/RISCV/RISCVSubtarget.h b/llvm/lib/Target/RISCV/RISCVSubtarget.h
index 7d0373a..605d4ab 100644
--- a/llvm/lib/Target/RISCV/RISCVSubtarget.h
+++ b/llvm/lib/Target/RISCV/RISCVSubtarget.h
@@ -46,6 +46,7 @@
   unsigned XLen = 32;
   MVT XLenVT = MVT::i32;
   RISCVABI::ABI TargetABI = RISCVABI::ABI_Unknown;
+  BitVector UserReservedRegister;
   RISCVFrameLowering FrameLowering;
   RISCVInstrInfo InstrInfo;
   RISCVRegisterInfo RegInfo;
@@ -93,6 +94,10 @@
   MVT getXLenVT() const { return XLenVT; }
   unsigned getXLen() const { return XLen; }
   RISCVABI::ABI getTargetABI() const { return TargetABI; }
+  bool isRegisterReservedByUser(Register i) const {
+    assert(i < RISCV::NUM_TARGET_REGS && "Register out of range");
+    return UserReservedRegister[i];
+  }
 
 protected:
   // GlobalISel related APIs.
diff --git a/llvm/test/CodeGen/RISCV/reserved-reg-errors.ll b/llvm/test/CodeGen/RISCV/reserved-reg-errors.ll
new file mode 100644
index 0000000..f10ef9a
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/reserved-reg-errors.ll
@@ -0,0 +1,36 @@
+; RUN: not llc -mtriple=riscv32 -mattr=+reserve-x1 < %s 2>&1 | FileCheck %s -check-prefix=X1
+; RUN: not llc -mtriple=riscv64 -mattr=+reserve-x1 < %s 2>&1 | FileCheck %s -check-prefix=X1
+; RUN: not llc -mtriple=riscv32 -mattr=+reserve-x2 < %s 2>&1 | FileCheck %s -check-prefix=X2
+; RUN: not llc -mtriple=riscv64 -mattr=+reserve-x2 < %s 2>&1 | FileCheck %s -check-prefix=X2
+; RUN: not llc -mtriple=riscv32 -mattr=+reserve-x8 < %s 2>&1 | FileCheck %s -check-prefix=X8
+; RUN: not llc -mtriple=riscv64 -mattr=+reserve-x8 < %s 2>&1 | FileCheck %s -check-prefix=X8
+; RUN: not llc -mtriple=riscv32 -mattr=+reserve-x10 < %s 2>&1 | FileCheck %s -check-prefix=X10
+; RUN: not llc -mtriple=riscv64 -mattr=+reserve-x10 < %s 2>&1 | FileCheck %s -check-prefix=X10
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x11 < %s 2>&1 | FileCheck %s -check-prefix=X11
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x11 < %s 2>&1 | FileCheck %s -check-prefix=X11
+; RUN: llc -mtriple=riscv32 <%s
+; RUN: llc -mtriple=riscv64 <%s
+
+; This tests combinations when we would expect an error to be produced because
+; a reserved register is required by the default ABI. The final test checks no
+; errors are produced when no registers are reserved.
+
+define i32 @caller(i32 %a) #0 {
+; X1: in function caller {{.*}} Return address register required, but has been reserved.
+; X2: in function caller {{.*}} Stack pointer required, but has been reserved.
+; X8: in function caller {{.*}} Frame pointer required, but has been reserved.
+; X10: in function caller {{.*}} Argument register required, but has been reserved.
+; X10: in function caller {{.*}} Return value register required, but has been reserved.
+  %call = call i32 @callee(i32 0)
+  ret i32 %call
+}
+
+declare i32 @callee(i32 %a)
+
+define void @clobber() {
+; X11: warning: inline asm clobber list contains reserved registers: X11
+  call void asm sideeffect "nop", "~{x11}"()
+  ret void
+}
+
+attributes #0 = { "frame-pointer"="all" }
diff --git a/llvm/test/CodeGen/RISCV/reserved-regs.ll b/llvm/test/CodeGen/RISCV/reserved-regs.ll
new file mode 100644
index 0000000..a4d0990
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/reserved-regs.ll
@@ -0,0 +1,130 @@
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x3 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X3
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x3 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X3
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x4 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X4
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x4 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X4
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x5 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X5
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x5 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X5
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x6 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X6
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x6 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X6
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x7 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X7
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x7 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X7
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x8 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X8
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x8 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X8
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x9 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X9
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x9 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X9
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x10 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X10
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x10 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X10
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x11 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X11
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x11 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X11
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x12 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X12
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x12 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X12
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x13 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X13
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x13 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X13
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x14 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X14
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x14 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X14
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x15 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X15
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x15 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X15
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x16 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X16
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x16 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X16
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x17 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X17
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x17 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X17
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x18 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X18
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x18 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X18
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x19 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X19
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x19 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X19
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x20 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X20
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x20 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X20
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x21 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X21
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x21 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X21
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x22 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X22
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x22 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X22
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x23 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X23
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x23 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X23
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x24 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X24
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x24 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X24
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x25 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X25
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x25 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X25
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x26 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X26
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x26 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X26
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x27 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X27
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x27 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X27
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x28 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X28
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x28 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X28
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x29 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X29
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x29 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X29
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x30 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X30
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x30 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X30
+; RUN: llc -mtriple=riscv32 -mattr=+reserve-x31 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X31
+; RUN: llc -mtriple=riscv64 -mattr=+reserve-x31 -verify-machineinstrs < %s | FileCheck %s -check-prefix=X31
+
+; This program is free to use all registers, but needs a stack pointer for
+; spill values, so do not test for reserving the stack pointer.
+
+; Used to exhaust all registers
+@var = global [32 x i64] zeroinitializer
+
+define void @foo() {
+  %1 = load volatile [32 x i64], [32 x i64]* @var
+  store volatile [32 x i64] %1, [32 x i64]* @var
+
+; X3-NOT: lw gp,
+; X3-NOT: ld gp,
+; X4-NOT: lw tp,
+; X4-NOT: ld tp,
+; X5-NOT: lw t0,
+; X5-NOT: ld t0,
+; X6-NOT: lw t1,
+; X6-NOT: ld t1,
+; X7-NOT: lw t2,
+; X7-NOT: ld t2,
+; X8-NOT: lw s0,
+; X8-NOT: ld s0,
+; X9-NOT: lw s1,
+; X9-NOT: ld s1,
+; X10-NOT: lw a0,
+; X10-NOT: ld a0,
+; X11-NOT: lw a1,
+; X11-NOT: ld a1,
+; X12-NOT: lw a2,
+; X12-NOT: ld a2,
+; X13-NOT: lw a3,
+; X13-NOT: ld a3,
+; X14-NOT: lw a4,
+; X14-NOT: ld a4,
+; X15-NOT: lw a5,
+; X15-NOT: ld a5,
+; X16-NOT: lw a6,
+; X16-NOT: ld a6,
+; X17-NOT: lw a7,
+; X17-NOT: ld a7,
+; X18-NOT: lw s2,
+; X18-NOT: ld s2,
+; X19-NOT: lw s3,
+; X19-NOT: ld s3,
+; X20-NOT: lw s4,
+; X20-NOT: ld s4,
+; X21-NOT: lw s5,
+; X21-NOT: ld s5,
+; X22-NOT: lw s6,
+; X22-NOT: ld s6,
+; X23-NOT: lw s7,
+; X23-NOT: ld s7,
+; X24-NOT: lw s8,
+; X24-NOT: ld s8,
+; X25-NOT: lw s9,
+; X25-NOT: ld s9,
+; X26-NOT: lw s10,
+; X26-NOT: ld s10,
+; X27-NOT: lw s11,
+; X27-NOT: ld s11,
+; X28-NOT: lw t3,
+; X28-NOT: ld t3,
+; X29-NOT: lw t4,
+; X29-NOT: ld t4,
+; X30-NOT: lw t5,
+; X30-NOT: ld t5,
+; X31-NOT: lw t6,
+; X31-NOT: ld t6,
+
+  ret void
+}