[X86] Move HasNOPL to a subtarget feature bit. Plumb MCSubtargetInfo through the MCAsmBackend constructor

[craig.topper]

Summary

After D41349, we can no get a MCSubtargetInfo into the MCAsmBackend constructor. This allows us to get NOPL from a subtarget feature rather than a CPU name blacklist.

[RKSimon]

Nice, I was half way through doing this myself....

PR22965 needs addressing as well - instead of driving off the silvermont feature bit - do we need a 'PreferNop15' feature bit for AMD (fam15/fam16/ryzen) and possibly recent Intel (???) targets and otherwise use 11 byte NOPs?

[craig.topper]

Limit NOP length to 10 on everything but AMD fam 16h and 17h. @RKSimon you mentioned fam 15h in your previous update, but the optimization manual I found for fam 15h only talks about 11 byte.

We could maybe go to 11 instead of 10. But Intel documentation only lists out to 9 bytes. And the current 10-15 byte sequences we do are different than the 10-15 byte sequences in AMD's manual. We use a CS prefix that's not mentioned in the optimization manuals. The CS prefix does appear in the binutils 10 byte sequence. I believe binutils stops at 10 bytes for all CPUs.

[RKSimon]

In D41721#967576, @craig.topper wrote:

Limit NOP length to 10 on everything but AMD fam 16h and 17h. @RKSimon you mentioned fam 15h in your previous update, but the optimization manual I found for fam 15h only talks about 11 byte.

Yes, I think you're right - the fam15 sog says 3 prefix bytes are the max to avoid a decode stall, so 11 bytes should be the limit, but going to just 10 bytes is probably OK. Sorry I was going off a comment in PR22965 without rechecking.

We could maybe go to 11 instead of 10. But Intel documentation only lists out to 9 bytes. And the current 10-15 byte sequences we do are different than the 10-15 byte sequences in AMD's manual. We use a CS prefix that's not mentioned in the optimization manuals. The CS prefix does appear in the binutils 10 byte sequence. I believe binutils stops at 10 bytes for all CPUs.

If we're limiting the 11-15 byte options to the AMD targets, I think it'd be better to follow their recommendations (which luckily are the same in both the 16h and 17h sogs).

I feel guilty for asking for this change as it looks like the max nop length change should be part of a separate patch as it might have performance effects that need reviewing.

@andreadb @pcordes do you have any suggestions?

[craig.topper]

Should I go back to my first patch that just does the plumbing for now?

[RKSimon]

In D41721#969305, @craig.topper wrote:

Should I go back to my first patch that just does the plumbing for now?

Yes please, and split off the NOP length changes to a seperate patch to allow for regression tests. That way I think this patch should have no effect on codegen and is just a cleanup?

[craig.topper]

Revert back to previous version of the patch which should be NFC

[RKSimon]

LGTM - thanks.

lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp

 class X86ELFObjectWriter : public MCELFObjectTargetWriter {
 public:
   X86ELFObjectWriter(bool is64Bit, uint8_t OSABI, uint16_t EMachine,
                      bool HasRelocationAddend, bool foobar)
     : MCELFObjectTargetWriter(is64Bit, OSABI, EMachine, HasRelocationAddend) {}
 };
 
 class X86AsmBackend : public MCAsmBackend {
-  const StringRef CPU;
-  bool HasNopl;
-  const uint64_t MaxNopLength;
-public:
-  X86AsmBackend(const Target &T, StringRef CPU)
-      : MCAsmBackend(), CPU(CPU),
-        MaxNopLength((CPU == "slm" || CPU == "silvermont") ? 7 : 15) {
-    HasNopl = CPU != "generic" && CPU != "i386" && CPU != "i486" &&
-              CPU != "i586" && CPU != "pentium" && CPU != "pentium-mmx" &&
-              CPU != "i686" && CPU != "k6" && CPU != "k6-2" && CPU != "k6-3" &&
-              CPU != "geode" && CPU != "winchip-c6" && CPU != "winchip2" &&
-              CPU != "c3" && CPU != "c3-2" && CPU != "lakemont" && CPU != "";
-  }
+  const MCSubtargetInfo &STI;
+public:
+  X86AsmBackend(const Target &T, const MCSubtargetInfo &STI)
+      : MCAsmBackend(), STI(STI) {}
 
   unsigned getNumFixupKinds() const override {
     return X86::NumTargetFixupKinds;
   }
 
   const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override {
     const static MCFixupKindInfo Infos[X86::NumTargetFixupKinds] = {
         {"reloc_riprel_4byte", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
static const uint8_t Nops[10][10] = {
     {0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00},
     // nopw 0L(%[re]ax,%[re]ax,1)
     {0x66, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00},
     // nopw %cs:0L(%[re]ax,%[re]ax,1)
     {0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00},
   };
 
   // This CPU doesn't support long nops. If needed add more.
-  // FIXME: Can we get this from the subtarget somehow?
   // FIXME: We could generated something better than plain 0x90.
-  if (!HasNopl) {
+  if (!STI.getFeatureBits()[X86::FeatureNOPL]) {
     for (uint64_t i = 0; i < Count; ++i)
       OW->write8(0x90);
     return true;
   }
 
+  uint64_t MaxNopLength = STI.getFeatureBits()[X86::ProcIntelSLM] ? 7 : 15;
+
   // 15 is the longest single nop instruction.  Emit as many 15-byte nops as
   // needed, then emit a nop of the remaining length.
   do {
     const uint8_t ThisNopLength = (uint8_t) std::min(Count, MaxNopLength);
     const uint8_t Prefixes = ThisNopLength <= 10 ? 0 : ThisNopLength - 10;
     for (uint8_t i = 0; i < Prefixes; i++)
       OW->write8(0x66);
     const uint8_t Rest = ThisNopLength - Prefixes;
     for (uint8_t i = 0; i < Rest; i++)
       OW->write8(Nops[Rest - 1][i]);
     Count -= ThisNopLength;
   } while (Count != 0);
 
   return true;
 }
 
 /* *** */
 
 namespace {
 
 class ELFX86AsmBackend : public X86AsmBackend {
 public:
   uint8_t OSABI;
-  ELFX86AsmBackend(const Target &T, uint8_t OSABI, StringRef CPU)
-      : X86AsmBackend(T, CPU), OSABI(OSABI) {}
+  ELFX86AsmBackend(const Target &T, uint8_t OSABI, const MCSubtargetInfo &STI)
+      : X86AsmBackend(T, STI), OSABI(OSABI) {}
 };
 
 class ELFX86_32AsmBackend : public ELFX86AsmBackend {
 public:
-  ELFX86_32AsmBackend(const Target &T, uint8_t OSABI, StringRef CPU)
-    : ELFX86AsmBackend(T, OSABI, CPU) {}
+  ELFX86_32AsmBackend(const Target &T, uint8_t OSABI,
+                      const MCSubtargetInfo &STI)
+    : ELFX86AsmBackend(T, OSABI, STI) {}
 
   std::unique_ptr<MCObjectWriter>
   createObjectWriter(raw_pwrite_stream &OS) const override {
     return createX86ELFObjectWriter(OS, /*IsELF64*/ false, OSABI, ELF::EM_386);
   }
 };
 
 class ELFX86_X32AsmBackend : public ELFX86AsmBackend {
 public:
-  ELFX86_X32AsmBackend(const Target &T, uint8_t OSABI, StringRef CPU)
-      : ELFX86AsmBackend(T, OSABI, CPU) {}
+  ELFX86_X32AsmBackend(const Target &T, uint8_t OSABI,
+                       const MCSubtargetInfo &STI)
+      : ELFX86AsmBackend(T, OSABI, STI) {}
 
   std::unique_ptr<MCObjectWriter>
   createObjectWriter(raw_pwrite_stream &OS) const override {
     return createX86ELFObjectWriter(OS, /*IsELF64*/ false, OSABI,
                                     ELF::EM_X86_64);
   }
 };
 
 class ELFX86_IAMCUAsmBackend : public ELFX86AsmBackend {
 public:
-  ELFX86_IAMCUAsmBackend(const Target &T, uint8_t OSABI, StringRef CPU)
-      : ELFX86AsmBackend(T, OSABI, CPU) {}
+  ELFX86_IAMCUAsmBackend(const Target &T, uint8_t OSABI,
+                         const MCSubtargetInfo &STI)
+      : ELFX86AsmBackend(T, OSABI, STI) {}
 
   std::unique_ptr<MCObjectWriter>
   createObjectWriter(raw_pwrite_stream &OS) const override {
     return createX86ELFObjectWriter(OS, /*IsELF64*/ false, OSABI,
                                     ELF::EM_IAMCU);
   }
 };
 
 class ELFX86_64AsmBackend : public ELFX86AsmBackend {
 public:
-  ELFX86_64AsmBackend(const Target &T, uint8_t OSABI, StringRef CPU)
-    : ELFX86AsmBackend(T, OSABI, CPU) {}
+  ELFX86_64AsmBackend(const Target &T, uint8_t OSABI,
+                      const MCSubtargetInfo &STI)
+    : ELFX86AsmBackend(T, OSABI, STI) {}
 
   std::unique_ptr<MCObjectWriter>
   createObjectWriter(raw_pwrite_stream &OS) const override {
     return createX86ELFObjectWriter(OS, /*IsELF64*/ true, OSABI, ELF::EM_X86_64);
   }
 };
 
 class WindowsX86AsmBackend : public X86AsmBackend {
   bool Is64Bit;
 
 public:
-  WindowsX86AsmBackend(const Target &T, bool is64Bit, StringRef CPU)
-    : X86AsmBackend(T, CPU)
+  WindowsX86AsmBackend(const Target &T, bool is64Bit,
+                       const MCSubtargetInfo &STI)
+    : X86AsmBackend(T, STI)
     , Is64Bit(is64Bit) {
   }
 
   Optional<MCFixupKind> getFixupKind(StringRef Name) const override {
     return StringSwitch<Optional<MCFixupKind>>(Name)
         .Case("dir32", FK_Data_4)
         .Case("secrel32", FK_SecRel_4)
         .Case("secidx", FK_SecRel_2)
uint32_t encodeCompactUnwindRegistersWithoutFrame(unsigned RegCount) const {
     }
 
     assert((permutationEncoding & 0x3FF) == permutationEncoding &&
            "Invalid compact register encoding!");
     return permutationEncoding;
   }
 
 public:
-  DarwinX86AsmBackend(const Target &T, const MCRegisterInfo &MRI, StringRef CPU,
-                      bool Is64Bit)
-    : X86AsmBackend(T, CPU), MRI(MRI), Is64Bit(Is64Bit) {
+  DarwinX86AsmBackend(const Target &T, const MCRegisterInfo &MRI,
+                      const MCSubtargetInfo &STI, bool Is64Bit)
+    : X86AsmBackend(T, STI), MRI(MRI), Is64Bit(Is64Bit) {
     memset(SavedRegs, 0, sizeof(SavedRegs));
     OffsetSize = Is64Bit ? 8 : 4;
     MoveInstrSize = Is64Bit ? 3 : 2;
     StackDivide = Is64Bit ? 8 : 4;
   }
 };
 
 class DarwinX86_32AsmBackend : public DarwinX86AsmBackend {
 public:
   DarwinX86_32AsmBackend(const Target &T, const MCRegisterInfo &MRI,
-                         StringRef CPU)
-      : DarwinX86AsmBackend(T, MRI, CPU, false) {}
+                         const MCSubtargetInfo &STI)
+      : DarwinX86AsmBackend(T, MRI, STI, false) {}
 
   std::unique_ptr<MCObjectWriter>
   createObjectWriter(raw_pwrite_stream &OS) const override {
     return createX86MachObjectWriter(OS, /*Is64Bit=*/false,
                                      MachO::CPU_TYPE_I386,
                                      MachO::CPU_SUBTYPE_I386_ALL);
   }
 
   /// \brief Generate the compact unwind encoding for the CFI instructions.
   uint32_t generateCompactUnwindEncoding(
                              ArrayRef<MCCFIInstruction> Instrs) const override {
     return generateCompactUnwindEncodingImpl(Instrs);
   }
 };
 
 class DarwinX86_64AsmBackend : public DarwinX86AsmBackend {
   const MachO::CPUSubTypeX86 Subtype;
 public:
   DarwinX86_64AsmBackend(const Target &T, const MCRegisterInfo &MRI,
-                         StringRef CPU, MachO::CPUSubTypeX86 st)
-      : DarwinX86AsmBackend(T, MRI, CPU, true), Subtype(st) {}
+                         const MCSubtargetInfo &STI, MachO::CPUSubTypeX86 st)
+      : DarwinX86AsmBackend(T, MRI, STI, true), Subtype(st) {}
 
   std::unique_ptr<MCObjectWriter>
   createObjectWriter(raw_pwrite_stream &OS) const override {
     return createX86MachObjectWriter(OS, /*Is64Bit=*/true,
                                      MachO::CPU_TYPE_X86_64, Subtype);
   }
 
   /// \brief Generate the compact unwind encoding for the CFI instructions.
   uint32_t generateCompactUnwindEncoding(
                              ArrayRef<MCCFIInstruction> Instrs) const override {
     return generateCompactUnwindEncodingImpl(Instrs);
   }
 };
 
 } // end anonymous namespace
 
 MCAsmBackend *llvm::createX86_32AsmBackend(const Target &T,
                                            const MCSubtargetInfo &STI,
                                            const MCRegisterInfo &MRI,
                                            const MCTargetOptions &Options) {
   const Triple &TheTriple = STI.getTargetTriple();
-  StringRef CPU = STI.getCPU();
   if (TheTriple.isOSBinFormatMachO())
-    return new DarwinX86_32AsmBackend(T, MRI, CPU);
+    return new DarwinX86_32AsmBackend(T, MRI, STI);
 
   if (TheTriple.isOSWindows() && TheTriple.isOSBinFormatCOFF())
-    return new WindowsX86AsmBackend(T, false, CPU);
+    return new WindowsX86AsmBackend(T, false, STI);
 
   uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
 
   if (TheTriple.isOSIAMCU())
-    return new ELFX86_IAMCUAsmBackend(T, OSABI, CPU);
+    return new ELFX86_IAMCUAsmBackend(T, OSABI, STI);
 
-  return new ELFX86_32AsmBackend(T, OSABI, CPU);
+  return new ELFX86_32AsmBackend(T, OSABI, STI);
 }
 
 MCAsmBackend *llvm::createX86_64AsmBackend(const Target &T,
                                            const MCSubtargetInfo &STI,
                                            const MCRegisterInfo &MRI,
                                            const MCTargetOptions &Options) {
   const Triple &TheTriple = STI.getTargetTriple();
-  StringRef CPU = STI.getCPU();
   if (TheTriple.isOSBinFormatMachO()) {
     MachO::CPUSubTypeX86 CS =
         StringSwitch<MachO::CPUSubTypeX86>(TheTriple.getArchName())
             .Case("x86_64h", MachO::CPU_SUBTYPE_X86_64_H)
             .Default(MachO::CPU_SUBTYPE_X86_64_ALL);
-    return new DarwinX86_64AsmBackend(T, MRI, CPU, CS);
+    return new DarwinX86_64AsmBackend(T, MRI, STI, CS);
   }
 
   if (TheTriple.isOSWindows() && TheTriple.isOSBinFormatCOFF())
-    return new WindowsX86AsmBackend(T, true, CPU);
+    return new WindowsX86AsmBackend(T, true, STI);
 
   uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
 
   if (TheTriple.getEnvironment() == Triple::GNUX32)
-    return new ELFX86_X32AsmBackend(T, OSABI, CPU);
-  return new ELFX86_64AsmBackend(T, OSABI, CPU);
+    return new ELFX86_X32AsmBackend(T, OSABI, STI);
+  return new ELFX86_64AsmBackend(T, OSABI, STI);
 }

lib/Target/X86/X86.td

 
 //===----------------------------------------------------------------------===//
 // X86 Subtarget features
 //===----------------------------------------------------------------------===//
 
 def FeatureX87     : SubtargetFeature<"x87","HasX87", "true",
                                       "Enable X87 float instructions">;
 
+def FeatureNOPL    : SubtargetFeature<"nopl", "HasNOPL", "true",
+                                      "Enable NOPL instruction">;
+
 def FeatureCMOV    : SubtargetFeature<"cmov","HasCMov", "true",
                                       "Enable conditional move instructions">;
 
 def FeaturePOPCNT   : SubtargetFeature<"popcnt", "HasPOPCNT", "true",
                                        "Support POPCNT instruction">;
 
 def FeatureFXSR    : SubtargetFeature<"fxsr", "HasFXSR", "true",
                                       "Support fxsave/fxrestore instructions">;

 
 def : Proc<"generic",         [FeatureX87, FeatureSlowUAMem16]>;
 def : Proc<"i386",            [FeatureX87, FeatureSlowUAMem16]>;
 def : Proc<"i486",            [FeatureX87, FeatureSlowUAMem16]>;
 def : Proc<"i586",            [FeatureX87, FeatureSlowUAMem16]>;
 def : Proc<"pentium",         [FeatureX87, FeatureSlowUAMem16]>;
 def : Proc<"pentium-mmx",     [FeatureX87, FeatureSlowUAMem16, FeatureMMX]>;
 
-foreach P = ["i686", "pentiumpro"] in {
-  def : Proc<P, [FeatureX87, FeatureSlowUAMem16, FeatureCMOV]>;
-}
+def : Proc<"i686", [FeatureX87, FeatureSlowUAMem16, FeatureCMOV]>;
+def : Proc<"pentiumpro", [FeatureX87, FeatureSlowUAMem16, FeatureCMOV,
+                          FeatureNOPL]>;
 
 def : Proc<"pentium2",        [FeatureX87, FeatureSlowUAMem16, FeatureMMX,
-                               FeatureCMOV, FeatureFXSR]>;
+                               FeatureCMOV, FeatureFXSR, FeatureNOPL]>;
 
 foreach P = ["pentium3", "pentium3m"] in {
   def : Proc<P, [FeatureX87, FeatureSlowUAMem16, FeatureMMX, FeatureSSE1,
-                 FeatureFXSR]>;
+                 FeatureFXSR, FeatureNOPL]>;
 }
 
 // Enable the PostRAScheduler for SSE2 and SSE3 class cpus.
 // The intent is to enable it for pentium4 which is the current default
 // processor in a vanilla 32-bit clang compilation when no specific
 // architecture is specified.  This generally gives a nice performance
 // increase on silvermont, with largely neutral behavior on other
 // contemporary large core processors.
 // pentium-m, pentium4m, prescott and nocona are included as a preventative
 // measure to avoid performance surprises, in case clang's default cpu
 // changes slightly.
 
 def : ProcessorModel<"pentium-m", GenericPostRAModel,
                      [FeatureX87, FeatureSlowUAMem16, FeatureMMX,
-                      FeatureSSE2, FeatureFXSR]>;
+                      FeatureSSE2, FeatureFXSR, FeatureNOPL]>;
 
 foreach P = ["pentium4", "pentium4m"] in {
   def : ProcessorModel<P, GenericPostRAModel,
                        [FeatureX87, FeatureSlowUAMem16, FeatureMMX,
-                        FeatureSSE2, FeatureFXSR]>;
+                        FeatureSSE2, FeatureFXSR, FeatureNOPL]>;
 }
 
 // Intel Quark.
 def : Proc<"lakemont",        []>;
 
 // Intel Core Duo.
 def : ProcessorModel<"yonah", SandyBridgeModel,
                      [FeatureX87, FeatureSlowUAMem16, FeatureMMX, FeatureSSE3,
-                      FeatureFXSR]>;
+                      FeatureFXSR, FeatureNOPL]>;
 
 // NetBurst.
 def : ProcessorModel<"prescott", GenericPostRAModel,
                      [FeatureX87, FeatureSlowUAMem16, FeatureMMX, FeatureSSE3,
-                      FeatureFXSR]>;
+                      FeatureFXSR, FeatureNOPL]>;
 def : ProcessorModel<"nocona", GenericPostRAModel, [
   FeatureX87,
   FeatureSlowUAMem16,
   FeatureMMX,
   FeatureSSE3,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureCMPXCHG16B
 ]>;
 
 // Intel Core 2 Solo/Duo.
 def : ProcessorModel<"core2", SandyBridgeModel, [
   FeatureX87,
   FeatureSlowUAMem16,
   FeatureMMX,
   FeatureSSSE3,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureCMPXCHG16B,
   FeatureLAHFSAHF,
   FeatureMacroFusion
 ]>;
 def : ProcessorModel<"penryn", SandyBridgeModel, [
   FeatureX87,
   FeatureSlowUAMem16,
   FeatureMMX,
   FeatureSSE41,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureCMPXCHG16B,
   FeatureLAHFSAHF,
   FeatureMacroFusion
 ]>;
 
 // Atom CPUs.
 class BonnellProc<string Name> : ProcessorModel<Name, AtomModel, [
   ProcIntelAtom,
   FeatureX87,
   FeatureSlowUAMem16,
   FeatureMMX,
   FeatureSSSE3,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureCMPXCHG16B,
   FeatureMOVBE,
   FeatureLEAForSP,
   FeatureSlowDivide32,
   FeatureSlowDivide64,
   FeatureSlowTwoMemOps,
   FeatureLEAUsesAG,
   FeaturePadShortFunctions,
   FeatureLAHFSAHF
 ]>;
 def : BonnellProc<"bonnell">;
 def : BonnellProc<"atom">; // Pin the generic name to the baseline.
 
 class SilvermontProc<string Name> : ProcessorModel<Name, SLMModel, [
   ProcIntelSLM,
   FeatureX87,
   FeatureMMX,
   FeatureSSE42,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureCMPXCHG16B,
   FeatureMOVBE,
   FeaturePOPCNT,
   FeaturePCLMUL,
   FeatureAES,
   FeatureSlowDivide64,
   FeatureSlowTwoMemOps,
   FeaturePRFCHW,
   FeatureSlowLEA,
   FeatureSlowIncDec,
   FeatureSlowPMULLD,
   FeatureLAHFSAHF
 ]>;
 def : SilvermontProc<"silvermont">;
 def : SilvermontProc<"slm">; // Legacy alias.
 
 class GoldmontProc<string Name> : ProcessorModel<Name, SLMModel, [
   ProcIntelGLM,
   FeatureX87,
   FeatureMMX,
   FeatureSSE42,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureCMPXCHG16B,
   FeatureMOVBE,
   FeaturePOPCNT,
   FeaturePCLMUL,
   FeatureAES,
   FeaturePRFCHW,
   FeatureSlowTwoMemOps,
   FeatureSlowLEA,

 def : GoldmontProc<"goldmont">;
 
 // "Arrandale" along with corei3 and corei5
 class NehalemProc<string Name> : ProcessorModel<Name, SandyBridgeModel, [
   FeatureX87,
   FeatureMMX,
   FeatureSSE42,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureCMPXCHG16B,
   FeaturePOPCNT,
   FeatureLAHFSAHF,
   FeatureMacroFusion
 ]>;
 def : NehalemProc<"nehalem">;
 def : NehalemProc<"corei7">;
 
 // Westmere is a similar machine to nehalem with some additional features.
 // Westmere is the corei3/i5/i7 path from nehalem to sandybridge
 class WestmereProc<string Name> : ProcessorModel<Name, SandyBridgeModel, [
   FeatureX87,
   FeatureMMX,
   FeatureSSE42,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureCMPXCHG16B,
   FeaturePOPCNT,
   FeatureAES,
   FeaturePCLMUL,
   FeatureLAHFSAHF,
   FeatureMacroFusion
 ]>;
 def : WestmereProc<"westmere">;

 
 // SSE is not listed here since llvm treats AVX as a reimplementation of SSE,
 // rather than a superset.
 def SNBFeatures : ProcessorFeatures<[], [
   FeatureX87,
   FeatureMMX,
   FeatureAVX,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureCMPXCHG16B,
   FeaturePOPCNT,
   FeatureAES,
   FeatureSlowDivide64,
   FeaturePCLMUL,
   FeatureXSAVE,
   FeatureXSAVEOPT,
   FeatureLAHFSAHF,

 
 // AMD CPUs.
 
 def : Proc<"k6",              [FeatureX87, FeatureSlowUAMem16, FeatureMMX]>;
 def : Proc<"k6-2",            [FeatureX87, FeatureSlowUAMem16, Feature3DNow]>;
 def : Proc<"k6-3",            [FeatureX87, FeatureSlowUAMem16, Feature3DNow]>;
 
 foreach P = ["athlon", "athlon-tbird"] in {
-  def : Proc<P, [FeatureX87, FeatureSlowUAMem16, Feature3DNowA, FeatureSlowSHLD]>;
+  def : Proc<P, [FeatureX87, FeatureSlowUAMem16, Feature3DNowA,
+                 FeatureNOPL, FeatureSlowSHLD]>;
 }
 
 foreach P = ["athlon-4", "athlon-xp", "athlon-mp"] in {
   def : Proc<P, [FeatureX87, FeatureSlowUAMem16, FeatureSSE1,
-                 Feature3DNowA, FeatureFXSR, FeatureSlowSHLD]>;
+                 Feature3DNowA, FeatureFXSR, FeatureNOPL, FeatureSlowSHLD]>;
 }
 
 foreach P = ["k8", "opteron", "athlon64", "athlon-fx"] in {
   def : Proc<P, [FeatureX87, FeatureSlowUAMem16, FeatureSSE2, Feature3DNowA,
-                 FeatureFXSR, Feature64Bit, FeatureSlowSHLD]>;
+                 FeatureFXSR, FeatureNOPL, Feature64Bit, FeatureSlowSHLD]>;
 }
 
 foreach P = ["k8-sse3", "opteron-sse3", "athlon64-sse3"] in {
   def : Proc<P, [FeatureX87, FeatureSlowUAMem16, FeatureSSE3, Feature3DNowA,
-                 FeatureFXSR, FeatureCMPXCHG16B, FeatureSlowSHLD]>;
+                 FeatureFXSR, FeatureNOPL, FeatureCMPXCHG16B, FeatureSlowSHLD]>;
 }
 
 foreach P = ["amdfam10", "barcelona"] in {
   def : Proc<P, [FeatureX87, FeatureSSE4A, Feature3DNowA, FeatureFXSR,
-                 FeatureCMPXCHG16B, FeatureLZCNT, FeaturePOPCNT,
+                 FeatureNOPL, FeatureCMPXCHG16B, FeatureLZCNT, FeaturePOPCNT,
                  FeatureSlowSHLD, FeatureLAHFSAHF]>;
 }
 
 // Bobcat
 def : Proc<"btver1", [
   FeatureX87,
   FeatureMMX,
   FeatureSSSE3,
   FeatureSSE4A,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureCMPXCHG16B,
   FeaturePRFCHW,
   FeatureLZCNT,
   FeaturePOPCNT,
   FeatureSlowSHLD,
   FeatureLAHFSAHF
 ]>;
 
 // Jaguar
 def : ProcessorModel<"btver2", BtVer2Model, [
   FeatureX87,
   FeatureMMX,
   FeatureAVX,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureSSE4A,
   FeatureCMPXCHG16B,
   FeaturePRFCHW,
   FeatureAES,
   FeaturePCLMUL,
   FeatureBMI,
   FeatureF16C,
   FeatureMOVBE,
def : Proc<"bdver1", [
   FeatureFMA4,
   FeatureCMPXCHG16B,
   FeatureAES,
   FeaturePRFCHW,
   FeaturePCLMUL,
   FeatureMMX,
   FeatureAVX,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureSSE4A,
   FeatureLZCNT,
   FeaturePOPCNT,
   FeatureXSAVE,
   FeatureLWP,
   FeatureSlowSHLD,
   FeatureLAHFSAHF,
   FeatureMacroFusion
 ]>;
 // Piledriver
 def : Proc<"bdver2", [
   FeatureX87,
   FeatureXOP,
   FeatureFMA4,
   FeatureCMPXCHG16B,
   FeatureAES,
   FeaturePRFCHW,
   FeaturePCLMUL,
   FeatureMMX,
   FeatureAVX,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureSSE4A,
   FeatureF16C,
   FeatureLZCNT,
   FeaturePOPCNT,
   FeatureXSAVE,
   FeatureBMI,
   FeatureTBM,
   FeatureLWP,
def : Proc<"bdver3", [
   FeatureFMA4,
   FeatureCMPXCHG16B,
   FeatureAES,
   FeaturePRFCHW,
   FeaturePCLMUL,
   FeatureMMX,
   FeatureAVX,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureSSE4A,
   FeatureF16C,
   FeatureLZCNT,
   FeaturePOPCNT,
   FeatureXSAVE,
   FeatureBMI,
   FeatureTBM,
   FeatureLWP,
   FeatureFMA,
   FeatureXSAVEOPT,
   FeatureSlowSHLD,
   FeatureFSGSBase,
   FeatureLAHFSAHF,
   FeatureMacroFusion
 ]>;
 
 // Excavator
 def : Proc<"bdver4", [
   FeatureX87,
   FeatureMMX,
   FeatureAVX2,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureXOP,
   FeatureFMA4,
   FeatureCMPXCHG16B,
   FeatureAES,
   FeaturePRFCHW,
   FeaturePCLMUL,
   FeatureF16C,
   FeatureLZCNT,
def: ProcessorModel<"znver1", Znver1Model, [
   FeatureBMI2,
   FeatureCLFLUSHOPT,
   FeatureCLZERO,
   FeatureCMPXCHG16B,
   FeatureF16C,
   FeatureFMA,
   FeatureFSGSBase,
   FeatureFXSR,
+  FeatureNOPL,
   FeatureFastLZCNT,
   FeatureLAHFSAHF,
   FeatureLZCNT,
   FeatureMacroFusion,
   FeatureMMX,
   FeatureMOVBE,
   FeatureMWAITX,
   FeaturePCLMUL,

 // covers a huge swath of x86 processors. If there are specific scheduling
 // knobs which need to be tuned differently for AMD chips, we might consider
 // forming a common base for them.
 def : ProcessorModel<"x86-64", SandyBridgeModel, [
   FeatureX87,
   FeatureMMX,
   FeatureSSE2,
   FeatureFXSR,
+  FeatureNOPL,
   Feature64Bit,
   FeatureSlow3OpsLEA,
   FeatureSlowIncDec,
   FeatureMacroFusion
 ]>;
 
 //===----------------------------------------------------------------------===//
 // Calling Conventions

lib/Target/X86/X86Subtarget.h

protected:
   X86SSEEnum X86SSELevel;
 
   /// MMX, 3DNow, 3DNow Athlon, or none supported.
   X863DNowEnum X863DNowLevel;
 
   /// True if the processor supports X87 instructions.
   bool HasX87;
 
+  /// True if this processor has NOPL instruction
+  /// (generally pentium pro+).
+  bool HasNOPL;
+
   /// True if this processor has conditional move instructions
   /// (generally pentium pro+).
   bool HasCMov;
 
   /// True if the processor supports X86-64 instructions.
   bool HasX86_64;
 
   /// True if the processor supports POPCNT.
bool isTarget64BitLP64() const {
     return In64BitMode && (TargetTriple.getEnvironment() != Triple::GNUX32 &&
                            !TargetTriple.isOSNaCl());
   }
 
   PICStyles::Style getPICStyle() const { return PICStyle; }
   void setPICStyle(PICStyles::Style Style)  { PICStyle = Style; }
 
   bool hasX87() const { return HasX87; }
+  bool hasNOPL() const { return HasNOPL; }
   bool hasCMov() const { return HasCMov; }
   bool hasSSE1() const { return X86SSELevel >= SSE1; }
   bool hasSSE2() const { return X86SSELevel >= SSE2; }
   bool hasSSE3() const { return X86SSELevel >= SSE3; }
   bool hasSSSE3() const { return X86SSELevel >= SSSE3; }
   bool hasSSE41() const { return X86SSELevel >= SSE41; }
   bool hasSSE42() const { return X86SSELevel >= SSE42; }
   bool hasAVX() const { return X86SSELevel >= AVX; }

lib/Target/X86/X86Subtarget.cpp

void X86Subtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
   if (hasAVX512())
     ScatterOverhead = 2;
 }
 
 void X86Subtarget::initializeEnvironment() {
   X86SSELevel = NoSSE;
   X863DNowLevel = NoThreeDNow;
   HasX87 = false;
+  HasNOPL = false;
   HasCMov = false;
   HasX86_64 = false;
   HasPOPCNT = false;
   HasSSE4A = false;
   HasAES = false;
   HasVAES = false;
   HasFXSR = false;
   HasXSAVE = false;