[AArch64] Add support for the SPE-EEF feature

[pratlucas]

Summary

This is an addition to the existing Statistical Profiling extension, which
introduces an extra system register that is enabled by the new 'spe-eef'
subtarget feature.

Patch written by Simon Tatham.

[pratlucas]

Ping.

[pratlucas]

Rebasing.

[ostannard]

LGTM

llvm/lib/Target/AArch64/AArch64.td

def FeatureHCX : SubtargetFeature<
     "hcx", "HasHCX", "true", "Enable Armv8.7-A HCRX_EL2 system register">;
 
 def FeatureLS64 : SubtargetFeature<"ls64", "HasLS64",
     "true", "Enable Armv8.7-A LD64B/ST64B Accelerator Extension">;
 
 def FeatureBRBE : SubtargetFeature<"brbe", "HasBRBE",
     "true", "Enable Branch Record Buffer Extension">;
 
+def FeatureSPE_EEF : SubtargetFeature<"spe-eef", "HasSPE_EEF",
+    "true", "Enable extra register in the Statistical Profiling Extension">;
+
 def FeatureFineGrainedTraps : SubtargetFeature<"fgt", "HasFineGrainedTraps",
     "true", "Enable fine grained virtualization traps extension">;
 
 def FeatureEnhancedCounterVirtualization :
       SubtargetFeature<"ecv", "HasEnhancedCounterVirtualization",
       "true", "Enable enhanced counter virtualization extension">;
 
 //===----------------------------------------------------------------------===//

llvm/lib/Target/AArch64/AArch64InstrInfo.td

 def HasXS            : Predicate<"Subtarget->hasXS()">,
                        AssemblerPredicate<(all_of FeatureXS), "xs">;
 def HasWFxT          : Predicate<"Subtarget->hasWFxT()">,
                        AssemblerPredicate<(all_of FeatureWFxT), "wfxt">;
 def HasLS64          : Predicate<"Subtarget->hasLS64()">,
                        AssemblerPredicate<(all_of FeatureLS64), "ls64">;
 def HasBRBE          : Predicate<"Subtarget->hasBRBE()">,
                        AssemblerPredicate<(all_of FeatureBRBE), "brbe">;
+def HasSPE_EEF       : Predicate<"Subtarget->hasSPE_EEF()">,
+                       AssemblerPredicate<(all_of FeatureSPE_EEF), "spe-eef">;
 def IsLE             : Predicate<"Subtarget->isLittleEndian()">;
 def IsBE             : Predicate<"!Subtarget->isLittleEndian()">;
 def IsWindows        : Predicate<"Subtarget->isTargetWindows()">;
 def UseExperimentalZeroingPseudos
     : Predicate<"Subtarget->useExperimentalZeroingPseudos()">;
 def UseAlternateSExtLoadCVTF32
     : Predicate<"Subtarget->useAlternateSExtLoadCVTF32Pattern()">;
 

llvm/lib/Target/AArch64/AArch64Subtarget.h

protected:
   bool HasSVE2SM4 = false;
   bool HasSVE2SHA3 = false;
   bool HasSVE2BitPerm = false;
 
   // Future architecture extensions.
   bool HasETE = false;
   bool HasTRBE = false;
   bool HasBRBE = false;
+  bool HasSPE_EEF = false;
 
   // HasZeroCycleRegMove - Has zero-cycle register mov instructions.
   bool HasZeroCycleRegMove = false;
 
   // HasZeroCycleZeroing - Has zero-cycle zeroing instructions.
   bool HasZeroCycleZeroing = false;
   bool HasZeroCycleZeroingGP = false;
   bool HasZeroCycleZeroingFP = false;

llvm/lib/Target/AArch64/AArch64SystemOperands.td

 foreach n = 0-31 in {
   defvar nb = !cast<bits<5>>(n);
   def : ROSysReg<"BRBINF"#n#"_EL1", 0b10, 0b001, 0b1000, nb{3-0}, {nb{4},0b00}>;
   def : ROSysReg<"BRBSRC"#n#"_EL1", 0b10, 0b001, 0b1000, nb{3-0}, {nb{4},0b01}>;
   def : ROSysReg<"BRBTGT"#n#"_EL1", 0b10, 0b001, 0b1000, nb{3-0}, {nb{4},0b10}>;
 }
 }
 
+// Statistical Profiling Extension system register
+let Requires = [{ {AArch64::FeatureSPE_EEF} }] in
+def : RWSysReg<"PMSNEVFR_EL1",      0b11, 0b000, 0b1001, 0b1001, 0b001>;
+
 // Cyclone specific system registers
 //                                 Op0    Op1     CRn     CRm    Op2
 let Requires = [{ {AArch64::ProcAppleA7} }] in
 def : RWSysReg<"CPM_IOACC_CTL_EL3", 0b11, 0b111, 0b1111, 0b0010, 0b000>;

llvm/test/MC/AArch64/spe.s

+// RUN: llvm-mc -triple aarch64 -mattr +spe-eef -show-encoding %s 2>%t | FileCheck %s
+
+msr PMSNEVFR_EL1, x0
+mrs x1, PMSNEVFR_EL1
+// CHECK: msr     PMSNEVFR_EL1, x0        // encoding: [0x20,0x99,0x18,0xd5]
+// CHECK: mrs     x1, PMSNEVFR_EL1        // encoding: [0x21,0x99,0x38,0xd5]