Index: llvm/trunk/lib/Target/AArch64/AArch64.td
===================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64.td
+++ llvm/trunk/lib/Target/AArch64/AArch64.td
@@ -345,6 +345,13 @@
 def FeatureMTE : SubtargetFeature<"mte", "HasMTE",
     "true", "Enable Memory Tagging Extension" >;
 
+def FeatureTRBE : SubtargetFeature<"trbe", "HasTRBE",
+    "true", "Enable Trace Buffer Extension">;
+
+def FeatureETE : SubtargetFeature<"ete", "HasETE",
+    "true", "Enable Embedded Trace Extension",
+    [FeatureTRBE]>;
+
 //===----------------------------------------------------------------------===//
 // Architectures.
 //
@@ -772,7 +779,13 @@
                      FeatureFuseAES,
                      FeatureNEON,
                      FeaturePerfMon,
-                     FeaturePostRAScheduler
+                     FeaturePostRAScheduler,
+// ETE and TRBE are future architecture extensions. We temporariliy enable them
+// by default for users targeting generic AArch64, until it is decided in which
+// armv8.x-a architecture revision they will end up. The extensions do not
+// affect code generated by the compiler and can be used only by explicitly
+// mentioning the new system register names in assembly.
+                     FeatureETE
                      ]>;
 
 def : ProcessorModel<"cortex-a35", CortexA53Model, [ProcA35]>;
Index: llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.td
===================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.td
+++ llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.td
@@ -133,6 +133,10 @@
                        AssemblerPredicate<"FeatureBranchTargetId", "bti">;
 def HasMTE           : Predicate<"Subtarget->hasMTE()">,
                        AssemblerPredicate<"FeatureMTE", "mte">;
+def HasETE           : Predicate<"Subtarget->hasETE()">,
+                       AssemblerPredicate<"FeatureETE", "ete">;
+def HasTRBE          : Predicate<"Subtarget->hasTRBE()">,
+                       AssemblerPredicate<"FeatureTRBE", "trbe">;
 def IsLE             : Predicate<"Subtarget->isLittleEndian()">;
 def IsBE             : Predicate<"!Subtarget->isLittleEndian()">;
 def IsWindows        : Predicate<"Subtarget->isTargetWindows()">;
Index: llvm/trunk/lib/Target/AArch64/AArch64Subtarget.h
===================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64Subtarget.h
+++ llvm/trunk/lib/Target/AArch64/AArch64Subtarget.h
@@ -144,6 +144,10 @@
   bool HasSVE2SHA3 = false;
   bool HasSVE2BitPerm = false;
 
+  // Future architecture extensions.
+  bool HasETE = false;
+  bool HasTRBE = false;
+
   // HasZeroCycleRegMove - Has zero-cycle register mov instructions.
   bool HasZeroCycleRegMove = false;
 
Index: llvm/trunk/lib/Target/AArch64/AArch64SystemOperands.td
===================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64SystemOperands.td
+++ llvm/trunk/lib/Target/AArch64/AArch64SystemOperands.td
@@ -1460,6 +1460,29 @@
 def : ROSysReg<"GMID_EL1",         0b11, 0b001, 0b0000, 0b0000, 0b100>;
 } // HasMTE
 
+// Embedded Trace Extension R/W System registers
+let Requires = [{ {AArch64::FeatureETE} }] in {
+//              Name            Op0   Op1    CRn     CRm     Op2
+def : RWSysReg<"TRCRSR",        0b10, 0b001, 0b0000, 0b1010, 0b000>;
+//  TRCEXTINSELR0 has the same encoding as ETM TRCEXTINSELR
+def : RWSysReg<"TRCEXTINSELR0", 0b10, 0b001, 0b0000, 0b1000, 0b100>;
+def : RWSysReg<"TRCEXTINSELR1", 0b10, 0b001, 0b0000, 0b1001, 0b100>;
+def : RWSysReg<"TRCEXTINSELR2", 0b10, 0b001, 0b0000, 0b1010, 0b100>;
+def : RWSysReg<"TRCEXTINSELR3", 0b10, 0b001, 0b0000, 0b1011, 0b100>;
+} // FeatureETE
+
+// Trace Buffer Extension System registers
+let Requires = [{ {AArch64::FeatureTRBE} }] in {
+//                   Name       Op0   Op1    CRn     CRm     Op2
+def : RWSysReg<"TRBLIMITR_EL1", 0b11, 0b000, 0b1001, 0b1011, 0b000>;
+def : RWSysReg<"TRBPTR_EL1",    0b11, 0b000, 0b1001, 0b1011, 0b001>;
+def : RWSysReg<"TRBBASER_EL1",  0b11, 0b000, 0b1001, 0b1011, 0b010>;
+def : RWSysReg<"TRBSR_EL1",     0b11, 0b000, 0b1001, 0b1011, 0b011>;
+def : RWSysReg<"TRBMAR_EL1",    0b11, 0b000, 0b1001, 0b1011, 0b100>;
+def : RWSysReg<"TRBTRG_EL1",    0b11, 0b000, 0b1001, 0b1011, 0b110>;
+def : ROSysReg<"TRBIDR_EL1",    0b11, 0b000, 0b1001, 0b1011, 0b111>;
+} // FeatureTRBE
+
 // Cyclone specific system registers
 //                                 Op0    Op1     CRn     CRm    Op2
 let Requires = [{ {AArch64::ProcCyclone} }] in
Index: llvm/trunk/test/MC/AArch64/ete-sysregs.s
===================================================================
--- llvm/trunk/test/MC/AArch64/ete-sysregs.s
+++ llvm/trunk/test/MC/AArch64/ete-sysregs.s
@@ -0,0 +1,33 @@
+// ETE System registers
+//
+// RUN: llvm-mc -triple aarch64 -show-encoding < %s | FileCheck %s
+
+// Read from system register
+mrs x0, TRCRSR
+mrs x0, TRCEXTINSELR
+mrs x0, TRCEXTINSELR0
+mrs x0, TRCEXTINSELR1
+mrs x0, TRCEXTINSELR2
+mrs x0, TRCEXTINSELR3
+
+// CHECK: mrs x0, TRCRSR        // encoding: [0x00,0x0a,0x31,0xd5]
+// CHECK: mrs x0, TRCEXTINSELR  // encoding: [0x80,0x08,0x31,0xd5]
+// CHECK: mrs x0, TRCEXTINSELR  // encoding: [0x80,0x08,0x31,0xd5]
+// CHECK: mrs x0, TRCEXTINSELR1 // encoding: [0x80,0x09,0x31,0xd5]
+// CHECK: mrs x0, TRCEXTINSELR2 // encoding: [0x80,0x0a,0x31,0xd5]
+// CHECK: mrs x0, TRCEXTINSELR3 // encoding: [0x80,0x0b,0x31,0xd5]
+
+// Write to system register
+msr TRCRSR, x0
+msr TRCEXTINSELR,  x0
+msr TRCEXTINSELR0, x0
+msr TRCEXTINSELR1, x0
+msr TRCEXTINSELR2, x0
+msr TRCEXTINSELR3, x0
+
+// CHECK: msr TRCRSR, x0        // encoding: [0x00,0x0a,0x11,0xd5]
+// CHECK: msr TRCEXTINSELR,  x0 // encoding: [0x80,0x08,0x11,0xd5]
+// CHECK: msr TRCEXTINSELR,  x0 // encoding: [0x80,0x08,0x11,0xd5]
+// CHECK: msr TRCEXTINSELR1, x0 // encoding: [0x80,0x09,0x11,0xd5]
+// CHECK: msr TRCEXTINSELR2, x0 // encoding: [0x80,0x0a,0x11,0xd5]
+// CHECK: msr TRCEXTINSELR3, x0 // encoding: [0x80,0x0b,0x11,0xd5]
Index: llvm/trunk/test/MC/AArch64/trbe-sysreg-diag.s
===================================================================
--- llvm/trunk/test/MC/AArch64/trbe-sysreg-diag.s
+++ llvm/trunk/test/MC/AArch64/trbe-sysreg-diag.s
@@ -0,0 +1,9 @@
+// TRBE RO System register
+//
+// RUN: not llvm-mc -triple aarch64 -show-encoding < %s 2>&1 | FileCheck %s
+
+// Write to system register
+msr TRBIDR_EL1, x0
+
+// CHECK:      expected writable system register or pstate
+// CHECK-NEXT: msr TRBIDR_EL1, x0
Index: llvm/trunk/test/MC/AArch64/trbe-sysreg.s
===================================================================
--- llvm/trunk/test/MC/AArch64/trbe-sysreg.s
+++ llvm/trunk/test/MC/AArch64/trbe-sysreg.s
@@ -0,0 +1,35 @@
+// TRBE System registers
+//
+// RUN:     llvm-mc -triple aarch64 -show-encoding < %s      | FileCheck %s
+
+// Read from system register
+mrs x0, TRBLIMITR_EL1
+mrs x0, TRBPTR_EL1
+mrs x0, TRBBASER_EL1
+mrs x0, TRBSR_EL1
+mrs x0, TRBMAR_EL1
+mrs x0, TRBTRG_EL1
+mrs x0, TRBIDR_EL1
+
+// CHECK: mrs x0, TRBLIMITR_EL1 // encoding: [0x00,0x9b,0x38,0xd5]
+// CHECK: mrs x0, TRBPTR_EL1    // encoding: [0x20,0x9b,0x38,0xd5]
+// CHECK: mrs x0, TRBBASER_EL1  // encoding: [0x40,0x9b,0x38,0xd5]
+// CHECK: mrs x0, TRBSR_EL1     // encoding: [0x60,0x9b,0x38,0xd5]
+// CHECK: mrs x0, TRBMAR_EL1    // encoding: [0x80,0x9b,0x38,0xd5]
+// CHECK: mrs x0, TRBTRG_EL1    // encoding: [0xc0,0x9b,0x38,0xd5]
+// CHECK: mrs x0, TRBIDR_EL1    // encoding: [0xe0,0x9b,0x38,0xd5]
+
+// Write to system register
+msr TRBLIMITR_EL1, x0
+msr TRBPTR_EL1, x0
+msr TRBBASER_EL1, x0
+msr TRBSR_EL1, x0
+msr TRBMAR_EL1, x0
+msr TRBTRG_EL1, x0
+
+// CHECK: msr TRBLIMITR_EL1, x0 // encoding: [0x00,0x9b,0x18,0xd5]
+// CHECK: msr TRBPTR_EL1, x0    // encoding: [0x20,0x9b,0x18,0xd5]
+// CHECK: msr TRBBASER_EL1, x0  // encoding: [0x40,0x9b,0x18,0xd5]
+// CHECK: msr TRBSR_EL1, x0     // encoding: [0x60,0x9b,0x18,0xd5]
+// CHECK: msr TRBMAR_EL1, x0    // encoding: [0x80,0x9b,0x18,0xd5]
+// CHECK: msr TRBTRG_EL1, x0    // encoding: [0xc0,0x9b,0x18,0xd5]
Index: llvm/trunk/test/MC/Disassembler/AArch64/ete.txt
===================================================================
--- llvm/trunk/test/MC/Disassembler/AArch64/ete.txt
+++ llvm/trunk/test/MC/Disassembler/AArch64/ete.txt
@@ -0,0 +1,36 @@
+# ETE System registers
+#
+# RUN: llvm-mc -triple aarch64             -disassemble < %s | FileCheck %s
+
+# Read from system register
+[0x00,0x0a,0x31,0xd5]
+# CHECK:   mrs x0, TRCRSR
+
+[0x80,0x08,0x31,0xd5]
+# CHECK:   mrs x0, TRCEXTINSELR
+
+[0x80,0x09,0x31,0xd5]
+# CHECK:   mrs x0, TRCEXTINSELR1
+
+[0x80,0x0a,0x31,0xd5]
+# CHECK:   mrs x0, TRCEXTINSELR2
+
+[0x80,0x0b,0x31,0xd5]
+# CHECK:  mrs x0, TRCEXTINSELR3
+
+
+# Write to system register
+[0x00,0x0a,0x11,0xd5]
+# CHECK:   msr TRCRSR, x0
+
+[0x80,0x08,0x11,0xd5]
+# CHECK:   msr TRCEXTINSELR, x0
+
+[0x80,0x09,0x11,0xd5]
+# CHECK:   msr TRCEXTINSELR1, x0
+
+[0x80,0x0a,0x11,0xd5]
+# CHECK:   msr TRCEXTINSELR2, x0
+
+[0x80,0x0b,0x11,0xd5]
+# CHECK:   msr TRCEXTINSELR3, x0
Index: llvm/trunk/test/MC/Disassembler/AArch64/trbe.txt
===================================================================
--- llvm/trunk/test/MC/Disassembler/AArch64/trbe.txt
+++ llvm/trunk/test/MC/Disassembler/AArch64/trbe.txt
@@ -0,0 +1,35 @@
+# TRBE System registers
+#
+# RUN: llvm-mc -triple aarch64 -disassemble < %s | FileCheck %s
+
+# Read from system register
+[0x00,0x9b,0x38,0xd5]
+[0x20,0x9b,0x38,0xd5]
+[0x40,0x9b,0x38,0xd5]
+[0x60,0x9b,0x38,0xd5]
+[0x80,0x9b,0x38,0xd5]
+[0xc0,0x9b,0x38,0xd5]
+[0xe0,0x9b,0x38,0xd5]
+
+# CHECK: mrs x0, TRBLIMITR_EL1
+# CHECK: mrs x0, TRBPTR_EL1
+# CHECK: mrs x0, TRBBASER_EL1
+# CHECK: mrs x0, TRBSR_EL1
+# CHECK: mrs x0, TRBMAR_EL1
+# CHECK: mrs x0, TRBTRG_EL1
+# CHECK: mrs x0, TRBIDR_EL1
+
+# Write to system register
+[0x00,0x9b,0x18,0xd5]
+[0x20,0x9b,0x18,0xd5]
+[0x40,0x9b,0x18,0xd5]
+[0x60,0x9b,0x18,0xd5]
+[0x80,0x9b,0x18,0xd5]
+[0xc0,0x9b,0x18,0xd5]
+
+# CHECK: msr TRBLIMITR_EL1, x0
+# CHECK: msr TRBPTR_EL1, x0
+# CHECK: msr TRBBASER_EL1, x0
+# CHECK: msr TRBSR_EL1, x0
+# CHECK: msr TRBMAR_EL1, x0
+# CHECK: msr TRBTRG_EL1, x0