Add support for CSDB in AArch64

Add support for CSDB, equivalent to hint #20, in the system instruction space.

Additionally, relax the "unallocated" identification of hint instructions that
we don't support, such that they'll now disassemble as "unimplemented (System)"
rather than "unallocated".

Change-Id: I87f8d2688f1203ca77cb717de19702cc53328e0f

9 files changed, 22 insertions, 7 deletions

diff --git a/src/aarch64/assembler-aarch64.cc b/src/aarch64/assembler-aarch64.cc
index db30811a..2606dbea 100644
--- a/src/aarch64/assembler-aarch64.cc
+++ b/src/aarch64/assembler-aarch64.cc
@@ -2075,6 +2075,7 @@ void Assembler::isb() {
   Emit(ISB | ImmBarrierDomain(FullSystem) | ImmBarrierType(BarrierAll));
 }
 
+void Assembler::csdb() { hint(CSDB); }
 
 void Assembler::fmov(const VRegister& vd, double imm) {
   if (vd.IsScalar()) {
diff --git a/src/aarch64/assembler-aarch64.h b/src/aarch64/assembler-aarch64.h
index 0931f46f..8d0fcd0c 100644
--- a/src/aarch64/assembler-aarch64.h
+++ b/src/aarch64/assembler-aarch64.h
@@ -1264,6 +1264,9 @@ class Assembler : public vixl::internal::AssemblerBase {
   // Instruction synchronization barrier.
   void isb();
 
+  // Conditional speculation dependency barrier.
+  void csdb();
+
   // Alias for system instructions.
   // No-op.
   void nop() { hint(NOP); }
diff --git a/src/aarch64/constants-aarch64.h b/src/aarch64/constants-aarch64.h
index 984c765d..b9b9064e 100644
--- a/src/aarch64/constants-aarch64.h
+++ b/src/aarch64/constants-aarch64.h
@@ -299,7 +299,8 @@ enum SystemHint {
   WFE   = 2,
   WFI   = 3,
   SEV   = 4,
-  SEVL  = 5
+  SEVL  = 5,
+  CSDB  = 20
 };
 
 enum BarrierDomain {
diff --git a/src/aarch64/decoder-aarch64.cc b/src/aarch64/decoder-aarch64.cc
index cc4e1a74..ef3c9247 100644
--- a/src/aarch64/decoder-aarch64.cc
+++ b/src/aarch64/decoder-aarch64.cc
@@ -246,11 +246,6 @@ void Decoder::DecodeBranchSystemException(const Instruction* instr) {
                 (instr->Mask(0x0039E000) == 0x00002000) ||
                 (instr->Mask(0x003AE000) == 0x00002000) ||
                 (instr->Mask(0x003CE000) == 0x00042000) ||
-                (instr->Mask(0x003FFFC0) == 0x000320C0) ||
-                (instr->Mask(0x003FF100) == 0x00032100) ||
-                (instr->Mask(0x003FF200) == 0x00032200) ||
-                (instr->Mask(0x003FF400) == 0x00032400) ||
-                (instr->Mask(0x003FF800) == 0x00032800) ||
                 (instr->Mask(0x0038F000) == 0x00005000) ||
                 (instr->Mask(0x0038E000) == 0x00006000)) {
               VisitUnallocated(instr);
diff --git a/src/aarch64/disasm-aarch64.cc b/src/aarch64/disasm-aarch64.cc
index c6d7a8e6..f4dcc621 100644
--- a/src/aarch64/disasm-aarch64.cc
+++ b/src/aarch64/disasm-aarch64.cc
@@ -1752,8 +1752,13 @@ void Disassembler::VisitSystem(const Instruction *instr) {
   } else if (instr->Mask(SystemHintFMask) == SystemHintFixed) {
     switch (instr->GetImmHint()) {
       case NOP: {
+        form = NULL;
         mnemonic = "nop";
+        break;
+      }
+      case CSDB: {
         form = NULL;
+        mnemonic = "csdb";
         break;
       }
     }
diff --git a/src/aarch64/macro-assembler-aarch64.h b/src/aarch64/macro-assembler-aarch64.h
index 84aef1ea..77444182 100644
--- a/src/aarch64/macro-assembler-aarch64.h
+++ b/src/aarch64/macro-assembler-aarch64.h
@@ -1109,6 +1109,11 @@ class MacroAssembler : public Assembler, public MacroAssemblerInterface {
     SingleEmissionCheckScope guard(this);
     cneg(rd, rn, cond);
   }
+  void Csdb() {
+    VIXL_ASSERT(allow_macro_instructions_);
+    SingleEmissionCheckScope guard(this);
+    csdb();
+  }
   void Cset(const Register& rd, Condition cond) {
     VIXL_ASSERT(allow_macro_instructions_);
     VIXL_ASSERT(!rd.IsZero());
diff --git a/src/aarch64/simulator-aarch64.cc b/src/aarch64/simulator-aarch64.cc
index 8214f583..66ae820d 100644
--- a/src/aarch64/simulator-aarch64.cc
+++ b/src/aarch64/simulator-aarch64.cc
@@ -2918,6 +2918,7 @@ void Simulator::VisitSystem(const Instruction* instr) {
     VIXL_ASSERT(instr->Mask(SystemHintMask) == HINT);
     switch (instr->GetImmHint()) {
       case NOP:
+      case CSDB:
         break;
       default:
         VIXL_UNIMPLEMENTED();
diff --git a/test/aarch64/test-assembler-aarch64.cc b/test/aarch64/test-assembler-aarch64.cc
index f365dd25..9da96488 100644
--- a/test/aarch64/test-assembler-aarch64.cc
+++ b/test/aarch64/test-assembler-aarch64.cc
@@ -13366,13 +13366,14 @@ TEST(system_msr) {
 }
 
 
-TEST(system_nop) {
+TEST(system) {
   SETUP();
   RegisterDump before;
 
   START();
   before.Dump(&masm);
   __ Nop();
+  __ Csdb();
   END();
 
   RUN();
diff --git a/test/aarch64/test-disasm-aarch64.cc b/test/aarch64/test-disasm-aarch64.cc
index f78abb95..df8de85c 100644
--- a/test/aarch64/test-disasm-aarch64.cc
+++ b/test/aarch64/test-disasm-aarch64.cc
@@ -3068,6 +3068,9 @@ TEST(barriers) {
   // ISB
   COMPARE_MACRO(Isb(), "isb");
 
+  // CSDB
+  COMPARE_MACRO(Csdb(), "csdb");
+
   CLEANUP();
 }