[PATCH, BINUTULS, AARCH64, 9/9] Add SSBS to MSR/MRS

This patch is part of the patch series to add support for ARMv8.5-A
extensions.
(https://developer.arm.com/products/architecture/cpu-architecture/a-profile/exploration-tools)
The encodings can be found in the System Register XML.

This patch adds support for the mitigation for Spectre Variant 4 by
adding the PSTATE bit SSBS which are accessible using MSR and MRS
instructions. Although this is a mandatory addition to the ARMv8.5-A,
it is permitted to be added to any version of the ARMv8 architecture.
This is enabled using the command line option of +ssbs for older
versions.

*** include/ChangeLog ***

2018-10-09  Sudakshina Das  <sudi.das@arm.com>

	* opcode/aarch64.h (AARCH64_FEATURE_SSBS): New.
	(AARCH64_ARCH_V8_5): Add AARCH64_FEATURE_SSBS by default.

*** opcodes/ChangeLog ***

2018-10-09  Sudakshina Das  <sudi.das@arm.com>

	* aarch64-opc.c (operand_general_constraint_met_p): Add
	SSBS in the check for one-bit immediate.
	(aarch64_sys_regs): New entry for SSBS.
	(aarch64_sys_reg_supported_p): New check for above.
	(aarch64_pstatefields): New entry for SSBS.
	(aarch64_pstatefield_supported_p): New check for above.

*** gas/ChangeLog ***

2018-10-09  Sudakshina Das  <sudi.das@arm.com>

	* config/tc-aarch64.c (aarch64_features): Add new "ssbs".
	* doc/c-aarch64.texi: Document the same.
	* testsuite/gas/aarch64/ssbs-illegal1.d: New test.
	* testsuite/gas/aarch64/ssbs-illegal1.l: New test.
	* testsuite/gas/aarch64/ssbs-illegal2.d: New test.
	* testsuite/gas/aarch64/ssbs-illegal2.l: New test.
	* testsuite/gas/aarch64/ssbs.s: New test.
	* testsuite/gas/aarch64/ssbs1.d: Test with +ssbs
	* testsuite/gas/aarch64/ssbs2.d: Test with armv8.5-a.

diff --git a/gas/ChangeLog b/gas/ChangeLog
index fc6dc90004c7b5fddcd568ba5117c0d665278ea4..64735413ba44ff9b95585dc35ad6d252fbaaf1c4 100644 (file)
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,15 @@
+2018-10-09  Sudakshina Das  <sudi.das@arm.com>
+
+       * config/tc-aarch64.c (aarch64_features): Add new "ssbs".
+       * doc/c-aarch64.texi: Document the same.
+       * testsuite/gas/aarch64/ssbs-illegal1.d: New test.
+       * testsuite/gas/aarch64/ssbs-illegal1.l: New test.
+       * testsuite/gas/aarch64/ssbs-illegal2.d: New test.
+       * testsuite/gas/aarch64/ssbs-illegal2.l: New test.
+       * testsuite/gas/aarch64/ssbs.s: New test.
+       * testsuite/gas/aarch64/ssbs1.d: Test with +ssbs
+       * testsuite/gas/aarch64/ssbs2.d: Test with armv8.5-a.
+
 2018-10-09  Sudakshina Das  <sudi.das@arm.com>
 
        * testsuite/gas/aarch64/sysreg-4.s: Test registers

diff --git a/gas/config/tc-aarch64.c b/gas/config/tc-aarch64.c
index 582c3ec0357654f394f84df45296e5c66ca494e2..4ae27f76ed9a9bdc6f058ca43f5f58b9cc30345f 100644 (file)
--- a/gas/config/tc-aarch64.c
+++ b/gas/config/tc-aarch64.c
@@ -8827,6 +8827,8 @@ static const struct aarch64_option_cpu_value_table aarch64_features[] = {
                        AARCH64_ARCH_NONE},
   {"rng",              AARCH64_FEATURE (AARCH64_FEATURE_RNG, 0),
                        AARCH64_ARCH_NONE},
+  {"ssbs",             AARCH64_FEATURE (AARCH64_FEATURE_SSBS, 0),
+                       AARCH64_ARCH_NONE},
   {NULL,               AARCH64_ARCH_NONE, AARCH64_ARCH_NONE},
 };
 

diff --git a/gas/doc/c-aarch64.texi b/gas/doc/c-aarch64.texi
index 009a379ce755e1a046589dc98528c1e79aac7e2f..4941c57c48113676cfbdd9ae38b691d468692179 100644 (file)
--- a/gas/doc/c-aarch64.texi
+++ b/gas/doc/c-aarch64.texi
@@ -187,6 +187,8 @@ automatically cause those extensions to be disabled.
  @tab Enable the Execution and Data and Prediction instructions.
 @item @code{rng} @tab ARMv8.5-A @tab No
  @tab Enable ARMv8.5-A random number instructions.
+@item @code{ssbs} @tab ARMv8-A @tab ARMv8.5-A or later
+ @tab Enable Speculative Store Bypassing Safe state read and write.
 @end multitable
 
 @node AArch64 Syntax

diff --git a/gas/testsuite/gas/aarch64/ssbs-illegal1.d b/gas/testsuite/gas/aarch64/ssbs-illegal1.d
new file mode 100644 (file)
index 0000000..e6f8281
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/ssbs-illegal1.d
@@ -0,0 +1,3 @@
+#as: -march=armv8-a+ssbs --defsym ERROR1=1
+#source: ssbs.s
+#error_output: ssbs-illegal1.l

diff --git a/gas/testsuite/gas/aarch64/ssbs-illegal1.l b/gas/testsuite/gas/aarch64/ssbs-illegal1.l
new file mode 100644 (file)
index 0000000..74a8b74
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/ssbs-illegal1.l
@@ -0,0 +1,15 @@
+[^:]*: Assembler messages:
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#2'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#3'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#4'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#5'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#6'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#7'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#8'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#9'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#10'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#11'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#12'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#13'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#14'
+[^:]*:[0-9]+: Error: immediate value out of range 0 to 1 at operand 1 -- `msr ssbs,#15'

diff --git a/gas/testsuite/gas/aarch64/ssbs-illegal2.d b/gas/testsuite/gas/aarch64/ssbs-illegal2.d
new file mode 100644 (file)
index 0000000..d35757c
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/ssbs-illegal2.d
@@ -0,0 +1,3 @@
+#as: -march=armv8-a --defsym ERROR2=1
+#source: ssbs.s
+#error_output: ssbs-illegal2.l

diff --git a/gas/testsuite/gas/aarch64/ssbs-illegal2.l b/gas/testsuite/gas/aarch64/ssbs-illegal2.l
new file mode 100644 (file)
index 0000000..5443b9a
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/ssbs-illegal2.l
@@ -0,0 +1,6 @@
+[^:]*: Assembler messages:
+[^:]*:[0-9]+: Error: selected processor does not support PSTATE field name 'ssbs'
+[^:]*:[0-9]+: Error: selected processor does not support PSTATE field name 'ssbs'
+[^:]*:[0-9]+: Error: selected processor does not support PSTATE field name 'ssbs'
+[^:]*:[0-9]+: Error: selected processor does not support system register name 'ssbs'
+[^:]*:[0-9]+: Error: selected processor does not support system register name 'ssbs'

diff --git a/gas/testsuite/gas/aarch64/ssbs.s b/gas/testsuite/gas/aarch64/ssbs.s
new file mode 100644 (file)
index 0000000..3938d45
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/ssbs.s
@@ -0,0 +1,31 @@
+/* Test SSBS.  */
+func:
+       .ifdef SUCCESS
+       msr ssbs, #1
+       msr ssbs, #0
+
+       .irp N,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
+       msr ssbs, x\N
+       mrs x\N, ssbs
+       .endr
+
+       .irp N,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30
+       msr ssbs, x\N
+       mrs x\N, ssbs
+       .endr
+       .endif
+
+       /* Constant >1 Failure.  */
+       .ifdef ERROR1
+       .irp N,2,3,4,5,6,7,8,9,10,11,12,13,14,15
+       msr ssbs, #\N
+       .endr
+       .endif
+
+       /* No +ssbs Failure.  */
+       .ifdef ERROR2
+       msr ssbs, #0
+       msr ssbs, #1
+       msr ssbs, x6
+       mrs x25, ssbs
+       .endif

diff --git a/gas/testsuite/gas/aarch64/ssbs1.d b/gas/testsuite/gas/aarch64/ssbs1.d
new file mode 100644 (file)
index 0000000..daeda76
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/ssbs1.d
@@ -0,0 +1,73 @@
+#source: ssbs.s
+#objdump: -dr
+#as: -march=armv8-a+ssbs --defsym SUCCESS=1
+
+.*:     file format .*
+
+Disassembly of section \.text:
+
+0+ <.*>:
+.*:    d503413f        msr     ssbs, #0x1
+.*:    d503403f        msr     ssbs, #0x0
+.*:    d51b42c0        msr     ssbs, x0
+.*:    d53b42c0        mrs     x0, ssbs
+.*:    d51b42c1        msr     ssbs, x1
+.*:    d53b42c1        mrs     x1, ssbs
+.*:    d51b42c2        msr     ssbs, x2
+.*:    d53b42c2        mrs     x2, ssbs
+.*:    d51b42c3        msr     ssbs, x3
+.*:    d53b42c3        mrs     x3, ssbs
+.*:    d51b42c4        msr     ssbs, x4
+.*:    d53b42c4        mrs     x4, ssbs
+.*:    d51b42c5        msr     ssbs, x5
+.*:    d53b42c5        mrs     x5, ssbs
+.*:    d51b42c6        msr     ssbs, x6
+.*:    d53b42c6        mrs     x6, ssbs
+.*:    d51b42c7        msr     ssbs, x7
+.*:    d53b42c7        mrs     x7, ssbs
+.*:    d51b42c8        msr     ssbs, x8
+.*:    d53b42c8        mrs     x8, ssbs
+.*:    d51b42c9        msr     ssbs, x9
+.*:    d53b42c9        mrs     x9, ssbs
+.*:    d51b42ca        msr     ssbs, x10
+.*:    d53b42ca        mrs     x10, ssbs
+.*:    d51b42cb        msr     ssbs, x11
+.*:    d53b42cb        mrs     x11, ssbs
+.*:    d51b42cc        msr     ssbs, x12
+.*:    d53b42cc        mrs     x12, ssbs
+.*:    d51b42cd        msr     ssbs, x13
+.*:    d53b42cd        mrs     x13, ssbs
+.*:    d51b42ce        msr     ssbs, x14
+.*:    d53b42ce        mrs     x14, ssbs
+.*:    d51b42cf        msr     ssbs, x15
+.*:    d53b42cf        mrs     x15, ssbs
+.*:    d51b42d0        msr     ssbs, x16
+.*:    d53b42d0        mrs     x16, ssbs
+.*:    d51b42d1        msr     ssbs, x17
+.*:    d53b42d1        mrs     x17, ssbs
+.*:    d51b42d2        msr     ssbs, x18
+.*:    d53b42d2        mrs     x18, ssbs
+.*:    d51b42d3        msr     ssbs, x19
+.*:    d53b42d3        mrs     x19, ssbs
+.*:    d51b42d4        msr     ssbs, x20
+.*:    d53b42d4        mrs     x20, ssbs
+.*:    d51b42d5        msr     ssbs, x21
+.*:    d53b42d5        mrs     x21, ssbs
+.*:    d51b42d6        msr     ssbs, x22
+.*:    d53b42d6        mrs     x22, ssbs
+.*:    d51b42d7        msr     ssbs, x23
+.*:    d53b42d7        mrs     x23, ssbs
+.*:    d51b42d8        msr     ssbs, x24
+.*:    d53b42d8        mrs     x24, ssbs
+.*:    d51b42d9        msr     ssbs, x25
+.*:    d53b42d9        mrs     x25, ssbs
+.*:    d51b42da        msr     ssbs, x26
+.*:    d53b42da        mrs     x26, ssbs
+.*:    d51b42db        msr     ssbs, x27
+.*:    d53b42db        mrs     x27, ssbs
+.*:    d51b42dc        msr     ssbs, x28
+.*:    d53b42dc        mrs     x28, ssbs
+.*:    d51b42dd        msr     ssbs, x29
+.*:    d53b42dd        mrs     x29, ssbs
+.*:    d51b42de        msr     ssbs, x30
+.*:    d53b42de        mrs     x30, ssbs

diff --git a/gas/testsuite/gas/aarch64/ssbs2.d b/gas/testsuite/gas/aarch64/ssbs2.d
new file mode 100644 (file)
index 0000000..0027026
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/ssbs2.d
@@ -0,0 +1,73 @@
+#source: ssbs.s
+#objdump: -dr
+#as: -march=armv8.5-a --defsym SUCCESS=1
+
+.*:     file format .*
+
+Disassembly of section \.text:
+
+0+ <.*>:
+.*:    d503413f        msr     ssbs, #0x1
+.*:    d503403f        msr     ssbs, #0x0
+.*:    d51b42c0        msr     ssbs, x0
+.*:    d53b42c0        mrs     x0, ssbs
+.*:    d51b42c1        msr     ssbs, x1
+.*:    d53b42c1        mrs     x1, ssbs
+.*:    d51b42c2        msr     ssbs, x2
+.*:    d53b42c2        mrs     x2, ssbs
+.*:    d51b42c3        msr     ssbs, x3
+.*:    d53b42c3        mrs     x3, ssbs
+.*:    d51b42c4        msr     ssbs, x4
+.*:    d53b42c4        mrs     x4, ssbs
+.*:    d51b42c5        msr     ssbs, x5
+.*:    d53b42c5        mrs     x5, ssbs
+.*:    d51b42c6        msr     ssbs, x6
+.*:    d53b42c6        mrs     x6, ssbs
+.*:    d51b42c7        msr     ssbs, x7
+.*:    d53b42c7        mrs     x7, ssbs
+.*:    d51b42c8        msr     ssbs, x8
+.*:    d53b42c8        mrs     x8, ssbs
+.*:    d51b42c9        msr     ssbs, x9
+.*:    d53b42c9        mrs     x9, ssbs
+.*:    d51b42ca        msr     ssbs, x10
+.*:    d53b42ca        mrs     x10, ssbs
+.*:    d51b42cb        msr     ssbs, x11
+.*:    d53b42cb        mrs     x11, ssbs
+.*:    d51b42cc        msr     ssbs, x12
+.*:    d53b42cc        mrs     x12, ssbs
+.*:    d51b42cd        msr     ssbs, x13
+.*:    d53b42cd        mrs     x13, ssbs
+.*:    d51b42ce        msr     ssbs, x14
+.*:    d53b42ce        mrs     x14, ssbs
+.*:    d51b42cf        msr     ssbs, x15
+.*:    d53b42cf        mrs     x15, ssbs
+.*:    d51b42d0        msr     ssbs, x16
+.*:    d53b42d0        mrs     x16, ssbs
+.*:    d51b42d1        msr     ssbs, x17
+.*:    d53b42d1        mrs     x17, ssbs
+.*:    d51b42d2        msr     ssbs, x18
+.*:    d53b42d2        mrs     x18, ssbs
+.*:    d51b42d3        msr     ssbs, x19
+.*:    d53b42d3        mrs     x19, ssbs
+.*:    d51b42d4        msr     ssbs, x20
+.*:    d53b42d4        mrs     x20, ssbs
+.*:    d51b42d5        msr     ssbs, x21
+.*:    d53b42d5        mrs     x21, ssbs
+.*:    d51b42d6        msr     ssbs, x22
+.*:    d53b42d6        mrs     x22, ssbs
+.*:    d51b42d7        msr     ssbs, x23
+.*:    d53b42d7        mrs     x23, ssbs
+.*:    d51b42d8        msr     ssbs, x24
+.*:    d53b42d8        mrs     x24, ssbs
+.*:    d51b42d9        msr     ssbs, x25
+.*:    d53b42d9        mrs     x25, ssbs
+.*:    d51b42da        msr     ssbs, x26
+.*:    d53b42da        mrs     x26, ssbs
+.*:    d51b42db        msr     ssbs, x27
+.*:    d53b42db        mrs     x27, ssbs
+.*:    d51b42dc        msr     ssbs, x28
+.*:    d53b42dc        mrs     x28, ssbs
+.*:    d51b42dd        msr     ssbs, x29
+.*:    d53b42dd        mrs     x29, ssbs
+.*:    d51b42de        msr     ssbs, x30
+.*:    d53b42de        mrs     x30, ssbs

diff --git a/include/ChangeLog b/include/ChangeLog
index ed5dcf2cc32dfc1ba40b1497be5d8390ad716e54..0c692ee0e8871f89574c5fbd52f099e55122b7ac 100644 (file)
--- a/include/ChangeLog
+++ b/include/ChangeLog
@@ -1,3 +1,8 @@
+2018-10-09  Sudakshina Das  <sudi.das@arm.com>
+
+       * opcode/aarch64.h (AARCH64_FEATURE_SSBS): New.
+       (AARCH64_ARCH_V8_5): Add AARCH64_FEATURE_SSBS by default.
+
 2018-10-09  Sudakshina Das  <sudi.das@arm.com>
 
        * opcode/aarch64.h (AARCH64_FEATURE_SCXTNUM): New.

diff --git a/include/opcode/aarch64.h b/include/opcode/aarch64.h
index b56f9070149e592824bc95f84da492615d875ff2..8487767349e3ec9d5d9d0ee8bc693c2dbe48f67c 100644 (file)
--- a/include/opcode/aarch64.h
+++ b/include/opcode/aarch64.h
@@ -82,6 +82,8 @@ typedef uint32_t aarch64_insn;
 #define AARCH64_FEATURE_SCXTNUM                0x200000000000ULL
 /* ID_PFR2 instructions.  */
 #define AARCH64_FEATURE_ID_PFR2                0x400000000000ULL
+/* SSBS mechanism enabled.  */
+#define AARCH64_FEATURE_SSBS           0x800000000000ULL
 
 
 /* Architectures are the sum of the base and extensions.  */
@@ -115,7 +117,8 @@ typedef uint32_t aarch64_insn;
                                                 | AARCH64_FEATURE_CVADP \
                                                 | AARCH64_FEATURE_BTI  \
                                                 | AARCH64_FEATURE_SCXTNUM \
-                                                | AARCH64_FEATURE_ID_PFR2)
+                                                | AARCH64_FEATURE_ID_PFR2 \
+                                                | AARCH64_FEATURE_SSBS)
 
 
 #define AARCH64_ARCH_NONE      AARCH64_FEATURE (0, 0)

diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index 776aa0fee2433559050b1c2cc01388112539be5d..c23452484600489c3889987f45dfae96566ee183 100644 (file)
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,3 +1,12 @@
+2018-10-09  Sudakshina Das  <sudi.das@arm.com>
+
+       * aarch64-opc.c (operand_general_constraint_met_p): Add
+       SSBS in the check for one-bit immediate.
+       (aarch64_sys_regs): New entry for SSBS.
+       (aarch64_sys_reg_supported_p): New check for above.
+       (aarch64_pstatefields): New entry for SSBS.
+       (aarch64_pstatefield_supported_p): New check for above.
+
 2018-10-09  Sudakshina Das  <sudi.das@arm.com>
 
        * aarch64-opc.c (aarch64_sys_regs): New entries for

diff --git a/opcodes/aarch64-opc.c b/opcodes/aarch64-opc.c
index 4cf39d262c99ce12a9b024b835f1b3a671ec7d72..5cd57d5966ed294206556ab3b6906946305e3097 100644 (file)
--- a/opcodes/aarch64-opc.c
+++ b/opcodes/aarch64-opc.c
@@ -2490,9 +2490,11 @@ operand_general_constraint_met_p (const aarch64_opnd_info *opnds, int idx,
          assert (idx == 0 && opnds[1].type == AARCH64_OPND_UIMM4);
          /* MSR UAO, #uimm4
             MSR PAN, #uimm4
+            MSR SSBS,#uimm4
             The immediate must be #0 or #1.  */
          if ((opnd->pstatefield == 0x03        /* UAO.  */
               || opnd->pstatefield == 0x04     /* PAN.  */
+              || opnd->pstatefield == 0x19     /* SSBS.  */
               || opnd->pstatefield == 0x1a)    /* DIT.  */
              && opnds[1].imm.value > 1)
            {
@@ -3708,6 +3710,7 @@ const aarch64_sys_reg aarch64_sys_regs [] =
   { "pan",             CPEN_(0,C2,3),  F_ARCHEXT },
   { "uao",             CPEN_ (0, C2, 4), F_ARCHEXT },
   { "nzcv",             CPEN_(3,C2,0), 0 },
+  { "ssbs",            CPEN_(3,C2,6),  F_ARCHEXT },
   { "fpcr",             CPEN_(3,C4,0), 0 },
   { "fpsr",             CPEN_(3,C4,1), 0 },
   { "dspsr_el0",        CPEN_(3,C5,0), 0 },
@@ -4128,6 +4131,11 @@ aarch64_sys_reg_supported_p (const aarch64_feature_set features,
       && !AARCH64_CPU_HAS_FEATURE (features, AARCH64_FEATURE_ID_PFR2))
     return FALSE;
 
+  /* SSBS.  Values are from aarch64_sys_regs.  */
+  if (reg->value == CPEN_(3,C2,6)
+      && !AARCH64_CPU_HAS_FEATURE (features, AARCH64_FEATURE_SSBS))
+    return FALSE;
+
   /* Virtualization host extensions: system registers.  */
   if ((reg->value == CPENC (3, 4, C2, C0, 1)
        || reg->value == CPENC (3, 4, C13, C0, 1)
@@ -4340,6 +4348,7 @@ const aarch64_sys_reg aarch64_pstatefields [] =
   { "daifclr",          0x1f,  0 },
   { "pan",             0x04,   F_ARCHEXT },
   { "uao",             0x03,   F_ARCHEXT },
+  { "ssbs",            0x19,   F_ARCHEXT },
   { "dit",             0x1a,   F_ARCHEXT },
   { 0,          CPENC(0,0,0,0,0), 0 },
 };
@@ -4361,6 +4370,11 @@ aarch64_pstatefield_supported_p (const aarch64_feature_set features,
       && !AARCH64_CPU_HAS_FEATURE (features, AARCH64_FEATURE_V8_2))
     return FALSE;
 
+  /* SSBS.  Values are from aarch64_pstatefields.  */
+  if (reg->value == 0x19
+      && !AARCH64_CPU_HAS_FEATURE (features, AARCH64_FEATURE_SSBS))
+    return FALSE;
+
   /* DIT.  Values are from aarch64_pstatefields.  */
   if (reg->value == 0x1a
       && !AARCH64_CPU_HAS_FEATURE (features, AARCH64_FEATURE_V8_4))