[Lldb-commits] [lldb] [llvm] [AArch64][llvm] Tighten SYSP parsing; don't disassemble invalid encodings (PR #182410)

Jonathan Thackray via lldb-commits lldb-commits at lists.llvm.org
Tue Mar 10 09:13:09 PDT 2026


https://github.com/jthackray updated https://github.com/llvm/llvm-project/pull/182410

>From 901abf72ad98a2d677d04401d18e7c7ceb3830e3 Mon Sep 17 00:00:00 2001
From: Jonathan Thackray <jonathan.thackray at arm.com>
Date: Thu, 19 Feb 2026 23:54:20 +0000
Subject: [PATCH 1/4] [AArch64][llvm] Tighten SYSP; don't disassemble invalid
 encodings

Tighten SYSP aliases, so that invalid encodings are disassembled
to `<unknown>`. This is because:

```
  Cn is a 4-bit unsigned immediate, in the range 8 to 9
  Cm is a 4-bit unsigned immediate, in the range 0 to 7
  op1 is a 3-bit unsigned immediate, in the range 0 to 6
  op2 is a 3-bit unsigned immediate, in the range 0 to 7
```

Ensure we check this when disassembling, and also constrain
tablegen for compile-time errors of invalid encodings.

Also adjust the testcases in `armv9-sysp-diagnostics.s` and
`llvm/test/MC/AArch64/armv9a-sysp.s` as they were invalid,
and added a few invalid (outside of range) SYSP-alikes to
test that `<unknown>` is printed
---
 .../command-disassemble-aarch64-color.s       |   4 +-
 .../command-disassemble-aarch64-extensions.s  |   4 +-
 .../lib/Target/AArch64/AArch64InstrFormats.td |  27 ++-
 llvm/lib/Target/AArch64/AArch64InstrInfo.td   |  10 +-
 .../Disassembler/AArch64Disassembler.cpp      |  25 ++
 .../MCTargetDesc/AArch64InstPrinter.cpp       |   8 +
 llvm/test/MC/AArch64/armv9-sysp-diagnostics.s |  15 +-
 llvm/test/MC/AArch64/armv9-sysp-invalid.s     |  20 ++
 llvm/test/MC/AArch64/armv9a-sysp.s            | 222 +++++++++---------
 9 files changed, 208 insertions(+), 127 deletions(-)
 create mode 100644 llvm/test/MC/AArch64/armv9-sysp-invalid.s

diff --git a/lldb/test/Shell/Commands/command-disassemble-aarch64-color.s b/lldb/test/Shell/Commands/command-disassemble-aarch64-color.s
index bb97680a32970..6ddde3d974adc 100644
--- a/lldb/test/Shell/Commands/command-disassemble-aarch64-color.s
+++ b/lldb/test/Shell/Commands/command-disassemble-aarch64-color.s
@@ -17,7 +17,7 @@ fn:
   crc32b w0, w0, w0                     // AEK_CRC
   // AEK_CRYPTO enables a combination of other features
   smin x0, x0, #0                       // AEK_CSSC
-  sysp	#0, c2, c0, #0, x0, x1          // AEK_D128
+  sysp	#0, c8, c0, #0, x0, x1          // AEK_D128
   sdot v0.2s, v1.8b, v2.8b              // AEK_DOTPROD
   fmmla z0.s, z1.s, z2.s                // AEK_F32MM
 
@@ -28,6 +28,6 @@ fn:
 # CHECK-NEXT: [0xc] <+12>:   brb    iall
 # CHECK-NEXT: [0x10] <+16>:  crc32b w0, w0, w0
 # CHECK-NEXT: [0x14] <+20>:  smin   x0, x0, #0x0
-# CHECK-NEXT: [0x18] <+24>:  sysp   #0x0, c2, c0, #0x0, x0, x1
+# CHECK-NEXT: [0x18] <+24>:  sysp   #0x0, c8, c0, #0x0, x0, x1
 # CHECK-NEXT: [0x1c] <+28>:  sdot   v0.2s, v1.8b, v2.8b
 # CHECK-NEXT: [0x20] <+32>:  fmmla  z0.s, z1.s, z2.s
diff --git a/lldb/test/Shell/Commands/command-disassemble-aarch64-extensions.s b/lldb/test/Shell/Commands/command-disassemble-aarch64-extensions.s
index 4e281332a33bb..945654e905876 100644
--- a/lldb/test/Shell/Commands/command-disassemble-aarch64-extensions.s
+++ b/lldb/test/Shell/Commands/command-disassemble-aarch64-extensions.s
@@ -17,7 +17,7 @@ fn:
   crc32b w0, w0, w0                     // AEK_CRC
   // AEK_CRYPTO enables a combination of other features
   smin x0, x0, #0                       // AEK_CSSC
-  sysp	#0, c2, c0, #0, x0, x1          // AEK_D128
+  sysp	#0, c8, c0, #0, x0, x1          // AEK_D128
   sdot v0.2s, v1.8b, v2.8b              // AEK_DOTPROD
   fmmla z0.s, z1.s, z2.s                // AEK_F32MM
   fmmla z0.d, z1.d, z2.d                // AEK_F64MM
@@ -72,7 +72,7 @@ lbl:
 # CHECK-NEXT: brb    iall
 # CHECK-NEXT: crc32b w0, w0, w0
 # CHECK-NEXT: smin   x0, x0, #0
-# CHECK-NEXT: sysp   #0x0, c2, c0, #0x0, x0, x1
+# CHECK-NEXT: sysp   #0x0, c8, c0, #0x0, x0, x1
 # CHECK-NEXT: sdot   v0.2s, v1.8b, v2.8b
 # CHECK-NEXT: fmmla  z0.s, z1.s, z2.s
 # CHECK-NEXT: fmmla  z0.d, z1.d, z2.d
diff --git a/llvm/lib/Target/AArch64/AArch64InstrFormats.td b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
index 5fdb9814cc2e8..36550c72be98d 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -2122,6 +2122,30 @@ def sys_cr_op : Operand<i32> {
   let OperandType = "OPERAND_IMMEDIATE";
 }
 
+// SYSP operands are more restricted than generic system CR/imm fields.
+def sysp_op1 : Operand<i64>, ImmLeaf<i64, [{
+  return Imm >= 0 && Imm <= 6;
+}]> {
+  let ParserMatchClass = Imm0_7Operand;
+  let OperandType = "OPERAND_IMMEDIATE";
+}
+
+def sysp_crn_op : Operand<i32>, ImmLeaf<i32, [{
+  return Imm == 8 || Imm == 9;
+}]> {
+  let PrintMethod = "printSysCROperand";
+  let ParserMatchClass = SysCRAsmOperand;
+  let OperandType = "OPERAND_IMMEDIATE";
+}
+
+def sysp_crm_op : Operand<i32>, ImmLeaf<i32, [{
+  return Imm >= 0 && Imm <= 7;
+}]> {
+  let PrintMethod = "printSysCROperand";
+  let ParserMatchClass = SysCRAsmOperand;
+  let OperandType = "OPERAND_IMMEDIATE";
+}
+
 class SystemXtI<bit L, string asm>
   : RtSystemI<L, (outs),
        (ins imm0_7:$op1, sys_cr_op:$Cn, sys_cr_op:$Cm, imm0_7:$op2, GPR64:$Rt),
@@ -13297,7 +13321,8 @@ class BaseSYSPEncoding<bit L, string asm, string operands, dag outputs, dag inpu
 }
 class SystemPXtI<bit L, string asm> :
   BaseSYSPEncoding<L, asm, "\t$op1, $Cn, $Cm, $op2, $Rt", (outs),
-  (ins imm0_7:$op1, sys_cr_op:$Cn, sys_cr_op:$Cm, imm0_7:$op2, XSeqPairClassOperand:$Rt)>;
+  (ins sysp_op1:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm, imm0_7:$op2,
+       XSeqPairClassOperand:$Rt)>;
 
 //----------------------------------------------------------------------------
 // 2023 Armv9.5 Extensions
diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.td b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
index 84566946260c3..8f221af3a3f63 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
@@ -11483,11 +11483,14 @@ let Predicates = [HasRCPC3, HasNEON] in {
 //===----------------------------------------------------------------------===//
 // 128-bit System Instructions (FEAT_SYSINSTR128)
 //===----------------------------------------------------------------------===//
-def SYSPxt  : SystemPXtI<0, "sysp">;
+def SYSPxt  : SystemPXtI<0, "sysp"> {
+  let DecoderMethod = "DecodeSyspInstruction";
+}
 
 def SYSPxt_XZR
   : BaseSystemI<0, (outs),
-      (ins imm0_7:$op1, sys_cr_op:$Cn, sys_cr_op:$Cm, imm0_7:$op2, SyspXzrPairOperand:$xzr_pair),
+      (ins sysp_op1:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm, imm0_7:$op2,
+           SyspXzrPairOperand:$xzr_pair),
       "sysp", "\t$op1, $Cn, $Cm, $op2, $xzr_pair">,
     Sched<[WriteSys]>
 {
@@ -11513,7 +11516,8 @@ def SYSPxt_XZR
 }
 
 def : InstAlias<"sysp $op1, $Cn, $Cm, $op2",
-                (SYSPxt_XZR imm0_7:$op1, sys_cr_op:$Cn, sys_cr_op:$Cm, imm0_7:$op2, XZR)>;
+                (SYSPxt_XZR sysp_op1:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm,
+                            imm0_7:$op2, XZR)>;
 
 //---
 // 128-bit System Registers (FEAT_SYSREG128)
diff --git a/llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp b/llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
index 8fa1913ce24e5..ef0f9cb515d0b 100644
--- a/llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
+++ b/llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
@@ -1395,6 +1395,10 @@ static DecodeStatus DecodeSyspXzrInstruction(MCInst &Inst, uint32_t insn,
   unsigned CRm = fieldFromInstruction(insn, 8, 4);
   unsigned op2 = fieldFromInstruction(insn, 5, 3);
   unsigned Rt = fieldFromInstruction(insn, 0, 5);
+
+  if (op1 > 6 || (CRn != 8 && CRn != 9) || CRm > 7 || op2 > 7)
+    return Fail;
+
   if (Rt != 0b11111)
     return Fail;
 
@@ -1408,6 +1412,27 @@ static DecodeStatus DecodeSyspXzrInstruction(MCInst &Inst, uint32_t insn,
   return Success;
 }
 
+static DecodeStatus DecodeSyspInstruction(MCInst &Inst, uint32_t insn,
+                                          uint64_t Addr,
+                                          const MCDisassembler *Decoder) {
+  unsigned op1 = fieldFromInstruction(insn, 16, 3);
+  unsigned CRn = fieldFromInstruction(insn, 12, 4);
+  unsigned CRm = fieldFromInstruction(insn, 8, 4);
+  unsigned op2 = fieldFromInstruction(insn, 5, 3);
+  unsigned Rt = fieldFromInstruction(insn, 0, 5);
+
+  if (op1 > 6 || (CRn != 8 && CRn != 9) || CRm > 7 || op2 > 7)
+    return Fail;
+
+  Inst.addOperand(MCOperand::createImm(op1));
+  Inst.addOperand(MCOperand::createImm(CRn));
+  Inst.addOperand(MCOperand::createImm(CRm));
+  Inst.addOperand(MCOperand::createImm(op2));
+  DecodeXSeqPairsClassRegisterClass(Inst, Rt, Addr, Decoder);
+
+  return Success;
+}
+
 static DecodeStatus
 DecodeSVELogicalImmInstruction(MCInst &Inst, uint32_t insn, uint64_t Addr,
                                const MCDisassembler *Decoder) {
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp
index 2fe162f930fdf..05d23f3055130 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp
@@ -1152,6 +1152,14 @@ bool AArch64InstPrinter::printSyspAlias(const MCInst *MI,
   unsigned CmVal = Cm.getImm();
   unsigned Op2Val = Op2.getImm();
 
+  // Early checks for invalid SYSP aliases
+  //   Op1 == 0..6
+  //   Op2 == 0..7
+  //    Cm == 0..7
+  //    Cn == 8 or 9
+  if (Op1Val > 6 || Op2Val > 7 || CmVal > 7 || (CnVal != 8 && CnVal != 9))
+    return false;
+
   uint16_t Encoding = Op2Val;
   Encoding |= CmVal << 3;
   Encoding |= CnVal << 7;
diff --git a/llvm/test/MC/AArch64/armv9-sysp-diagnostics.s b/llvm/test/MC/AArch64/armv9-sysp-diagnostics.s
index 8b466c10b0aa7..51bb307912fef 100644
--- a/llvm/test/MC/AArch64/armv9-sysp-diagnostics.s
+++ b/llvm/test/MC/AArch64/armv9-sysp-diagnostics.s
@@ -7,22 +7,21 @@
 // registers with 128-bit formats (op0, op1, Cn, Cm, op2)
 // For sysp, op0 is 0
 
-sysp #0, c2, c0, #0, x0, x2
+sysp #0, c8, c0, #0, x0, x2
 // ERRORS: error: expected second odd register of a consecutive same-size even/odd register pair
-sysp #0, c2, c0, #0, x0
+sysp #0, c8, c0, #0, x0
 // ERRORS: error: expected comma
-sysp #0, c2, c0, #0, x1, x2
+sysp #0, c8, c0, #0, x1, x2
 // ERRORS: error: expected first even register of a consecutive same-size even/odd register pair
-sysp #0, c2, c0, #0, x31, x0
+sysp #0, c8, c0, #0, x31, x0
 // ERRORS: error: xzr must be followed by xzr
-sysp #0, c2, c0, #0, xzr, x30
+sysp #0, c8, c0, #0, xzr, x30
 // ERRORS: error: xzr must be followed by xzr
-sysp #0, c2, c0, #0, xzr
+sysp #0, c8, c0, #0, xzr
 // ERRORS: error: expected comma
-sysp #0, c2, c0, #0, xzr,
+sysp #0, c8, c0, #0, xzr,
 // ERRORS: error: expected register operand
 
-
 tlbip RVAE3IS
 // ERRORS: error: expected comma
 tlbip RVAE3IS,
diff --git a/llvm/test/MC/AArch64/armv9-sysp-invalid.s b/llvm/test/MC/AArch64/armv9-sysp-invalid.s
new file mode 100644
index 0000000000000..248d5ccc5056a
--- /dev/null
+++ b/llvm/test/MC/AArch64/armv9-sysp-invalid.s
@@ -0,0 +1,20 @@
+// RUN: llvm-mc -triple=aarch64 -filetype=obj -mattr=+d128 < %s \
+// RUN:   | llvm-objdump -d --mattr=+d128 --no-print-imm-hex - \
+// RUN:   | FileCheck %s --check-prefix=DISASM
+
+// Ensure invalid SYSP encodings are not printed as TLBIP aliases.
+
+// op1 = 7 (outside architecturally valid SYSP range for op1)
+// Cn = 8, Cm = 0, op2 = 0, Rt = 0 (x0, x1)
+.inst 0xd54f8000
+
+// Cn = 0 (outside architecturally valid SYSP range for Cn)
+.inst 0xd5480000
+
+// Cm = 8 (outside architecturally valid SYSP range for Cm)
+.inst 0xd5488800
+
+// DISASM-NOT: tlbip
+// DISASM: <unknown>
+// DISASM: <unknown>
+// DISASM: <unknown>
diff --git a/llvm/test/MC/AArch64/armv9a-sysp.s b/llvm/test/MC/AArch64/armv9a-sysp.s
index f1e039f3e8770..349f75eb95424 100644
--- a/llvm/test/MC/AArch64/armv9a-sysp.s
+++ b/llvm/test/MC/AArch64/armv9a-sysp.s
@@ -13,150 +13,150 @@
 // registers with 128-bit formats (op0, op1, Cn, Cm, op2)
 // For sysp, op0 is 0
 
-sysp #0, c2, c0, #0, x0, x1// TTBR0_EL1     3  0  2  0  0
-// CHECK-INST: sysp #0, c2, c0, #0, x0, x1
-// CHECK-ENCODING: encoding: [0x00,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x0, x1
+// CHECK-INST: sysp #0, c8, c0, #0, x0, x1
+// CHECK-ENCODING: encoding: [0x00,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #1, x0, x1// TTBR1_EL1     3  0  2  0  1
-// CHECK-INST: sysp #0, c2, c0, #1, x0, x1
-// CHECK-ENCODING: encoding: [0x20,0x20,0x48,0xd5]
+sysp #0, c8, c0, #1, x0, x1
+// CHECK-INST: sysp #0, c8, c0, #1, x0, x1
+// CHECK-ENCODING: encoding: [0x20,0x80,0x48,0xd5]
 
-sysp #0, c7, c4, #0, x0, x1// PAR_EL1       3  0  7  4  0
-// CHECK-INST: sysp #0, c7, c4, #0, x0, x1
-// CHECK-ENCODING: encoding: [0x00,0x74,0x48,0xd5]
+sysp #0, c8, c4, #0, x0, x1
+// CHECK-INST: sysp #0, c8, c4, #0, x0, x1
+// CHECK-ENCODING: encoding: [0x00,0x84,0x48,0xd5]
 
-sysp #0, c13, c0, #3, x0, x1         // RCWSMASK_EL1  3  0 13  0  3
-// CHECK-INST: sysp #0, c13, c0, #3, x0, x1
-// CHECK-ENCODING: encoding: [0x60,0xd0,0x48,0xd5]
+sysp #0, c8, c0, #3, x0, x1
+// CHECK-INST: sysp #0, c8, c0, #3, x0, x1
+// CHECK-ENCODING: encoding: [0x60,0x80,0x48,0xd5]
 
-sysp #0, c13, c0, #6, x0, x1         // RCWMASK_EL1   3  0 13  0  6
-// CHECK-INST: sysp #0, c13, c0, #6, x0, x1
-// CHECK-ENCODING: encoding: [0xc0,0xd0,0x48,0xd5]
+sysp #0, c8, c0, #6, x0, x1
+// CHECK-INST: sysp #0, c8, c0, #6, x0, x1
+// CHECK-ENCODING: encoding: [0xc0,0x80,0x48,0xd5]
 
-sysp #4, c2, c0, #0, x0, x1// TTBR0_EL2     3  4  2  0  0
-// CHECK-INST: sysp #4, c2, c0, #0, x0, x1
-// CHECK-ENCODING: encoding: [0x00,0x20,0x4c,0xd5]
+sysp #4, c8, c0, #0, x0, x1
+// CHECK-INST: sysp #4, c8, c0, #0, x0, x1
+// CHECK-ENCODING: encoding: [0x00,0x80,0x4c,0xd5]
 
-sysp #4, c2, c0, #1, x0, x1// TTBR1_EL2     3  4  2  0  1
-// CHECK-INST: sysp #4, c2, c0, #1, x0, x1
-// CHECK-ENCODING: encoding: [0x20,0x20,0x4c,0xd5]
+sysp #4, c8, c0, #3, x0, x1
+// CHECK-INST: sysp #4, c8, c0, #3, x0, x1
+// CHECK-ENCODING: encoding: [0x60,0x80,0x4c,0xd5]
 
-sysp #4, c2, c1, #0, x0, x1// VTTBR_EL2     3  4  2  1  0
-// CHECK-INST: sysp #4, c2, c1, #0, x0, x1
-// CHECK-ENCODING: encoding: [0x00,0x21,0x4c,0xd5]
+sysp #4, c8, c1, #0, x0, x1
+// CHECK-INST: sysp #4, c8, c1, #0, x0, x1
+// CHECK-ENCODING: encoding: [0x00,0x81,0x4c,0xd5]
 
-sysp #0, c2, c0, #0, x0, x1
-// CHECK-INST: sysp #0, c2, c0, #0, x0, x1
-// CHECK-ENCODING: encoding: [0x00,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x0, x1
+// CHECK-INST: sysp #0, c8, c0, #0, x0, x1
+// CHECK-ENCODING: encoding: [0x00,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #1, x0, x1
-// CHECK-INST: sysp #0, c2, c0, #1, x0, x1
-// CHECK-ENCODING: encoding: [0x20,0x20,0x48,0xd5]
+sysp #0, c8, c0, #1, x0, x1
+// CHECK-INST: sysp #0, c8, c0, #1, x0, x1
+// CHECK-ENCODING: encoding: [0x20,0x80,0x48,0xd5]
 
-sysp #0, c7, c4, #0, x0, x1
-// CHECK-INST: sysp #0, c7, c4, #0, x0, x1
-// CHECK-ENCODING: encoding: [0x00,0x74,0x48,0xd5]
+sysp #0, c8, c4, #0, x0, x1
+// CHECK-INST: sysp #0, c8, c4, #0, x0, x1
+// CHECK-ENCODING: encoding: [0x00,0x84,0x48,0xd5]
 
-sysp #0, c13, c0, #3, x0, x1
-// CHECK-INST: sysp #0, c13, c0, #3, x0, x1
-// CHECK-ENCODING: encoding: [0x60,0xd0,0x48,0xd5]
+sysp #0, c8, c0, #3, x0, x1
+// CHECK-INST: sysp #0, c8, c0, #3, x0, x1
+// CHECK-ENCODING: encoding: [0x60,0x80,0x48,0xd5]
 
-sysp #0, c13, c0, #6, x0, x1
-// CHECK-INST: sysp #0, c13, c0, #6, x0, x1
-// CHECK-ENCODING: encoding: [0xc0,0xd0,0x48,0xd5]
+sysp #0, c8, c0, #6, x0, x1
+// CHECK-INST: sysp #0, c8, c0, #6, x0, x1
+// CHECK-ENCODING: encoding: [0xc0,0x80,0x48,0xd5]
 
-sysp #4, c2, c0, #0, x0, x1
-// CHECK-INST: sysp #4, c2, c0, #0, x0, x1
-// CHECK-ENCODING: encoding: [0x00,0x20,0x4c,0xd5]
+sysp #4, c8, c0, #0, x0, x1
+// CHECK-INST: sysp #4, c8, c0, #0, x0, x1
+// CHECK-ENCODING: encoding: [0x00,0x80,0x4c,0xd5]
 
-sysp #4, c2, c0, #1, x0, x1
-// CHECK-INST: sysp #4, c2, c0, #1, x0, x1
-// CHECK-ENCODING: encoding: [0x20,0x20,0x4c,0xd5]
+sysp #4, c8, c0, #3, x0, x1
+// CHECK-INST: sysp #4, c8, c0, #3, x0, x1
+// CHECK-ENCODING: encoding: [0x60,0x80,0x4c,0xd5]
 
-sysp #4, c2, c1, #0, x0, x1
-// CHECK-INST: sysp #4, c2, c1, #0, x0, x1
-// CHECK-ENCODING: encoding: [0x00,0x21,0x4c,0xd5]
+sysp #4, c8, c1, #0, x0, x1
+// CHECK-INST: sysp #4, c8, c1, #0, x0, x1
+// CHECK-ENCODING: encoding: [0x00,0x81,0x4c,0xd5]
 
-sysp #0, c2, c0, #0, x0, x1
-// CHECK-INST: sysp #0, c2, c0, #0, x0, x1
-// CHECK-ENCODING: encoding: [0x00,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x0, x1
+// CHECK-INST: sysp #0, c8, c0, #0, x0, x1
+// CHECK-ENCODING: encoding: [0x00,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x2, x3
-// CHECK-INST: sysp #0, c2, c0, #0, x2, x3
-// CHECK-ENCODING: encoding: [0x02,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x2, x3
+// CHECK-INST: sysp #0, c8, c0, #0, x2, x3
+// CHECK-ENCODING: encoding: [0x02,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x4, x5
-// CHECK-INST: sysp #0, c2, c0, #0, x4, x5
-// CHECK-ENCODING: encoding: [0x04,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x4, x5
+// CHECK-INST: sysp #0, c8, c0, #0, x4, x5
+// CHECK-ENCODING: encoding: [0x04,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x6, x7
-// CHECK-INST: sysp #0, c2, c0, #0, x6, x7
-// CHECK-ENCODING: encoding: [0x06,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x6, x7
+// CHECK-INST: sysp #0, c8, c0, #0, x6, x7
+// CHECK-ENCODING: encoding: [0x06,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x8, x9
-// CHECK-INST: sysp #0, c2, c0, #0, x8, x9
-// CHECK-ENCODING: encoding: [0x08,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x8, x9
+// CHECK-INST: sysp #0, c8, c0, #0, x8, x9
+// CHECK-ENCODING: encoding: [0x08,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x10, x11
-// CHECK-INST: sysp #0, c2, c0, #0, x10, x11
-// CHECK-ENCODING: encoding: [0x0a,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x10, x11
+// CHECK-INST: sysp #0, c8, c0, #0, x10, x11
+// CHECK-ENCODING: encoding: [0x0a,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x12, x13
-// CHECK-INST: sysp #0, c2, c0, #0, x12, x13
-// CHECK-ENCODING: encoding: [0x0c,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x12, x13
+// CHECK-INST: sysp #0, c8, c0, #0, x12, x13
+// CHECK-ENCODING: encoding: [0x0c,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x14, x15
-// CHECK-INST: sysp #0, c2, c0, #0, x14, x15
-// CHECK-ENCODING: encoding: [0x0e,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x14, x15
+// CHECK-INST: sysp #0, c8, c0, #0, x14, x15
+// CHECK-ENCODING: encoding: [0x0e,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x16, x17
-// CHECK-INST: sysp #0, c2, c0, #0, x16, x17
-// CHECK-ENCODING: encoding: [0x10,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x16, x17
+// CHECK-INST: sysp #0, c8, c0, #0, x16, x17
+// CHECK-ENCODING: encoding: [0x10,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x18, x19
-// CHECK-INST: sysp #0, c2, c0, #0, x18, x19
-// CHECK-ENCODING: encoding: [0x12,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x18, x19
+// CHECK-INST: sysp #0, c8, c0, #0, x18, x19
+// CHECK-ENCODING: encoding: [0x12,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x20, x21
-// CHECK-INST: sysp #0, c2, c0, #0, x20, x21
-// CHECK-ENCODING: encoding: [0x14,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x20, x21
+// CHECK-INST: sysp #0, c8, c0, #0, x20, x21
+// CHECK-ENCODING: encoding: [0x14,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x22, x23
-// CHECK-INST: sysp #0, c2, c0, #0, x22, x23
-// CHECK-ENCODING: encoding: [0x16,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x22, x23
+// CHECK-INST: sysp #0, c8, c0, #0, x22, x23
+// CHECK-ENCODING: encoding: [0x16,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x24, x25
-// CHECK-INST: sysp #0, c2, c0, #0, x24, x25
-// CHECK-ENCODING: encoding: [0x18,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x24, x25
+// CHECK-INST: sysp #0, c8, c0, #0, x24, x25
+// CHECK-ENCODING: encoding: [0x18,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x26, x27
-// CHECK-INST: sysp #0, c2, c0, #0, x26, x27
-// CHECK-ENCODING: encoding: [0x1a,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x26, x27
+// CHECK-INST: sysp #0, c8, c0, #0, x26, x27
+// CHECK-ENCODING: encoding: [0x1a,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x28, x29
-// CHECK-INST: sysp #0, c2, c0, #0, x28, x29
-// CHECK-ENCODING: encoding: [0x1c,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x28, x29
+// CHECK-INST: sysp #0, c8, c0, #0, x28, x29
+// CHECK-ENCODING: encoding: [0x1c,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x30, x31
-// CHECK-INST: sysp #0, c2, c0, #0, x30, xzr
-// CHECK-ENCODING: encoding: [0x1e,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x30, x31
+// CHECK-INST: sysp #0, c8, c0, #0, x30, xzr
+// CHECK-ENCODING: encoding: [0x1e,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x31, x31
-// CHECK-INST: sysp #0, c2, c0, #0
-// CHECK-ENCODING: encoding: [0x1f,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x31, x31
+// CHECK-INST: sysp #0, c8, c0, #0
+// CHECK-ENCODING: encoding: [0x1f,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, xzr, xzr
-// CHECK-INST: sysp #0, c2, c0, #0
-// CHECK-ENCODING: encoding: [0x1f,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, xzr, xzr
+// CHECK-INST: sysp #0, c8, c0, #0
+// CHECK-ENCODING: encoding: [0x1f,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, x31, xzr
-// CHECK-INST: sysp #0, c2, c0, #0
-// CHECK-ENCODING: encoding: [0x1f,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, x31, xzr
+// CHECK-INST: sysp #0, c8, c0, #0
+// CHECK-ENCODING: encoding: [0x1f,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0, xzr, x31
-// CHECK-INST: sysp #0, c2, c0, #0
-// CHECK-ENCODING: encoding: [0x1f,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0, xzr, x31
+// CHECK-INST: sysp #0, c8, c0, #0
+// CHECK-ENCODING: encoding: [0x1f,0x80,0x48,0xd5]
 
-sysp #0, c2, c0, #0
-// CHECK-INST: sysp #0, c2, c0, #0
-// CHECK-ENCODING: encoding: [0x1f,0x20,0x48,0xd5]
+sysp #0, c8, c0, #0
+// CHECK-INST: sysp #0, c8, c0, #0
+// CHECK-ENCODING: encoding: [0x1f,0x80,0x48,0xd5]

>From 53003ac311a4ac6fa3af81ecdbc802210c490b43 Mon Sep 17 00:00:00 2001
From: Jonathan Thackray <jonathan.thackray at arm.com>
Date: Thu, 5 Mar 2026 12:32:15 +0000
Subject: [PATCH 2/4] fixup! Address Marian's PR comments: use imm0_6 predicate

---
 llvm/lib/Target/AArch64/AArch64InstrFormats.td | 18 +++++++++---------
 llvm/lib/Target/AArch64/AArch64InstrInfo.td    |  4 ++--
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/llvm/lib/Target/AArch64/AArch64InstrFormats.td b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
index 36550c72be98d..bc3a2e120bac4 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -943,6 +943,7 @@ def Imm0_1Operand : AsmImmRange<0, 1>;
 def Imm1_1Operand : AsmImmRange<1, 1>;
 def Imm0_3Operand : AsmImmRange<0, 3>;
 def Imm1_3Operand : AsmImmRange<1, 3>;
+def Imm0_6Operand : AsmImmRange<0, 6>;
 def Imm0_7Operand : AsmImmRange<0, 7>;
 def Imm1_7Operand : AsmImmRange<1, 7>;
 def Imm0_15Operand : AsmImmRange<0, 15>;
@@ -1176,6 +1177,13 @@ def imm0_15 : Operand<i64>, ImmLeaf<i64, [{
   let ParserMatchClass = Imm0_15Operand;
 }
 
+// imm0_6 predicate - True if the immediate is in the range [0,6]
+def imm0_6 : Operand<i64>, ImmLeaf<i64, [{
+  return ((uint64_t)Imm) < 7;
+}]> {
+  let ParserMatchClass = Imm0_6Operand;
+}
+
 // imm0_7 predicate - True if the immediate is in the range [0,7]
 def imm0_7 : Operand<i64>, ImmLeaf<i64, [{
   return ((uint64_t)Imm) < 8;
@@ -2122,14 +2130,6 @@ def sys_cr_op : Operand<i32> {
   let OperandType = "OPERAND_IMMEDIATE";
 }
 
-// SYSP operands are more restricted than generic system CR/imm fields.
-def sysp_op1 : Operand<i64>, ImmLeaf<i64, [{
-  return Imm >= 0 && Imm <= 6;
-}]> {
-  let ParserMatchClass = Imm0_7Operand;
-  let OperandType = "OPERAND_IMMEDIATE";
-}
-
 def sysp_crn_op : Operand<i32>, ImmLeaf<i32, [{
   return Imm == 8 || Imm == 9;
 }]> {
@@ -13321,7 +13321,7 @@ class BaseSYSPEncoding<bit L, string asm, string operands, dag outputs, dag inpu
 }
 class SystemPXtI<bit L, string asm> :
   BaseSYSPEncoding<L, asm, "\t$op1, $Cn, $Cm, $op2, $Rt", (outs),
-  (ins sysp_op1:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm, imm0_7:$op2,
+  (ins imm0_6:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm, imm0_7:$op2,
        XSeqPairClassOperand:$Rt)>;
 
 //----------------------------------------------------------------------------
diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.td b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
index 8f221af3a3f63..16b28c14374ca 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
@@ -11489,7 +11489,7 @@ def SYSPxt  : SystemPXtI<0, "sysp"> {
 
 def SYSPxt_XZR
   : BaseSystemI<0, (outs),
-      (ins sysp_op1:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm, imm0_7:$op2,
+      (ins imm0_6:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm, imm0_7:$op2,
            SyspXzrPairOperand:$xzr_pair),
       "sysp", "\t$op1, $Cn, $Cm, $op2, $xzr_pair">,
     Sched<[WriteSys]>
@@ -11516,7 +11516,7 @@ def SYSPxt_XZR
 }
 
 def : InstAlias<"sysp $op1, $Cn, $Cm, $op2",
-                (SYSPxt_XZR sysp_op1:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm,
+                (SYSPxt_XZR imm0_6:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm,
                             imm0_7:$op2, XZR)>;
 
 //---

>From dc3c507a849a0002b836cad8418691480d1eb1f4 Mon Sep 17 00:00:00 2001
From: Jonathan Thackray <jonathan.thackray at arm.com>
Date: Thu, 5 Mar 2026 14:41:46 +0000
Subject: [PATCH 3/4] fixup! Templatise bounds checking and improve tests

---
 .../lib/Target/AArch64/AArch64InstrFormats.td | 17 ++++++++++++-----
 .../AArch64/AsmParser/AArch64AsmParser.cpp    | 18 ++++++++++++++++++
 .../MCTargetDesc/AArch64InstPrinter.cpp       |  8 --------
 llvm/test/MC/AArch64/armv9-sysp-diagnostics.s | 19 +++++++++++++++----
 4 files changed, 45 insertions(+), 17 deletions(-)

diff --git a/llvm/lib/Target/AArch64/AArch64InstrFormats.td b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
index bc3a2e120bac4..d8487b6c2d4e9 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -2119,14 +2119,21 @@ class MSRpstateImm0_1
 }
 
 // SYS and SYSL generic system instructions.
-def SysCRAsmOperand : AsmOperandClass {
-  let Name = "SysCR";
+class SysCRAsmOperand<int Low, int High> : AsmOperandClass {
+  let Name = "SysCR" # Low # "_" # High;
+  let RenderMethod = "addSysCROperands";
   let ParserMethod = "tryParseSysCROperand";
+  let PredicateMethod = "isSysCRInRange<" # Low # "," # High # ">";
+  let DiagnosticType = "InvalidSysCR" # Low # "_" # High;
 }
 
+def SysCRm0_7AsmOperand : SysCRAsmOperand<0, 7>;
+def SysCRn8_9AsmOperand : SysCRAsmOperand<8, 9>;
+def SysCR0_15AsmOperand : SysCRAsmOperand<0, 15>;
+
 def sys_cr_op : Operand<i32> {
   let PrintMethod = "printSysCROperand";
-  let ParserMatchClass = SysCRAsmOperand;
+  let ParserMatchClass = SysCR0_15AsmOperand;
   let OperandType = "OPERAND_IMMEDIATE";
 }
 
@@ -2134,7 +2141,7 @@ def sysp_crn_op : Operand<i32>, ImmLeaf<i32, [{
   return Imm == 8 || Imm == 9;
 }]> {
   let PrintMethod = "printSysCROperand";
-  let ParserMatchClass = SysCRAsmOperand;
+  let ParserMatchClass = SysCRn8_9AsmOperand;
   let OperandType = "OPERAND_IMMEDIATE";
 }
 
@@ -2142,7 +2149,7 @@ def sysp_crm_op : Operand<i32>, ImmLeaf<i32, [{
   return Imm >= 0 && Imm <= 7;
 }]> {
   let PrintMethod = "printSysCROperand";
-  let ParserMatchClass = SysCRAsmOperand;
+  let ParserMatchClass = SysCRm0_7AsmOperand;
   let OperandType = "OPERAND_IMMEDIATE";
 }
 
diff --git a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
index 590da8f93873d..9bd8bd56dd484 100644
--- a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
+++ b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
@@ -1551,6 +1551,12 @@ class AArch64Operand : public MCParsedAsmOperand {
     return Kind == k_Token && getToken() == Str;
   }
   bool isSysCR() const { return Kind == k_SysCR; }
+  template <unsigned low, unsigned high> bool isSysCRInRange() const {
+    if (!isSysCR())
+      return false;
+    unsigned Val = getSysCR();
+    return Val >= low && Val <= high;
+  }
   bool isPrefetch() const { return Kind == k_Prefetch; }
   bool isPSBHint() const { return Kind == k_PSBHint; }
   bool isPHint() const { return Kind == k_PHint; }
@@ -6293,6 +6299,8 @@ bool AArch64AsmParser::showMatchError(SMLoc Loc, unsigned ErrCode,
     return Error(Loc, "immediate must be an integer in range [0, 1].");
   case Match_InvalidImm0_3:
     return Error(Loc, "immediate must be an integer in range [0, 3].");
+  case Match_InvalidImm0_6:
+    return Error(Loc, "immediate must be an integer in range [0, 6].");
   case Match_InvalidImm0_7:
     return Error(Loc, "immediate must be an integer in range [0, 7].");
   case Match_InvalidImm0_15:
@@ -6317,6 +6325,12 @@ bool AArch64AsmParser::showMatchError(SMLoc Loc, unsigned ErrCode,
     return Error(Loc, "immediate must be an integer in range [1, 64].");
   case Match_InvalidImmM1_62:
     return Error(Loc, "immediate must be an integer in range [-1, 62].");
+  case Match_InvalidSysCR0_7:
+    return Error(Loc, "expected cM operand where 0 <= M <= 7");
+  case Match_InvalidSysCR8_9:
+    return Error(Loc, "expected cN operand where 8 <= N <= 9");
+  case Match_InvalidSysCR0_15:
+    return Error(Loc, "expected cN operand where 0 <= N <= 15");
   case Match_InvalidMemoryIndexedRange2UImm0:
     return Error(Loc, "vector select offset must be the immediate range 0:1.");
   case Match_InvalidMemoryIndexedRange2UImm1:
@@ -7081,6 +7095,7 @@ bool AArch64AsmParser::matchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
   case Match_InvalidImm0_0:
   case Match_InvalidImm0_1:
   case Match_InvalidImm0_3:
+  case Match_InvalidImm0_6:
   case Match_InvalidImm0_7:
   case Match_InvalidImm0_15:
   case Match_InvalidImm0_31:
@@ -7093,6 +7108,9 @@ bool AArch64AsmParser::matchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
   case Match_InvalidImm1_32:
   case Match_InvalidImm1_64:
   case Match_InvalidImmM1_62:
+  case Match_InvalidSysCR0_7:
+  case Match_InvalidSysCR8_9:
+  case Match_InvalidSysCR0_15:
   case Match_InvalidMemoryIndexedRange2UImm0:
   case Match_InvalidMemoryIndexedRange2UImm1:
   case Match_InvalidMemoryIndexedRange2UImm2:
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp
index 05d23f3055130..2fe162f930fdf 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp
@@ -1152,14 +1152,6 @@ bool AArch64InstPrinter::printSyspAlias(const MCInst *MI,
   unsigned CmVal = Cm.getImm();
   unsigned Op2Val = Op2.getImm();
 
-  // Early checks for invalid SYSP aliases
-  //   Op1 == 0..6
-  //   Op2 == 0..7
-  //    Cm == 0..7
-  //    Cn == 8 or 9
-  if (Op1Val > 6 || Op2Val > 7 || CmVal > 7 || (CnVal != 8 && CnVal != 9))
-    return false;
-
   uint16_t Encoding = Op2Val;
   Encoding |= CmVal << 3;
   Encoding |= CnVal << 7;
diff --git a/llvm/test/MC/AArch64/armv9-sysp-diagnostics.s b/llvm/test/MC/AArch64/armv9-sysp-diagnostics.s
index 51bb307912fef..4e0ba1bbb1772 100644
--- a/llvm/test/MC/AArch64/armv9-sysp-diagnostics.s
+++ b/llvm/test/MC/AArch64/armv9-sysp-diagnostics.s
@@ -9,16 +9,22 @@
 
 sysp #0, c8, c0, #0, x0, x2
 // ERRORS: error: expected second odd register of a consecutive same-size even/odd register pair
-sysp #0, c8, c0, #0, x0
-// ERRORS: error: expected comma
 sysp #0, c8, c0, #0, x1, x2
 // ERRORS: error: expected first even register of a consecutive same-size even/odd register pair
 sysp #0, c8, c0, #0, x31, x0
 // ERRORS: error: xzr must be followed by xzr
 sysp #0, c8, c0, #0, xzr, x30
 // ERRORS: error: xzr must be followed by xzr
-sysp #0, c8, c0, #0, xzr
-// ERRORS: error: expected comma
+sysp #7, c8, c0, #0, x0, x1
+// ERRORS: error: immediate must be an integer in range [0, 6].
+sysp #0, c7, c0, #0, x0, x1
+// ERRORS: error: expected cN operand where 8 <= N <= 9
+sysp #0, c10, c0, #0, x0, x1
+// ERRORS: error: expected cN operand where 8 <= N <= 9
+sysp #0, c8, c8, #0, x0, x1
+// ERRORS: error: expected cM operand where 0 <= M <= 7
+sysp #0, c8, c0, #8, x0, x1
+// ERRORS: error: immediate must be an integer in range [0, 7].
 sysp #0, c8, c0, #0, xzr,
 // ERRORS: error: expected register operand
 
@@ -32,3 +38,8 @@ tlbip IPAS2E1, x4, x8
 // ERRORS: error: specified tlbip op requires a pair of registers
 tlbip RVAE3, x11, x11
 // ERRORS: error: specified tlbip op requires a pair of registers
+
+sysp #0, c8, c0, #0, x0
+// ERRORS: error: expected comma
+sysp #0, c8, c0, #0, xzr
+// ERRORS: error: expected comma

>From 81e4fcd3949ac4d31c24753dabc7aa23951106e0 Mon Sep 17 00:00:00 2001
From: Jonathan Thackray <jonathan.thackray at arm.com>
Date: Mon, 9 Mar 2026 16:16:52 +0000
Subject: [PATCH 4/4] fixup! Remove SYSPxt_XZR and update code to reflect this

---
 .../lib/Target/AArch64/AArch64InstrFormats.td |  2 +-
 llvm/lib/Target/AArch64/AArch64InstrInfo.td   | 32 +---------
 .../lib/Target/AArch64/AArch64RegisterInfo.td | 16 ++---
 .../AArch64/AsmParser/AArch64AsmParser.cpp    | 61 ++++++++-----------
 .../Disassembler/AArch64Disassembler.cpp      | 29 +--------
 .../MCTargetDesc/AArch64InstPrinter.cpp       | 55 ++++++++++++-----
 .../AArch64/MCTargetDesc/AArch64InstPrinter.h |  4 +-
 llvm/test/MC/AArch64/armv9-sysp-diagnostics.s | 16 ++++-
 llvm/test/MC/AArch64/armv9-sysp-invalid.s     | 20 ------
 llvm/test/MC/AArch64/armv9a-sysp.s            |  4 ++
 10 files changed, 101 insertions(+), 138 deletions(-)
 delete mode 100644 llvm/test/MC/AArch64/armv9-sysp-invalid.s

diff --git a/llvm/lib/Target/AArch64/AArch64InstrFormats.td b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
index d8487b6c2d4e9..19a49f712b64f 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -13329,7 +13329,7 @@ class BaseSYSPEncoding<bit L, string asm, string operands, dag outputs, dag inpu
 class SystemPXtI<bit L, string asm> :
   BaseSYSPEncoding<L, asm, "\t$op1, $Cn, $Cm, $op2, $Rt", (outs),
   (ins imm0_6:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm, imm0_7:$op2,
-       XSeqPairClassOperand:$Rt)>;
+       SyspPairOperand:$Rt)>;
 
 //----------------------------------------------------------------------------
 // 2023 Armv9.5 Extensions
diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.td b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
index 16b28c14374ca..e2c94e18b78ec 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
@@ -11487,37 +11487,9 @@ def SYSPxt  : SystemPXtI<0, "sysp"> {
   let DecoderMethod = "DecodeSyspInstruction";
 }
 
-def SYSPxt_XZR
-  : BaseSystemI<0, (outs),
-      (ins imm0_6:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm, imm0_7:$op2,
-           SyspXzrPairOperand:$xzr_pair),
-      "sysp", "\t$op1, $Cn, $Cm, $op2, $xzr_pair">,
-    Sched<[WriteSys]>
-{
-  // Had to use a custom decoder because tablegen interprets this as having 4 fields (why?)
-  // and therefore autogenerates a decoder that builds an MC representation that has 4 fields
-  // (decodeToMCInst), but when printing we expect the MC representation to have 5 fields (one
-  // extra for the XZR) because AArch64InstPrinter::printInstruction in AArch64GenAsmWriter.inc
-  // is based off of the asm template (maybe) and therefore wants to print 5 operands.
-  // I could add a bits<5> xzr_pair. But without a way to constrain it to 0b11111 here it would
-  // overlap with the main SYSP instruction.
-  let DecoderMethod = "DecodeSyspXzrInstruction";
-  bits<3> op1;
-  bits<4> Cn;
-  bits<4> Cm;
-  bits<3> op2;
-  let Inst{22}    = 0b1; // override BaseSystemI
-  let Inst{20-19} = 0b01;
-  let Inst{18-16} = op1;
-  let Inst{15-12} = Cn;
-  let Inst{11-8}  = Cm;
-  let Inst{7-5}   = op2;
-  let Inst{4-0}   = 0b11111;
-}
-
 def : InstAlias<"sysp $op1, $Cn, $Cm, $op2",
-                (SYSPxt_XZR imm0_6:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm,
-                            imm0_7:$op2, XZR)>;
+                (SYSPxt imm0_6:$op1, sysp_crn_op:$Cn, sysp_crm_op:$Cm,
+                        imm0_7:$op2, XZR)>;
 
 //---
 // 128-bit System Registers (FEAT_SYSREG128)
diff --git a/llvm/lib/Target/AArch64/AArch64RegisterInfo.td b/llvm/lib/Target/AArch64/AArch64RegisterInfo.td
index cd94a2590c6d2..cc2798de60943 100644
--- a/llvm/lib/Target/AArch64/AArch64RegisterInfo.td
+++ b/llvm/lib/Target/AArch64/AArch64RegisterInfo.td
@@ -833,14 +833,14 @@ def MrrsMssrPairClassOperand :
     RegisterOperand<XSeqPairsClass, "printGPRSeqPairsClassOperand<64>"> {
   let ParserMatchClass = XSeqPairsAsmOperandClass;
 }
-def SyspXzrPairOperandMatcherClass : AsmOperandClass {
-  let Name = "SyspXzrPair";
-  let RenderMethod = "addSyspXzrPairOperand";
-  let ParserMethod = "tryParseSyspXzrPair";
-}
-def SyspXzrPairOperand :
-    RegisterOperand<GPR64, "printSyspXzrPair"> { // needed to allow alias with XZR operand
-  let ParserMatchClass = SyspXzrPairOperandMatcherClass;
+def SyspPairOperandMatcherClass : AsmOperandClass {
+  let Name = "SyspPair";
+  let RenderMethod = "addRegOperands";
+  let ParserMethod = "tryParseSyspPair";
+}
+def SyspPairOperand :
+    RegisterOperand<GPR64, "printSyspPair"> {
+  let ParserMatchClass = SyspPairOperandMatcherClass;
 }
 
 
diff --git a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
index 9bd8bd56dd484..d2962cc7231f4 100644
--- a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
+++ b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
@@ -279,7 +279,7 @@ class AArch64AsmParser : public MCTargetAsmParser {
   bool tryParseNeonVectorRegister(OperandVector &Operands);
   ParseStatus tryParseVectorIndex(OperandVector &Operands);
   ParseStatus tryParseGPRSeqPair(OperandVector &Operands);
-  ParseStatus tryParseSyspXzrPair(OperandVector &Operands);
+  ParseStatus tryParseSyspPair(OperandVector &Operands);
   template <bool ParseShiftExtend,
             RegConstraintEqualityTy EqTy = RegConstraintEqualityTy::EqualsReg>
   ParseStatus tryParseGPROperand(OperandVector &Operands);
@@ -1449,9 +1449,7 @@ class AArch64Operand : public MCParsedAsmOperand {
                Reg.Reg);
   }
 
-  bool isSyspXzrPair() const {
-    return isGPR64<AArch64::GPR64RegClassID>() && Reg.Reg == AArch64::XZR;
-  }
+  bool isSyspPair() const { return isGPR64<AArch64::GPR64RegClassID>(); }
 
   template<int64_t Angle, int64_t Remainder>
   DiagnosticPredicate isComplexRotation() const {
@@ -2271,21 +2269,6 @@ class AArch64Operand : public MCParsedAsmOperand {
     Inst.addOperand(MCOperand::createImm(Imm));
   }
 
-  void addSyspXzrPairOperand(MCInst &Inst, unsigned N) const {
-    assert(N == 1 && "Invalid number of operands!");
-
-    if (!isScalarReg())
-      return;
-
-    const MCRegisterInfo *RI = Ctx.getRegisterInfo();
-    MCRegister Reg = RI->getRegClass(AArch64::GPR64RegClassID)
-                         .getRegister(RI->getEncodingValue(getReg()));
-    if (Reg != AArch64::XZR)
-      llvm_unreachable("wrong register");
-
-    Inst.addOperand(MCOperand::createReg(AArch64::XZR));
-  }
-
   void addExtendOperands(MCInst &Inst, unsigned N) const {
     assert(N == 1 && "Invalid number of operands!");
     AArch64_AM::ShiftExtendType ET = getShiftExtendType();
@@ -3316,18 +3299,20 @@ ParseStatus AArch64AsmParser::tryParsePSBHint(OperandVector &Operands) {
   return ParseStatus::Success;
 }
 
-ParseStatus AArch64AsmParser::tryParseSyspXzrPair(OperandVector &Operands) {
+ParseStatus AArch64AsmParser::tryParseSyspPair(OperandVector &Operands) {
   SMLoc StartLoc = getLoc();
 
-  MCRegister RegNum;
-
-  // The case where xzr, xzr is not present is handled by an InstAlias.
+  MCRegister FirstReg;
+  MCRegister SecondReg;
+  const MCRegisterInfo *RI = getContext().getRegisterInfo();
+  const MCRegisterClass &XRegClass =
+      AArch64MCRegisterClasses[AArch64::GPR64RegClassID];
 
   auto RegTok = getTok(); // in case we need to backtrack
-  if (!tryParseScalarRegister(RegNum).isSuccess())
+  if (!tryParseScalarRegister(FirstReg).isSuccess())
     return ParseStatus::NoMatch;
 
-  if (RegNum != AArch64::XZR) {
+  if (!XRegClass.contains(FirstReg)) {
     getLexer().UnLex(RegTok);
     return ParseStatus::NoMatch;
   }
@@ -3335,16 +3320,26 @@ ParseStatus AArch64AsmParser::tryParseSyspXzrPair(OperandVector &Operands) {
   if (parseComma())
     return ParseStatus::Failure;
 
-  if (!tryParseScalarRegister(RegNum).isSuccess())
+  if (!tryParseScalarRegister(SecondReg).isSuccess())
     return TokError("expected register operand");
 
-  if (RegNum != AArch64::XZR)
-    return TokError("xzr must be followed by xzr");
+  if (FirstReg == AArch64::XZR) {
+    if (SecondReg != AArch64::XZR)
+      return TokError("xzr must be followed by xzr");
+    // The SYSP alias is UNDEFINED if Rt<0> == '1' && Rt != '11111'.
+  } else if (RI->getEncodingValue(FirstReg) & 1) {
+    return TokError("first register must be even-numbered or xzr");
+  } else if (!XRegClass.contains(SecondReg) ||
+             RI->getEncodingValue(SecondReg) !=
+                 RI->getEncodingValue(FirstReg) + 1) {
+    return TokError(
+        "second register must be the next consecutive register after the "
+        "first register");
+  }
 
-  // We need to push something, since we claim this is an operand in .td.
-  // See also AArch64AsmParser::parseKeywordOperand.
+  // SYSP encodes only the first register; the second is implied as Rt+1.
   Operands.push_back(AArch64Operand::CreateReg(
-      RegNum, RegKind::Scalar, StartLoc, getLoc(), getContext()));
+      FirstReg, RegKind::Scalar, StartLoc, getLoc(), getContext()));
 
   return ParseStatus::Success;
 }
@@ -4288,9 +4283,7 @@ bool AArch64AsmParser::parseSyspAlias(StringRef Name, SMLoc NameLoc,
 
   if (Tok.isNot(AsmToken::Identifier))
     return TokError("expected register identifier");
-  auto Result = tryParseSyspXzrPair(Operands);
-  if (Result.isNoMatch())
-    Result = tryParseGPRSeqPair(Operands);
+  auto Result = tryParseSyspPair(Operands);
   if (!Result.isSuccess())
     return TokError("specified " + Mnemonic +
                     " op requires a pair of registers");
diff --git a/llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp b/llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
index ef0f9cb515d0b..46ef93a21453b 100644
--- a/llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
+++ b/llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
@@ -1387,31 +1387,6 @@ DecodeXSeqPairsClassRegisterClass(MCInst &Inst, unsigned RegNo, uint64_t Addr,
       Inst, AArch64::XSeqPairsClassRegClassID, RegNo, Addr, Decoder);
 }
 
-static DecodeStatus DecodeSyspXzrInstruction(MCInst &Inst, uint32_t insn,
-                                             uint64_t Addr,
-                                             const MCDisassembler *Decoder) {
-  unsigned op1 = fieldFromInstruction(insn, 16, 3);
-  unsigned CRn = fieldFromInstruction(insn, 12, 4);
-  unsigned CRm = fieldFromInstruction(insn, 8, 4);
-  unsigned op2 = fieldFromInstruction(insn, 5, 3);
-  unsigned Rt = fieldFromInstruction(insn, 0, 5);
-
-  if (op1 > 6 || (CRn != 8 && CRn != 9) || CRm > 7 || op2 > 7)
-    return Fail;
-
-  if (Rt != 0b11111)
-    return Fail;
-
-  Inst.addOperand(MCOperand::createImm(op1));
-  Inst.addOperand(MCOperand::createImm(CRn));
-  Inst.addOperand(MCOperand::createImm(CRm));
-  Inst.addOperand(MCOperand::createImm(op2));
-  DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rt, Addr,
-                                                             Decoder);
-
-  return Success;
-}
-
 static DecodeStatus DecodeSyspInstruction(MCInst &Inst, uint32_t insn,
                                           uint64_t Addr,
                                           const MCDisassembler *Decoder) {
@@ -1428,7 +1403,9 @@ static DecodeStatus DecodeSyspInstruction(MCInst &Inst, uint32_t insn,
   Inst.addOperand(MCOperand::createImm(CRn));
   Inst.addOperand(MCOperand::createImm(CRm));
   Inst.addOperand(MCOperand::createImm(op2));
-  DecodeXSeqPairsClassRegisterClass(Inst, Rt, Addr, Decoder);
+  // SYSP just encodes Rt. Print Rt and Rt+1 as a pair.
+  DecodeSimpleRegisterClass<AArch64::GPR64RegClassID, 0, 32>(Inst, Rt, Addr,
+                                                             Decoder);
 
   return Success;
 }
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp
index 2fe162f930fdf..87daff4d06ef3 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp
@@ -90,12 +90,26 @@ void AArch64InstPrinter::printInst(const MCInst *MI, uint64_t Address,
       return;
     }
 
-  if (Opcode == AArch64::SYSPxt || Opcode == AArch64::SYSPxt_XZR)
+  if (Opcode == AArch64::SYSPxt) {
     if (printSyspAlias(MI, STI, O)) {
       printAnnotation(O, Annot);
       return;
     }
 
+    // Ok, so we should preserve compatibility when printing with the historic
+    // SYSP short form, when Rt encodes XZR (no explicit pair operand)
+    if (MI->getOperand(4).getReg() == AArch64::XZR) {
+      O << "\tsysp\t";
+      markup(O, Markup::Immediate) << "#" << MI->getOperand(0).getImm();
+      O << ", c" << MI->getOperand(1).getImm();
+      O << ", c" << MI->getOperand(2).getImm();
+      O << ", ";
+      markup(O, Markup::Immediate) << "#" << MI->getOperand(3).getImm();
+      printAnnotation(O, Annot);
+      return;
+    }
+  }
+
   // RPRFM overlaps PRFM (reg), so try to print it as RPRFM here.
   if ((Opcode == AArch64::PRFMroX) || (Opcode == AArch64::PRFMroW)) {
     if (printRangePrefetchAlias(MI, STI, O, Annot))
@@ -371,7 +385,12 @@ void AArch64InstPrinter::printInst(const MCInst *MI, uint64_t Address,
     return;
   }
 
-  if (!PrintAliases || !printAliasInstr(MI, Address, STI, O))
+  // SYSP alias printing is handled explicitly by printSyspAlias above.
+  // Skip the generic alias printer for SYSPxt, because its XSeqPair aliases
+  // are only valid for a subset of SYSP register pairs and can misprint
+  // odd-started regs or xzr,xzr encodings.
+  if (!PrintAliases || Opcode == AArch64::SYSPxt ||
+      !printAliasInstr(MI, Address, STI, O))
     printInstruction(MI, Address, STI, O);
 
   printAnnotation(O, Annot);
@@ -1138,8 +1157,7 @@ bool AArch64InstPrinter::printSyspAlias(const MCInst *MI,
                                         raw_ostream &O) {
 #ifndef NDEBUG
   unsigned Opcode = MI->getOpcode();
-  assert((Opcode == AArch64::SYSPxt || Opcode == AArch64::SYSPxt_XZR) &&
-         "Invalid opcode for SYSP alias!");
+  assert(Opcode == AArch64::SYSPxt && "Invalid opcode for SYSP alias!");
 #endif
 
   const MCOperand &Op1 = MI->getOperand(0);
@@ -1178,10 +1196,8 @@ bool AArch64InstPrinter::printSyspAlias(const MCInst *MI,
 
   O << '\t' << Str;
   O << ", ";
-  if (MI->getOperand(4).getReg() == AArch64::XZR)
-    printSyspXzrPair(MI, 4, STI, O);
-  else
-    printGPRSeqPairsClassOperand<64>(MI, 4, STI, O);
+  // TLBIP alias keeps SYSP's pair formatting rules for the trailing operand.
+  printSyspPair(MI, 4, STI, O);
 
   return true;
 }
@@ -2262,13 +2278,24 @@ void AArch64InstPrinter::printGPR64x8(const MCInst *MI, unsigned OpNum,
   printRegName(O, MRI.getSubReg(Reg, AArch64::x8sub_0));
 }
 
-void AArch64InstPrinter::printSyspXzrPair(const MCInst *MI, unsigned OpNum,
-                                          const MCSubtargetInfo &STI,
-                                          raw_ostream &O) {
+void AArch64InstPrinter::printSyspPair(const MCInst *MI, unsigned OpNum,
+                                       const MCSubtargetInfo &STI,
+                                       raw_ostream &O) {
   MCRegister Reg = MI->getOperand(OpNum).getReg();
-  assert(Reg == AArch64::XZR &&
-         "MC representation of SyspXzrPair should be XZR");
-  O << getRegisterName(Reg) << ", " << getRegisterName(Reg);
+  printRegName(O, Reg);
+  O << ", ";
+  if (Reg == AArch64::XZR) {
+    printRegName(O, AArch64::XZR);
+    return;
+  }
+
+  const MCRegisterClass &XRegClass =
+      AArch64MCRegisterClasses[AArch64::GPR64RegClassID];
+  // SYSP textual form prints the implied second register as Rt+1.
+  unsigned NextRegNo = MRI.getEncodingValue(Reg) + 1;
+  assert(NextRegNo < XRegClass.getNumRegs() &&
+         "SYSP pair starts from an invalid GPR64 register");
+  printRegName(O, XRegClass.getRegister(NextRegNo));
 }
 
 void AArch64InstPrinter::printPHintOp(const MCInst *MI, unsigned OpNum,
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.h b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.h
index 3f7a3b4b0667b..0b34d9edfa82b 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.h
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.h
@@ -237,8 +237,8 @@ class AArch64InstPrinter : public MCInstPrinter {
                       const MCSubtargetInfo &STI, raw_ostream &O);
   void printGPR64x8(const MCInst *MI, unsigned OpNum,
                     const MCSubtargetInfo &STI, raw_ostream &O);
-  void printSyspXzrPair(const MCInst *MI, unsigned OpNum,
-                        const MCSubtargetInfo &STI, raw_ostream &O);
+  void printSyspPair(const MCInst *MI, unsigned OpNum,
+                     const MCSubtargetInfo &STI, raw_ostream &O);
   template <int Width>
   void printZPRasFPR(const MCInst *MI, unsigned OpNum,
                      const MCSubtargetInfo &STI, raw_ostream &O);
diff --git a/llvm/test/MC/AArch64/armv9-sysp-diagnostics.s b/llvm/test/MC/AArch64/armv9-sysp-diagnostics.s
index 4e0ba1bbb1772..2426acce2d95e 100644
--- a/llvm/test/MC/AArch64/armv9-sysp-diagnostics.s
+++ b/llvm/test/MC/AArch64/armv9-sysp-diagnostics.s
@@ -8,13 +8,23 @@
 // For sysp, op0 is 0
 
 sysp #0, c8, c0, #0, x0, x2
-// ERRORS: error: expected second odd register of a consecutive same-size even/odd register pair
-sysp #0, c8, c0, #0, x1, x2
-// ERRORS: error: expected first even register of a consecutive same-size even/odd register pair
+// ERRORS: error: second register must be the next consecutive register after the first register
+sysp #4, c8, c4, #1, x1, x2
+// ERRORS: error: first register must be even-numbered or xzr
+sysp #4, c8, c4, #1, x2, x4
+// ERRORS: error: second register must be the next consecutive register after the first register
+sysp #0, c8, c0, #0, x29, x31
+// ERRORS: error: first register must be even-numbered or xzr
+sysp #0, c8, c0, #0, x30, x30
+// ERRORS: error: second register must be the next consecutive register after the first register
 sysp #0, c8, c0, #0, x31, x0
 // ERRORS: error: xzr must be followed by xzr
+sysp #4, c8, c4, #1, xzr, x1
+// ERRORS: error: xzr must be followed by xzr
 sysp #0, c8, c0, #0, xzr, x30
 // ERRORS: error: xzr must be followed by xzr
+sysp #0, c8, c0, #0, w0, w1
+// ERRORS: error: invalid operand for instruction
 sysp #7, c8, c0, #0, x0, x1
 // ERRORS: error: immediate must be an integer in range [0, 6].
 sysp #0, c7, c0, #0, x0, x1
diff --git a/llvm/test/MC/AArch64/armv9-sysp-invalid.s b/llvm/test/MC/AArch64/armv9-sysp-invalid.s
deleted file mode 100644
index 248d5ccc5056a..0000000000000
--- a/llvm/test/MC/AArch64/armv9-sysp-invalid.s
+++ /dev/null
@@ -1,20 +0,0 @@
-// RUN: llvm-mc -triple=aarch64 -filetype=obj -mattr=+d128 < %s \
-// RUN:   | llvm-objdump -d --mattr=+d128 --no-print-imm-hex - \
-// RUN:   | FileCheck %s --check-prefix=DISASM
-
-// Ensure invalid SYSP encodings are not printed as TLBIP aliases.
-
-// op1 = 7 (outside architecturally valid SYSP range for op1)
-// Cn = 8, Cm = 0, op2 = 0, Rt = 0 (x0, x1)
-.inst 0xd54f8000
-
-// Cn = 0 (outside architecturally valid SYSP range for Cn)
-.inst 0xd5480000
-
-// Cm = 8 (outside architecturally valid SYSP range for Cm)
-.inst 0xd5488800
-
-// DISASM-NOT: tlbip
-// DISASM: <unknown>
-// DISASM: <unknown>
-// DISASM: <unknown>
diff --git a/llvm/test/MC/AArch64/armv9a-sysp.s b/llvm/test/MC/AArch64/armv9a-sysp.s
index 349f75eb95424..c01e83c92fcfd 100644
--- a/llvm/test/MC/AArch64/armv9a-sysp.s
+++ b/llvm/test/MC/AArch64/armv9a-sysp.s
@@ -21,6 +21,10 @@ sysp #0, c8, c0, #1, x0, x1
 // CHECK-INST: sysp #0, c8, c0, #1, x0, x1
 // CHECK-ENCODING: encoding: [0x20,0x80,0x48,0xd5]
 
+sysp #0, c9, c0, #0, x0, x1
+// CHECK-INST: sysp #0, c9, c0, #0, x0, x1
+// CHECK-ENCODING: encoding: [0x00,0x90,0x48,0xd5]
+
 sysp #0, c8, c4, #0, x0, x1
 // CHECK-INST: sysp #0, c8, c4, #0, x0, x1
 // CHECK-ENCODING: encoding: [0x00,0x84,0x48,0xd5]



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