ARM: implement MRS/MSR (banked reg) system instructions.

These are system-only instructions for CPUs with virtualization
extensions, allowing a hypervisor easy access to all of the various
different AArch32 registers.

rdar://problem/17861345

llvm-svn: 215700

1 files changed, 25 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index 48bcc9b2dcd..0940e2a2407 100644
--- a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -281,6 +281,8 @@ static DecodeStatus DecodeInstSyncBarrierOption(MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
 static DecodeStatus DecodeMSRMask(MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
+static DecodeStatus DecodeBankedReg(MCInst &Inst, unsigned Insn,
+                               uint64_t Address, const void *Decoder);
 static DecodeStatus DecodeDoubleRegLoad(MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
 static DecodeStatus DecodeDoubleRegStore(MCInst &Inst, unsigned Insn,
@@ -4025,6 +4027,29 @@ static DecodeStatus DecodeMSRMask(MCInst &Inst, unsigned Val,
   return MCDisassembler::Success;
 }
 
+static DecodeStatus DecodeBankedReg(MCInst &Inst, unsigned Val,
+                                    uint64_t Address, const void *Decoder) {
+
+  unsigned R = fieldFromInstruction(Val, 5, 1);
+  unsigned SysM = fieldFromInstruction(Val, 0, 5);
+
+  // The table of encodings for these banked registers comes from B9.2.3 of the
+  // ARM ARM. There are patterns, but nothing regular enough to make this logic
+  // neater. So by fiat, these values are UNPREDICTABLE:
+  if (!R) {
+    if (SysM == 0x7 || SysM == 0xf || SysM == 0x18 || SysM == 0x19 ||
+        SysM == 0x1a || SysM == 0x1b)
+      return MCDisassembler::SoftFail;
+  } else {
+    if (SysM != 0xe && SysM != 0x10 && SysM != 0x12 && SysM != 0x14 &&
+        SysM != 0x16 && SysM != 0x1c && SysM != 0x1e)
+      return MCDisassembler::SoftFail;
+  }
+
+  Inst.addOperand(MCOperand::CreateImm(Val));
+  return MCDisassembler::Success;
+}
+
 static DecodeStatus DecodeDoubleRegLoad(MCInst &Inst, unsigned Insn,
                                         uint64_t Address, const void *Decoder) {
   DecodeStatus S = MCDisassembler::Success;