Fix BXJ is undefined in AArch32.

BXJ was incorrectly said to be unsupported in ARMv8-A. It is not
supported in the A64 instruction set, but it is supported in the T32
and A32 instruction sets, because it's listed as an instruction in the
ARM ARM section F7.1.28.

Using SP as an operand to BXJ changed from UNPREDICTABLE to
PREDICTABLE in v8-A. This patch reflects that update as well.

This was found by MCHammer.

llvm-svn: 235024

2 files changed, 10 insertions, 2 deletions

diff --git a/llvm/lib/Target/ARM/ARMInstrThumb2.td b/llvm/lib/Target/ARM/ARMInstrThumb2.td
index ac3d6f9e575..4515a8129f7 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb2.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb2.td
@@ -3630,8 +3630,8 @@ def t2IT : Thumb2XI<(outs), (ins it_pred:$cc, it_mask:$mask),
 
 // Branch and Exchange Jazelle -- for disassembly only
 // Rm = Inst{19-16}
-def t2BXJ : T2I<(outs), (ins rGPR:$func), NoItinerary, "bxj", "\t$func", []>,
-    Sched<[WriteBr]>, Requires<[IsThumb2, IsNotMClass, PreV8]> {
+def t2BXJ : T2I<(outs), (ins GPRnopc:$func), NoItinerary, "bxj", "\t$func", []>,
+    Sched<[WriteBr]>, Requires<[IsThumb2, IsNotMClass]> {
   bits<4> func;
   let Inst{31-27} = 0b11110;
   let Inst{26} = 0;
diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 0fa99a94f18..4b9fcbe38fc 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -6150,6 +6150,14 @@ bool ARMAsmParser::validateInstruction(MCInst &Inst,
                    "destination operands can't be identical");
     return false;
   }
+  case ARM::t2BXJ: {
+    const unsigned RmReg = Inst.getOperand(0).getReg();
+    // Rm = SP is no longer unpredictable in v8-A
+    if (RmReg == ARM::SP && !hasV8Ops())
+      return Error(Operands[2]->getStartLoc(),
+                   "r13 (SP) is an unpredictable operand to BXJ");
+    return false;
+  }
   case ARM::STRD: {
     // Rt2 must be Rt + 1.
     unsigned Rt = MRI->getEncodingValue(Inst.getOperand(0).getReg());