Thumb disassembler was erroneously rejecting "blx sp" instruction.

rdar://problem/9267838

llvm-svn: 129320

2 files changed, 14 insertions, 2 deletions

diff --git a/llvm/lib/Target/ARM/ARMInstrThumb.td b/llvm/lib/Target/ARM/ARMInstrThumb.td
index 15ab4557dea..e3a9742bc76 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb.td
@@ -369,6 +369,15 @@ let isReturn = 1, isTerminator = 1, isBarrier = 1 in {
     let Inst{2-0} = 0b000;
   }
 
+  def tBX_Rm : TI<(outs), (ins pred:$p, GPR:$Rm), IIC_Br, "bx${p}\t$Rm",
+                  [/* for disassembly only */]>,
+               T1Special<{1,1,0,?}> {
+    // A6.2.3 & A8.6.25
+    bits<4> Rm;
+    let Inst{6-3} = Rm;
+    let Inst{2-0} = 0b000;
+  }
+
   // Alternative return instruction used by vararg functions.
   def tBX_RET_vararg : TI<(outs), (ins tGPR:$Rm),
                           IIC_Br, "bx\t$Rm",
diff --git a/llvm/lib/Target/ARM/Disassembler/ThumbDisassemblerCore.h b/llvm/lib/Target/ARM/Disassembler/ThumbDisassemblerCore.h
index 727fc1332ad..85816e02fef 100644
--- a/llvm/lib/Target/ARM/Disassembler/ThumbDisassemblerCore.h
+++ b/llvm/lib/Target/ARM/Disassembler/ThumbDisassemblerCore.h
@@ -485,10 +485,13 @@ static bool DisassembleThumb1Special(MCInst &MI, unsigned Opcode, uint32_t insn,
     return true;
 
   // BX/BLX has 1 reg operand: Rm.
-  if (NumOps == 1) {
+  if (Opcode == ARM::tBLXr_r9 || Opcode == ARM::tBX_Rm) {
+    // Handling the two predicate operands before the reg operand.
+    if (!B->DoPredicateOperands(MI, Opcode, insn, NumOps))
+      return false;
     MI.addOperand(MCOperand::CreateReg(getRegisterEnum(B, ARM::GPRRegClassID,
                                                        getT1Rm(insn))));
-    NumOpsAdded = 1;
+    NumOpsAdded = 3;
     return true;
   }