[ARM][disassembler] Fix incorrect number of MCOperands generated by the disassembler

Try to fix bug 49974.

This patch fixes two issues:

 1. BL does not use predicate (BL_pred is the predicate version of BL),
    so we shouldn't add predicate operands in DecodeBranchImmInstruction.
 2. Inside DecodeT2AddSubSPImm, we shouldn't add predicate operands into
    the MCInst because ARMDisassembler::AddThumbPredicate will do that for us.
    However, we should handle CC-out operand for t2SUBspImm and t2AddspImm.

Differential Revision: https://reviews.llvm.org/D100585

1 files changed, 8 insertions, 7 deletions

diff --git a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index 8ea323a..51fd450 100644
--- a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -2676,8 +2676,12 @@ DecodeBranchImmInstruction(MCInst &Inst, unsigned Insn,
   if (!tryAddingSymbolicOperand(Address, Address + SignExtend32<26>(imm) + 8,
                                 true, 4, Inst, Decoder))
     Inst.addOperand(MCOperand::createImm(SignExtend32<26>(imm)));
-  if (!Check(S, DecodePredicateOperand(Inst, pred, Address, Decoder)))
-    return MCDisassembler::Fail;
+
+  // We already have BL_pred for BL w/ predicate, no need to add addition
+  // predicate opreands for BL
+  if (Inst.getOpcode() != ARM::BL)
+    if (!Check(S, DecodePredicateOperand(Inst, pred, Address, Decoder)))
+      return MCDisassembler::Fail;
 
   return S;
 }
@@ -6670,17 +6674,14 @@ static DecodeStatus DecodeT2AddSubSPImm(MCInst &Inst, unsigned Insn,
     return MCDisassembler::Fail;
   if (TypeT3) {
     Inst.setOpcode(sign1 ? ARM::t2SUBspImm12 : ARM::t2ADDspImm12);
-    S = 0;
     Inst.addOperand(MCOperand::createImm(Imm12)); // zext imm12
   } else {
     Inst.setOpcode(sign1 ? ARM::t2SUBspImm : ARM::t2ADDspImm);
     if (!Check(DS, DecodeT2SOImm(Inst, Imm12, Address, Decoder))) // imm12
       return MCDisassembler::Fail;
+    if (!Check(DS, DecodeCCOutOperand(Inst, S, Address, Decoder))) // cc_out
+      return MCDisassembler::Fail;
   }
-  if (!Check(DS, DecodeCCOutOperand(Inst, S, Address, Decoder))) // cc_out
-    return MCDisassembler::Fail;
-
-  Inst.addOperand(MCOperand::createReg(0)); // pred
 
   return DS;
 }