[MSP430] Minor fixes/improvements for assembler/disassembler

* Teach AsmParser to recognize @rn in distination operand as 0(rn).
* Do not allow Disassembler decoding instructions that have size more
  than a number of input bytes.
* Fix UB in MSP430MCCodeEmitter.

Patch by Kristina Bessonova!

Differential Revision: https://reviews.llvm.org/D56547

llvm-svn: 350903

3 files changed, 18 insertions, 2 deletions

diff --git a/llvm/lib/Target/MSP430/AsmParser/MSP430AsmParser.cpp b/llvm/lib/Target/MSP430/AsmParser/MSP430AsmParser.cpp
index 3cc6da2c21a..1ad70ac72c7 100644
--- a/llvm/lib/Target/MSP430/AsmParser/MSP430AsmParser.cpp
+++ b/llvm/lib/Target/MSP430/AsmParser/MSP430AsmParser.cpp
@@ -497,7 +497,11 @@ bool MSP430AsmParser::ParseOperand(OperandVector &Operands) {
         getLexer().Lex(); // Eat '+'
         return false;
       }
-      Operands.push_back(MSP430Operand::CreateIndReg(RegNo, StartLoc, EndLoc));
+      if (Operands.size() > 1) // Emulate @rd in destination position as 0(rd)
+        Operands.push_back(MSP430Operand::CreateMem(RegNo,
+            MCConstantExpr::create(0, getContext()), StartLoc, EndLoc));
+      else
+        Operands.push_back(MSP430Operand::CreateIndReg(RegNo, StartLoc, EndLoc));
       return false;
     }
     case AsmToken::Hash:
diff --git a/llvm/lib/Target/MSP430/Disassembler/MSP430Disassembler.cpp b/llvm/lib/Target/MSP430/Disassembler/MSP430Disassembler.cpp
index 2a66b4ed7f2..e5da130f9bb 100644
--- a/llvm/lib/Target/MSP430/Disassembler/MSP430Disassembler.cpp
+++ b/llvm/lib/Target/MSP430/Disassembler/MSP430Disassembler.cpp
@@ -249,6 +249,10 @@ DecodeStatus MSP430Disassembler::getInstructionI(MCInst &MI, uint64_t &Size,
   case amSymbolic:
   case amImmediate:
   case amAbsolute:
+    if (Bytes.size() < (Words + 1) * 2) {
+      Size = 2;
+      return DecodeStatus::Fail;
+    }
     Insn |= (uint64_t)support::endian::read16le(Bytes.data() + 2) << 16;
     ++Words;
     break;
@@ -259,6 +263,10 @@ DecodeStatus MSP430Disassembler::getInstructionI(MCInst &MI, uint64_t &Size,
   case amIndexed:
   case amSymbolic:
   case amAbsolute:
+    if (Bytes.size() < (Words + 1) * 2) {
+      Size = 2;
+      return DecodeStatus::Fail;
+    }
     Insn |= (uint64_t)support::endian::read16le(Bytes.data() + Words * 2)
         << (Words * 16);
     ++Words;
@@ -296,6 +304,10 @@ DecodeStatus MSP430Disassembler::getInstructionII(MCInst &MI, uint64_t &Size,
   case amSymbolic:
   case amImmediate:
   case amAbsolute:
+    if (Bytes.size() < (Words + 1) * 2) {
+      Size = 2;
+      return DecodeStatus::Fail;
+    }
     Insn |= (uint64_t)support::endian::read16le(Bytes.data() + 2) << 16;
     ++Words;
     break;
diff --git a/llvm/lib/Target/MSP430/MCTargetDesc/MSP430MCCodeEmitter.cpp b/llvm/lib/Target/MSP430/MCTargetDesc/MSP430MCCodeEmitter.cpp
index adf2384f6e9..06f9f307cb1 100644
--- a/llvm/lib/Target/MSP430/MCTargetDesc/MSP430MCCodeEmitter.cpp
+++ b/llvm/lib/Target/MSP430/MCTargetDesc/MSP430MCCodeEmitter.cpp
@@ -128,7 +128,7 @@ unsigned MSP430MCCodeEmitter::getMemOpValue(const MCInst &MI, unsigned Op,
   const MCOperand &MO2 = MI.getOperand(Op + 1);
   if (MO2.isImm()) {
     Offset += 2;
-    return (MO2.getImm() << 4) | Reg;
+    return ((unsigned)MO2.getImm() << 4) | Reg;
   }
 
   assert(MO2.isExpr() && "Expr operand expected");