[mips] Show an error if register number is out of range

Current code does not check that a register number is in the 0-31 range.
Sometimes the parser checks that later for some kinds of instructions,
but that leads to unclear / incorrect error messages like that:

  % cat test.s
  .text
  lb $4, 8($32)

  % llvm-mc test.s -triple=mips64-unknown-linux
  test.s:2:10: error: expected memory with 16-bit signed offset
    lb $4, 8($32)
           ^

Sometimes the parser just crashes:

  % cat test.s
  .text
  lw  $4, 8($32)

  % llvm-mc test.s -triple=mips64-unknown-linux

This patch resolves the problem by checking that register number after
'$' sign is in the 0-31 range. If the number is out of the range the
parser shows the `invalid register number` error, but treats invalid
register number as a normal one to continue parsing and catch other
possible errors.

Differential Revision: https://reviews.llvm.org/D45919

llvm-svn: 330732

1 files changed, 8 insertions, 1 deletions

diff --git a/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp b/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
index f7467e9de4a..869e037b22b 100644
--- a/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ b/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -6029,8 +6029,15 @@ MipsAsmParser::matchAnyRegisterWithoutDollar(OperandVector &Operands, SMLoc S) {
     return ResTy;
   } else if (Token.is(AsmToken::Integer)) {
     DEBUG(dbgs() << ".. integer\n");
+    int64_t RegNum = Token.getIntVal();
+    if (RegNum < 0 || RegNum > 31) {
+      // Show the error, but treat invalid register
+      // number as a normal one to continue parsing
+      // and catch other possible errors.
+      Error(getLexer().getLoc(), "invalid register number");
+    }
     Operands.push_back(MipsOperand::createNumericReg(
-        Token.getIntVal(), Token.getString(), getContext().getRegisterInfo(), S,
+        RegNum, Token.getString(), getContext().getRegisterInfo(), S,
         Token.getLoc(), *this));
     return MatchOperand_Success;
   }