[mips][mips64r6] [ls][wd]c2 were re-encoded with 11-bit signed immediates rather than 16-bit in MIPS32r6/MIPS64r6

Summary:
The error message for the invalid.s cases isn't very helpful. It happens because
there is an instruction with a wider immediate that would have matched if the
NotMips32r6 predicate were true. I have some WIP to improve the message but it
affects most error messages for removed/re-encoded instructions on
MIPS32r6/MIPS64r6 and should therefore be a separate commit.

Depens on D4115

Reviewers: zoran.jovanovic, jkolek, vmedic

Reviewed By: vmedic

Differential Revision: http://reviews.llvm.org/D4117

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211012 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

@@ -620,6 +620,12 @@ public:
     return Kind == k_Token;
   }
   bool isMem() const override { return Kind == k_Memory; }
+  bool isConstantMemOff() const {
+    return isMem() && dyn_cast<MCConstantExpr>(getMemOff());
+  }
+  template <unsigned Bits> bool isMemWithSimmOffset() const {
+    return isMem() && isConstantMemOff() && isInt<Bits>(getConstantMemOff());
+  }
   bool isInvNum() const { return Kind == k_Immediate; }
   bool isLSAImm() const {
     if (!isConstantImm())
@@ -664,6 +670,10 @@ public:
     return Mem.Off;
   }
 
+  int64_t getConstantMemOff() const {
+    return static_cast<const MCConstantExpr *>(getMemOff())->getValue();
+  }
+
   static std::unique_ptr<MipsOperand> CreateToken(StringRef Str, SMLoc S,
                                                   MipsAsmParser &Parser) {
     auto Op = make_unique<MipsOperand>(k_Token, Parser);