The patch adds CodeGen support for microMIPSr6 DIV, MOD, DIVU, MODU, DDIV, DMOD, DDIVU and DMODU instructions:
- fixed order of registers in encoding definition class for microMIPS64 DDIV, DMOD, DDIVU and DMODU instructions
- updated tests for the standard encodings of DDIV, DMOD, DDIVU and DMODU instructions
- changed description class for microMIPSr6 DIV, MOD, DIVU, MODU, DDIV, DMOD, DDIVU and DMODU instructions:
- enabled insert of "teq $divisor_reg, $zero, 7" instruction in case of division by zero
- added DAG patterns for proper selection of instructions
- separated microMIPSr6 instructions from equivalent MIPS instructions using NotInMicroMips predicate
- added microMIPS pseudo DIV and DIVU instructions with explicit accumulator register operands
- updated .ll files with tests for microMIPSr6 DIV, MOD, DIVU, MODU, DDIV, DMOD, DDIVU and DMODU instructions
- fixed "Cannot copy registers" assertion:
- added GPRMM16_64 register class and updated selection of register class for microMIPS64