Support local labels

[dylanmckay]

See lib/MC/MCParser/AsmParser.cpp:870.

For some reason, AsmParser::parsePrimaryExpr is not handling b and f suffixes on local labels.

[dylanmckay]

The problem lies in AVRAsmParser.cpp:466.

Whenever we try and parse an operand, we first check if it is a valid register. If it is, then we treat it as such. For situations like sbiw X, 24, X is parsed into a MCOperand of type register, and then we get to 24 (which is a valid register, our code currently allows 31 instead of r31 currently -- perhaps this is in error). 24 is parsed into an MCOperand of type register, even though it is not a register. We still get the correct output, however.

In the case of local labels, they are automatically taken to be registers. Because of this, the correct branch (in the else block) is not executed, and MCParser.parseExpression() doesn't handle it. MCParser.parseExpression() has code to handle a trailing b or f.

[dylanmckay]

There is an ambiguity when parsing integer operands without context, because AVR-GCC supports specifiying register names (r12) and register numbers (12) interchangeably. Without context, we can't tell the difference.

There are two solutions:

• Drop support for numbered registers and only support the r12 syntax. This would make us incompatible with AVR-GCC.
• Use context to disambiguate between the two cases. We could hook into the tablegen'd AVRGenInstrInfo.inc, check if the current operand is a register, then handle it appropriately.

[RandomInsano]

My opinion is to not support GCC numbered registers until someone comes along who needs it. It sounds like such a confusing idea.

[dylanmckay]

My opinion is to not support GCC numbered registers until someone comes along who needs it. It sounds like such a confusing idea.

I concur.

[dylanmckay]

I have removed support for numbered registers in d9c85f193f0bf40f776b7a6581c79419dd1bbe7a; local labels are now correctly handled.