Most clients only used these methods because they wanted to be able to
extend or truncate to the same bit width (which is a no-op). Now that
the standard zext, sext and trunc allow this, there is no reason to use
the OrSelf versions.
The OrSelf versions additionally have the strange behaviour of allowing
extending to a *smaller* width, or truncating to a *larger* width, which
are also treated as no-ops. A small amount of client code relied on this
(ConstantRange::castOp and MicrosoftCXXNameMangler::mangleNumber) and
needed rewriting.
Differential Revision: https://reviews.llvm.org/D125557
To support variable length instructions, I think of them as fixed length instructions with the "maximum length". For example, if there're three instructions with 2, 6 and 9 bytes, we can fit them into the algorithm by treating them all as 9 bytes.
Also, since we can't know the length of the instruction in advance, there is a function object with type `void(APInt &, uint64_t)` added in the parameter list of `decodeInstruction` and `fieldFromInstruction`. We can use this to supply the additional bits the decoder needs after we know the opcode of the instruction.
Finally, `InstrLenTable` is added to let the decoder know the length of the instructions.
See D120960 for its usage.
Reviewed By: myhsu
Differential Revision: https://reviews.llvm.org/D120958
This gives a approximate error location. Although not very
accurate, it suffices to debug.
Reviewed By: myhsu
Differential Revision: https://reviews.llvm.org/D119684
The new encoder directive can be used to specify custom encoder for a
single operand or slice. This is different from the EncoderMethod field
within an Operand, which affects every operands in the target.
In addition, this patch also changes the function signature of the
encoder method -- a new argument, InsertPost, is added to both the
default one (i.e. getMachineValue) and the custom one. This argument
provides the bit position where the operand will eventually be inserted.
Differential Revision: https://reviews.llvm.org/D119100
Full write up:
https://gist.github.com/mshockwave/66e98d099256deefc062633909bb7b5b
The existing CodeEmitterGen infrastructure is unable to generate encoder
function for ISAs with variable-length instructions. This patch
introduces a new infrastructure to support variable-length instruction
encoding, including a new TableGen syntax for writing instruction
encoding directives and a new TableGen backend component,
VarLenCodeEmitterGen, built on top of CodeEmitterGen.
Differential Revision: https://reviews.llvm.org/D115128
Jay Foad