Today, if any instruction uses EncodingInfos/EncodingByHwMode to
override the default encoding, the opcode field of the decoder table is
generated incorrectly. This causes failed disassemblies and other
problems.
Specifically, the main correctness issue is that the EncodingID is
inadvertently stored in the table rather than the actual opcode. This is
caused by having set up the IndexOfInstruction map incorrectly during
the loop to populate NumberedEncodings-- which is then propagated around
when OpcMap is set up with a bad EncodingIDAndOpcode.
Instead, do away with IndexOfInstruction altogether and use opcode value
queried from CodeGenTarget::getInstrIntValue to set up OpcMap. This
itself exposed another problem where emitTable was using the decoded
opcode to index into NumberedEncodings. Instead pass in the
EncodingIDAndOpcode vector, and create the reverse mapping from Opcode
to EncodingID, which is then used to index NumberedEncodings.
This problem is not currently exposed upstream since no in-tree targets
yet use the per-HwMode feature. It does show up in at least two
downstream targets.
Use the predicate condition instead of checkFeatures in *GenDAGISel.inc.
This makes the code similar to isel pattern predicates.
checkFeatures is still used by code created by SubtargetEmitter so
we can't remove the string. Backends need to be careful to keep
the string and predicates in sync, but I don't think that's a big issue.
I haven't measured it, but this should be a compile time improvement
for isel since we don't have to do any of the string processing that's
inside checkFeatures.
Reviewed By: kparzysz
Differential Revision: https://reviews.llvm.org/D146012
When an instruction has an encoding definition for only a subset of
the available HwModes, ensure we just avoid generating an encoding
rather than crash.
llvm-svn: 374150
Much like ValueTypeByHwMode/RegInfoByHwMode, this patch allows targets
to modify an instruction's encoding based on HwMode. When the
EncodingInfos field is non-empty the Inst and Size fields of the Instruction
are ignored and taken from EncodingInfos instead.
As part of this promote getHwMode() from TargetSubtargetInfo to MCSubtargetInfo.
This is NFC for all existing targets - new code is generated only if targets
use EncodingByHwMode.
llvm-svn: 372320
