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Add a "clobbers_flags" flag to encoding recipes.

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On some ISAs like Intel's, all arithmetic instructions set all or some
of the CPU flags, so flag values can't be live across these
instructions. On ISAs like ARM's Aarch32, flags are clobbered by compact
16-bit encodings but not necessarily by 32-bit encodings of the same
instruction.

The "clobbers_flags" bit on the encoding recipe is used to indicate if
CPU flag values can be live across an instruction, or conversely whether
the encoding can be used where flag values are live.
This commit is contained in:
Jakob Stoklund Olesen
2017-10-16 14:06:04 -07:00
parent 5d065c4d8f
commit 620eb7effe
4 changed files with 75 additions and 16 deletions
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37
lib/cretonne/meta/cdsl/isa.py
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@@ -310,29 +310,35 @@ class EncRecipe(object):
branch instructions. It is an `(origin, bits)` tuple describing the exact
range that can be encoded in a branch instruction.
For ISAs that use CPU flags in `iflags` and `fflags` value types, the
`clobbers_flags` is used to indicate instruction encodings that clobbers
the CPU flags, so they can't be used where a flag value is live.
:param name: Short mnemonic name for this recipe.
:param format: All encoded instructions must have this
:py:class:`InstructionFormat`.
:param size: Number of bytes in the binary encoded instruction.
:param: ins Tuple of register constraints for value operands.
:param: outs Tuple of register constraints for results.
:param: branch_range `(origin, bits)` range for branches.
:param: instp Instruction predicate.
:param: isap ISA predicate.
:param: emit Rust code for binary emission.
:param ins: Tuple of register constraints for value operands.
:param outs: Tuple of register constraints for results.
:param branch_range: `(origin, bits)` range for branches.
:param clobbers_flags: This instruction clobbers `iflags` and `fflags`.
:param instp: Instruction predicate.
:param isap: ISA predicate.
:param emit: Rust code for binary emission.
"""
def __init__(
self,
name, # type: str
format, # type: InstructionFormat
size, # type: int
ins, # type: ConstraintSeq
outs, # type: ConstraintSeq
branch_range=None, # type: BranchRange
instp=None, # type: PredNode
isap=None, # type: PredNode
emit=None # type: str
name, # type: str
format, # type: InstructionFormat
size, # type: int
ins, # type: ConstraintSeq
outs, # type: ConstraintSeq
branch_range=None, # type: BranchRange
clobbers_flags=True, # type: bool
instp=None, # type: PredNode
isap=None, # type: PredNode
emit=None # type: str
):
# type: (...) -> None
self.name = name
@@ -340,6 +346,7 @@ class EncRecipe(object):
assert size >= 0
self.size = size
self.branch_range = branch_range
self.clobbers_flags = clobbers_flags
self.instp = instp
self.isap = isap
self.emit = emit