Add operand register constraints.

Every encoding recipe must specify register constraints on input and
output values.

Generate recipe constraint tables along with the other encoding tables.

docs/metaref.rst

@@ -331,8 +331,6 @@ encoded:
 - The CPU mode that must be active.
 - A :term:`sub-target predicate` that must be satisfied by the currently active
   sub-target.
-- :term:`Register constraint`\s that must be satisfied by the instruction's value
-  operands and results.
 
 An encoding specifies an *encoding recipe* along with some *encoding bits* that
 the recipe can use for native opcode fields etc. The encoding recipe has
@@ -349,6 +347,83 @@ encodings only need the recipe predicates.
 
 .. autoclass:: EncRecipe
 
+Register constraints
+====================
+
+After an encoding recipe has been chosen for an instruction, it is the register
+allocator's job to make sure that the recipe's :term:`Register constraint`\s
+are satisfied. Most ISAs have separate integer and floating point registers,
+and instructions can usually only use registers from one of the banks. Some
+instruction encodings are even more constrained and can only use a subset of
+the registers in a bank. These constraints are expressed in terms of register
+classes.
+
+Sometimes the result of an instruction is placed in a register that must be the
+same as one of the input registers. Some instructions even use a fixed register
+for inputs or results.
+
+Each encoding recipe specifies separate constraints for its value operands and
+result. These constraints are separate from the instruction predicate which can
+only evaluate the instruction's immediate operands.
+
+.. module:: cdsl.registers
+.. autoclass:: RegBank
+
+Register class constraints
+--------------------------
+
+The most common type of register constraint is the register class. It specifies
+that an operand or result must be allocated one of the registers from the given
+register class::
+
+    IntRegs = RegBank('IntRegs', ISA, 'General purpose registers', units=16, prefix='r')
+    GPR = RegClass(IntRegs)
+    R = EncRecipe('R', Binary, ins=(GPR, GPR), outs=GPR)
+
+This defines an encoding recipe for the ``Binary`` instruction format where
+both input operands must be allocated from the ``GPR`` register class.
+
+.. autoclass:: RegClass
+
+Tied register operands
+----------------------
+
+In more compact machine code encodings, it is common to require that the result
+register is the same as one of the inputs. This is represented with tied
+operands::
+
+    CR = EncRecipe('CR', Binary, ins=(GPR, GPR), outs=0)
+
+This indicates that the result value must be allocated to the same register as
+the first input value. Tied operand constraints can only be used for result
+values, so the number always refers to one of the input values.
+
+Fixed register operands
+-----------------------
+
+Some instructions use hard-coded input and output registers for some value
+operands. An example is the ``pblendvb`` Intel SSE instruction which takes one
+of its three value operands in the hard-coded ``%xmm0`` register::
+
+    XMM0 = FPR[0]
+    SSE66_XMM0 = EncRecipe('SSE66_XMM0', Ternary, ins=(FPR, FPR, XMM0), outs=0)
+
+The syntax ``FPR[0]`` selects the first register from the ``FPR`` register
+class which consists of all the XMM registers.
+
+Stack operands
+--------------
+
+Cretonne's register allocator can assign an SSA value to a stack slot if there
+isn't enough registers. It will insert :cton:inst:`spill` and :cton:inst:`fill`
+instructions as needed to satisfy instruction operand constraints, but it is
+also possible to have instructions that can access stack slots directly::
+
+    CSS = EncRecipe('CSS', Unary, ins=GPR, outs=Stack(GPR))
+
+An output stack value implies a store to the stack, an input value implies a
+load.
+
 .. module:: cdsl.isa
 
 Targets
@@ -366,6 +441,9 @@ The definitions for each supported target live in a package under
     :members:
 
 .. automodule:: isa.riscv
+.. automodule:: isa.intel
+.. automodule:: isa.arm32
+.. automodule:: isa.arm64
 
 
 Glossary

lib/cretonne/meta/cdsl/isa.py

@@ -1,6 +1,7 @@
 """Defining instruction set architectures."""
 from __future__ import absolute_import
 from .predicates import And
+from .registers import RegClass, Register
 
 # The typing module is only required by mypy, and we don't use these imports
 # outside type comments.
@@ -12,6 +13,8 @@ try:
     from .types import ValueType  # noqa
     from .registers import RegBank  # noqa
     AnyPredicate = Union[Predicate, FieldPredicate]
+    OperandConstraint = Union[RegClass, Register, int]
+    ConstraintSeq = Union[OperandConstraint, Tuple[OperandConstraint, ...]]
 except ImportError:
     pass
 
@@ -133,13 +136,24 @@ class EncRecipe(object):
     Many different instructions can be encoded by the same recipe, but they
     must all have the same instruction format.
 
+    The `ins` and `outs` arguments are tuples specifying the register
+    allocation constraints for the value operands and results respectively. The
+    possible constraints for an operand are:
+
+    - A `RegClass` specifying the set of allowed registers.
+    - A `Register` specifying a fixed-register operand.
+    - An integer indicating that this result is tied to a value operand, so
+      they must use the same register.
+
     :param name: Short mnemonic name for this recipe.
     :param format: All encoded instructions must have this
             :py:class:`InstructionFormat`.
+    :param: ins Tuple of register constraints for value operands.
+    :param: outs Tuple of register constraints for results.
     """
 
-    def __init__(self, name, format, instp=None, isap=None):
-        # type: (str, InstructionFormat, AnyPredicate, AnyPredicate) -> None
+    def __init__(self, name, format, ins, outs, instp=None, isap=None):
+        # type: (str, InstructionFormat, ConstraintSeq, ConstraintSeq, AnyPredicate, AnyPredicate) -> None  # noqa
         self.name = name
         self.format = format
         self.instp = instp
@@ -148,10 +162,29 @@ class EncRecipe(object):
             assert instp.predicate_context() == format
         self.number = None  # type: int
 
+        self.ins = self._verify_constraints(ins)
+        assert len(self.ins) == len(format.value_operands)
+        self.outs = self._verify_constraints(outs)
+        if len(self.outs) > 1:
+            assert format.multiple_results
+
     def __str__(self):
         # type: () -> str
         return self.name
 
+    def _verify_constraints(self, seq):
+        # (ConstraintSeq) -> Sequence[OperandConstraint]
+        if not isinstance(seq, tuple):
+            seq = (seq,)
+        for c in seq:
+            if isinstance(c, int):
+                # An integer constraint is bound to a value operand.
+                # Check that it is in range.
+                assert c >= 0 and c < len(self.format.value_operands)
+            else:
+                assert isinstance(c, RegClass) or isinstance(c, Register)
+        return seq
+
 
 class Encoding(object):
     """

lib/cretonne/meta/cdsl/registers.py

@@ -62,7 +62,7 @@ class RegBank(object):
                   `units`, the remaining units are named using `prefix`.
     """
 
-    def __init__(self, name, isa, doc, units, prefix='p', names=()):
+    def __init__(self, name, isa, doc, units, prefix='r', names=()):
         # type: (str, TargetISA, str, int, str, Sequence[str]) -> None
         self.name = name
         self.isa = isa
@@ -124,12 +124,16 @@ class RegClass(object):
 
         bank.classes.append(self)
 
+    def __str__(self):
+        return self.name
+
     def __getitem__(self, sliced):
         """
         Create a sub-class of a register class using slice notation. The slice
         indexes refer to allocations in the parent register class, not register
         units.
         """
+        print(repr(sliced))
         assert isinstance(sliced, slice), "RegClass slicing can't be 1 reg"
         # We could add strided sub-classes if needed.
         assert sliced.step is None, 'Subclass striding not supported'
@@ -142,6 +146,7 @@ class RegClass(object):
         return RegClass(self.bank, count=c, width=w, start=s)
 
     def mask(self):
+        # type: () -> List[int]
         """
         Compute a bit-mask of the register units allocated by this register
         class.
@@ -173,3 +178,22 @@ class RegClass(object):
             if isinstance(obj, RegClass):
                 assert obj.name is None
                 obj.name = name
+
+
+class Register(object):
+    """
+    A specific register in a register class.
+
+    A register is identified by the top-level register class it belongs to and
+    its first register unit.
+
+    Specific registers are used to describe constraints on instructions where
+    some operands must use a fixed register.
+
+    Register objects should be created using the indexing syntax on the
+    register class.
+    """
+    def __init__(self, rc, unit):
+        # type: (RegClass, int) -> None
+        self.regclass = rc
+        self.unit = unit

lib/cretonne/meta/gen_encoding.py

@@ -1,7 +1,7 @@
 """
 Generate sources for instruction encoding.
 
-The tables and functions generated here support the `TargetIsa::encode()`
+The tables and functions generated here support the `TargetISA::encode()`
 function which determines if a given instruction is legal, and if so, it's
 `Encoding` data which consists of a *recipe* and some *encoding* bits.
 
@@ -56,6 +56,13 @@ from unique_table import UniqueSeqTable
 from collections import OrderedDict, defaultdict
 import math
 import itertools
+from cdsl.registers import RegClass, Register
+
+try:
+    from typing import Sequence  # noqa
+    from cdsl.isa import TargetISA, OperandConstraint  # noqa
+except ImportError:
+    pass
 
 
 def emit_instp(instp, fmt):
@@ -399,6 +406,7 @@ def offset_type(length):
 
 
 def emit_recipe_names(isa, fmt):
+    # type: (TargetISA, srcgen.Formatter) -> None
     """
     Emit a table of encoding recipe names keyed by recipe number.
 
@@ -411,6 +419,48 @@ def emit_recipe_names(isa, fmt):
             fmt.line('"{}",'.format(r.name))
 
 
+def emit_recipe_constraints(isa, fmt):
+    # type: (TargetISA, srcgen.Formatter) -> None
+    """
+    Emit a table of encoding recipe operand constraints keyed by recipe number.
+
+    These are used by the register allocator to pick registers that can be
+    properly encoded.
+    """
+    with fmt.indented(
+            'pub static RECIPE_CONSTRAINTS: [RecipeConstraints; {}] = ['
+            .format(len(isa.all_recipes)), '];'):
+        for r in isa.all_recipes:
+            fmt.comment(r.name)
+            with fmt.indented('RecipeConstraints {', '},'):
+                emit_operand_constraints(r.ins, 'ins', fmt)
+                emit_operand_constraints(r.outs, 'outs', fmt)
+
+
+def emit_operand_constraints(seq, field, fmt):
+    # type: (Sequence[OperandConstraint], str, srcgen.Formatter) -> None
+    """
+    Emit a struct field initializer for an array of operand constraints.
+    """
+    if len(seq) == 0:
+        fmt.line('{}: &[],'.format(field))
+        return
+    with fmt.indented('{}: &['.format(field), '],'):
+        for cons in seq:
+            with fmt.indented('OperandConstraint {', '},'):
+                if isinstance(cons, RegClass):
+                    fmt.line('kind: ConstraintKind::Reg,')
+                    fmt.line('regclass: {},'.format(cons))
+                elif isinstance(cons, Register):
+                    fmt.line(
+                            'kind: ConstraintKind::FixedReg({}),'
+                            .format(cons.unit))
+                    fmt.line('regclass: {},'.format(cons.regclass))
+                else:
+                    raise AssertionError(
+                            'Unsupported constraint {}'.format(cons))
+
+
 def gen_isa(isa, fmt):
     # First assign numbers to relevant instruction predicates and generate the
     # check_instp() function..
@@ -446,6 +496,7 @@ def gen_isa(isa, fmt):
                 cpumode, level1_tables[cpumode], level1_offt, fmt)
 
     emit_recipe_names(isa, fmt)
+    emit_recipe_constraints(isa, fmt)
 
 
 def generate(isas, out_dir):

lib/cretonne/meta/isa/riscv/recipes.py

@@ -12,6 +12,7 @@ from __future__ import absolute_import
 from cdsl.isa import EncRecipe
 from cdsl.predicates import IsSignedInt
 from base.formats import Binary, BinaryImm
+from .registers import GPR
 
 # The low 7 bits of a RISC-V instruction is the base opcode. All 32-bit
 # instructions have 11 as the two low bits, with bits 6:2 determining the base
@@ -67,9 +68,11 @@ def OP32(funct3, funct7):
 
 # R-type 32-bit instructions: These are mostly binary arithmetic instructions.
 # The encbits are `opcode[6:2] | (funct3 << 5) | (funct7 << 8)
-R = EncRecipe('R', Binary)
+R = EncRecipe('R', Binary, ins=(GPR, GPR), outs=GPR)
 
 # R-type with an immediate shift amount instead of rs2.
-Rshamt = EncRecipe('Rshamt', BinaryImm)
+Rshamt = EncRecipe('Rshamt', BinaryImm, ins=GPR, outs=GPR)
 
-I = EncRecipe('I', BinaryImm, instp=IsSignedInt(BinaryImm.imm, 12))
+I = EncRecipe(
+        'I', BinaryImm, ins=GPR, outs=GPR,
+        instp=IsSignedInt(BinaryImm.imm, 12))

lib/cretonne/src/isa/arm32/enc_tables.rs

@@ -4,5 +4,6 @@ use ir::InstructionData;
 use ir::instructions::InstructionFormat;
 use ir::types;
 use isa::enc_tables::{Level1Entry, Level2Entry};
+use isa::constraints::*;
 
 include!(concat!(env!("OUT_DIR"), "/encoding-arm32.rs"));

lib/cretonne/src/isa/arm32/mod.rs

@@ -7,7 +7,7 @@ mod registers;
 use super::super::settings as shared_settings;
 use isa::enc_tables::{self as shared_enc_tables, lookup_enclist, general_encoding};
 use isa::Builder as IsaBuilder;
-use isa::{TargetIsa, RegInfo, Encoding, Legalize};
+use isa::{TargetIsa, RegInfo, Encoding, Legalize, RecipeConstraints};
 use ir::{InstructionData, DataFlowGraph};
 
 #[allow(dead_code)]
@@ -70,4 +70,8 @@ impl TargetIsa for Isa {
     fn recipe_names(&self) -> &'static [&'static str] {
         &enc_tables::RECIPE_NAMES[..]
     }
+
+    fn recipe_constraints(&self) -> &'static [RecipeConstraints] {
+        &enc_tables::RECIPE_CONSTRAINTS
+    }
 }

lib/cretonne/src/isa/arm64/enc_tables.rs

@@ -4,5 +4,6 @@ use ir::InstructionData;
 use ir::instructions::InstructionFormat;
 use ir::types;
 use isa::enc_tables::{Level1Entry, Level2Entry};
+use isa::constraints::*;
 
 include!(concat!(env!("OUT_DIR"), "/encoding-arm64.rs"));

lib/cretonne/src/isa/arm64/mod.rs

@@ -7,7 +7,7 @@ mod registers;
 use super::super::settings as shared_settings;
 use isa::enc_tables::{lookup_enclist, general_encoding};
 use isa::Builder as IsaBuilder;
-use isa::{TargetIsa, RegInfo, Encoding, Legalize};
+use isa::{TargetIsa, RegInfo, Encoding, Legalize, RecipeConstraints};
 use ir::{InstructionData, DataFlowGraph};
 
 #[allow(dead_code)]
@@ -63,4 +63,8 @@ impl TargetIsa for Isa {
     fn recipe_names(&self) -> &'static [&'static str] {
         &enc_tables::RECIPE_NAMES[..]
     }
+
+    fn recipe_constraints(&self) -> &'static [RecipeConstraints] {
+        &enc_tables::RECIPE_CONSTRAINTS
+    }
 }

lib/cretonne/src/isa/constraints.rs

@@ -0,0 +1,66 @@
+//! Register constraints for instruction operands.
+//!
+//! An encoding recipe specifies how an instruction is encoded as binary machine code, but it only
+//! works if the operands and results satisfy certain constraints. Constraints on immediate
+//! operands are checked by instruction predicates when the recipe is chosen.
+//!
+//! It is the register allocator's job to make sure that the register constraints on value operands
+//! are satisfied.
+
+use isa::{RegClass, RegUnit};
+
+/// Register constraint for a single value operand or instruction result.
+pub struct OperandConstraint {
+    /// The kind of constraint.
+    pub kind: ConstraintKind,
+
+    /// The register class of the operand.
+    ///
+    /// This applies to all kinds of constraints, but with slightly different meaning.
+    pub regclass: RegClass,
+}
+
+/// The different kinds of operand constraints.
+pub enum ConstraintKind {
+    /// This operand or result must be a register from the given register class.
+    Reg,
+
+    /// This operand or result must be a fixed register.
+    ///
+    /// The constraint's `regclass` field is the top-level register class containing the fixed
+    /// register.
+    FixedReg(RegUnit),
+
+    /// This result value must use the same register as an input value operand. Input operands
+    /// can't be tied.
+    ///
+    /// The associated number is the index of the input value operand this result is tied to.
+    ///
+    /// The constraint's `regclass` field is the top-level register class containing the tied
+    /// operand's register class.
+    Tied(u8),
+
+    /// This operand must be a value in a stack slot.
+    ///
+    /// The constraint's `regclass` field is the register class that would normally be used to load
+    /// and store values of this type.
+    Stack,
+}
+
+/// Constraints for an encoding recipe.
+pub struct RecipeConstraints {
+    /// Constraints for the instruction's fixed value operands.
+    ///
+    /// If the instruction takes a variable number of operands, the register constraints for those
+    /// operands must be computed dynamically.
+    ///
+    /// - For branches and jumps, EBB arguments must match the expectations of the destination EBB.
+    /// - For calls and returns, the calling convention ABI specifies constraints.
+    pub ins: &'static [OperandConstraint],
+
+    /// Constraints for the instruction's fixed results.
+    ///
+    /// If the instruction produces a variable number of results, it's probably a call and the
+    /// constraints must be derived from the calling convention ABI.
+    pub outs: &'static [OperandConstraint],
+}

lib/cretonne/src/isa/intel/enc_tables.rs

@@ -4,5 +4,6 @@ use ir::InstructionData;
 use ir::instructions::InstructionFormat;
 use ir::types;
 use isa::enc_tables::{Level1Entry, Level2Entry};
+use isa::constraints::*;
 
 include!(concat!(env!("OUT_DIR"), "/encoding-intel.rs"));

lib/cretonne/src/isa/intel/mod.rs

@@ -7,7 +7,7 @@ mod registers;
 use super::super::settings as shared_settings;
 use isa::enc_tables::{self as shared_enc_tables, lookup_enclist, general_encoding};
 use isa::Builder as IsaBuilder;
-use isa::{TargetIsa, RegInfo, Encoding, Legalize};
+use isa::{TargetIsa, RegInfo, Encoding, Legalize, RecipeConstraints};
 use ir::{InstructionData, DataFlowGraph};
 
 #[allow(dead_code)]
@@ -70,4 +70,8 @@ impl TargetIsa for Isa {
     fn recipe_names(&self) -> &'static [&'static str] {
         &enc_tables::RECIPE_NAMES[..]
     }
+
+    fn recipe_constraints(&self) -> &'static [RecipeConstraints] {
+        &enc_tables::RECIPE_CONSTRAINTS
+    }
 }

lib/cretonne/src/isa/mod.rs

@@ -42,6 +42,8 @@
 
 pub use isa::encoding::Encoding;
 pub use isa::registers::{RegInfo, RegUnit, RegClass};
+pub use isa::constraints::RecipeConstraints;
+
 use settings;
 use ir::{InstructionData, DataFlowGraph};
 
@@ -52,6 +54,7 @@ pub mod arm64;
 pub mod registers;
 mod encoding;
 mod enc_tables;
+mod constraints;
 
 /// Look for a supported ISA with the given `name`.
 /// Return a builder that can create a corresponding `TargetIsa`.
@@ -140,11 +143,17 @@ pub trait TargetIsa {
     fn encode(&self, dfg: &DataFlowGraph, inst: &InstructionData) -> Result<Encoding, Legalize>;
 
     /// Get a static array of names associated with encoding recipes in this ISA. Encoding recipes
-    /// are numbered starting from 0, corresponding to indexes into th name array.
+    /// are numbered starting from 0, corresponding to indexes into the name array.
     ///
     /// This is just used for printing and parsing encodings in the textual IL format.
     fn recipe_names(&self) -> &'static [&'static str];
 
+    /// Get a static array of value operand constraints associated with encoding recipes in this
+    /// ISA.
+    ///
+    /// The constraints describe which registers can be used with an encoding recipe.
+    fn recipe_constraints(&self) -> &'static [RecipeConstraints];
+
     /// Create an object that can display an ISA-dependent encoding properly.
     fn display_enc(&self, enc: Encoding) -> encoding::DisplayEncoding {
         encoding::DisplayEncoding {

lib/cretonne/src/isa/riscv/enc_tables.rs

@@ -5,6 +5,8 @@ use ir::instructions::InstructionFormat;
 use ir::types;
 use predicates;
 use isa::enc_tables::{Level1Entry, Level2Entry};
+use isa::constraints::*;
+use super::registers::*;
 
 // Include the generated encoding tables:
 // - `LEVEL1_RV32`

lib/cretonne/src/isa/riscv/mod.rs

@@ -7,7 +7,7 @@ mod registers;
 use super::super::settings as shared_settings;
 use isa::enc_tables::{self as shared_enc_tables, lookup_enclist, general_encoding};
 use isa::Builder as IsaBuilder;
-use isa::{TargetIsa, RegInfo, Encoding, Legalize};
+use isa::{TargetIsa, RegInfo, Encoding, Legalize, RecipeConstraints};
 use ir::{InstructionData, DataFlowGraph};
 
 #[allow(dead_code)]
@@ -70,6 +70,10 @@ impl TargetIsa for Isa {
     fn recipe_names(&self) -> &'static [&'static str] {
         &enc_tables::RECIPE_NAMES[..]
     }
+
+    fn recipe_constraints(&self) -> &'static [RecipeConstraints] {
+        &enc_tables::RECIPE_CONSTRAINTS
+    }
 }
 
 #[cfg(test)]