Add RISC-V encodings for spill and fill.

Add a Stack() class for specifying operand constraints for values on the
stack.

Add encoding recipes for RISC-V spill and fill instructions. Don't
implement the encoding recipe functions yet since we don't have the
stack slot layout yet.

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

@@ -6,8 +6,9 @@ from base import instructions as base
 from base.immediates import intcc
 from .defs import RV32, RV64
 from .recipes import OPIMM, OPIMM32, OP, OP32, LUI, BRANCH, JALR, JAL
+from .recipes import LOAD, STORE
 from .recipes import R, Rshamt, Ricmp, I, Iicmp, Iret
-from .recipes import U, UJ, UJcall, SB, SBzero
+from .recipes import U, UJ, UJcall, SB, SBzero, GPsp, GPfi
 from .settings import use_m
 from cdsl.ast import Var
 
@@ -114,3 +115,11 @@ for inst,           f3 in [
 # is added by legalize_signature().
 RV32.enc(base.x_return, Iret, JALR())
 RV64.enc(base.x_return, Iret, JALR())
+
+# Spill and fill.
+RV32.enc(base.spill.i32, GPsp, STORE(0b010))
+RV64.enc(base.spill.i32, GPsp, STORE(0b010))
+RV64.enc(base.spill.i64, GPsp, STORE(0b011))
+RV32.enc(base.fill.i32, GPfi, LOAD(0b010))
+RV64.enc(base.fill.i32, GPfi, LOAD(0b010))
+RV64.enc(base.fill.i64, GPfi, LOAD(0b011))

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

@@ -11,8 +11,9 @@ instruction formats described in the reference:
 from __future__ import absolute_import
 from cdsl.isa import EncRecipe
 from cdsl.predicates import IsSignedInt
+from cdsl.registers import Stack
 from base.formats import Binary, BinaryImm, MultiAry, IntCompare, IntCompareImm
-from base.formats import UnaryImm, BranchIcmp, Branch, Jump, Call
+from base.formats import Unary, UnaryImm, BranchIcmp, Branch, Jump, Call
 from .registers import GPR
 
 # The low 7 bits of a RISC-V instruction is the base opcode. All 32-bit
@@ -134,3 +135,13 @@ SBzero = EncRecipe(
         'SBzero', Branch, size=4,
         ins=(GPR), outs=(),
         branch_range=(0, 13))
+
+# Spill of a GPR.
+GPsp = EncRecipe(
+        'GPsp', Unary, size=4,
+        ins=GPR, outs=Stack(GPR))
+
+# Fill of a GPR.
+GPfi = EncRecipe(
+        'GPfi', Unary, size=4,
+        ins=Stack(GPR), outs=GPR)