130 lines
3.6 KiB
Nim
130 lines
3.6 KiB
Nim
# Nimbus
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# Copyright (c) 2018 Status Research & Development GmbH
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# Licensed under either of
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# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
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# * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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# ##################################################################
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# Macros to facilitate opcode enum and table creation
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import macros, strformat, strutils
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# Due to https://github.com/nim-lang/Nim/issues/8007, we can't
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# use compile-time Tables of object variants, so instead, we use
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# const arrays to map Op --> gas prices.
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# Arrays require an enum without hole. This macro will fill the holes
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# in the enum.
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# This has an added benefits that we can use computed gotos (direct threaded interpreter)
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# instead of call or subroutine threading to dispatch opcode.
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# see: https://github.com/nim-lang/Nim/issues/7699 (computed gotos, bad codegen with enum with holes)
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# see: https://github.com/status-im/nimbus/wiki/Interpreter-optimization-resources
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# for interpreter dispatch strategies
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macro fill_enum_holes*(body: untyped): untyped =
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## Fill the holes of an enum
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## For example
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## type Foo = enum
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## A = 0x00,
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## B = 0x10
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# Sanity checks
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#
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# StmtList
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# TypeSection
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# TypeDef
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# PragmaExpr
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# Postfix
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# Ident "*"
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# Ident "Op"
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# Pragma
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# Ident "pure"
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# Empty
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# EnumTy
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# Empty
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# EnumFieldDef
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# Ident "Stop"
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# IntLit 0
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# EnumFieldDef
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# Ident "Add"
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# IntLit 1
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body[0].expectKind(nnkTypeSection)
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body[0][0][2].expectKind(nnkEnumTy)
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let opcodes = body[0][0][2]
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# We will iterate over all the opcodes
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# check if the i-th value is declared, if not add a no-op
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# and accumulate that in a "dense opcodes" declaration
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var
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opcode = 0
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holes_idx = 1
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dense_opcs = nnkEnumTy.newTree()
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dense_opcs.add newEmptyNode()
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# Iterate on the enum with holes
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while holes_idx < opcodes.len:
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let curr_ident = opcodes[holes_idx]
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if curr_ident.kind in {nnkIdent, nnkEmpty} or
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(curr_ident.kind == nnkEnumFieldDef and
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curr_ident[1].intVal == opcode):
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dense_opcs.add curr_ident
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inc holes_idx
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else:
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dense_opcs.add newIdentNode(&"Nop0x{opcode.toHex(2)}")
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inc opcode
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result = body
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result[0][0][2] = dense_opcs
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macro fill_enum_table_holes*(enumTy: typedesc[enum], nop_filler, body: untyped): untyped =
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## Fill the holes of table mapping for enum with a default value
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##
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## For example for enum
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## type Foo = enum
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## A = 0x00,
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## B = 0x01,
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## C = 0x02
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## let foo = fill_enum_table_holes(Foo, 999):
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## [A: 10, C: 20]
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##
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## will result into `[A: 10, B: 999, C: 20]`
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# Sanity checks - body
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# StmtList
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# Bracket
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# ExprColonExpr
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# Ident "Stop"
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# Command
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# Ident "fixed"
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# Ident "GasZero"
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# ExprColonExpr
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# Ident "Add"
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# Command
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# Ident "fixed"
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# Ident "GasVeryLow"
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body[0].expectKind(nnkBracket)
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let
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enumImpl = enumTy.getType[1]
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opctable = body[0]
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result = nnkBracket.newTree()
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var
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opcode = 1 # enumImpl[0] is an empty node
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body_idx = 0
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while opcode < enumImpl.len:
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opctable[body_idx].expectKind(nnkExprColonExpr)
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if eqIdent(enumImpl[opcode], opctable[body_idx][0]):
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result.add opctable[body_idx]
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inc body_idx
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else:
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result.add nop_filler
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inc opcode
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