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Constant folding for integer casts (#8095)

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LemonBoy 2018-08-31 13:45:42 +02:00 • committed by Andreas Rumpf
commit 2c8361bd39
3 changed files with 86 additions and 8 deletions
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32
compiler/semfold.nim
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@ -450,21 +450,38 @@ proc rangeCheck(n: PNode, value: BiggestInt; g: ModuleGraph) =
localError(g.config, n.info, "cannot convert " & $value &
" to " & typeToString(n.typ))
proc foldConv*(n, a: PNode; g: ModuleGraph; check = false): PNode =
proc foldConv(n, a: PNode; g: ModuleGraph; check = false): PNode =
let dstTyp = skipTypes(n.typ, abstractRange)
let srcTyp = skipTypes(a.typ, abstractRange)
# XXX range checks?
case skipTypes(n.typ, abstractRange).kind
of tyInt..tyInt64, tyUInt..tyUInt64:
case skipTypes(a.typ, abstractRange).kind
case dstTyp.kind
of tyInt..tyInt64, tyUint..tyUInt64:
case srcTyp.kind
of tyFloat..tyFloat64:
result = newIntNodeT(int(getFloat(a)), n, g)
of tyChar: result = newIntNodeT(getOrdValue(a), n, g)
of tyChar:
result = newIntNodeT(getOrdValue(a), n, g)
of tyUInt8..tyUInt32, tyInt8..tyInt32:
let fromSigned = srcTyp.kind in tyInt..tyInt64
let toSigned = dstTyp.kind in tyInt..tyInt64
let mask = lastOrd(g.config, dstTyp, fixedUnsigned=true)
var val =
if toSigned:
a.getOrdValue mod mask
else:
a.getOrdValue and mask
result = newIntNodeT(val, n, g)
else:
result = a
result.typ = n.typ
if check and result.kind in {nkCharLit..nkUInt64Lit}:
rangeCheck(n, result.intVal, g)
of tyFloat..tyFloat64:
case skipTypes(a.typ, abstractRange).kind
case srcTyp.kind
of tyInt..tyInt64, tyEnum, tyBool, tyChar:
result = newFloatNodeT(toBiggestFloat(getOrdValue(a)), n, g)
else:
@ -742,7 +759,8 @@ proc getConstExpr(m: PSym, n: PNode; g: ModuleGraph): PNode =
of nkHiddenStdConv, nkHiddenSubConv, nkConv:
var a = getConstExpr(m, n.sons[1], g)
if a == nil: return
result = foldConv(n, a, g, check=n.kind == nkHiddenStdConv)
# XXX: we should enable `check` for other conversion types too
result = foldConv(n, a, g, check=n.kind == nkHiddenSubConv)
of nkCast:
var a = getConstExpr(m, n.sons[1], g)
if a == nil: return