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cmd/compile: optimize integer "in range" expressions
Use unsigned comparisons to reduce from two comparisons to one for integer "in range" checks, such as a <= b && b < c. We already do this for bounds checks. Extend it to user code. This is much easier to do in the front end than SSA. A back end optimization would be more powerful, but this is a good start. This reduces the power of some of SSA prove inferences (#16653), but those regressions appear to be rare and not worth holding this CL for. Fixes #15844. Fixes #16697. strconv benchmarks: name old time/op new time/op delta Atof64Decimal-8 41.4ns ± 3% 38.9ns ± 2% -5.89% (p=0.000 n=24+25) Atof64Float-8 48.5ns ± 0% 46.8ns ± 3% -3.64% (p=0.000 n=20+23) Atof64FloatExp-8 97.7ns ± 4% 93.5ns ± 1% -4.25% (p=0.000 n=25+20) Atof64Big-8 187ns ± 8% 162ns ± 2% -13.54% (p=0.000 n=24+22) Atof64RandomBits-8 250ns ± 6% 233ns ± 5% -6.76% (p=0.000 n=25+25) Atof64RandomFloats-8 160ns ± 0% 152ns ± 0% -5.00% (p=0.000 n=21+22) Atof32Decimal-8 41.1ns ± 1% 38.7ns ± 2% -5.86% (p=0.000 n=24+24) Atof32Float-8 46.1ns ± 1% 43.5ns ± 3% -5.63% (p=0.000 n=21+24) Atof32FloatExp-8 101ns ± 4% 100ns ± 2% -1.59% (p=0.000 n=24+23) Atof32Random-8 136ns ± 3% 133ns ± 3% -2.83% (p=0.000 n=22+22) Atoi-8 33.8ns ± 3% 30.6ns ± 3% -9.51% (p=0.000 n=24+25) AtoiNeg-8 31.6ns ± 3% 29.1ns ± 2% -8.05% (p=0.000 n=23+24) Atoi64-8 48.6ns ± 1% 43.8ns ± 1% -9.81% (p=0.000 n=20+23) Atoi64Neg-8 47.1ns ± 4% 42.0ns ± 2% -10.83% (p=0.000 n=25+25) FormatFloatDecimal-8 177ns ± 9% 178ns ± 6% ~ (p=0.460 n=25+25) FormatFloat-8 282ns ± 6% 282ns ± 3% ~ (p=0.954 n=25+22) FormatFloatExp-8 259ns ± 7% 255ns ± 6% ~ (p=0.089 n=25+24) FormatFloatNegExp-8 253ns ± 6% 254ns ± 6% ~ (p=0.941 n=25+24) FormatFloatBig-8 340ns ± 6% 341ns ± 8% ~ (p=0.600 n=22+25) AppendFloatDecimal-8 79.4ns ± 0% 80.6ns ± 6% ~ (p=0.861 n=20+25) AppendFloat-8 175ns ± 3% 174ns ± 0% ~ (p=0.722 n=25+20) AppendFloatExp-8 142ns ± 4% 142ns ± 2% ~ (p=0.948 n=25+24) AppendFloatNegExp-8 137ns ± 2% 138ns ± 2% +0.70% (p=0.001 n=24+25) AppendFloatBig-8 218ns ± 3% 218ns ± 4% ~ (p=0.596 n=25+25) AppendFloatBinaryExp-8 80.0ns ± 4% 78.0ns ± 1% -2.43% (p=0.000 n=24+21) AppendFloat32Integer-8 82.3ns ± 3% 79.3ns ± 4% -3.69% (p=0.000 n=24+25) AppendFloat32ExactFraction-8 143ns ± 2% 143ns ± 0% ~ (p=0.177 n=23+19) AppendFloat32Point-8 175ns ± 3% 175ns ± 3% ~ (p=0.062 n=24+25) AppendFloat32Exp-8 139ns ± 2% 137ns ± 4% -1.05% (p=0.001 n=24+24) AppendFloat32NegExp-8 134ns ± 0% 137ns ± 4% +2.06% (p=0.000 n=22+25) AppendFloat64Fixed1-8 97.8ns ± 0% 98.6ns ± 3% ~ (p=0.711 n=20+25) AppendFloat64Fixed2-8 110ns ± 3% 110ns ± 5% -0.45% (p=0.037 n=24+24) AppendFloat64Fixed3-8 102ns ± 3% 102ns ± 3% ~ (p=0.684 n=24+24) AppendFloat64Fixed4-8 112ns ± 3% 110ns ± 0% -1.43% (p=0.000 n=25+18) FormatInt-8 3.18µs ± 4% 3.10µs ± 6% -2.54% (p=0.001 n=24+25) AppendInt-8 1.81µs ± 5% 1.80µs ± 5% ~ (p=0.648 n=25+25) FormatUint-8 812ns ± 6% 816ns ± 6% ~ (p=0.777 n=25+25) AppendUint-8 536ns ± 4% 538ns ± 3% ~ (p=0.798 n=20+22) Quote-8 605ns ± 6% 602ns ± 9% ~ (p=0.573 n=25+25) QuoteRune-8 99.5ns ± 8% 100.2ns ± 7% ~ (p=0.432 n=25+25) AppendQuote-8 361ns ± 3% 363ns ± 4% ~ (p=0.085 n=25+25) AppendQuoteRune-8 23.3ns ± 3% 22.4ns ± 2% -3.79% (p=0.000 n=25+24) UnquoteEasy-8 146ns ± 4% 145ns ± 5% ~ (p=0.112 n=24+24) UnquoteHard-8 804ns ± 6% 771ns ± 6% -4.10% (p=0.000 n=25+24) Change-Id: Ibd384e46e90f1cfa40503c8c6352a54c65b72980 Reviewed-on: https://go-review.googlesource.com/27652 Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com> Reviewed-by: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Josh Bleecher Snyder
parent
d61c07ffd8
commit
6286188986
@ -2130,37 +2130,6 @@ func powtwo(n *Node) int {
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return -1
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}
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// return the unsigned type for
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// a signed integer type.
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// returns T if input is not a
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// signed integer type.
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func tounsigned(t *Type) *Type {
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// this is types[et+1], but not sure
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// that this relation is immutable
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switch t.Etype {
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default:
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fmt.Printf("tounsigned: unknown type %v\n", t)
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t = nil
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case TINT:
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t = Types[TUINT]
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case TINT8:
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t = Types[TUINT8]
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case TINT16:
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t = Types[TUINT16]
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case TINT32:
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t = Types[TUINT32]
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case TINT64:
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t = Types[TUINT64]
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}
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return t
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}
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func ngotype(n *Node) *Sym {
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if n.Type != nil {
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return typenamesym(n.Type)
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@ -1076,6 +1076,28 @@ func (t *Type) IsBoolean() bool {
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return t.Etype == TBOOL
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}
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var unsignedEType = [...]EType{
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TINT8: TUINT8,
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TUINT8: TUINT8,
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TINT16: TUINT16,
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TUINT16: TUINT16,
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TINT32: TUINT32,
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TUINT32: TUINT32,
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TINT64: TUINT64,
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TUINT64: TUINT64,
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TINT: TUINT,
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TUINT: TUINT,
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TUINTPTR: TUINTPTR,
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}
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// toUnsigned returns the unsigned equivalent of integer type t.
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func (t *Type) toUnsigned() *Type {
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if !t.IsInteger() {
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Fatalf("unsignedType(%v)", t)
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}
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return Types[unsignedEType[t.Etype]]
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}
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func (t *Type) IsInteger() bool {
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switch t.Etype {
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case TINT8, TUINT8, TINT16, TUINT16, TINT32, TUINT32, TINT64, TUINT64, TINT, TUINT, TUINTPTR:
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@ -631,6 +631,7 @@ opswitch:
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n.Right = walkexpr(n.Right, &ll)
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n.Right = addinit(n.Right, ll.Slice())
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n = walkinrange(n, init)
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case OPRINT, OPRINTN:
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walkexprlist(n.List.Slice(), init)
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@ -3406,6 +3407,134 @@ func walkrotate(n *Node) *Node {
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return n
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}
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// isIntOrdering reports whether n is a <, ≤, >, or ≥ ordering between integers.
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func (n *Node) isIntOrdering() bool {
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switch n.Op {
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case OLE, OLT, OGE, OGT:
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default:
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return false
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}
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return n.Left.Type.IsInteger() && n.Right.Type.IsInteger()
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}
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// walkinrange optimizes integer-in-range checks, such as 4 <= x && x < 10.
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// n must be an OANDAND or OOROR node.
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// The result of walkinrange MUST be assigned back to n, e.g.
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// n.Left = walkinrange(n.Left)
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func walkinrange(n *Node, init *Nodes) *Node {
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// We are looking for something equivalent to a opl b OP b opr c, where:
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// * a, b, and c have integer type
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// * b is side-effect-free
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// * opl and opr are each < or ≤
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// * OP is &&
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l := n.Left
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r := n.Right
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if !l.isIntOrdering() || !r.isIntOrdering() {
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return n
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}
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// Find b, if it exists, and rename appropriately.
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// Input is: l.Left l.Op l.Right ANDAND/OROR r.Left r.Op r.Right
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// Output is: a opl b(==x) ANDAND/OROR b(==x) opr c
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a, opl, b := l.Left, l.Op, l.Right
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x, opr, c := r.Left, r.Op, r.Right
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for i := 0; ; i++ {
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if samesafeexpr(b, x) {
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break
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}
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if i == 3 {
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// Tried all permutations and couldn't find an appropriate b == x.
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return n
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}
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if i&1 == 0 {
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a, opl, b = b, Brrev(opl), a
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} else {
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x, opr, c = c, Brrev(opr), x
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}
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}
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// If n.Op is ||, apply de Morgan.
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// Negate the internal ops now; we'll negate the top level op at the end.
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// Henceforth assume &&.
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negateResult := n.Op == OOROR
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if negateResult {
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opl = Brcom(opl)
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opr = Brcom(opr)
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}
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cmpdir := func(o Op) int {
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switch o {
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case OLE, OLT:
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return -1
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case OGE, OGT:
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return +1
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}
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Fatalf("walkinrange cmpdir %v", o)
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return 0
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}
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if cmpdir(opl) != cmpdir(opr) {
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// Not a range check; something like b < a && b < c.
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return n
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}
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switch opl {
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case OGE, OGT:
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// We have something like a > b && b ≥ c.
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// Switch and reverse ops and rename constants,
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// to make it look like a ≤ b && b < c.
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a, c = c, a
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opl, opr = Brrev(opr), Brrev(opl)
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}
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// We must ensure that c-a is non-negative.
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// For now, require a and c to be constants.
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// In the future, we could also support a == 0 and c == len/cap(...).
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// Unfortunately, by this point, most len/cap expressions have been
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// stored into temporary variables.
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if !Isconst(a, CTINT) || !Isconst(c, CTINT) {
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return n
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}
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if opl == OLT {
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// We have a < b && ...
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// We need a ≤ b && ... to safely use unsigned comparison tricks.
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// If a is not the maximum constant for b's type,
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// we can increment a and switch to ≤.
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if a.Int64() >= Maxintval[b.Type.Etype].Int64() {
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return n
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}
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a = Nodintconst(a.Int64() + 1)
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opl = OLE
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}
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bound := c.Int64() - a.Int64()
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if bound < 0 {
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// Bad news. Something like 5 <= x && x < 3.
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// Rare in practice, and we still need to generate side-effects,
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// so just leave it alone.
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return n
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}
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// We have a ≤ b && b < c (or a ≤ b && b ≤ c).
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// This is equivalent to (a-a) ≤ (b-a) && (b-a) < (c-a),
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// which is equivalent to 0 ≤ (b-a) && (b-a) < (c-a),
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// which is equivalent to uint(b-a) < uint(c-a).
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ut := b.Type.toUnsigned()
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lhs := conv(Nod(OSUB, b, a), ut)
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rhs := Nodintconst(bound)
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if negateResult {
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// Negate top level.
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opr = Brcom(opr)
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}
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cmp := Nod(opr, lhs, rhs)
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cmp.Lineno = n.Lineno
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cmp = addinit(cmp, l.Ninit.Slice())
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cmp = addinit(cmp, r.Ninit.Slice())
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cmp = typecheck(cmp, Erv)
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cmp = walkexpr(cmp, init)
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return cmp
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}
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// walkmul rewrites integer multiplication by powers of two as shifts.
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// The result of walkmul MUST be assigned back to n, e.g.
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// n.Left = walkmul(n.Left, init)
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@ -3694,7 +3823,7 @@ func walkdiv(n *Node, init *Nodes) *Node {
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var nc Node
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Nodconst(&nc, Types[Simtype[TUINT]], int64(w)-int64(pow))
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n2 := Nod(ORSH, conv(n1, tounsigned(nl.Type)), &nc)
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n2 := Nod(ORSH, conv(n1, nl.Type.toUnsigned()), &nc)
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n.Left = Nod(OADD, nl, conv(n2, nl.Type))
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}
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@ -21,7 +21,9 @@ func f1(a [256]int, i int) {
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if 4 <= i && i < len(a) {
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useInt(a[i])
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useInt(a[i-1]) // ERROR "Found IsInBounds$"
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useInt(a[i-4]) // ERROR "Found IsInBounds$"
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// TODO: 'if 4 <= i && i < len(a)' gets rewritten to 'if uint(i - 4) < 256 - 4',
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// which the bounds checker cannot yet use to infer that the next line doesn't need a bounds check.
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useInt(a[i-4])
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}
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}
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