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cmd/compile: avoid extra mapaccess in "m[k] op= r"
Currently, order desugars map assignment operations like m[k] op= r into m[k] = m[k] op r which in turn is transformed during walk into: tmp := *mapaccess(m, k) tmp = tmp op r *mapassign(m, k) = tmp However, this is suboptimal, as we could instead produce just: *mapassign(m, k) op= r One complication though is if "r == 0", then "m[k] /= r" and "m[k] %= r" will panic, and they need to do so *before* calling mapassign, otherwise we may insert a new zero-value element into the map. It would be spec compliant to just emit the "r != 0" check before calling mapassign (see #23735), but currently these checks aren't generated until SSA construction. For now, it's simpler to continue desugaring /= and %= into two map indexing operations. Fixes #23661. Change-Id: I46e3739d9adef10e92b46fdd78b88d5aabe68952 Reviewed-on: https://go-review.googlesource.com/91557 Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Austin Clements <austin@google.com>
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@ -14,7 +14,7 @@ import (
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// order of evaluation. Makes walk easier, because it
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// can (after this runs) reorder at will within an expression.
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//
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// Rewrite x op= y into x = x op y.
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// Rewrite m[k] op= r into m[k] = m[k] op r if op is / or %.
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//
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// Introduce temporaries as needed by runtime routines.
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// For example, the map runtime routines take the map key
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@ -434,7 +434,7 @@ func (o *Order) mapAssign(n *Node) {
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default:
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Fatalf("ordermapassign %v", n.Op)
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case OAS:
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case OAS, OASOP:
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if n.Left.Op == OINDEXMAP {
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// Make sure we evaluate the RHS before starting the map insert.
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// We need to make sure the RHS won't panic. See issue 22881.
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@ -514,26 +514,31 @@ func (o *Order) stmt(n *Node) {
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o.cleanTemp(t)
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case OASOP:
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// Special: rewrite l op= r into l = l op r.
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// This simplifies quite a few operations;
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// most important is that it lets us separate
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// out map read from map write when l is
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// a map index expression.
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t := o.markTemp()
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n.Left = o.expr(n.Left, nil)
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n.Right = o.expr(n.Right, nil)
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n.Left = o.safeExpr(n.Left)
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tmp1 := treecopy(n.Left, src.NoXPos)
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if tmp1.Op == OINDEXMAP {
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tmp1.SetIndexMapLValue(false)
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if instrumenting || n.Left.Op == OINDEXMAP && (n.SubOp() == ODIV || n.SubOp() == OMOD) {
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// Rewrite m[k] op= r into m[k] = m[k] op r so
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// that we can ensure that if op panics
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// because r is zero, the panic happens before
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// the map assignment.
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n.Left = o.safeExpr(n.Left)
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l := treecopy(n.Left, src.NoXPos)
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if l.Op == OINDEXMAP {
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l.SetIndexMapLValue(false)
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}
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l = o.copyExpr(l, n.Left.Type, false)
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n.Right = nod(n.SubOp(), l, n.Right)
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n.Right = typecheck(n.Right, Erv)
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n.Right = o.expr(n.Right, nil)
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n.Op = OAS
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n.ResetAux()
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}
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tmp1 = o.copyExpr(tmp1, n.Left.Type, false)
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n.Right = nod(n.SubOp(), tmp1, n.Right)
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n.Right = typecheck(n.Right, Erv)
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n.Right = o.expr(n.Right, nil)
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n.Op = OAS
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n.ResetAux()
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o.mapAssign(n)
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o.cleanTemp(t)
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@ -667,12 +667,21 @@ opswitch:
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updateHasCall(n.Left)
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n.List.Set(reorder1(ll))
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case OAS:
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case OAS, OASOP:
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init.AppendNodes(&n.Ninit)
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n.Left = walkexpr(n.Left, init)
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n.Left = safeexpr(n.Left, init)
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if n.Op == OASOP {
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// Rewrite x op= y into x = x op y.
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n.Right = nod(n.SubOp(), n.Left, n.Right)
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n.Right = typecheck(n.Right, Erv)
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n.Op = OAS
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n.ResetAux()
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}
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if oaslit(n, init) {
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break
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}
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@ -52,14 +52,7 @@ func TestNegativeZero(t *testing.T) {
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}
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}
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// nan is a good test because nan != nan, and nan has
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// a randomized hash value.
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func TestNan(t *testing.T) {
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m := make(map[float64]int, 0)
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nan := math.NaN()
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m[nan] = 1
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m[nan] = 2
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m[nan] = 4
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func testMapNan(t *testing.T, m map[float64]int) {
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if len(m) != 3 {
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t.Error("length wrong")
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}
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@ -78,6 +71,49 @@ func TestNan(t *testing.T) {
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}
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}
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// nan is a good test because nan != nan, and nan has
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// a randomized hash value.
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func TestMapAssignmentNan(t *testing.T) {
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m := make(map[float64]int, 0)
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nan := math.NaN()
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// Test assignment.
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m[nan] = 1
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m[nan] = 2
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m[nan] = 4
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testMapNan(t, m)
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}
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// nan is a good test because nan != nan, and nan has
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// a randomized hash value.
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func TestMapOperatorAssignmentNan(t *testing.T) {
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m := make(map[float64]int, 0)
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nan := math.NaN()
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// Test assignment operations.
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m[nan] += 1
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m[nan] += 2
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m[nan] += 4
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testMapNan(t, m)
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}
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func TestMapOperatorAssignment(t *testing.T) {
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m := make(map[int]int, 0)
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// "m[k] op= x" is rewritten into "m[k] = m[k] op x"
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// differently when op is / or % than when it isn't.
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// Simple test to make sure they all work as expected.
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m[0] = 12345
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m[0] += 67890
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m[0] /= 123
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m[0] %= 456
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const want = (12345 + 67890) / 123 % 456
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if got := m[0]; got != want {
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t.Errorf("got %d, want %d", got, want)
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}
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}
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// Maps aren't actually copied on assignment.
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func TestAlias(t *testing.T) {
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m := make(map[int]int, 0)
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@ -92,18 +128,25 @@ func TestAlias(t *testing.T) {
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func TestGrowWithNaN(t *testing.T) {
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m := make(map[float64]int, 4)
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nan := math.NaN()
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// Use both assignment and assignment operations as they may
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// behave differently.
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m[nan] = 1
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m[nan] = 2
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m[nan] = 4
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m[nan] += 4
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cnt := 0
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s := 0
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growflag := true
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for k, v := range m {
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if growflag {
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// force a hashtable resize
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for i := 0; i < 100; i++ {
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for i := 0; i < 50; i++ {
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m[float64(i)] = i
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}
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for i := 50; i < 100; i++ {
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m[float64(i)] += i
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}
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growflag = false
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}
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if k != k {
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@ -128,8 +171,8 @@ func TestGrowWithNegativeZero(t *testing.T) {
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negzero := math.Copysign(0.0, -1.0)
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m := make(map[FloatInt]int, 4)
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m[FloatInt{0.0, 0}] = 1
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m[FloatInt{0.0, 1}] = 2
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m[FloatInt{0.0, 2}] = 4
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m[FloatInt{0.0, 1}] += 2
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m[FloatInt{0.0, 2}] += 4
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m[FloatInt{0.0, 3}] = 8
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growflag := true
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s := 0
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@ -211,9 +254,12 @@ func TestIterGrowAndDelete(t *testing.T) {
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// an iterator is still using them.
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func TestIterGrowWithGC(t *testing.T) {
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m := make(map[int]int, 4)
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for i := 0; i < 16; i++ {
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for i := 0; i < 8; i++ {
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m[i] = i
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}
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for i := 8; i < 16; i++ {
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m[i] += i
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}
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growflag := true
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bitmask := 0
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for k := range m {
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@ -786,6 +832,13 @@ func benchmarkMapAssignInt32(b *testing.B, n int) {
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}
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}
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func benchmarkMapOperatorAssignInt32(b *testing.B, n int) {
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a := make(map[int32]int)
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for i := 0; i < b.N; i++ {
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a[int32(i&(n-1))] += i
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}
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}
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func benchmarkMapDeleteInt32(b *testing.B, n int) {
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a := make(map[int32]int, n)
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b.ResetTimer()
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@ -808,6 +861,13 @@ func benchmarkMapAssignInt64(b *testing.B, n int) {
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}
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}
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func benchmarkMapOperatorAssignInt64(b *testing.B, n int) {
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a := make(map[int64]int)
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for i := 0; i < b.N; i++ {
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a[int64(i&(n-1))] += i
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}
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}
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func benchmarkMapDeleteInt64(b *testing.B, n int) {
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a := make(map[int64]int, n)
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b.ResetTimer()
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@ -835,6 +895,19 @@ func benchmarkMapAssignStr(b *testing.B, n int) {
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}
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}
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func benchmarkMapOperatorAssignStr(b *testing.B, n int) {
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k := make([]string, n)
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for i := 0; i < len(k); i++ {
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k[i] = strconv.Itoa(i)
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}
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b.ResetTimer()
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a := make(map[string]string)
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for i := 0; i < b.N; i++ {
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key := k[i&(n-1)]
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a[key] += key
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}
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}
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func benchmarkMapDeleteStr(b *testing.B, n int) {
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i2s := make([]string, n)
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for i := 0; i < n; i++ {
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@ -870,6 +943,12 @@ func BenchmarkMapAssign(b *testing.B) {
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b.Run("Str", runWith(benchmarkMapAssignStr, 1<<8, 1<<16))
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}
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func BenchmarkMapOperatorAssign(b *testing.B) {
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b.Run("Int32", runWith(benchmarkMapOperatorAssignInt32, 1<<8, 1<<16))
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b.Run("Int64", runWith(benchmarkMapOperatorAssignInt64, 1<<8, 1<<16))
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b.Run("Str", runWith(benchmarkMapOperatorAssignStr, 1<<8, 1<<16))
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}
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func BenchmarkMapDelete(b *testing.B) {
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b.Run("Int32", runWith(benchmarkMapDeleteInt32, 100, 1000, 10000))
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b.Run("Int64", runWith(benchmarkMapDeleteInt64, 100, 1000, 10000))
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@ -28,10 +28,38 @@ func del(m map[interface{}]interface{}, key interface{}) (err error) {
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return nil
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}
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func addInt(m map[interface{}]int, key interface{}) (err error) {
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defer func() {
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if r := recover(); r != nil {
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err = fmt.Errorf("addInt failed: %v", r)
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}
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}()
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m[key] += 2018
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return nil
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}
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func addStr(m map[interface{}]string, key interface{}) (err error) {
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defer func() {
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if r := recover(); r != nil {
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err = fmt.Errorf("addStr failed: %v", r)
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}
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}()
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m[key] += "hello, go"
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return nil
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}
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func main() {
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m := make(map[interface{}]interface{})
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set(m, []int{1, 2, 3})
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set(m, "abc") // used to throw
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del(m, []int{1, 2, 3})
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del(m, "abc") // used to throw
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mi := make(map[interface{}]int)
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addInt(mi, []int{1, 2, 3})
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addInt(mi, "abc") // used to throw
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ms := make(map[interface{}]string)
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addStr(ms, []int{1, 2, 3})
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addStr(ms, "abc") // used to throw
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}
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@ -13,7 +13,7 @@ import "fmt"
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func main() {
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for i, f := range []func(map[int]int){
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f0, f1, f2, f3, f4, f5, f6, f7,
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f0, f1, f2, f3, f4, f5, f6, f7, f8,
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} {
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m := map[int]int{}
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func() { // wrapper to scope the defer.
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@ -69,4 +69,9 @@ func f7(m map[int]int) {
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m[0] = a[0]
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}
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func f8(m map[int]int) {
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var z int
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m[0] %= z
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}
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var sink bool
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