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[dev.unified] cmd/compile: refactor range desugaring

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This CL refactors the code responsible for emitting the user-visible
assignments within a range statement. This will make it easier to
propagate RTTI from the frontend into any implicit conversions.

Updates #53328.

Change-Id: Ibed15e3b4951b0a6a726067b401a630977f4c6c2
Reviewed-on: https://go-review.googlesource.com/c/go/+/415158
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Matthew Dempsky 2022-06-29 19:23:34 -07:00
parent 3635b07d16
commit 0a503cf43a
1 changed files with 22 additions and 15 deletions
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37
src/cmd/compile/internal/walk/range.go
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@ -103,7 +103,7 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
// for v1 := range ha { body }
if v2 == nil {
body = []ir.Node{ir.NewAssignStmt(base.Pos, v1, hv1)}
body = []ir.Node{rangeAssign(nrange, hv1)}
break
}
@ -112,10 +112,7 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
// v1, v2 = hv1, ha[hv1]
tmp := ir.NewIndexExpr(base.Pos, ha, hv1)
tmp.SetBounded(true)
// Use OAS2 to correctly handle assignments
// of the form "v1, a[v1] := range".
a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{v1, v2}, []ir.Node{hv1, tmp})
body = []ir.Node{a}
body = []ir.Node{rangeAssign2(nrange, hv1, tmp)}
break
}
@ -140,9 +137,7 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
tmp.SetBounded(true)
init = append(init, ir.NewAssignStmt(base.Pos, hp, typecheck.NodAddr(tmp)))
// Use OAS2 to correctly handle assignments
// of the form "v1, a[v1] := range".
a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{v1, v2}, []ir.Node{hv1, ir.NewStarExpr(base.Pos, hp)})
a := rangeAssign2(nrange, hv1, ir.NewStarExpr(base.Pos, hp))
body = append(body, a)
// Advance pointer as part of the late increment.
@ -179,11 +174,10 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
if v1 == nil {
body = nil
} else if v2 == nil {
body = []ir.Node{ir.NewAssignStmt(base.Pos, v1, key)}
body = []ir.Node{rangeAssign(nrange, key)}
} else {
elem := ir.NewStarExpr(base.Pos, ir.NewSelectorExpr(base.Pos, ir.ODOT, hit, elemsym))
a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{v1, v2}, []ir.Node{key, elem})
body = []ir.Node{a}
body = []ir.Node{rangeAssign2(nrange, key, elem)}
}
case types.TCHAN:
@ -206,7 +200,7 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
if v1 == nil {
body = nil
} else {
body = []ir.Node{ir.NewAssignStmt(base.Pos, v1, hv1)}
body = []ir.Node{rangeAssign(nrange, hv1)}
}
// Zero hv1. This prevents hv1 from being the sole, inaccessible
// reference to an otherwise GC-able value during the next channel receive.
@ -271,11 +265,10 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
if v1 != nil {
if v2 != nil {
// v1, v2 = hv1t, hv2
a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{v1, v2}, []ir.Node{hv1t, hv2})
body = append(body, a)
body = append(body, rangeAssign2(nrange, hv1t, hv2))
} else {
// v1 = hv1t
body = append(body, ir.NewAssignStmt(base.Pos, v1, hv1t))
body = append(body, rangeAssign(nrange, hv1t))
}
}
}
@ -310,6 +303,20 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
return n
}
// rangeAssign returns "n.Key = key".
func rangeAssign(n *ir.RangeStmt, key ir.Node) ir.Node {
// TODO(mdempsky): Implicit conversions for test/typeparam/mdempsky/17.go.
return ir.NewAssignStmt(n.Pos(), n.Key, key)
}
// rangeAssign2 returns "n.Key, n.Value = key, value".
func rangeAssign2(n *ir.RangeStmt, key, value ir.Node) ir.Node {
// Use OAS2 to correctly handle assignments
// of the form "v1, a[v1] = range".
// TODO(mdempsky): Implicit conversions for test/typeparam/mdempsky/17.go.
return ir.NewAssignListStmt(n.Pos(), ir.OAS2, []ir.Node{n.Key, n.Value}, []ir.Node{key, value})
}
// isMapClear checks if n is of the form:
//
// for k := range m {