From: Josh Bleecher Snyder Date: Tue, 28 Jul 2015 17:56:39 +0000 (-0700) Subject: [dev.ssa] cmd/compile: implement static data generation X-Git-Tag: go1.7beta1~1623^2^2~338 X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=6b41665039e278a83823051b44628e25415b0205;p=gostls13.git [dev.ssa] cmd/compile: implement static data generation The existing backend recognizes special assignment statements as being implementable with static data rather than code. Unfortunately, it assumes that it is in the middle of codegen; it emits data and modifies the AST. This does not play well with SSA's two-phase bootstrapping approach, in which we attempt to compile code but fall back to the existing backend if something goes wrong. To work around this: * Add the ability to inquire about static data without side-effects. * Save the static data required for a function. * Emit that static data during SSA codegen. Change-Id: I2e8a506c866ea3e27dffb597095833c87f62d87e Reviewed-on: https://go-review.googlesource.com/12790 Reviewed-by: Keith Randall --- diff --git a/src/cmd/compile/internal/gc/gen.go b/src/cmd/compile/internal/gc/gen.go index 6390818e16..4ff4f7a2c8 100644 --- a/src/cmd/compile/internal/gc/gen.go +++ b/src/cmd/compile/internal/gc/gen.go @@ -853,7 +853,7 @@ func gen(n *Node) { cgen_dcl(n.Left) case OAS: - if gen_as_init(n) { + if gen_as_init(n, false) { break } Cgen_as(n.Left, n.Right) diff --git a/src/cmd/compile/internal/gc/sinit.go b/src/cmd/compile/internal/gc/sinit.go index 7875d16380..099c10a8bc 100644 --- a/src/cmd/compile/internal/gc/sinit.go +++ b/src/cmd/compile/internal/gc/sinit.go @@ -1236,6 +1236,7 @@ func getlit(lit *Node) int { return -1 } +// stataddr sets nam to the static address of n and reports whether it succeeeded. func stataddr(nam *Node, n *Node) bool { if n == nil { return false @@ -1408,7 +1409,9 @@ func entry(p *InitPlan) *InitEntry { return &p.E[len(p.E)-1] } -func gen_as_init(n *Node) bool { +// gen_as_init attempts to emit static data for n and reports whether it succeeded. +// If reportOnly is true, it does not emit static data and does not modify the AST. +func gen_as_init(n *Node, reportOnly bool) bool { var nr *Node var nl *Node var nam Node @@ -1457,7 +1460,9 @@ func gen_as_init(n *Node) bool { case OSLICEARR: if nr.Right.Op == OKEY && nr.Right.Left == nil && nr.Right.Right == nil { nr = nr.Left - gused(nil) // in case the data is the dest of a goto + if !reportOnly { + gused(nil) // in case the data is the dest of a goto + } nl := nr if nr == nil || nr.Op != OADDR { goto no @@ -1472,16 +1477,18 @@ func gen_as_init(n *Node) bool { goto no } - nam.Xoffset += int64(Array_array) - gdata(&nam, nl, int(Types[Tptr].Width)) + if !reportOnly { + nam.Xoffset += int64(Array_array) + gdata(&nam, nl, int(Types[Tptr].Width)) - nam.Xoffset += int64(Array_nel) - int64(Array_array) - var nod1 Node - Nodconst(&nod1, Types[TINT], nr.Type.Bound) - gdata(&nam, &nod1, Widthint) + nam.Xoffset += int64(Array_nel) - int64(Array_array) + var nod1 Node + Nodconst(&nod1, Types[TINT], nr.Type.Bound) + gdata(&nam, &nod1, Widthint) - nam.Xoffset += int64(Array_cap) - int64(Array_nel) - gdata(&nam, &nod1, Widthint) + nam.Xoffset += int64(Array_cap) - int64(Array_nel) + gdata(&nam, &nod1, Widthint) + } return true } @@ -1512,13 +1519,19 @@ func gen_as_init(n *Node) bool { TPTR64, TFLOAT32, TFLOAT64: - gdata(&nam, nr, int(nr.Type.Width)) + if !reportOnly { + gdata(&nam, nr, int(nr.Type.Width)) + } case TCOMPLEX64, TCOMPLEX128: - gdatacomplex(&nam, nr.Val().U.(*Mpcplx)) + if !reportOnly { + gdatacomplex(&nam, nr.Val().U.(*Mpcplx)) + } case TSTRING: - gdatastring(&nam, nr.Val().U.(string)) + if !reportOnly { + gdatastring(&nam, nr.Val().U.(string)) + } } return true diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go index b6b345f205..29b6a141a5 100644 --- a/src/cmd/compile/internal/gc/ssa.go +++ b/src/cmd/compile/internal/gc/ssa.go @@ -462,6 +462,17 @@ func (s *state) stmt(n *Node) { addEdge(b, lab.target) case OAS, OASWB: + // Check whether we can generate static data rather than code. + // If so, ignore n and defer data generation until codegen. + // Failure to do this causes writes to readonly symbols. + if gen_as_init(n, true) { + var data []*Node + if s.f.StaticData != nil { + data = s.f.StaticData.([]*Node) + } + s.f.StaticData = append(data, n) + return + } s.assign(n.Op, n.Left, n.Right) case OIF: @@ -1484,6 +1495,15 @@ func genssa(f *ssa.Func, ptxt *obj.Prog, gcargs, gclocals *Sym) { Pc.As = obj.ARET // overwrite AEND + // Emit static data + if f.StaticData != nil { + for _, n := range f.StaticData.([]*Node) { + if !gen_as_init(n, false) { + Fatal("non-static data marked as static: %v\n\n", n, f) + } + } + } + // TODO: liveness // TODO: gcargs // TODO: gclocals diff --git a/src/cmd/compile/internal/ssa/func.go b/src/cmd/compile/internal/ssa/func.go index 34d2780104..e0f7c9ff60 100644 --- a/src/cmd/compile/internal/ssa/func.go +++ b/src/cmd/compile/internal/ssa/func.go @@ -9,13 +9,14 @@ import "sync" // A Func represents a Go func declaration (or function literal) and // its body. This package compiles each Func independently. type Func struct { - Config *Config // architecture information - Name string // e.g. bytes·Compare - Type Type // type signature of the function. - Blocks []*Block // unordered set of all basic blocks (note: not indexable by ID) - Entry *Block // the entry basic block - bid idAlloc // block ID allocator - vid idAlloc // value ID allocator + Config *Config // architecture information + Name string // e.g. bytes·Compare + Type Type // type signature of the function. + StaticData interface{} // associated static data, untouched by the ssa package + Blocks []*Block // unordered set of all basic blocks (note: not indexable by ID) + Entry *Block // the entry basic block + bid idAlloc // block ID allocator + vid idAlloc // value ID allocator // when register allocation is done, maps value ids to locations RegAlloc []Location