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// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ssa
import (
"cmd/internal/obj"
"sort"
)
// A Cache holds reusable compiler state.
// It is intended to be re-used for multiple Func compilations.
type Cache struct {
// Storage for low-numbered values and blocks.
values [2000]Value
blocks [200]Block
locs [2000]Location
// Reusable stackAllocState.
// See stackalloc.go's {new,put}StackAllocState.
stackAllocState *stackAllocState
domblockstore []ID // scratch space for computing dominators
scrSparseSet []*sparseSet // scratch sparse sets to be re-used.
scrSparseMap []*sparseMap // scratch sparse maps to be re-used.
scrPoset []*poset // scratch poset to be reused
// deadcode contains reusable slices specifically for the deadcode pass.
// It gets special treatment because of the frequency with which it is run.
deadcode struct {
liveOrderStmts []*Value
live []bool
q []*Value
}
// Reusable regalloc state.
regallocValues []valState
ValueToProgAfter []*obj.Prog
debugState debugState
Liveness interface{} // *gc.livenessFuncCache
}
func (c *Cache) Reset() {
nv := sort.Search(len(c.values), func(i int) bool { return c.values[i].ID == 0 })
xv := c.values[:nv]
for i := range xv {
xv[i] = Value{}
}
nb := sort.Search(len(c.blocks), func(i int) bool { return c.blocks[i].ID == 0 })
xb := c.blocks[:nb]
for i := range xb {
xb[i] = Block{}
}
nl := sort.Search(len(c.locs), func(i int) bool { return c.locs[i] == nil })
xl := c.locs[:nl]
for i := range xl {
xl[i] = nil
}
// regalloc sets the length of c.regallocValues to whatever it may use,
// so clear according to length.
for i := range c.regallocValues {
c.regallocValues[i] = valState{}
}
// liveOrderStmts gets used multiple times during compilation of a function.
// We don't know where the high water mark was, so reslice to cap and search.
c.deadcode.liveOrderStmts = c.deadcode.liveOrderStmts[:cap(c.deadcode.liveOrderStmts)]
no := sort.Search(len(c.deadcode.liveOrderStmts), func(i int) bool { return c.deadcode.liveOrderStmts[i] == nil })
xo := c.deadcode.liveOrderStmts[:no]
for i := range xo {
xo[i] = nil
}
c.deadcode.q = c.deadcode.q[:cap(c.deadcode.q)]
nq := sort.Search(len(c.deadcode.q), func(i int) bool { return c.deadcode.q[i] == nil })
xq := c.deadcode.q[:nq]
for i := range xq {
xq[i] = nil
}
}
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