Source file src/pkg/cmd/compile/internal/ssa/cache.go

     1	// Copyright 2017 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	package ssa
     6	
     7	import (
     8		"cmd/internal/obj"
     9		"sort"
    10	)
    11	
    12	// A Cache holds reusable compiler state.
    13	// It is intended to be re-used for multiple Func compilations.
    14	type Cache struct {
    15		// Storage for low-numbered values and blocks.
    16		values [2000]Value
    17		blocks [200]Block
    18		locs   [2000]Location
    19	
    20		// Reusable stackAllocState.
    21		// See stackalloc.go's {new,put}StackAllocState.
    22		stackAllocState *stackAllocState
    23	
    24		domblockstore []ID         // scratch space for computing dominators
    25		scrSparseSet  []*sparseSet // scratch sparse sets to be re-used.
    26		scrSparseMap  []*sparseMap // scratch sparse maps to be re-used.
    27		scrPoset      []*poset     // scratch poset to be reused
    28		// deadcode contains reusable slices specifically for the deadcode pass.
    29		// It gets special treatment because of the frequency with which it is run.
    30		deadcode struct {
    31			liveOrderStmts []*Value
    32			live           []bool
    33			q              []*Value
    34		}
    35		// Reusable regalloc state.
    36		regallocValues []valState
    37	
    38		ValueToProgAfter []*obj.Prog
    39		debugState       debugState
    40	
    41		Liveness interface{} // *gc.livenessFuncCache
    42	}
    43	
    44	func (c *Cache) Reset() {
    45		nv := sort.Search(len(c.values), func(i int) bool { return c.values[i].ID == 0 })
    46		xv := c.values[:nv]
    47		for i := range xv {
    48			xv[i] = Value{}
    49		}
    50		nb := sort.Search(len(c.blocks), func(i int) bool { return c.blocks[i].ID == 0 })
    51		xb := c.blocks[:nb]
    52		for i := range xb {
    53			xb[i] = Block{}
    54		}
    55		nl := sort.Search(len(c.locs), func(i int) bool { return c.locs[i] == nil })
    56		xl := c.locs[:nl]
    57		for i := range xl {
    58			xl[i] = nil
    59		}
    60	
    61		// regalloc sets the length of c.regallocValues to whatever it may use,
    62		// so clear according to length.
    63		for i := range c.regallocValues {
    64			c.regallocValues[i] = valState{}
    65		}
    66	
    67		// liveOrderStmts gets used multiple times during compilation of a function.
    68		// We don't know where the high water mark was, so reslice to cap and search.
    69		c.deadcode.liveOrderStmts = c.deadcode.liveOrderStmts[:cap(c.deadcode.liveOrderStmts)]
    70		no := sort.Search(len(c.deadcode.liveOrderStmts), func(i int) bool { return c.deadcode.liveOrderStmts[i] == nil })
    71		xo := c.deadcode.liveOrderStmts[:no]
    72		for i := range xo {
    73			xo[i] = nil
    74		}
    75		c.deadcode.q = c.deadcode.q[:cap(c.deadcode.q)]
    76		nq := sort.Search(len(c.deadcode.q), func(i int) bool { return c.deadcode.q[i] == nil })
    77		xq := c.deadcode.q[:nq]
    78		for i := range xq {
    79			xq[i] = nil
    80		}
    81	}
    82	

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