compile.go

Documentation: cmd/compile/internal/gc

     1  // Copyright 2011 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 gc
     6  
     7  import (
     8  	"internal/race"
     9  	"math/rand"
    10  	"sort"
    11  	"sync"
    12  
    13  	"cmd/compile/internal/base"
    14  	"cmd/compile/internal/ir"
    15  	"cmd/compile/internal/liveness"
    16  	"cmd/compile/internal/objw"
    17  	"cmd/compile/internal/ssagen"
    18  	"cmd/compile/internal/staticinit"
    19  	"cmd/compile/internal/types"
    20  	"cmd/compile/internal/walk"
    21  	"cmd/internal/obj"
    22  )
    23  
    24  // "Portable" code generation.
    25  
    26  var (
    27  	compilequeue []*ir.Func // functions waiting to be compiled
    28  )
    29  
    30  func enqueueFunc(fn *ir.Func) {
    31  	if ir.CurFunc != nil {
    32  		base.FatalfAt(fn.Pos(), "enqueueFunc %v inside %v", fn, ir.CurFunc)
    33  	}
    34  
    35  	if ir.FuncName(fn) == "_" {
    36  		// Skip compiling blank functions.
    37  		// Frontend already reported any spec-mandated errors (#29870).
    38  		return
    39  	}
    40  
    41  	// Don't try compiling dead hidden closure.
    42  	if fn.IsDeadcodeClosure() {
    43  		return
    44  	}
    45  
    46  	if clo := fn.OClosure; clo != nil && !ir.IsTrivialClosure(clo) {
    47  		return // we'll get this as part of its enclosing function
    48  	}
    49  
    50  	if ssagen.CreateWasmImportWrapper(fn) {
    51  		return
    52  	}
    53  
    54  	if len(fn.Body) == 0 {
    55  		// Initialize ABI wrappers if necessary.
    56  		ir.InitLSym(fn, false)
    57  		types.CalcSize(fn.Type())
    58  		a := ssagen.AbiForBodylessFuncStackMap(fn)
    59  		abiInfo := a.ABIAnalyzeFuncType(fn.Type()) // abiInfo has spill/home locations for wrapper
    60  		liveness.WriteFuncMap(fn, abiInfo)
    61  		if fn.ABI == obj.ABI0 {
    62  			x := ssagen.EmitArgInfo(fn, abiInfo)
    63  			objw.Global(x, int32(len(x.P)), obj.RODATA|obj.LOCAL)
    64  		}
    65  		return
    66  	}
    67  
    68  	errorsBefore := base.Errors()
    69  
    70  	todo := []*ir.Func{fn}
    71  	for len(todo) > 0 {
    72  		next := todo[len(todo)-1]
    73  		todo = todo[:len(todo)-1]
    74  
    75  		prepareFunc(next)
    76  		todo = append(todo, next.Closures...)
    77  	}
    78  
    79  	if base.Errors() > errorsBefore {
    80  		return
    81  	}
    82  
    83  	// Enqueue just fn itself. compileFunctions will handle
    84  	// scheduling compilation of its closures after it's done.
    85  	compilequeue = append(compilequeue, fn)
    86  }
    87  
    88  // prepareFunc handles any remaining frontend compilation tasks that
    89  // aren't yet safe to perform concurrently.
    90  func prepareFunc(fn *ir.Func) {
    91  	// Set up the function's LSym early to avoid data races with the assemblers.
    92  	// Do this before walk, as walk needs the LSym to set attributes/relocations
    93  	// (e.g. in MarkTypeUsedInInterface).
    94  	ir.InitLSym(fn, true)
    95  
    96  	// If this function is a compiler-generated outlined global map
    97  	// initializer function, register its LSym for later processing.
    98  	if staticinit.MapInitToVar != nil {
    99  		if _, ok := staticinit.MapInitToVar[fn]; ok {
   100  			ssagen.RegisterMapInitLsym(fn.Linksym())
   101  		}
   102  	}
   103  
   104  	// Calculate parameter offsets.
   105  	types.CalcSize(fn.Type())
   106  
   107  	ir.CurFunc = fn
   108  	walk.Walk(fn)
   109  	ir.CurFunc = nil // enforce no further uses of CurFunc
   110  }
   111  
   112  // compileFunctions compiles all functions in compilequeue.
   113  // It fans out nBackendWorkers to do the work
   114  // and waits for them to complete.
   115  func compileFunctions() {
   116  	if race.Enabled {
   117  		// Randomize compilation order to try to shake out races.
   118  		tmp := make([]*ir.Func, len(compilequeue))
   119  		perm := rand.Perm(len(compilequeue))
   120  		for i, v := range perm {
   121  			tmp[v] = compilequeue[i]
   122  		}
   123  		copy(compilequeue, tmp)
   124  	} else {
   125  		// Compile the longest functions first,
   126  		// since they're most likely to be the slowest.
   127  		// This helps avoid stragglers.
   128  		sort.Slice(compilequeue, func(i, j int) bool {
   129  			return len(compilequeue[i].Body) > len(compilequeue[j].Body)
   130  		})
   131  	}
   132  
   133  	// By default, we perform work right away on the current goroutine
   134  	// as the solo worker.
   135  	queue := func(work func(int)) {
   136  		work(0)
   137  	}
   138  
   139  	if nWorkers := base.Flag.LowerC; nWorkers > 1 {
   140  		// For concurrent builds, we allow the work queue
   141  		// to grow arbitrarily large, but only nWorkers work items
   142  		// can be running concurrently.
   143  		workq := make(chan func(int))
   144  		done := make(chan int)
   145  		go func() {
   146  			ids := make([]int, nWorkers)
   147  			for i := range ids {
   148  				ids[i] = i
   149  			}
   150  			var pending []func(int)
   151  			for {
   152  				select {
   153  				case work := <-workq:
   154  					pending = append(pending, work)
   155  				case id := <-done:
   156  					ids = append(ids, id)
   157  				}
   158  				for len(pending) > 0 && len(ids) > 0 {
   159  					work := pending[len(pending)-1]
   160  					id := ids[len(ids)-1]
   161  					pending = pending[:len(pending)-1]
   162  					ids = ids[:len(ids)-1]
   163  					go func() {
   164  						work(id)
   165  						done <- id
   166  					}()
   167  				}
   168  			}
   169  		}()
   170  		queue = func(work func(int)) {
   171  			workq <- work
   172  		}
   173  	}
   174  
   175  	var wg sync.WaitGroup
   176  	var compile func([]*ir.Func)
   177  	compile = func(fns []*ir.Func) {
   178  		wg.Add(len(fns))
   179  		for _, fn := range fns {
   180  			fn := fn
   181  			queue(func(worker int) {
   182  				ssagen.Compile(fn, worker)
   183  				compile(fn.Closures)
   184  				wg.Done()
   185  			})
   186  		}
   187  	}
   188  
   189  	types.CalcSizeDisabled = true // not safe to calculate sizes concurrently
   190  	base.Ctxt.InParallel = true
   191  
   192  	compile(compilequeue)
   193  	compilequeue = nil
   194  	wg.Wait()
   195  
   196  	base.Ctxt.InParallel = false
   197  	types.CalcSizeDisabled = false
   198  }
   199
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