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/pgoir"
    18  	"cmd/compile/internal/ssagen"
    19  	"cmd/compile/internal/staticinit"
    20  	"cmd/compile/internal/types"
    21  	"cmd/compile/internal/walk"
    22  	"cmd/internal/obj"
    23  )
    24  
    25  // "Portable" code generation.
    26  
    27  var (
    28  	compilequeue []*ir.Func // functions waiting to be compiled
    29  )
    30  
    31  func enqueueFunc(fn *ir.Func) {
    32  	if ir.CurFunc != nil {
    33  		base.FatalfAt(fn.Pos(), "enqueueFunc %v inside %v", fn, ir.CurFunc)
    34  	}
    35  
    36  	if ir.FuncName(fn) == "_" {
    37  		// Skip compiling blank functions.
    38  		// Frontend already reported any spec-mandated errors (#29870).
    39  		return
    40  	}
    41  
    42  	// Don't try compiling dead hidden closure.
    43  	if fn.IsDeadcodeClosure() {
    44  		return
    45  	}
    46  
    47  	if clo := fn.OClosure; clo != nil && !ir.IsTrivialClosure(clo) {
    48  		return // we'll get this as part of its enclosing function
    49  	}
    50  
    51  	if ssagen.CreateWasmImportWrapper(fn) {
    52  		return
    53  	}
    54  
    55  	if len(fn.Body) == 0 {
    56  		// Initialize ABI wrappers if necessary.
    57  		ir.InitLSym(fn, false)
    58  		types.CalcSize(fn.Type())
    59  		a := ssagen.AbiForBodylessFuncStackMap(fn)
    60  		abiInfo := a.ABIAnalyzeFuncType(fn.Type()) // abiInfo has spill/home locations for wrapper
    61  		if fn.ABI == obj.ABI0 {
    62  			// The current args_stackmap generation assumes the function
    63  			// is ABI0, and only ABI0 assembly function can have a FUNCDATA
    64  			// reference to args_stackmap (see cmd/internal/obj/plist.go:Flushplist).
    65  			// So avoid introducing an args_stackmap if the func is not ABI0.
    66  			liveness.WriteFuncMap(fn, abiInfo)
    67  
    68  			x := ssagen.EmitArgInfo(fn, abiInfo)
    69  			objw.Global(x, int32(len(x.P)), obj.RODATA|obj.LOCAL)
    70  		}
    71  		return
    72  	}
    73  
    74  	errorsBefore := base.Errors()
    75  
    76  	todo := []*ir.Func{fn}
    77  	for len(todo) > 0 {
    78  		next := todo[len(todo)-1]
    79  		todo = todo[:len(todo)-1]
    80  
    81  		prepareFunc(next)
    82  		todo = append(todo, next.Closures...)
    83  	}
    84  
    85  	if base.Errors() > errorsBefore {
    86  		return
    87  	}
    88  
    89  	// Enqueue just fn itself. compileFunctions will handle
    90  	// scheduling compilation of its closures after it's done.
    91  	compilequeue = append(compilequeue, fn)
    92  }
    93  
    94  // prepareFunc handles any remaining frontend compilation tasks that
    95  // aren't yet safe to perform concurrently.
    96  func prepareFunc(fn *ir.Func) {
    97  	// Set up the function's LSym early to avoid data races with the assemblers.
    98  	// Do this before walk, as walk needs the LSym to set attributes/relocations
    99  	// (e.g. in MarkTypeUsedInInterface).
   100  	ir.InitLSym(fn, true)
   101  
   102  	// If this function is a compiler-generated outlined global map
   103  	// initializer function, register its LSym for later processing.
   104  	if staticinit.MapInitToVar != nil {
   105  		if _, ok := staticinit.MapInitToVar[fn]; ok {
   106  			ssagen.RegisterMapInitLsym(fn.Linksym())
   107  		}
   108  	}
   109  
   110  	// Calculate parameter offsets.
   111  	types.CalcSize(fn.Type())
   112  
   113  	ir.CurFunc = fn
   114  	walk.Walk(fn)
   115  	ir.CurFunc = nil // enforce no further uses of CurFunc
   116  }
   117  
   118  // compileFunctions compiles all functions in compilequeue.
   119  // It fans out nBackendWorkers to do the work
   120  // and waits for them to complete.
   121  func compileFunctions(profile *pgoir.Profile) {
   122  	if race.Enabled {
   123  		// Randomize compilation order to try to shake out races.
   124  		tmp := make([]*ir.Func, len(compilequeue))
   125  		perm := rand.Perm(len(compilequeue))
   126  		for i, v := range perm {
   127  			tmp[v] = compilequeue[i]
   128  		}
   129  		copy(compilequeue, tmp)
   130  	} else {
   131  		// Compile the longest functions first,
   132  		// since they're most likely to be the slowest.
   133  		// This helps avoid stragglers.
   134  		sort.Slice(compilequeue, func(i, j int) bool {
   135  			return len(compilequeue[i].Body) > len(compilequeue[j].Body)
   136  		})
   137  	}
   138  
   139  	// By default, we perform work right away on the current goroutine
   140  	// as the solo worker.
   141  	queue := func(work func(int)) {
   142  		work(0)
   143  	}
   144  
   145  	if nWorkers := base.Flag.LowerC; nWorkers > 1 {
   146  		// For concurrent builds, we allow the work queue
   147  		// to grow arbitrarily large, but only nWorkers work items
   148  		// can be running concurrently.
   149  		workq := make(chan func(int))
   150  		done := make(chan int)
   151  		go func() {
   152  			ids := make([]int, nWorkers)
   153  			for i := range ids {
   154  				ids[i] = i
   155  			}
   156  			var pending []func(int)
   157  			for {
   158  				select {
   159  				case work := <-workq:
   160  					pending = append(pending, work)
   161  				case id := <-done:
   162  					ids = append(ids, id)
   163  				}
   164  				for len(pending) > 0 && len(ids) > 0 {
   165  					work := pending[len(pending)-1]
   166  					id := ids[len(ids)-1]
   167  					pending = pending[:len(pending)-1]
   168  					ids = ids[:len(ids)-1]
   169  					go func() {
   170  						work(id)
   171  						done <- id
   172  					}()
   173  				}
   174  			}
   175  		}()
   176  		queue = func(work func(int)) {
   177  			workq <- work
   178  		}
   179  	}
   180  
   181  	var wg sync.WaitGroup
   182  	var compile func([]*ir.Func)
   183  	compile = func(fns []*ir.Func) {
   184  		wg.Add(len(fns))
   185  		for _, fn := range fns {
   186  			fn := fn
   187  			queue(func(worker int) {
   188  				ssagen.Compile(fn, worker, profile)
   189  				compile(fn.Closures)
   190  				wg.Done()
   191  			})
   192  		}
   193  	}
   194  
   195  	types.CalcSizeDisabled = true // not safe to calculate sizes concurrently
   196  	base.Ctxt.InParallel = true
   197  
   198  	compile(compilequeue)
   199  	compilequeue = nil
   200  	wg.Wait()
   201  
   202  	base.Ctxt.InParallel = false
   203  	types.CalcSizeDisabled = false
   204  }
   205
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