compile.go

     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  	"cmp"
     9  	"internal/race"
    10  	"math/rand"
    11  	"slices"
    12  	"sync"
    13  
    14  	"cmd/compile/internal/base"
    15  	"cmd/compile/internal/ir"
    16  	"cmd/compile/internal/liveness"
    17  	"cmd/compile/internal/objw"
    18  	"cmd/compile/internal/pgoir"
    19  	"cmd/compile/internal/ssagen"
    20  	"cmd/compile/internal/staticinit"
    21  	"cmd/compile/internal/types"
    22  	"cmd/compile/internal/walk"
    23  	"cmd/internal/obj"
    24  )
    25  
    26  // "Portable" code generation.
    27  
    28  var (
    29  	compilequeue []*ir.Func // functions waiting to be compiled
    30  )
    31  
    32  func enqueueFunc(fn *ir.Func, symABIs *ssagen.SymABIs) {
    33  	if ir.CurFunc != nil {
    34  		base.FatalfAt(fn.Pos(), "enqueueFunc %v inside %v", fn, ir.CurFunc)
    35  	}
    36  
    37  	if ir.FuncName(fn) == "_" {
    38  		// Skip compiling blank functions.
    39  		// Frontend already reported any spec-mandated errors (#29870).
    40  		return
    41  	}
    42  
    43  	if fn.IsClosure() {
    44  		return // we'll get this as part of its enclosing function
    45  	}
    46  
    47  	if ssagen.CreateWasmImportWrapper(fn) {
    48  		return
    49  	}
    50  
    51  	if len(fn.Body) == 0 {
    52  		if ir.IsIntrinsicSym(fn.Sym()) && fn.Sym().Linkname == "" && !symABIs.HasDef(fn.Sym()) {
    53  			// Generate the function body for a bodyless intrinsic, in case it
    54  			// is used in a non-call context (e.g. as a function pointer).
    55  			// We skip functions defined in assembly, or has a linkname (which
    56  			// could be defined in another package).
    57  			ssagen.GenIntrinsicBody(fn)
    58  		} else {
    59  			// Initialize ABI wrappers if necessary.
    60  			ir.InitLSym(fn, false)
    61  			types.CalcSize(fn.Type())
    62  			a := ssagen.AbiForBodylessFuncStackMap(fn)
    63  			abiInfo := a.ABIAnalyzeFuncType(fn.Type()) // abiInfo has spill/home locations for wrapper
    64  			if fn.ABI == obj.ABI0 {
    65  				// The current args_stackmap generation assumes the function
    66  				// is ABI0, and only ABI0 assembly function can have a FUNCDATA
    67  				// reference to args_stackmap (see cmd/internal/obj/plist.go:Flushplist).
    68  				// So avoid introducing an args_stackmap if the func is not ABI0.
    69  				liveness.WriteFuncMap(fn, abiInfo)
    70  
    71  				x := ssagen.EmitArgInfo(fn, abiInfo)
    72  				objw.Global(x, int32(len(x.P)), obj.RODATA|obj.LOCAL)
    73  			}
    74  			return
    75  		}
    76  	}
    77  
    78  	errorsBefore := base.Errors()
    79  
    80  	todo := []*ir.Func{fn}
    81  	for len(todo) > 0 {
    82  		next := todo[len(todo)-1]
    83  		todo = todo[:len(todo)-1]
    84  
    85  		prepareFunc(next)
    86  		todo = append(todo, next.Closures...)
    87  	}
    88  
    89  	if base.Errors() > errorsBefore {
    90  		return
    91  	}
    92  
    93  	// Enqueue just fn itself. compileFunctions will handle
    94  	// scheduling compilation of its closures after it's done.
    95  	compilequeue = append(compilequeue, fn)
    96  }
    97  
    98  // prepareFunc handles any remaining frontend compilation tasks that
    99  // aren't yet safe to perform concurrently.
   100  func prepareFunc(fn *ir.Func) {
   101  	// Set up the function's LSym early to avoid data races with the assemblers.
   102  	// Do this before walk, as walk needs the LSym to set attributes/relocations
   103  	// (e.g. in MarkTypeUsedInInterface).
   104  	ir.InitLSym(fn, true)
   105  
   106  	// If this function is a compiler-generated outlined global map
   107  	// initializer function, register its LSym for later processing.
   108  	if staticinit.MapInitToVar != nil {
   109  		if _, ok := staticinit.MapInitToVar[fn]; ok {
   110  			ssagen.RegisterMapInitLsym(fn.Linksym())
   111  		}
   112  	}
   113  
   114  	// Calculate parameter offsets.
   115  	types.CalcSize(fn.Type())
   116  
   117  	// Generate wrappers between Go ABI and Wasm ABI, for a wasmexport
   118  	// function.
   119  	// Must be done after InitLSym and CalcSize.
   120  	ssagen.GenWasmExportWrapper(fn)
   121  
   122  	ir.CurFunc = fn
   123  	walk.Walk(fn)
   124  	ir.CurFunc = nil // enforce no further uses of CurFunc
   125  
   126  	base.Ctxt.DwTextCount++
   127  }
   128  
   129  // compileFunctions compiles all functions in compilequeue.
   130  // It fans out nBackendWorkers to do the work
   131  // and waits for them to complete.
   132  func compileFunctions(profile *pgoir.Profile) {
   133  	if race.Enabled {
   134  		// Randomize compilation order to try to shake out races.
   135  		tmp := make([]*ir.Func, len(compilequeue))
   136  		perm := rand.Perm(len(compilequeue))
   137  		for i, v := range perm {
   138  			tmp[v] = compilequeue[i]
   139  		}
   140  		copy(compilequeue, tmp)
   141  	} else {
   142  		// Compile the longest functions first,
   143  		// since they're most likely to be the slowest.
   144  		// This helps avoid stragglers.
   145  		slices.SortFunc(compilequeue, func(a, b *ir.Func) int {
   146  			return cmp.Compare(len(b.Body), len(a.Body))
   147  		})
   148  	}
   149  
   150  	// By default, we perform work right away on the current goroutine
   151  	// as the solo worker.
   152  	queue := func(work func(int)) {
   153  		work(0)
   154  	}
   155  
   156  	if nWorkers := base.Flag.LowerC; nWorkers > 1 {
   157  		// For concurrent builds, we allow the work queue
   158  		// to grow arbitrarily large, but only nWorkers work items
   159  		// can be running concurrently.
   160  		workq := make(chan func(int))
   161  		done := make(chan int)
   162  		go func() {
   163  			ids := make([]int, nWorkers)
   164  			for i := range ids {
   165  				ids[i] = i
   166  			}
   167  			var pending []func(int)
   168  			for {
   169  				select {
   170  				case work := <-workq:
   171  					pending = append(pending, work)
   172  				case id := <-done:
   173  					ids = append(ids, id)
   174  				}
   175  				for len(pending) > 0 && len(ids) > 0 {
   176  					work := pending[len(pending)-1]
   177  					id := ids[len(ids)-1]
   178  					pending = pending[:len(pending)-1]
   179  					ids = ids[:len(ids)-1]
   180  					go func() {
   181  						work(id)
   182  						done <- id
   183  					}()
   184  				}
   185  			}
   186  		}()
   187  		queue = func(work func(int)) {
   188  			workq <- work
   189  		}
   190  	}
   191  
   192  	var wg sync.WaitGroup
   193  	var compile func([]*ir.Func)
   194  	compile = func(fns []*ir.Func) {
   195  		wg.Add(len(fns))
   196  		for _, fn := range fns {
   197  			fn := fn
   198  			queue(func(worker int) {
   199  				ssagen.Compile(fn, worker, profile)
   200  				compile(fn.Closures)
   201  				wg.Done()
   202  			})
   203  		}
   204  	}
   205  
   206  	types.CalcSizeDisabled = true // not safe to calculate sizes concurrently
   207  	base.Ctxt.InParallel = true
   208  
   209  	compile(compilequeue)
   210  	compilequeue = nil
   211  	wg.Wait()
   212  
   213  	base.Ctxt.InParallel = false
   214  	types.CalcSizeDisabled = false
   215  }
   216
View as plain text