main.go

Documentation: cmd/compile/internal/gc

     1  // Copyright 2009 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  	"bufio"
     9  	"bytes"
    10  	"cmd/compile/internal/base"
    11  	"cmd/compile/internal/coverage"
    12  	"cmd/compile/internal/dwarfgen"
    13  	"cmd/compile/internal/escape"
    14  	"cmd/compile/internal/inline"
    15  	"cmd/compile/internal/inline/interleaved"
    16  	"cmd/compile/internal/ir"
    17  	"cmd/compile/internal/logopt"
    18  	"cmd/compile/internal/loopvar"
    19  	"cmd/compile/internal/noder"
    20  	"cmd/compile/internal/pgo"
    21  	"cmd/compile/internal/pkginit"
    22  	"cmd/compile/internal/reflectdata"
    23  	"cmd/compile/internal/rttype"
    24  	"cmd/compile/internal/ssa"
    25  	"cmd/compile/internal/ssagen"
    26  	"cmd/compile/internal/staticinit"
    27  	"cmd/compile/internal/typecheck"
    28  	"cmd/compile/internal/types"
    29  	"cmd/internal/dwarf"
    30  	"cmd/internal/obj"
    31  	"cmd/internal/objabi"
    32  	"cmd/internal/src"
    33  	"flag"
    34  	"fmt"
    35  	"internal/buildcfg"
    36  	"log"
    37  	"os"
    38  	"runtime"
    39  )
    40  
    41  // handlePanic ensures that we print out an "internal compiler error" for any panic
    42  // or runtime exception during front-end compiler processing (unless there have
    43  // already been some compiler errors). It may also be invoked from the explicit panic in
    44  // hcrash(), in which case, we pass the panic on through.
    45  func handlePanic() {
    46  	if err := recover(); err != nil {
    47  		if err == "-h" {
    48  			// Force real panic now with -h option (hcrash) - the error
    49  			// information will have already been printed.
    50  			panic(err)
    51  		}
    52  		base.Fatalf("panic: %v", err)
    53  	}
    54  }
    55  
    56  // Main parses flags and Go source files specified in the command-line
    57  // arguments, type-checks the parsed Go package, compiles functions to machine
    58  // code, and finally writes the compiled package definition to disk.
    59  func Main(archInit func(*ssagen.ArchInfo)) {
    60  	base.Timer.Start("fe", "init")
    61  
    62  	defer handlePanic()
    63  
    64  	archInit(&ssagen.Arch)
    65  
    66  	base.Ctxt = obj.Linknew(ssagen.Arch.LinkArch)
    67  	base.Ctxt.DiagFunc = base.Errorf
    68  	base.Ctxt.DiagFlush = base.FlushErrors
    69  	base.Ctxt.Bso = bufio.NewWriter(os.Stdout)
    70  
    71  	// UseBASEntries is preferred because it shaves about 2% off build time, but LLDB, dsymutil, and dwarfdump
    72  	// on Darwin don't support it properly, especially since macOS 10.14 (Mojave).  This is exposed as a flag
    73  	// to allow testing with LLVM tools on Linux, and to help with reporting this bug to the LLVM project.
    74  	// See bugs 31188 and 21945 (CLs 170638, 98075, 72371).
    75  	base.Ctxt.UseBASEntries = base.Ctxt.Headtype != objabi.Hdarwin
    76  
    77  	base.DebugSSA = ssa.PhaseOption
    78  	base.ParseFlags()
    79  
    80  	if os.Getenv("GOGC") == "" { // GOGC set disables starting heap adjustment
    81  		// More processors will use more heap, but assume that more memory is available.
    82  		// So 1 processor -> 40MB, 4 -> 64MB, 12 -> 128MB
    83  		base.AdjustStartingHeap(uint64(32+8*base.Flag.LowerC) << 20)
    84  	}
    85  
    86  	types.LocalPkg = types.NewPkg(base.Ctxt.Pkgpath, "")
    87  
    88  	// pseudo-package, for scoping
    89  	types.BuiltinPkg = types.NewPkg("go.builtin", "") // TODO(gri) name this package go.builtin?
    90  	types.BuiltinPkg.Prefix = "go:builtin"
    91  
    92  	// pseudo-package, accessed by import "unsafe"
    93  	types.UnsafePkg = types.NewPkg("unsafe", "unsafe")
    94  
    95  	// Pseudo-package that contains the compiler's builtin
    96  	// declarations for package runtime. These are declared in a
    97  	// separate package to avoid conflicts with package runtime's
    98  	// actual declarations, which may differ intentionally but
    99  	// insignificantly.
   100  	ir.Pkgs.Runtime = types.NewPkg("go.runtime", "runtime")
   101  	ir.Pkgs.Runtime.Prefix = "runtime"
   102  
   103  	// pseudo-packages used in symbol tables
   104  	ir.Pkgs.Itab = types.NewPkg("go.itab", "go.itab")
   105  	ir.Pkgs.Itab.Prefix = "go:itab"
   106  
   107  	// pseudo-package used for methods with anonymous receivers
   108  	ir.Pkgs.Go = types.NewPkg("go", "")
   109  
   110  	// pseudo-package for use with code coverage instrumentation.
   111  	ir.Pkgs.Coverage = types.NewPkg("go.coverage", "runtime/coverage")
   112  	ir.Pkgs.Coverage.Prefix = "runtime/coverage"
   113  
   114  	// Record flags that affect the build result. (And don't
   115  	// record flags that don't, since that would cause spurious
   116  	// changes in the binary.)
   117  	dwarfgen.RecordFlags("B", "N", "l", "msan", "race", "asan", "shared", "dynlink", "dwarf", "dwarflocationlists", "dwarfbasentries", "smallframes", "spectre")
   118  
   119  	if !base.EnableTrace && base.Flag.LowerT {
   120  		log.Fatalf("compiler not built with support for -t")
   121  	}
   122  
   123  	// Enable inlining (after RecordFlags, to avoid recording the rewritten -l).  For now:
   124  	//	default: inlining on.  (Flag.LowerL == 1)
   125  	//	-l: inlining off  (Flag.LowerL == 0)
   126  	//	-l=2, -l=3: inlining on again, with extra debugging (Flag.LowerL > 1)
   127  	if base.Flag.LowerL <= 1 {
   128  		base.Flag.LowerL = 1 - base.Flag.LowerL
   129  	}
   130  
   131  	if base.Flag.SmallFrames {
   132  		ir.MaxStackVarSize = 128 * 1024
   133  		ir.MaxImplicitStackVarSize = 16 * 1024
   134  	}
   135  
   136  	if base.Flag.Dwarf {
   137  		base.Ctxt.DebugInfo = dwarfgen.Info
   138  		base.Ctxt.GenAbstractFunc = dwarfgen.AbstractFunc
   139  		base.Ctxt.DwFixups = obj.NewDwarfFixupTable(base.Ctxt)
   140  	} else {
   141  		// turn off inline generation if no dwarf at all
   142  		base.Flag.GenDwarfInl = 0
   143  		base.Ctxt.Flag_locationlists = false
   144  	}
   145  	if base.Ctxt.Flag_locationlists && len(base.Ctxt.Arch.DWARFRegisters) == 0 {
   146  		log.Fatalf("location lists requested but register mapping not available on %v", base.Ctxt.Arch.Name)
   147  	}
   148  
   149  	types.ParseLangFlag()
   150  
   151  	symABIs := ssagen.NewSymABIs()
   152  	if base.Flag.SymABIs != "" {
   153  		symABIs.ReadSymABIs(base.Flag.SymABIs)
   154  	}
   155  
   156  	if objabi.LookupPkgSpecial(base.Ctxt.Pkgpath).NoInstrument {
   157  		base.Flag.Race = false
   158  		base.Flag.MSan = false
   159  		base.Flag.ASan = false
   160  	}
   161  
   162  	ssagen.Arch.LinkArch.Init(base.Ctxt)
   163  	startProfile()
   164  	if base.Flag.Race || base.Flag.MSan || base.Flag.ASan {
   165  		base.Flag.Cfg.Instrumenting = true
   166  	}
   167  	if base.Flag.Dwarf {
   168  		dwarf.EnableLogging(base.Debug.DwarfInl != 0)
   169  	}
   170  	if base.Debug.SoftFloat != 0 {
   171  		ssagen.Arch.SoftFloat = true
   172  	}
   173  
   174  	if base.Flag.JSON != "" { // parse version,destination from json logging optimization.
   175  		logopt.LogJsonOption(base.Flag.JSON)
   176  	}
   177  
   178  	ir.EscFmt = escape.Fmt
   179  	ir.IsIntrinsicCall = ssagen.IsIntrinsicCall
   180  	inline.SSADumpInline = ssagen.DumpInline
   181  	ssagen.InitEnv()
   182  	ssagen.InitTables()
   183  
   184  	types.PtrSize = ssagen.Arch.LinkArch.PtrSize
   185  	types.RegSize = ssagen.Arch.LinkArch.RegSize
   186  	types.MaxWidth = ssagen.Arch.MAXWIDTH
   187  
   188  	typecheck.Target = new(ir.Package)
   189  
   190  	base.AutogeneratedPos = makePos(src.NewFileBase("<autogenerated>", "<autogenerated>"), 1, 0)
   191  
   192  	typecheck.InitUniverse()
   193  	typecheck.InitRuntime()
   194  	rttype.Init()
   195  
   196  	// Parse and typecheck input.
   197  	noder.LoadPackage(flag.Args())
   198  
   199  	// As a convenience to users (toolchain maintainers, in particular),
   200  	// when compiling a package named "main", we default the package
   201  	// path to "main" if the -p flag was not specified.
   202  	if base.Ctxt.Pkgpath == obj.UnlinkablePkg && types.LocalPkg.Name == "main" {
   203  		base.Ctxt.Pkgpath = "main"
   204  		types.LocalPkg.Path = "main"
   205  		types.LocalPkg.Prefix = "main"
   206  	}
   207  
   208  	dwarfgen.RecordPackageName()
   209  
   210  	// Prepare for backend processing.
   211  	ssagen.InitConfig()
   212  
   213  	// Apply coverage fixups, if applicable.
   214  	coverage.Fixup()
   215  
   216  	// Read profile file and build profile-graph and weighted-call-graph.
   217  	base.Timer.Start("fe", "pgo-load-profile")
   218  	var profile *pgo.Profile
   219  	if base.Flag.PgoProfile != "" {
   220  		var err error
   221  		profile, err = pgo.New(base.Flag.PgoProfile)
   222  		if err != nil {
   223  			log.Fatalf("%s: PGO error: %v", base.Flag.PgoProfile, err)
   224  		}
   225  	}
   226  
   227  	// Interleaved devirtualization and inlining.
   228  	base.Timer.Start("fe", "devirtualize-and-inline")
   229  	interleaved.DevirtualizeAndInlinePackage(typecheck.Target, profile)
   230  
   231  	noder.MakeWrappers(typecheck.Target) // must happen after inlining
   232  
   233  	// Get variable capture right in for loops.
   234  	var transformed []loopvar.VarAndLoop
   235  	for _, fn := range typecheck.Target.Funcs {
   236  		transformed = append(transformed, loopvar.ForCapture(fn)...)
   237  	}
   238  	ir.CurFunc = nil
   239  
   240  	// Build init task, if needed.
   241  	pkginit.MakeTask()
   242  
   243  	// Generate ABI wrappers. Must happen before escape analysis
   244  	// and doesn't benefit from dead-coding or inlining.
   245  	symABIs.GenABIWrappers()
   246  
   247  	// Escape analysis.
   248  	// Required for moving heap allocations onto stack,
   249  	// which in turn is required by the closure implementation,
   250  	// which stores the addresses of stack variables into the closure.
   251  	// If the closure does not escape, it needs to be on the stack
   252  	// or else the stack copier will not update it.
   253  	// Large values are also moved off stack in escape analysis;
   254  	// because large values may contain pointers, it must happen early.
   255  	base.Timer.Start("fe", "escapes")
   256  	escape.Funcs(typecheck.Target.Funcs)
   257  
   258  	loopvar.LogTransformations(transformed)
   259  
   260  	// Collect information for go:nowritebarrierrec
   261  	// checking. This must happen before transforming closures during Walk
   262  	// We'll do the final check after write barriers are
   263  	// inserted.
   264  	if base.Flag.CompilingRuntime {
   265  		ssagen.EnableNoWriteBarrierRecCheck()
   266  	}
   267  
   268  	ir.CurFunc = nil
   269  
   270  	reflectdata.WriteBasicTypes()
   271  
   272  	// Compile top-level declarations.
   273  	//
   274  	// There are cyclic dependencies between all of these phases, so we
   275  	// need to iterate all of them until we reach a fixed point.
   276  	base.Timer.Start("be", "compilefuncs")
   277  	for nextFunc, nextExtern := 0, 0; ; {
   278  		reflectdata.WriteRuntimeTypes()
   279  
   280  		if nextExtern < len(typecheck.Target.Externs) {
   281  			switch n := typecheck.Target.Externs[nextExtern]; n.Op() {
   282  			case ir.ONAME:
   283  				dumpGlobal(n)
   284  			case ir.OLITERAL:
   285  				dumpGlobalConst(n)
   286  			case ir.OTYPE:
   287  				reflectdata.NeedRuntimeType(n.Type())
   288  			}
   289  			nextExtern++
   290  			continue
   291  		}
   292  
   293  		if nextFunc < len(typecheck.Target.Funcs) {
   294  			enqueueFunc(typecheck.Target.Funcs[nextFunc])
   295  			nextFunc++
   296  			continue
   297  		}
   298  
   299  		// The SSA backend supports using multiple goroutines, so keep it
   300  		// as late as possible to maximize how much work we can batch and
   301  		// process concurrently.
   302  		if len(compilequeue) != 0 {
   303  			compileFunctions()
   304  			continue
   305  		}
   306  
   307  		// Finalize DWARF inline routine DIEs, then explicitly turn off
   308  		// further DWARF inlining generation to avoid problems with
   309  		// generated method wrappers.
   310  		//
   311  		// Note: The DWARF fixup code for inlined calls currently doesn't
   312  		// allow multiple invocations, so we intentionally run it just
   313  		// once after everything else. Worst case, some generated
   314  		// functions have slightly larger DWARF DIEs.
   315  		if base.Ctxt.DwFixups != nil {
   316  			base.Ctxt.DwFixups.Finalize(base.Ctxt.Pkgpath, base.Debug.DwarfInl != 0)
   317  			base.Ctxt.DwFixups = nil
   318  			base.Flag.GenDwarfInl = 0
   319  			continue // may have called reflectdata.TypeLinksym (#62156)
   320  		}
   321  
   322  		break
   323  	}
   324  
   325  	base.Timer.AddEvent(int64(len(typecheck.Target.Funcs)), "funcs")
   326  
   327  	if base.Flag.CompilingRuntime {
   328  		// Write barriers are now known. Check the call graph.
   329  		ssagen.NoWriteBarrierRecCheck()
   330  	}
   331  
   332  	// Add keep relocations for global maps.
   333  	if base.Debug.WrapGlobalMapCtl != 1 {
   334  		staticinit.AddKeepRelocations()
   335  	}
   336  
   337  	// Write object data to disk.
   338  	base.Timer.Start("be", "dumpobj")
   339  	dumpdata()
   340  	base.Ctxt.NumberSyms()
   341  	dumpobj()
   342  	if base.Flag.AsmHdr != "" {
   343  		dumpasmhdr()
   344  	}
   345  
   346  	ssagen.CheckLargeStacks()
   347  	typecheck.CheckFuncStack()
   348  
   349  	if len(compilequeue) != 0 {
   350  		base.Fatalf("%d uncompiled functions", len(compilequeue))
   351  	}
   352  
   353  	logopt.FlushLoggedOpts(base.Ctxt, base.Ctxt.Pkgpath)
   354  	base.ExitIfErrors()
   355  
   356  	base.FlushErrors()
   357  	base.Timer.Stop()
   358  
   359  	if base.Flag.Bench != "" {
   360  		if err := writebench(base.Flag.Bench); err != nil {
   361  			log.Fatalf("cannot write benchmark data: %v", err)
   362  		}
   363  	}
   364  }
   365  
   366  func writebench(filename string) error {
   367  	f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0666)
   368  	if err != nil {
   369  		return err
   370  	}
   371  
   372  	var buf bytes.Buffer
   373  	fmt.Fprintln(&buf, "commit:", buildcfg.Version)
   374  	fmt.Fprintln(&buf, "goos:", runtime.GOOS)
   375  	fmt.Fprintln(&buf, "goarch:", runtime.GOARCH)
   376  	base.Timer.Write(&buf, "BenchmarkCompile:"+base.Ctxt.Pkgpath+":")
   377  
   378  	n, err := f.Write(buf.Bytes())
   379  	if err != nil {
   380  		return err
   381  	}
   382  	if n != buf.Len() {
   383  		panic("bad writer")
   384  	}
   385  
   386  	return f.Close()
   387  }
   388  
   389  func makePos(b *src.PosBase, line, col uint) src.XPos {
   390  	return base.Ctxt.PosTable.XPos(src.MakePos(b, line, col))
   391  }
   392
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