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/pgoir"
    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  	"cmd/internal/telemetry/counter"
    34  	"flag"
    35  	"fmt"
    36  	"internal/buildcfg"
    37  	"log"
    38  	"os"
    39  	"runtime"
    40  )
    41  
    42  // handlePanic ensures that we print out an "internal compiler error" for any panic
    43  // or runtime exception during front-end compiler processing (unless there have
    44  // already been some compiler errors). It may also be invoked from the explicit panic in
    45  // hcrash(), in which case, we pass the panic on through.
    46  func handlePanic() {
    47  	if err := recover(); err != nil {
    48  		if err == "-h" {
    49  			// Force real panic now with -h option (hcrash) - the error
    50  			// information will have already been printed.
    51  			panic(err)
    52  		}
    53  		base.Fatalf("panic: %v", err)
    54  	}
    55  }
    56  
    57  // Main parses flags and Go source files specified in the command-line
    58  // arguments, type-checks the parsed Go package, compiles functions to machine
    59  // code, and finally writes the compiled package definition to disk.
    60  func Main(archInit func(*ssagen.ArchInfo)) {
    61  	base.Timer.Start("fe", "init")
    62  	counter.Open()
    63  	counter.Inc("compile/invocations")
    64  
    65  	defer handlePanic()
    66  
    67  	archInit(&ssagen.Arch)
    68  
    69  	base.Ctxt = obj.Linknew(ssagen.Arch.LinkArch)
    70  	base.Ctxt.DiagFunc = base.Errorf
    71  	base.Ctxt.DiagFlush = base.FlushErrors
    72  	base.Ctxt.Bso = bufio.NewWriter(os.Stdout)
    73  
    74  	// UseBASEntries is preferred because it shaves about 2% off build time, but LLDB, dsymutil, and dwarfdump
    75  	// on Darwin don't support it properly, especially since macOS 10.14 (Mojave).  This is exposed as a flag
    76  	// to allow testing with LLVM tools on Linux, and to help with reporting this bug to the LLVM project.
    77  	// See bugs 31188 and 21945 (CLs 170638, 98075, 72371).
    78  	base.Ctxt.UseBASEntries = base.Ctxt.Headtype != objabi.Hdarwin
    79  
    80  	base.DebugSSA = ssa.PhaseOption
    81  	base.ParseFlags()
    82  
    83  	if os.Getenv("GOGC") == "" { // GOGC set disables starting heap adjustment
    84  		// More processors will use more heap, but assume that more memory is available.
    85  		// So 1 processor -> 40MB, 4 -> 64MB, 12 -> 128MB
    86  		base.AdjustStartingHeap(uint64(32+8*base.Flag.LowerC) << 20)
    87  	}
    88  
    89  	types.LocalPkg = types.NewPkg(base.Ctxt.Pkgpath, "")
    90  
    91  	// pseudo-package, for scoping
    92  	types.BuiltinPkg = types.NewPkg("go.builtin", "") // TODO(gri) name this package go.builtin?
    93  	types.BuiltinPkg.Prefix = "go:builtin"
    94  
    95  	// pseudo-package, accessed by import "unsafe"
    96  	types.UnsafePkg = types.NewPkg("unsafe", "unsafe")
    97  
    98  	// Pseudo-package that contains the compiler's builtin
    99  	// declarations for package runtime. These are declared in a
   100  	// separate package to avoid conflicts with package runtime's
   101  	// actual declarations, which may differ intentionally but
   102  	// insignificantly.
   103  	ir.Pkgs.Runtime = types.NewPkg("go.runtime", "runtime")
   104  	ir.Pkgs.Runtime.Prefix = "runtime"
   105  
   106  	// pseudo-packages used in symbol tables
   107  	ir.Pkgs.Itab = types.NewPkg("go.itab", "go.itab")
   108  	ir.Pkgs.Itab.Prefix = "go:itab"
   109  
   110  	// pseudo-package used for methods with anonymous receivers
   111  	ir.Pkgs.Go = types.NewPkg("go", "")
   112  
   113  	// pseudo-package for use with code coverage instrumentation.
   114  	ir.Pkgs.Coverage = types.NewPkg("go.coverage", "runtime/coverage")
   115  	ir.Pkgs.Coverage.Prefix = "runtime/coverage"
   116  
   117  	// Record flags that affect the build result. (And don't
   118  	// record flags that don't, since that would cause spurious
   119  	// changes in the binary.)
   120  	dwarfgen.RecordFlags("B", "N", "l", "msan", "race", "asan", "shared", "dynlink", "dwarf", "dwarflocationlists", "dwarfbasentries", "smallframes", "spectre")
   121  
   122  	if !base.EnableTrace && base.Flag.LowerT {
   123  		log.Fatalf("compiler not built with support for -t")
   124  	}
   125  
   126  	// Enable inlining (after RecordFlags, to avoid recording the rewritten -l).  For now:
   127  	//	default: inlining on.  (Flag.LowerL == 1)
   128  	//	-l: inlining off  (Flag.LowerL == 0)
   129  	//	-l=2, -l=3: inlining on again, with extra debugging (Flag.LowerL > 1)
   130  	if base.Flag.LowerL <= 1 {
   131  		base.Flag.LowerL = 1 - base.Flag.LowerL
   132  	}
   133  
   134  	if base.Flag.SmallFrames {
   135  		ir.MaxStackVarSize = 128 * 1024
   136  		ir.MaxImplicitStackVarSize = 16 * 1024
   137  	}
   138  
   139  	if base.Flag.Dwarf {
   140  		base.Ctxt.DebugInfo = dwarfgen.Info
   141  		base.Ctxt.GenAbstractFunc = dwarfgen.AbstractFunc
   142  		base.Ctxt.DwFixups = obj.NewDwarfFixupTable(base.Ctxt)
   143  	} else {
   144  		// turn off inline generation if no dwarf at all
   145  		base.Flag.GenDwarfInl = 0
   146  		base.Ctxt.Flag_locationlists = false
   147  	}
   148  	if base.Ctxt.Flag_locationlists && len(base.Ctxt.Arch.DWARFRegisters) == 0 {
   149  		log.Fatalf("location lists requested but register mapping not available on %v", base.Ctxt.Arch.Name)
   150  	}
   151  
   152  	types.ParseLangFlag()
   153  
   154  	symABIs := ssagen.NewSymABIs()
   155  	if base.Flag.SymABIs != "" {
   156  		symABIs.ReadSymABIs(base.Flag.SymABIs)
   157  	}
   158  
   159  	if objabi.LookupPkgSpecial(base.Ctxt.Pkgpath).NoInstrument {
   160  		base.Flag.Race = false
   161  		base.Flag.MSan = false
   162  		base.Flag.ASan = false
   163  	}
   164  
   165  	ssagen.Arch.LinkArch.Init(base.Ctxt)
   166  	startProfile()
   167  	if base.Flag.Race || base.Flag.MSan || base.Flag.ASan {
   168  		base.Flag.Cfg.Instrumenting = true
   169  	}
   170  	if base.Flag.Dwarf {
   171  		dwarf.EnableLogging(base.Debug.DwarfInl != 0)
   172  	}
   173  	if base.Debug.SoftFloat != 0 {
   174  		ssagen.Arch.SoftFloat = true
   175  	}
   176  
   177  	if base.Flag.JSON != "" { // parse version,destination from json logging optimization.
   178  		logopt.LogJsonOption(base.Flag.JSON)
   179  	}
   180  
   181  	ir.EscFmt = escape.Fmt
   182  	ir.IsIntrinsicCall = ssagen.IsIntrinsicCall
   183  	inline.SSADumpInline = ssagen.DumpInline
   184  	ssagen.InitEnv()
   185  	ssagen.InitTables()
   186  
   187  	types.PtrSize = ssagen.Arch.LinkArch.PtrSize
   188  	types.RegSize = ssagen.Arch.LinkArch.RegSize
   189  	types.MaxWidth = ssagen.Arch.MAXWIDTH
   190  
   191  	typecheck.Target = new(ir.Package)
   192  
   193  	base.AutogeneratedPos = makePos(src.NewFileBase("<autogenerated>", "<autogenerated>"), 1, 0)
   194  
   195  	typecheck.InitUniverse()
   196  	typecheck.InitRuntime()
   197  	rttype.Init()
   198  
   199  	// Parse and typecheck input.
   200  	noder.LoadPackage(flag.Args())
   201  
   202  	// As a convenience to users (toolchain maintainers, in particular),
   203  	// when compiling a package named "main", we default the package
   204  	// path to "main" if the -p flag was not specified.
   205  	if base.Ctxt.Pkgpath == obj.UnlinkablePkg && types.LocalPkg.Name == "main" {
   206  		base.Ctxt.Pkgpath = "main"
   207  		types.LocalPkg.Path = "main"
   208  		types.LocalPkg.Prefix = "main"
   209  	}
   210  
   211  	dwarfgen.RecordPackageName()
   212  
   213  	// Prepare for backend processing.
   214  	ssagen.InitConfig()
   215  
   216  	// Apply coverage fixups, if applicable.
   217  	coverage.Fixup()
   218  
   219  	// Read profile file and build profile-graph and weighted-call-graph.
   220  	base.Timer.Start("fe", "pgo-load-profile")
   221  	var profile *pgoir.Profile
   222  	if base.Flag.PgoProfile != "" {
   223  		var err error
   224  		profile, err = pgoir.New(base.Flag.PgoProfile)
   225  		if err != nil {
   226  			log.Fatalf("%s: PGO error: %v", base.Flag.PgoProfile, err)
   227  		}
   228  	}
   229  
   230  	// Interleaved devirtualization and inlining.
   231  	base.Timer.Start("fe", "devirtualize-and-inline")
   232  	interleaved.DevirtualizeAndInlinePackage(typecheck.Target, profile)
   233  
   234  	noder.MakeWrappers(typecheck.Target) // must happen after inlining
   235  
   236  	// Get variable capture right in for loops.
   237  	var transformed []loopvar.VarAndLoop
   238  	for _, fn := range typecheck.Target.Funcs {
   239  		transformed = append(transformed, loopvar.ForCapture(fn)...)
   240  	}
   241  	ir.CurFunc = nil
   242  
   243  	// Build init task, if needed.
   244  	pkginit.MakeTask()
   245  
   246  	// Generate ABI wrappers. Must happen before escape analysis
   247  	// and doesn't benefit from dead-coding or inlining.
   248  	symABIs.GenABIWrappers()
   249  
   250  	// Escape analysis.
   251  	// Required for moving heap allocations onto stack,
   252  	// which in turn is required by the closure implementation,
   253  	// which stores the addresses of stack variables into the closure.
   254  	// If the closure does not escape, it needs to be on the stack
   255  	// or else the stack copier will not update it.
   256  	// Large values are also moved off stack in escape analysis;
   257  	// because large values may contain pointers, it must happen early.
   258  	base.Timer.Start("fe", "escapes")
   259  	escape.Funcs(typecheck.Target.Funcs)
   260  
   261  	loopvar.LogTransformations(transformed)
   262  
   263  	// Collect information for go:nowritebarrierrec
   264  	// checking. This must happen before transforming closures during Walk
   265  	// We'll do the final check after write barriers are
   266  	// inserted.
   267  	if base.Flag.CompilingRuntime {
   268  		ssagen.EnableNoWriteBarrierRecCheck()
   269  	}
   270  
   271  	ir.CurFunc = nil
   272  
   273  	reflectdata.WriteBasicTypes()
   274  
   275  	// Compile top-level declarations.
   276  	//
   277  	// There are cyclic dependencies between all of these phases, so we
   278  	// need to iterate all of them until we reach a fixed point.
   279  	base.Timer.Start("be", "compilefuncs")
   280  	for nextFunc, nextExtern := 0, 0; ; {
   281  		reflectdata.WriteRuntimeTypes()
   282  
   283  		if nextExtern < len(typecheck.Target.Externs) {
   284  			switch n := typecheck.Target.Externs[nextExtern]; n.Op() {
   285  			case ir.ONAME:
   286  				dumpGlobal(n)
   287  			case ir.OLITERAL:
   288  				dumpGlobalConst(n)
   289  			case ir.OTYPE:
   290  				reflectdata.NeedRuntimeType(n.Type())
   291  			}
   292  			nextExtern++
   293  			continue
   294  		}
   295  
   296  		if nextFunc < len(typecheck.Target.Funcs) {
   297  			enqueueFunc(typecheck.Target.Funcs[nextFunc])
   298  			nextFunc++
   299  			continue
   300  		}
   301  
   302  		// The SSA backend supports using multiple goroutines, so keep it
   303  		// as late as possible to maximize how much work we can batch and
   304  		// process concurrently.
   305  		if len(compilequeue) != 0 {
   306  			compileFunctions(profile)
   307  			continue
   308  		}
   309  
   310  		// Finalize DWARF inline routine DIEs, then explicitly turn off
   311  		// further DWARF inlining generation to avoid problems with
   312  		// generated method wrappers.
   313  		//
   314  		// Note: The DWARF fixup code for inlined calls currently doesn't
   315  		// allow multiple invocations, so we intentionally run it just
   316  		// once after everything else. Worst case, some generated
   317  		// functions have slightly larger DWARF DIEs.
   318  		if base.Ctxt.DwFixups != nil {
   319  			base.Ctxt.DwFixups.Finalize(base.Ctxt.Pkgpath, base.Debug.DwarfInl != 0)
   320  			base.Ctxt.DwFixups = nil
   321  			base.Flag.GenDwarfInl = 0
   322  			continue // may have called reflectdata.TypeLinksym (#62156)
   323  		}
   324  
   325  		break
   326  	}
   327  
   328  	base.Timer.AddEvent(int64(len(typecheck.Target.Funcs)), "funcs")
   329  
   330  	if base.Flag.CompilingRuntime {
   331  		// Write barriers are now known. Check the call graph.
   332  		ssagen.NoWriteBarrierRecCheck()
   333  	}
   334  
   335  	// Add keep relocations for global maps.
   336  	if base.Debug.WrapGlobalMapCtl != 1 {
   337  		staticinit.AddKeepRelocations()
   338  	}
   339  
   340  	// Write object data to disk.
   341  	base.Timer.Start("be", "dumpobj")
   342  	dumpdata()
   343  	base.Ctxt.NumberSyms()
   344  	dumpobj()
   345  	if base.Flag.AsmHdr != "" {
   346  		dumpasmhdr()
   347  	}
   348  
   349  	ssagen.CheckLargeStacks()
   350  	typecheck.CheckFuncStack()
   351  
   352  	if len(compilequeue) != 0 {
   353  		base.Fatalf("%d uncompiled functions", len(compilequeue))
   354  	}
   355  
   356  	logopt.FlushLoggedOpts(base.Ctxt, base.Ctxt.Pkgpath)
   357  	base.ExitIfErrors()
   358  
   359  	base.FlushErrors()
   360  	base.Timer.Stop()
   361  
   362  	if base.Flag.Bench != "" {
   363  		if err := writebench(base.Flag.Bench); err != nil {
   364  			log.Fatalf("cannot write benchmark data: %v", err)
   365  		}
   366  	}
   367  }
   368  
   369  func writebench(filename string) error {
   370  	f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0666)
   371  	if err != nil {
   372  		return err
   373  	}
   374  
   375  	var buf bytes.Buffer
   376  	fmt.Fprintln(&buf, "commit:", buildcfg.Version)
   377  	fmt.Fprintln(&buf, "goos:", runtime.GOOS)
   378  	fmt.Fprintln(&buf, "goarch:", runtime.GOARCH)
   379  	base.Timer.Write(&buf, "BenchmarkCompile:"+base.Ctxt.Pkgpath+":")
   380  
   381  	n, err := f.Write(buf.Bytes())
   382  	if err != nil {
   383  		return err
   384  	}
   385  	if n != buf.Len() {
   386  		panic("bad writer")
   387  	}
   388  
   389  	return f.Close()
   390  }
   391  
   392  func makePos(b *src.PosBase, line, col uint) src.XPos {
   393  	return base.Ctxt.PosTable.XPos(src.MakePos(b, line, col))
   394  }
   395
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