stdlib_test.go

Documentation: golang.org/x/tools/go/ssa

     1  // Copyright 2013 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  // Incomplete source tree on Android.
     6  
     7  //go:build !android
     8  // +build !android
     9  
    10  package ssa_test
    11  
    12  // This file runs the SSA builder in sanity-checking mode on all
    13  // packages beneath $GOROOT and prints some summary information.
    14  //
    15  // Run with "go test -cpu=8 to" set GOMAXPROCS.
    16  
    17  import (
    18  	"go/ast"
    19  	"go/token"
    20  	"go/types"
    21  	"runtime"
    22  	"testing"
    23  	"time"
    24  
    25  	"golang.org/x/tools/go/packages"
    26  	"golang.org/x/tools/go/ssa"
    27  	"golang.org/x/tools/go/ssa/ssautil"
    28  	"golang.org/x/tools/internal/testenv"
    29  )
    30  
    31  func bytesAllocated() uint64 {
    32  	runtime.GC()
    33  	var stats runtime.MemStats
    34  	runtime.ReadMemStats(&stats)
    35  	return stats.Alloc
    36  }
    37  
    38  // TestStdlib loads the entire standard library and its tools.
    39  //
    40  // Apart from a small number of internal packages that are not
    41  // returned by the 'std' query, the set is essentially transitively
    42  // closed, so marginal per-dependency costs are invisible.
    43  func TestStdlib(t *testing.T) {
    44  	testLoad(t, 500, "std", "cmd")
    45  }
    46  
    47  // TestNetHTTP builds a single SSA package but not its dependencies.
    48  // It may help reveal costs related to dependencies (e.g. unnecessary building).
    49  func TestNetHTTP(t *testing.T) {
    50  	testLoad(t, 120, "net/http")
    51  }
    52  
    53  func testLoad(t *testing.T, minPkgs int, patterns ...string) {
    54  	// Note: most of the commentary below applies to TestStdlib.
    55  
    56  	if testing.Short() {
    57  		t.Skip("skipping in short mode; too slow (https://golang.org/issue/14113)") // ~5s
    58  	}
    59  	testenv.NeedsTool(t, "go")
    60  
    61  	// Load, parse and type-check the program.
    62  	t0 := time.Now()
    63  	alloc0 := bytesAllocated()
    64  
    65  	cfg := &packages.Config{Mode: packages.LoadSyntax}
    66  	pkgs, err := packages.Load(cfg, patterns...)
    67  	if err != nil {
    68  		t.Fatal(err)
    69  	}
    70  
    71  	t1 := time.Now()
    72  	alloc1 := bytesAllocated()
    73  
    74  	// Create SSA packages.
    75  	var mode ssa.BuilderMode
    76  	// Comment out these lines during benchmarking.  Approx SSA build costs are noted.
    77  	mode |= ssa.SanityCheckFunctions // + 2% space, + 4% time
    78  	mode |= ssa.GlobalDebug          // +30% space, +18% time
    79  	mode |= ssa.InstantiateGenerics  // + 0% space, + 2% time (unlikely to reproduce outside of stdlib)
    80  	prog, _ := ssautil.Packages(pkgs, mode)
    81  
    82  	t2 := time.Now()
    83  
    84  	// Build SSA.
    85  	prog.Build()
    86  
    87  	t3 := time.Now()
    88  	alloc3 := bytesAllocated()
    89  
    90  	// Sanity check to ensure we haven't dropped large numbers of packages.
    91  	numPkgs := len(prog.AllPackages())
    92  	if numPkgs < minPkgs {
    93  		t.Errorf("Loaded only %d packages, want at least %d", numPkgs, minPkgs)
    94  	}
    95  
    96  	// Keep pkgs reachable until after we've measured memory usage.
    97  	if len(pkgs) == 0 {
    98  		panic("unreachable")
    99  	}
   100  
   101  	srcFuncs := srcFunctions(prog, pkgs)
   102  	allFuncs := ssautil.AllFunctions(prog)
   103  
   104  	// The assertion below is not valid if the program contains
   105  	// variants of the same package, such as the test variants
   106  	// (e.g. package p as compiled for test executable x) obtained
   107  	// when cfg.Tests=true. Profile-guided optimization may
   108  	// lead to similar variation for non-test executables.
   109  	//
   110  	// Ideally, the test would assert that all functions within
   111  	// each executable (more generally: within any singly rooted
   112  	// transitively closed subgraph of the import graph) have
   113  	// distinct names, but that isn't so easy to compute efficiently.
   114  	// Disabling for now.
   115  	if false {
   116  		// Check that all non-synthetic functions have distinct names.
   117  		// Synthetic wrappers for exported methods should be distinct too,
   118  		// except for unexported ones (explained at (*Function).RelString).
   119  		byName := make(map[string]*ssa.Function)
   120  		for fn := range allFuncs {
   121  			if fn.Synthetic == "" || ast.IsExported(fn.Name()) {
   122  				str := fn.String()
   123  				prev := byName[str]
   124  				byName[str] = fn
   125  				if prev != nil {
   126  					t.Errorf("%s: duplicate function named %s",
   127  						prog.Fset.Position(fn.Pos()), str)
   128  					t.Errorf("%s:   (previously defined here)",
   129  						prog.Fset.Position(prev.Pos()))
   130  				}
   131  			}
   132  		}
   133  	}
   134  
   135  	// Dump some statistics.
   136  	var numInstrs int
   137  	for fn := range allFuncs {
   138  		for _, b := range fn.Blocks {
   139  			numInstrs += len(b.Instrs)
   140  		}
   141  	}
   142  
   143  	// determine line count
   144  	var lineCount int
   145  	prog.Fset.Iterate(func(f *token.File) bool {
   146  		lineCount += f.LineCount()
   147  		return true
   148  	})
   149  
   150  	// NB: when benchmarking, don't forget to clear the debug +
   151  	// sanity builder flags for better performance.
   152  
   153  	t.Log("GOMAXPROCS:           ", runtime.GOMAXPROCS(0))
   154  	t.Log("#Source lines:        ", lineCount)
   155  	t.Log("Load/parse/typecheck: ", t1.Sub(t0))
   156  	t.Log("SSA create:           ", t2.Sub(t1))
   157  	t.Log("SSA build:            ", t3.Sub(t2))
   158  
   159  	// SSA stats:
   160  	t.Log("#Packages:            ", numPkgs)
   161  	t.Log("#SrcFunctions:        ", len(srcFuncs))
   162  	t.Log("#AllFunctions:        ", len(allFuncs))
   163  	t.Log("#Instructions:        ", numInstrs)
   164  	t.Log("#MB AST+types:        ", int64(alloc1-alloc0)/1e6)
   165  	t.Log("#MB SSA:              ", int64(alloc3-alloc1)/1e6)
   166  }
   167  
   168  // srcFunctions gathers all ssa.Functions corresponding to syntax.
   169  // (Includes generics but excludes instances and all wrappers.)
   170  //
   171  // This is essentially identical to the SrcFunctions logic in
   172  // go/analysis/passes/buildssa.
   173  func srcFunctions(prog *ssa.Program, pkgs []*packages.Package) (res []*ssa.Function) {
   174  	var addSrcFunc func(fn *ssa.Function)
   175  	addSrcFunc = func(fn *ssa.Function) {
   176  		res = append(res, fn)
   177  		for _, anon := range fn.AnonFuncs {
   178  			addSrcFunc(anon)
   179  		}
   180  	}
   181  	for _, pkg := range pkgs {
   182  		for _, file := range pkg.Syntax {
   183  			for _, decl := range file.Decls {
   184  				if decl, ok := decl.(*ast.FuncDecl); ok {
   185  					obj := pkg.TypesInfo.Defs[decl.Name].(*types.Func)
   186  					if obj == nil {
   187  						panic("nil *Func")
   188  					}
   189  					addSrcFunc(prog.FuncValue(obj))
   190  				}
   191  			}
   192  		}
   193  	}
   194  	return res
   195  }
   196
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