callsite.go

     1  // Copyright 2023 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 inlheur
     6  
     7  import (
     8  	"cmd/compile/internal/base"
     9  	"cmd/compile/internal/ir"
    10  	"cmd/internal/src"
    11  	"fmt"
    12  	"io"
    13  	"path/filepath"
    14  	"sort"
    15  	"strings"
    16  )
    17  
    18  // CallSite records useful information about a potentially inlinable
    19  // (direct) function call. "Callee" is the target of the call, "Call"
    20  // is the ir node corresponding to the call itself, "Assign" is
    21  // the top-level assignment statement containing the call (if the call
    22  // appears in the form of a top-level statement, e.g. "x := foo()"),
    23  // "Flags" contains properties of the call that might be useful for
    24  // making inlining decisions, "Score" is the final score assigned to
    25  // the site, and "ID" is a numeric ID for the site within its
    26  // containing function.
    27  type CallSite struct {
    28  	Callee *ir.Func
    29  	Call   *ir.CallExpr
    30  	parent *CallSite
    31  	Assign ir.Node
    32  	Flags  CSPropBits
    33  
    34  	ArgProps  []ActualExprPropBits
    35  	Score     int
    36  	ScoreMask scoreAdjustTyp
    37  	ID        uint
    38  	aux       uint8
    39  }
    40  
    41  // CallSiteTab is a table of call sites, keyed by call expr.
    42  // Ideally it would be nice to key the table by src.XPos, but
    43  // this results in collisions for calls on very long lines (the
    44  // front end saturates column numbers at 255). We also wind up
    45  // with many calls that share the same auto-generated pos.
    46  type CallSiteTab map[*ir.CallExpr]*CallSite
    47  
    48  // ActualExprPropBits describes a property of an actual expression (value
    49  // passed to some specific func argument at a call site).
    50  type ActualExprPropBits uint8
    51  
    52  const (
    53  	ActualExprConstant ActualExprPropBits = 1 << iota
    54  	ActualExprIsConcreteConvIface
    55  	ActualExprIsFunc
    56  	ActualExprIsInlinableFunc
    57  )
    58  
    59  type CSPropBits uint32
    60  
    61  const (
    62  	CallSiteInLoop CSPropBits = 1 << iota
    63  	CallSiteOnPanicPath
    64  	CallSiteInInitFunc
    65  )
    66  
    67  type csAuxBits uint8
    68  
    69  const (
    70  	csAuxInlined = 1 << iota
    71  )
    72  
    73  // encodedCallSiteTab is a table keyed by "encoded" callsite
    74  // (stringified src.XPos plus call site ID) mapping to a value of call
    75  // property bits and score.
    76  type encodedCallSiteTab map[string]propsAndScore
    77  
    78  type propsAndScore struct {
    79  	props CSPropBits
    80  	score int
    81  	mask  scoreAdjustTyp
    82  }
    83  
    84  func (pas propsAndScore) String() string {
    85  	return fmt.Sprintf("P=%s|S=%d|M=%s", pas.props.String(),
    86  		pas.score, pas.mask.String())
    87  }
    88  
    89  func (cst CallSiteTab) merge(other CallSiteTab) error {
    90  	for k, v := range other {
    91  		if prev, ok := cst[k]; ok {
    92  			return fmt.Errorf("internal error: collision during call site table merge, fn=%s callsite=%s", prev.Callee.Sym().Name, fmtFullPos(prev.Call.Pos()))
    93  		}
    94  		cst[k] = v
    95  	}
    96  	return nil
    97  }
    98  
    99  func fmtFullPos(p src.XPos) string {
   100  	var sb strings.Builder
   101  	sep := ""
   102  	base.Ctxt.AllPos(p, func(pos src.Pos) {
   103  		sb.WriteString(sep)
   104  		sep = "|"
   105  		file := filepath.Base(pos.Filename())
   106  		fmt.Fprintf(&sb, "%s:%d:%d", file, pos.Line(), pos.Col())
   107  	})
   108  	return sb.String()
   109  }
   110  
   111  func EncodeCallSiteKey(cs *CallSite) string {
   112  	var sb strings.Builder
   113  	// FIXME: maybe rewrite line offsets relative to function start?
   114  	sb.WriteString(fmtFullPos(cs.Call.Pos()))
   115  	fmt.Fprintf(&sb, "|%d", cs.ID)
   116  	return sb.String()
   117  }
   118  
   119  func buildEncodedCallSiteTab(tab CallSiteTab) encodedCallSiteTab {
   120  	r := make(encodedCallSiteTab)
   121  	for _, cs := range tab {
   122  		k := EncodeCallSiteKey(cs)
   123  		r[k] = propsAndScore{
   124  			props: cs.Flags,
   125  			score: cs.Score,
   126  			mask:  cs.ScoreMask,
   127  		}
   128  	}
   129  	return r
   130  }
   131  
   132  // dumpCallSiteComments emits comments into the dump file for the
   133  // callsites in the function of interest. If "ecst" is non-nil, we use
   134  // that, otherwise generated a fresh encodedCallSiteTab from "tab".
   135  func dumpCallSiteComments(w io.Writer, tab CallSiteTab, ecst encodedCallSiteTab) {
   136  	if ecst == nil {
   137  		ecst = buildEncodedCallSiteTab(tab)
   138  	}
   139  	tags := make([]string, 0, len(ecst))
   140  	for k := range ecst {
   141  		tags = append(tags, k)
   142  	}
   143  	sort.Strings(tags)
   144  	for _, s := range tags {
   145  		v := ecst[s]
   146  		fmt.Fprintf(w, "// callsite: %s flagstr %q flagval %d score %d mask %d maskstr %q\n", s, v.props.String(), v.props, v.score, v.mask, v.mask.String())
   147  	}
   148  	fmt.Fprintf(w, "// %s\n", csDelimiter)
   149  }
   150
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