1 files changed, 271 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssa/numberlines.go b/src/cmd/compile/internal/ssa/numberlines.go
new file mode 100644
index 0000000..f4e62b8
--- /dev/null
+++ b/src/cmd/compile/internal/ssa/numberlines.go
@@ -0,0 +1,271 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+import (
+	"cmd/internal/obj"
+	"cmd/internal/src"
+	"fmt"
+	"sort"
+)
+
+func isPoorStatementOp(op Op) bool {
+	switch op {
+	// Note that Nilcheck often vanishes, but when it doesn't, you'd love to start the statement there
+	// so that a debugger-user sees the stop before the panic, and can examine the value.
+	case OpAddr, OpLocalAddr, OpOffPtr, OpStructSelect, OpPhi, OpITab, OpIData,
+		OpIMake, OpStringMake, OpSliceMake, OpStructMake0, OpStructMake1, OpStructMake2, OpStructMake3, OpStructMake4,
+		OpConstBool, OpConst8, OpConst16, OpConst32, OpConst64, OpConst32F, OpConst64F:
+		return true
+	}
+	return false
+}
+
+// LosesStmtMark reports whether a prog with op as loses its statement mark on the way to DWARF.
+// The attributes from some opcodes are lost in translation.
+// TODO: this is an artifact of how funcpctab combines information for instructions at a single PC.
+// Should try to fix it there.
+func LosesStmtMark(as obj.As) bool {
+	// is_stmt does not work for these; it DOES for ANOP even though that generates no code.
+	return as == obj.APCDATA || as == obj.AFUNCDATA
+}
+
+// nextGoodStatementIndex returns an index at i or later that is believed
+// to be a good place to start the statement for b.  This decision is
+// based on v's Op, the possibility of a better later operation, and
+// whether the values following i are the same line as v.
+// If a better statement index isn't found, then i is returned.
+func nextGoodStatementIndex(v *Value, i int, b *Block) int {
+	// If the value is the last one in the block, too bad, it will have to do
+	// (this assumes that the value ordering vaguely corresponds to the source
+	// program execution order, which tends to be true directly after ssa is
+	// first built.
+	if i >= len(b.Values)-1 {
+		return i
+	}
+	// Skip the likely-ephemeral/fragile opcodes expected to vanish in a rewrite.
+	if !isPoorStatementOp(v.Op) {
+		return i
+	}
+	// Look ahead to see what the line number is on the next thing that could be a boundary.
+	for j := i + 1; j < len(b.Values); j++ {
+		u := b.Values[j]
+		if u.Pos.IsStmt() == src.PosNotStmt { // ignore non-statements
+			continue
+		}
+		if u.Pos.SameFileAndLine(v.Pos) {
+			if isPoorStatementOp(u.Op) {
+				continue // Keep looking, this is also not a good statement op
+			}
+			return j
+		}
+		return i
+	}
+	return i
+}
+
+// notStmtBoundary reports whether a value with opcode op can never be a statement
+// boundary. Such values don't correspond to a user's understanding of a
+// statement boundary.
+func notStmtBoundary(op Op) bool {
+	switch op {
+	case OpCopy, OpPhi, OpVarKill, OpVarDef, OpVarLive, OpUnknown, OpFwdRef, OpArg:
+		return true
+	}
+	return false
+}
+
+func (b *Block) FirstPossibleStmtValue() *Value {
+	for _, v := range b.Values {
+		if notStmtBoundary(v.Op) {
+			continue
+		}
+		return v
+	}
+	return nil
+}
+
+func flc(p src.XPos) string {
+	if p == src.NoXPos {
+		return "none"
+	}
+	return fmt.Sprintf("(%d):%d:%d", p.FileIndex(), p.Line(), p.Col())
+}
+
+type fileAndPair struct {
+	f  int32
+	lp lineRange
+}
+
+type fileAndPairs []fileAndPair
+
+func (fap fileAndPairs) Len() int {
+	return len(fap)
+}
+func (fap fileAndPairs) Less(i, j int) bool {
+	return fap[i].f < fap[j].f
+}
+func (fap fileAndPairs) Swap(i, j int) {
+	fap[i], fap[j] = fap[j], fap[i]
+}
+
+// -d=ssa/number_lines/stats=1 (that bit) for line and file distribution statistics
+// -d=ssa/number_lines/debug for information about why particular values are marked as statements.
+func numberLines(f *Func) {
+	po := f.Postorder()
+	endlines := make(map[ID]src.XPos)
+	ranges := make(map[int]lineRange)
+	note := func(p src.XPos) {
+		line := uint32(p.Line())
+		i := int(p.FileIndex())
+		lp, found := ranges[i]
+		change := false
+		if line < lp.first || !found {
+			lp.first = line
+			change = true
+		}
+		if line > lp.last {
+			lp.last = line
+			change = true
+		}
+		if change {
+			ranges[i] = lp
+		}
+	}
+
+	// Visit in reverse post order so that all non-loop predecessors come first.
+	for j := len(po) - 1; j >= 0; j-- {
+		b := po[j]
+		// Find the first interesting position and check to see if it differs from any predecessor
+		firstPos := src.NoXPos
+		firstPosIndex := -1
+		if b.Pos.IsStmt() != src.PosNotStmt {
+			note(b.Pos)
+		}
+		for i := 0; i < len(b.Values); i++ {
+			v := b.Values[i]
+			if v.Pos.IsStmt() != src.PosNotStmt {
+				note(v.Pos)
+				// skip ahead to better instruction for this line if possible
+				i = nextGoodStatementIndex(v, i, b)
+				v = b.Values[i]
+				firstPosIndex = i
+				firstPos = v.Pos
+				v.Pos = firstPos.WithDefaultStmt() // default to default
+				break
+			}
+		}
+
+		if firstPosIndex == -1 { // Effectively empty block, check block's own Pos, consider preds.
+			line := src.NoXPos
+			for _, p := range b.Preds {
+				pbi := p.Block().ID
+				if !endlines[pbi].SameFileAndLine(line) {
+					if line == src.NoXPos {
+						line = endlines[pbi]
+						continue
+					} else {
+						line = src.NoXPos
+						break
+					}
+
+				}
+			}
+			// If the block has no statement itself and is effectively empty, tag it w/ predecessor(s) but not as a statement
+			if b.Pos.IsStmt() == src.PosNotStmt {
+				b.Pos = line
+				endlines[b.ID] = line
+				continue
+			}
+			// If the block differs from its predecessors, mark it as a statement
+			if line == src.NoXPos || !line.SameFileAndLine(b.Pos) {
+				b.Pos = b.Pos.WithIsStmt()
+				if f.pass.debug > 0 {
+					fmt.Printf("Mark stmt effectively-empty-block %s %s %s\n", f.Name, b, flc(b.Pos))
+				}
+			}
+			endlines[b.ID] = b.Pos
+			continue
+		}
+		// check predecessors for any difference; if firstPos differs, then it is a boundary.
+		if len(b.Preds) == 0 { // Don't forget the entry block
+			b.Values[firstPosIndex].Pos = firstPos.WithIsStmt()
+			if f.pass.debug > 0 {
+				fmt.Printf("Mark stmt entry-block %s %s %s %s\n", f.Name, b, b.Values[firstPosIndex], flc(firstPos))
+			}
+		} else { // differing pred
+			for _, p := range b.Preds {
+				pbi := p.Block().ID
+				if !endlines[pbi].SameFileAndLine(firstPos) {
+					b.Values[firstPosIndex].Pos = firstPos.WithIsStmt()
+					if f.pass.debug > 0 {
+						fmt.Printf("Mark stmt differing-pred %s %s %s %s, different=%s ending %s\n",
+							f.Name, b, b.Values[firstPosIndex], flc(firstPos), p.Block(), flc(endlines[pbi]))
+					}
+					break
+				}
+			}
+		}
+		// iterate forward setting each new (interesting) position as a statement boundary.
+		for i := firstPosIndex + 1; i < len(b.Values); i++ {
+			v := b.Values[i]
+			if v.Pos.IsStmt() == src.PosNotStmt {
+				continue
+			}
+			note(v.Pos)
+			// skip ahead if possible
+			i = nextGoodStatementIndex(v, i, b)
+			v = b.Values[i]
+			if !v.Pos.SameFileAndLine(firstPos) {
+				if f.pass.debug > 0 {
+					fmt.Printf("Mark stmt new line %s %s %s %s prev pos = %s\n", f.Name, b, v, flc(v.Pos), flc(firstPos))
+				}
+				firstPos = v.Pos
+				v.Pos = v.Pos.WithIsStmt()
+			} else {
+				v.Pos = v.Pos.WithDefaultStmt()
+			}
+		}
+		if b.Pos.IsStmt() != src.PosNotStmt && !b.Pos.SameFileAndLine(firstPos) {
+			if f.pass.debug > 0 {
+				fmt.Printf("Mark stmt end of block differs %s %s %s prev pos = %s\n", f.Name, b, flc(b.Pos), flc(firstPos))
+			}
+			b.Pos = b.Pos.WithIsStmt()
+			firstPos = b.Pos
+		}
+		endlines[b.ID] = firstPos
+	}
+	if f.pass.stats&1 != 0 {
+		// Report summary statistics on the shape of the sparse map about to be constructed
+		// TODO use this information to make sparse maps faster.
+		var entries fileAndPairs
+		for k, v := range ranges {
+			entries = append(entries, fileAndPair{int32(k), v})
+		}
+		sort.Sort(entries)
+		total := uint64(0)            // sum over files of maxline(file) - minline(file)
+		maxfile := int32(0)           // max(file indices)
+		minline := uint32(0xffffffff) // min over files of minline(file)
+		maxline := uint32(0)          // max over files of maxline(file)
+		for _, v := range entries {
+			if f.pass.stats > 1 {
+				f.LogStat("file", v.f, "low", v.lp.first, "high", v.lp.last)
+			}
+			total += uint64(v.lp.last - v.lp.first)
+			if maxfile < v.f {
+				maxfile = v.f
+			}
+			if minline > v.lp.first {
+				minline = v.lp.first
+			}
+			if maxline < v.lp.last {
+				maxline = v.lp.last
+			}
+		}
+		f.LogStat("SUM_LINE_RANGE", total, "MAXMIN_LINE_RANGE", maxline-minline, "MAXFILE", maxfile, "NFILES", len(entries))
+	}
+	// cachedLineStarts is an empty sparse map for values that are included within ranges.
+	f.cachedLineStarts = newXposmap(ranges)
+}