1 files changed, 425 insertions, 0 deletions
diff --git a/src/cmd/internal/obj/pcln.go b/src/cmd/internal/obj/pcln.go
new file mode 100644
index 0000000..49b425b
--- /dev/null
+++ b/src/cmd/internal/obj/pcln.go
@@ -0,0 +1,425 @@
+// Copyright 2013 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 obj
+
+import (
+	"cmd/internal/goobj"
+	"cmd/internal/objabi"
+	"encoding/binary"
+	"fmt"
+	"log"
+)
+
+// funcpctab writes to dst a pc-value table mapping the code in func to the values
+// returned by valfunc parameterized by arg. The invocation of valfunc to update the
+// current value is, for each p,
+//
+//	sym = valfunc(func, p, 0, arg);
+//	record sym.P as value at p->pc;
+//	sym = valfunc(func, p, 1, arg);
+//
+// where func is the function, val is the current value, p is the instruction being
+// considered, and arg can be used to further parameterize valfunc.
+func funcpctab(ctxt *Link, func_ *LSym, desc string, valfunc func(*Link, *LSym, int32, *Prog, int32, interface{}) int32, arg interface{}) *LSym {
+	dbg := desc == ctxt.Debugpcln
+	dst := []byte{}
+	sym := &LSym{
+		Type:      objabi.SRODATA,
+		Attribute: AttrContentAddressable | AttrPcdata,
+	}
+
+	if dbg {
+		ctxt.Logf("funcpctab %s [valfunc=%s]\n", func_.Name, desc)
+	}
+
+	val := int32(-1)
+	oldval := val
+	fn := func_.Func()
+	if fn.Text == nil {
+		// Return the empty symbol we've built so far.
+		return sym
+	}
+
+	pc := fn.Text.Pc
+
+	if dbg {
+		ctxt.Logf("%6x %6d %v\n", uint64(pc), val, fn.Text)
+	}
+
+	buf := make([]byte, binary.MaxVarintLen32)
+	started := false
+	for p := fn.Text; p != nil; p = p.Link {
+		// Update val. If it's not changing, keep going.
+		val = valfunc(ctxt, func_, val, p, 0, arg)
+
+		if val == oldval && started {
+			val = valfunc(ctxt, func_, val, p, 1, arg)
+			if dbg {
+				ctxt.Logf("%6x %6s %v\n", uint64(p.Pc), "", p)
+			}
+			continue
+		}
+
+		// If the pc of the next instruction is the same as the
+		// pc of this instruction, this instruction is not a real
+		// instruction. Keep going, so that we only emit a delta
+		// for a true instruction boundary in the program.
+		if p.Link != nil && p.Link.Pc == p.Pc {
+			val = valfunc(ctxt, func_, val, p, 1, arg)
+			if dbg {
+				ctxt.Logf("%6x %6s %v\n", uint64(p.Pc), "", p)
+			}
+			continue
+		}
+
+		// The table is a sequence of (value, pc) pairs, where each
+		// pair states that the given value is in effect from the current position
+		// up to the given pc, which becomes the new current position.
+		// To generate the table as we scan over the program instructions,
+		// we emit a "(value" when pc == func->value, and then
+		// each time we observe a change in value we emit ", pc) (value".
+		// When the scan is over, we emit the closing ", pc)".
+		//
+		// The table is delta-encoded. The value deltas are signed and
+		// transmitted in zig-zag form, where a complement bit is placed in bit 0,
+		// and the pc deltas are unsigned. Both kinds of deltas are sent
+		// as variable-length little-endian base-128 integers,
+		// where the 0x80 bit indicates that the integer continues.
+
+		if dbg {
+			ctxt.Logf("%6x %6d %v\n", uint64(p.Pc), val, p)
+		}
+
+		if started {
+			pcdelta := (p.Pc - pc) / int64(ctxt.Arch.MinLC)
+			n := binary.PutUvarint(buf, uint64(pcdelta))
+			dst = append(dst, buf[:n]...)
+			pc = p.Pc
+		}
+
+		delta := val - oldval
+		n := binary.PutVarint(buf, int64(delta))
+		dst = append(dst, buf[:n]...)
+		oldval = val
+		started = true
+		val = valfunc(ctxt, func_, val, p, 1, arg)
+	}
+
+	if started {
+		if dbg {
+			ctxt.Logf("%6x done\n", uint64(fn.Text.Pc+func_.Size))
+		}
+		v := (func_.Size - pc) / int64(ctxt.Arch.MinLC)
+		if v < 0 {
+			ctxt.Diag("negative pc offset: %v", v)
+		}
+		n := binary.PutUvarint(buf, uint64(v))
+		dst = append(dst, buf[:n]...)
+		// add terminating varint-encoded 0, which is just 0
+		dst = append(dst, 0)
+	}
+
+	if dbg {
+		ctxt.Logf("wrote %d bytes to %p\n", len(dst), dst)
+		for _, p := range dst {
+			ctxt.Logf(" %02x", p)
+		}
+		ctxt.Logf("\n")
+	}
+
+	sym.Size = int64(len(dst))
+	sym.P = dst
+	return sym
+}
+
+// pctofileline computes either the file number (arg == 0)
+// or the line number (arg == 1) to use at p.
+// Because p.Pos applies to p, phase == 0 (before p)
+// takes care of the update.
+func pctofileline(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg interface{}) int32 {
+	if p.As == ATEXT || p.As == ANOP || p.Pos.Line() == 0 || phase == 1 {
+		return oldval
+	}
+	f, l := getFileIndexAndLine(ctxt, p.Pos)
+	if arg == nil {
+		return l
+	}
+	pcln := arg.(*Pcln)
+	pcln.UsedFiles[goobj.CUFileIndex(f)] = struct{}{}
+	return int32(f)
+}
+
+// pcinlineState holds the state used to create a function's inlining
+// tree and the PC-value table that maps PCs to nodes in that tree.
+type pcinlineState struct {
+	globalToLocal map[int]int
+	localTree     InlTree
+}
+
+// addBranch adds a branch from the global inlining tree in ctxt to
+// the function's local inlining tree, returning the index in the local tree.
+func (s *pcinlineState) addBranch(ctxt *Link, globalIndex int) int {
+	if globalIndex < 0 {
+		return -1
+	}
+
+	localIndex, ok := s.globalToLocal[globalIndex]
+	if ok {
+		return localIndex
+	}
+
+	// Since tracebacks don't include column information, we could
+	// use one node for multiple calls of the same function on the
+	// same line (e.g., f(x) + f(y)). For now, we use one node for
+	// each inlined call.
+	call := ctxt.InlTree.nodes[globalIndex]
+	call.Parent = s.addBranch(ctxt, call.Parent)
+	localIndex = len(s.localTree.nodes)
+	s.localTree.nodes = append(s.localTree.nodes, call)
+	s.globalToLocal[globalIndex] = localIndex
+	return localIndex
+}
+
+func (s *pcinlineState) setParentPC(ctxt *Link, globalIndex int, pc int32) {
+	localIndex, ok := s.globalToLocal[globalIndex]
+	if !ok {
+		// We know where to unwind to when we need to unwind a body identified
+		// by globalIndex. But there may be no instructions generated by that
+		// body (it's empty, or its instructions were CSEd with other things, etc.).
+		// In that case, we don't need an unwind entry.
+		// TODO: is this really right? Seems to happen a whole lot...
+		return
+	}
+	s.localTree.setParentPC(localIndex, pc)
+}
+
+// pctoinline computes the index into the local inlining tree to use at p.
+// If p is not the result of inlining, pctoinline returns -1. Because p.Pos
+// applies to p, phase == 0 (before p) takes care of the update.
+func (s *pcinlineState) pctoinline(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg interface{}) int32 {
+	if phase == 1 {
+		return oldval
+	}
+
+	posBase := ctxt.PosTable.Pos(p.Pos).Base()
+	if posBase == nil {
+		return -1
+	}
+
+	globalIndex := posBase.InliningIndex()
+	if globalIndex < 0 {
+		return -1
+	}
+
+	if s.globalToLocal == nil {
+		s.globalToLocal = make(map[int]int)
+	}
+
+	return int32(s.addBranch(ctxt, globalIndex))
+}
+
+// pctospadj computes the sp adjustment in effect.
+// It is oldval plus any adjustment made by p itself.
+// The adjustment by p takes effect only after p, so we
+// apply the change during phase == 1.
+func pctospadj(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg interface{}) int32 {
+	if oldval == -1 { // starting
+		oldval = 0
+	}
+	if phase == 0 {
+		return oldval
+	}
+	if oldval+p.Spadj < -10000 || oldval+p.Spadj > 1100000000 {
+		ctxt.Diag("overflow in spadj: %d + %d = %d", oldval, p.Spadj, oldval+p.Spadj)
+		ctxt.DiagFlush()
+		log.Fatalf("bad code")
+	}
+
+	return oldval + p.Spadj
+}
+
+// pctopcdata computes the pcdata value in effect at p.
+// A PCDATA instruction sets the value in effect at future
+// non-PCDATA instructions.
+// Since PCDATA instructions have no width in the final code,
+// it does not matter which phase we use for the update.
+func pctopcdata(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg interface{}) int32 {
+	if phase == 0 || p.As != APCDATA || p.From.Offset != int64(arg.(uint32)) {
+		return oldval
+	}
+	if int64(int32(p.To.Offset)) != p.To.Offset {
+		ctxt.Diag("overflow in PCDATA instruction: %v", p)
+		ctxt.DiagFlush()
+		log.Fatalf("bad code")
+	}
+
+	return int32(p.To.Offset)
+}
+
+func linkpcln(ctxt *Link, cursym *LSym) {
+	pcln := &cursym.Func().Pcln
+	pcln.UsedFiles = make(map[goobj.CUFileIndex]struct{})
+
+	npcdata := 0
+	nfuncdata := 0
+	for p := cursym.Func().Text; p != nil; p = p.Link {
+		// Find the highest ID of any used PCDATA table. This ignores PCDATA table
+		// that consist entirely of "-1", since that's the assumed default value.
+		//   From.Offset is table ID
+		//   To.Offset is data
+		if p.As == APCDATA && p.From.Offset >= int64(npcdata) && p.To.Offset != -1 { // ignore -1 as we start at -1, if we only see -1, nothing changed
+			npcdata = int(p.From.Offset + 1)
+		}
+		// Find the highest ID of any FUNCDATA table.
+		//   From.Offset is table ID
+		if p.As == AFUNCDATA && p.From.Offset >= int64(nfuncdata) {
+			nfuncdata = int(p.From.Offset + 1)
+		}
+	}
+
+	pcln.Pcdata = make([]*LSym, npcdata)
+	pcln.Funcdata = make([]*LSym, nfuncdata)
+
+	pcln.Pcsp = funcpctab(ctxt, cursym, "pctospadj", pctospadj, nil)
+	pcln.Pcfile = funcpctab(ctxt, cursym, "pctofile", pctofileline, pcln)
+	pcln.Pcline = funcpctab(ctxt, cursym, "pctoline", pctofileline, nil)
+
+	// Check that all the Progs used as inline markers are still reachable.
+	// See issue #40473.
+	fn := cursym.Func()
+	inlMarkProgs := make(map[*Prog]struct{}, len(fn.InlMarks))
+	for _, inlMark := range fn.InlMarks {
+		inlMarkProgs[inlMark.p] = struct{}{}
+	}
+	for p := fn.Text; p != nil; p = p.Link {
+		if _, ok := inlMarkProgs[p]; ok {
+			delete(inlMarkProgs, p)
+		}
+	}
+	if len(inlMarkProgs) > 0 {
+		ctxt.Diag("one or more instructions used as inline markers are no longer reachable")
+	}
+
+	pcinlineState := new(pcinlineState)
+	pcln.Pcinline = funcpctab(ctxt, cursym, "pctoinline", pcinlineState.pctoinline, nil)
+	for _, inlMark := range fn.InlMarks {
+		pcinlineState.setParentPC(ctxt, int(inlMark.id), int32(inlMark.p.Pc))
+	}
+	pcln.InlTree = pcinlineState.localTree
+	if ctxt.Debugpcln == "pctoinline" && len(pcln.InlTree.nodes) > 0 {
+		ctxt.Logf("-- inlining tree for %s:\n", cursym)
+		dumpInlTree(ctxt, pcln.InlTree)
+		ctxt.Logf("--\n")
+	}
+
+	// tabulate which pc and func data we have.
+	havepc := make([]uint32, (npcdata+31)/32)
+	havefunc := make([]uint32, (nfuncdata+31)/32)
+	for p := fn.Text; p != nil; p = p.Link {
+		if p.As == AFUNCDATA {
+			if (havefunc[p.From.Offset/32]>>uint64(p.From.Offset%32))&1 != 0 {
+				ctxt.Diag("multiple definitions for FUNCDATA $%d", p.From.Offset)
+			}
+			havefunc[p.From.Offset/32] |= 1 << uint64(p.From.Offset%32)
+		}
+
+		if p.As == APCDATA && p.To.Offset != -1 {
+			havepc[p.From.Offset/32] |= 1 << uint64(p.From.Offset%32)
+		}
+	}
+
+	// pcdata.
+	for i := 0; i < npcdata; i++ {
+		if (havepc[i/32]>>uint(i%32))&1 == 0 {
+			// use an empty symbol.
+			pcln.Pcdata[i] = &LSym{
+				Type:      objabi.SRODATA,
+				Attribute: AttrContentAddressable | AttrPcdata,
+			}
+		} else {
+			pcln.Pcdata[i] = funcpctab(ctxt, cursym, "pctopcdata", pctopcdata, interface{}(uint32(i)))
+		}
+	}
+
+	// funcdata
+	if nfuncdata > 0 {
+		for p := fn.Text; p != nil; p = p.Link {
+			if p.As != AFUNCDATA {
+				continue
+			}
+			i := int(p.From.Offset)
+			if p.To.Type != TYPE_MEM || p.To.Offset != 0 {
+				panic(fmt.Sprintf("bad funcdata: %v", p))
+			}
+			pcln.Funcdata[i] = p.To.Sym
+		}
+	}
+}
+
+// PCIter iterates over encoded pcdata tables.
+type PCIter struct {
+	p       []byte
+	PC      uint32
+	NextPC  uint32
+	PCScale uint32
+	Value   int32
+	start   bool
+	Done    bool
+}
+
+// newPCIter creates a PCIter with a scale factor for the PC step size.
+func NewPCIter(pcScale uint32) *PCIter {
+	it := new(PCIter)
+	it.PCScale = pcScale
+	return it
+}
+
+// Next advances it to the Next pc.
+func (it *PCIter) Next() {
+	it.PC = it.NextPC
+	if it.Done {
+		return
+	}
+	if len(it.p) == 0 {
+		it.Done = true
+		return
+	}
+
+	// Value delta
+	val, n := binary.Varint(it.p)
+	if n <= 0 {
+		log.Fatalf("bad Value varint in pciterNext: read %v", n)
+	}
+	it.p = it.p[n:]
+
+	if val == 0 && !it.start {
+		it.Done = true
+		return
+	}
+
+	it.start = false
+	it.Value += int32(val)
+
+	// pc delta
+	pc, n := binary.Uvarint(it.p)
+	if n <= 0 {
+		log.Fatalf("bad pc varint in pciterNext: read %v", n)
+	}
+	it.p = it.p[n:]
+
+	it.NextPC = it.PC + uint32(pc)*it.PCScale
+}
+
+// init prepares it to iterate over p,
+// and advances it to the first pc.
+func (it *PCIter) Init(p []byte) {
+	it.p = p
+	it.PC = 0
+	it.NextPC = 0
+	it.Value = -1
+	it.start = true
+	it.Done = false
+	it.Next()
+}