1 files changed, 281 insertions, 0 deletions
diff --git a/vendor/github.com/google/gops/internal/obj/pcln.go b/vendor/github.com/google/gops/internal/obj/pcln.go
new file mode 100644
index 00000000..d9893e42
--- /dev/null
+++ b/vendor/github.com/google/gops/internal/obj/pcln.go
@@ -0,0 +1,281 @@
+// 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 "log"
+
+func addvarint(ctxt *Link, d *Pcdata, val uint32) {
+	var v uint32
+	for v = val; v >= 0x80; v >>= 7 {
+		d.P = append(d.P, uint8(v|0x80))
+	}
+	d.P = append(d.P, uint8(v))
+}
+
+// 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,
+//
+//	val = valfunc(func, val, p, 0, arg);
+//	record val as value at p->pc;
+//	val = valfunc(func, val, 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, dst *Pcdata, func_ *LSym, desc string, valfunc func(*Link, *LSym, int32, *Prog, int32, interface{}) int32, arg interface{}) {
+	// To debug a specific function, uncomment lines and change name.
+	dbg := 0
+
+	//if func_.Name == "main.main" || desc == "pctospadj" {
+	//	dbg = 1
+	//}
+
+	ctxt.Debugpcln += int32(dbg)
+
+	dst.P = dst.P[:0]
+
+	if ctxt.Debugpcln != 0 {
+		ctxt.Logf("funcpctab %s [valfunc=%s]\n", func_.Name, desc)
+	}
+
+	val := int32(-1)
+	oldval := val
+	if func_.Text == nil {
+		ctxt.Debugpcln -= int32(dbg)
+		return
+	}
+
+	pc := func_.Text.Pc
+
+	if ctxt.Debugpcln != 0 {
+		ctxt.Logf("%6x %6d %v\n", uint64(pc), val, func_.Text)
+	}
+
+	started := int32(0)
+	var delta uint32
+	for p := func_.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 != 0 {
+			val = valfunc(ctxt, func_, val, p, 1, arg)
+			if ctxt.Debugpcln != 0 {
+				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 ctxt.Debugpcln != 0 {
+				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 ctxt.Debugpcln != 0 {
+			ctxt.Logf("%6x %6d %v\n", uint64(p.Pc), val, p)
+		}
+
+		if started != 0 {
+			addvarint(ctxt, dst, uint32((p.Pc-pc)/int64(ctxt.Arch.MinLC)))
+			pc = p.Pc
+		}
+
+		delta = uint32(val) - uint32(oldval)
+		if delta>>31 != 0 {
+			delta = 1 | ^(delta << 1)
+		} else {
+			delta <<= 1
+		}
+		addvarint(ctxt, dst, delta)
+		oldval = val
+		started = 1
+		val = valfunc(ctxt, func_, val, p, 1, arg)
+	}
+
+	if started != 0 {
+		if ctxt.Debugpcln != 0 {
+			ctxt.Logf("%6x done\n", uint64(func_.Text.Pc+func_.Size))
+		}
+		addvarint(ctxt, dst, uint32((func_.Size-pc)/int64(ctxt.Arch.MinLC)))
+		addvarint(ctxt, dst, 0) // terminator
+	}
+
+	if ctxt.Debugpcln != 0 {
+		ctxt.Logf("wrote %d bytes to %p\n", len(dst.P), dst)
+		for i := 0; i < len(dst.P); i++ {
+			ctxt.Logf(" %02x", dst.P[i])
+		}
+		ctxt.Logf("\n")
+	}
+
+	ctxt.Debugpcln -= int32(dbg)
+}
+
+// pctofileline computes either the file number (arg == 0)
+// or the line number (arg == 1) to use at p.
+// Because p->lineno 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.As == AUSEFIELD || p.Lineno == 0 || phase == 1 {
+		return oldval
+	}
+	f, l := linkgetline(ctxt, p.Lineno)
+	if f == nil {
+		//	print("getline failed for %s %v\n", ctxt->cursym->name, p);
+		return oldval
+	}
+
+	if arg == nil {
+		return l
+	}
+	pcln := arg.(*Pcln)
+
+	if f == pcln.Lastfile {
+		return int32(pcln.Lastindex)
+	}
+
+	for i, file := range pcln.File {
+		if file == f {
+			pcln.Lastfile = f
+			pcln.Lastindex = i
+			return int32(i)
+		}
+	}
+	i := len(pcln.File)
+	pcln.File = append(pcln.File, f)
+	pcln.Lastfile = f
+	pcln.Lastindex = i
+	return int32(i)
+}
+
+// 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)
+		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)
+		log.Fatalf("bad code")
+	}
+
+	return int32(p.To.Offset)
+}
+
+func linkpcln(ctxt *Link, cursym *LSym) {
+	ctxt.Cursym = cursym
+
+	pcln := new(Pcln)
+	cursym.Pcln = pcln
+
+	npcdata := 0
+	nfuncdata := 0
+	for p := cursym.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([]Pcdata, npcdata)
+	pcln.Pcdata = pcln.Pcdata[:npcdata]
+	pcln.Funcdata = make([]*LSym, nfuncdata)
+	pcln.Funcdataoff = make([]int64, nfuncdata)
+	pcln.Funcdataoff = pcln.Funcdataoff[:nfuncdata]
+
+	funcpctab(ctxt, &pcln.Pcsp, cursym, "pctospadj", pctospadj, nil)
+	funcpctab(ctxt, &pcln.Pcfile, cursym, "pctofile", pctofileline, pcln)
+	funcpctab(ctxt, &pcln.Pcline, cursym, "pctoline", pctofileline, nil)
+
+	// tabulate which pc and func data we have.
+	havepc := make([]uint32, (npcdata+31)/32)
+	havefunc := make([]uint32, (nfuncdata+31)/32)
+	for p := cursym.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 {
+			continue
+		}
+		funcpctab(ctxt, &pcln.Pcdata[i], cursym, "pctopcdata", pctopcdata, interface{}(uint32(i)))
+	}
+
+	// funcdata
+	if nfuncdata > 0 {
+		var i int
+		for p := cursym.Text; p != nil; p = p.Link {
+			if p.As == AFUNCDATA {
+				i = int(p.From.Offset)
+				pcln.Funcdataoff[i] = p.To.Offset
+				if p.To.Type != TYPE_CONST {
+					// TODO: Dedup.
+					//funcdata_bytes += p->to.sym->size;
+					pcln.Funcdata[i] = p.To.Sym
+				}
+			}
+		}
+	}
+}