cmd/link, cmd/internal/obj: use encoding/binary for varint

This code was written before the c2go toolchain conversion.
Replace the handwritten varint encoding routines
and the handwritten unsigned-to-signed conversions
with calls to encoding/binary.

Passes toolstash-check.

Change-Id: I30d7f408cde3772ee98a3825e83075c4e1ec96d8
Reviewed-on: https://go-review.googlesource.com/c/go/+/171769
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/cmd/internal/obj/pcln.go b/src/cmd/internal/obj/pcln.go
index 84dd494930ee3355f3c9f1fe59dc09e3baaa9a2b..e7f340595fd571435a818ea6459a0fa8fd384731 100644 (file)
--- a/src/cmd/internal/obj/pcln.go
+++ b/src/cmd/internal/obj/pcln.go
@@ -6,6 +6,7 @@ package obj
 
 import (
        "cmd/internal/src"
+       "encoding/binary"
        "log"
 )
 
@@ -14,13 +15,6 @@ const (
        EpilogueBegin            // overload "is_stmt" to include epilogue_end
 )
 
-func addvarint(d *Pcdata, v uint32) {
-       for ; 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,
@@ -52,8 +46,8 @@ func funcpctab(ctxt *Link, dst *Pcdata, func_ *LSym, desc string, valfunc func(*
                ctxt.Logf("%6x %6d %v\n", uint64(pc), val, func_.Func.Text)
        }
 
+       buf := make([]byte, binary.MaxVarintLen32)
        started := false
-       var delta uint32
        for p := func_.Func.Text; p != nil; p = p.Link {
                // Update val. If it's not changing, keep going.
                val = valfunc(ctxt, func_, val, p, 0, arg)
@@ -97,17 +91,15 @@ func funcpctab(ctxt *Link, dst *Pcdata, func_ *LSym, desc string, valfunc func(*
                }
 
                if started {
-                       addvarint(dst, uint32((p.Pc-pc)/int64(ctxt.Arch.MinLC)))
+                       pcdelta := (p.Pc - pc) / int64(ctxt.Arch.MinLC)
+                       n := binary.PutUvarint(buf, uint64(pcdelta))
+                       dst.P = append(dst.P, buf[:n]...)
                        pc = p.Pc
                }
 
-               delta = uint32(val) - uint32(oldval)
-               if delta>>31 != 0 {
-                       delta = 1 | ^(delta << 1)
-               } else {
-                       delta <<= 1
-               }
-               addvarint(dst, delta)
+               delta := val - oldval
+               n := binary.PutVarint(buf, int64(delta))
+               dst.P = append(dst.P, buf[:n]...)
                oldval = val
                started = true
                val = valfunc(ctxt, func_, val, p, 1, arg)
@@ -117,8 +109,14 @@ func funcpctab(ctxt *Link, dst *Pcdata, func_ *LSym, desc string, valfunc func(*
                if dbg {
                        ctxt.Logf("%6x done\n", uint64(func_.Func.Text.Pc+func_.Size))
                }
-               addvarint(dst, uint32((func_.Size-pc)/int64(ctxt.Arch.MinLC)))
-               addvarint(dst, 0) // terminator
+               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.P = append(dst.P, buf[:n]...)
+               // add terminating varint-encoded 0, which is just 0
+               dst.P = append(dst.P, 0)
        }
 
        if dbg {

diff --git a/src/cmd/link/internal/ld/pcln.go b/src/cmd/link/internal/ld/pcln.go
index 5924acc0b08591fe50a0e8236a3b9c95cbad3c0c..33bbd37b36fed9ce6723952add7959b1e9f08f3a 100644 (file)
--- a/src/cmd/link/internal/ld/pcln.go
+++ b/src/cmd/link/internal/ld/pcln.go
@@ -9,6 +9,7 @@ import (
        "cmd/internal/src"
        "cmd/internal/sys"
        "cmd/link/internal/sym"
+       "encoding/binary"
        "log"
        "os"
        "path/filepath"
@@ -17,22 +18,6 @@ import (
 
 // iteration over encoded pcdata tables.
 
-func getvarint(pp *[]byte) uint32 {
-       v := uint32(0)
-       p := *pp
-       for shift := 0; ; shift += 7 {
-               v |= uint32(p[0]&0x7F) << uint(shift)
-               tmp4 := p
-               p = p[1:]
-               if tmp4[0]&0x80 == 0 {
-                       break
-               }
-       }
-
-       *pp = p
-       return v
-}
-
 func pciternext(it *Pciter) {
        it.pc = it.nextpc
        if it.done != 0 {
@@ -44,21 +29,28 @@ func pciternext(it *Pciter) {
        }
 
        // value delta
-       v := getvarint(&it.p)
+       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 v == 0 && it.start == 0 {
+       if val == 0 && it.start == 0 {
                it.done = 1
                return
        }
 
        it.start = 0
-       dv := int32(v>>1) ^ (int32(v<<31) >> 31)
-       it.value += dv
+       it.value += int32(val)
 
        // pc delta
-       v = getvarint(&it.p)
+       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 + v*it.pcscale
+       it.nextpc = it.pc + uint32(pc)*it.pcscale
 }
 
 func pciterinit(ctxt *Link, it *Pciter, d *sym.Pcdata) {
@@ -73,28 +65,6 @@ func pciterinit(ctxt *Link, it *Pciter, d *sym.Pcdata) {
        pciternext(it)
 }
 
-func addvarint(d *sym.Pcdata, val uint32) {
-       n := int32(0)
-       for v := val; v >= 0x80; v >>= 7 {
-               n++
-       }
-       n++
-
-       old := len(d.P)
-       for cap(d.P) < len(d.P)+int(n) {
-               d.P = append(d.P[:cap(d.P)], 0)
-       }
-       d.P = d.P[:old+int(n)]
-
-       p := d.P[old:]
-       var v uint32
-       for v = val; v >= 0x80; v >>= 7 {
-               p[0] = byte(v | 0x80)
-               p = p[1:]
-       }
-       p[0] = byte(v)
-}
-
 func addpctab(ctxt *Link, ftab *sym.Symbol, off int32, d *sym.Pcdata) int32 {
        var start int32
        if len(d.P) > 0 {
@@ -128,6 +98,7 @@ func renumberfiles(ctxt *Link, files []*sym.Symbol, d *sym.Pcdata) {
                numberfile(ctxt, f)
        }
 
+       buf := make([]byte, binary.MaxVarintLen32)
        newval := int32(-1)
        var out sym.Pcdata
        var it Pciter
@@ -147,15 +118,20 @@ func renumberfiles(ctxt *Link, files []*sym.Symbol, d *sym.Pcdata) {
 
                dv := val - newval
                newval = val
-               v := (uint32(dv) << 1) ^ uint32(dv>>31)
-               addvarint(&out, v)
+
+               // value
+               n := binary.PutVarint(buf, int64(dv))
+               out.P = append(out.P, buf[:n]...)
 
                // pc delta
-               addvarint(&out, (it.nextpc-it.pc)/it.pcscale)
+               pc := (it.nextpc - it.pc) / it.pcscale
+               n = binary.PutUvarint(buf, uint64(pc))
+               out.P = append(out.P, buf[:n]...)
        }
 
        // terminating value delta
-       addvarint(&out, 0)
+       // we want to write varint-encoded 0, which is just 0
+       out.P = append(out.P, 0)
 
        *d = out
 }