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| author | David Crawshaw <crawshaw@golang.org> | 2016-03-27 10:21:48 -0400 |
|---|---|---|
| committer | David Crawshaw <crawshaw@golang.org> | 2016-04-12 20:32:41 +0000 |
| commit | f028b9f9e2433662502283850d06e9e07e72a6bb (patch) | |
| tree | 4143e317fd9cea9762d9a76dc4ddc83ec4f997d3 /src/cmd/internal/obj/data.go | |
| parent | 23cbfa2545a735eca5ffc1ffd6c0e93c2eecac2a (diff) | |
| download | go-f028b9f9e2433662502283850d06e9e07e72a6bb.tar.xz | |
cmd/link, etc: store typelinks as offsets
This is the first in a series of CLs to replace the use of pointers
in binary read-only data with offsets.
In standard Go binaries these CLs have a small effect, shrinking
8-byte pointers to 4-bytes. In position-independent code, it also
saves the dynamic relocation for the pointer. This has a significant
effect on the binary size when building as PIE, c-archive, or
c-shared.
darwin/amd64:
cmd/go: -12KB (0.1%)
jujud: -82KB (0.1%)
linux/amd64 PIE:
cmd/go: -86KB (0.7%)
jujud: -569KB (0.7%)
For #6853.
Change-Id: Iad5625bbeba58dabfd4d334dbee3fcbfe04b2dcf
Reviewed-on: https://go-review.googlesource.com/21284
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Diffstat (limited to 'src/cmd/internal/obj/data.go')
| -rw-r--r-- | src/cmd/internal/obj/data.go | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/src/cmd/internal/obj/data.go b/src/cmd/internal/obj/data.go index 37ab70bb0e..546ff37269 100644 --- a/src/cmd/internal/obj/data.go +++ b/src/cmd/internal/obj/data.go @@ -111,17 +111,36 @@ func (s *LSym) WriteInt(ctxt *Link, off int64, siz int, i int64) { // rsym and roff specify the relocation for the address. func (s *LSym) WriteAddr(ctxt *Link, off int64, siz int, rsym *LSym, roff int64) { if siz != ctxt.Arch.PtrSize { - ctxt.Diag("WriteAddr: bad address size: %d", siz) + ctxt.Diag("WriteAddr: bad address size %d in %s", siz, s.Name) } s.prepwrite(ctxt, off, siz) r := Addrel(s) r.Off = int32(off) + if int64(r.Off) != off { + ctxt.Diag("WriteAddr: off overflow %d in %s", off, s.Name) + } r.Siz = uint8(siz) r.Sym = rsym r.Type = R_ADDR r.Add = roff } +// WriteOff writes a 4 byte offset to rsym+roff into s at offset off. +// After linking the 4 bytes stored at s+off will be +// rsym+roff-(start of section that s is in). +func (s *LSym) WriteOff(ctxt *Link, off int64, rsym *LSym, roff int64) { + s.prepwrite(ctxt, off, 4) + r := Addrel(s) + r.Off = int32(off) + if int64(r.Off) != off { + ctxt.Diag("WriteOff: off overflow %d in %s", off, s.Name) + } + r.Siz = 4 + r.Sym = rsym + r.Type = R_ADDROFF + r.Add = roff +} + // WriteString writes a string of size siz into s at offset off. func (s *LSym) WriteString(ctxt *Link, off int64, siz int, str string) { if siz < len(str) { |