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cmd/internal/goobj: store relocation type as uint16

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Currently, relocation type is stored as uint8 in object files, as
Go relocations do not exceed 255. In the linker, however, it is
used as a 16-bit type, because external relocations can exceed
255. The linker has to store the extra byte in a side table. This
complicates many things.

Just store it as uint16 in object files. This simplifies things,
with a small cost of increasing the object file sizes.

               before      after
hello.o         1672        1678
runtime.a    7927784     8056194

Change-Id: I313cf44ad0b8b3b76e35055ae55d911ff35e3158
Reviewed-on: https://go-review.googlesource.com/c/go/+/268477
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
This commit is contained in:
Cherry Zhang 2020-11-08 11:27:53 -05:00
parent 87d29939c8
commit f901ea701d
6 changed files with 40 additions and 64 deletions
Download patch file Download diff file Expand all files Collapse all files

8
src/cmd/link/internal/loader/symbolbuilder.go
View file

@ -121,13 +121,11 @@ func (sb *SymbolBuilder) Relocs() Relocs {
// ResetRelocs removes all relocations on this symbol.
func (sb *SymbolBuilder) ResetRelocs() {
sb.relocs = sb.relocs[:0]
sb.reltypes = sb.reltypes[:0]
}
// SetRelocType sets the type of the 'i'-th relocation on this sym to 't'
func (sb *SymbolBuilder) SetRelocType(i int, t objabi.RelocType) {
sb.relocs[i].SetType(0)
sb.reltypes[i] = t
sb.relocs[i].SetType(uint16(t))
}
// SetRelocSym sets the target sym of the 'i'-th relocation on this sym to 's'
@ -143,7 +141,6 @@ func (sb *SymbolBuilder) SetRelocAdd(i int, a int64) {
// Add n relocations, return a handle to the relocations.
func (sb *SymbolBuilder) AddRelocs(n int) Relocs {
sb.relocs = append(sb.relocs, make([]goobj.Reloc, n)...)
sb.reltypes = append(sb.reltypes, make([]objabi.RelocType, n)...)
return sb.l.Relocs(sb.symIdx)
}
@ -152,7 +149,7 @@ func (sb *SymbolBuilder) AddRelocs(n int) Relocs {
func (sb *SymbolBuilder) AddRel(typ objabi.RelocType) (Reloc, int) {
j := len(sb.relocs)
sb.relocs = append(sb.relocs, goobj.Reloc{})
sb.reltypes = append(sb.reltypes, typ)
sb.relocs[j].SetType(uint16(typ))
relocs := sb.Relocs()
return relocs.At(j), j
}
@ -169,7 +166,6 @@ func (p *relocsByOff) Len() int { return len(p.relocs) }
func (p *relocsByOff) Less(i, j int) bool { return p.relocs[i].Off() < p.relocs[j].Off() }
func (p *relocsByOff) Swap(i, j int) {
p.relocs[i], p.relocs[j] = p.relocs[j], p.relocs[i]
p.reltypes[i], p.reltypes[j] = p.reltypes[j], p.reltypes[i]
}
func (sb *SymbolBuilder) Reachable() bool {