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[dev.ssa] cmd/compile: more fixes for 386 shared libraries

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Use the destination register for materializing the pc
for GOT references also. See https://go-review.googlesource.com/c/25442/
The SSA backend assumes CX does not get clobbered for these instructions.

Mark duffzero as clobbering CX. The linker needs to clobber CX
to materialize the address to call. (This affects the non-shared-library
duffzero also, but hopefully forbidding one register across duffzero
won't be a big deal.)

Hopefully this is all the cases where the linker is clobbering CX
under the hood and SSA assumes it isn't.

Change-Id: I080c938170193df57cd5ce1f2a956b68a34cc886
Reviewed-on: https://go-review.googlesource.com/26611
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>
This commit is contained in:
Keith Randall 2016-08-09 13:58:06 -07:00
parent ff37d0e681
commit 77ef597f38
4 changed files with 19 additions and 10 deletions
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3
src/cmd/compile/internal/ssa/gen/386.rules
View file

@ -669,7 +669,8 @@
// We need to fold LEAQ into the MOVx ops so that the live variable analysis knows
// what variables are being read/written by the ops.
// Note: we turn off this merging for operations on globals when building position-independent code.
// Note: we turn off this merging for operations on globals when building
// position-independent code (when Flag_shared is set).
// PIC needs a spare register to load the PC into. For loads from globals into integer registers we use
// the target register, but for other loads and all stores, we need a free register. Having the LEAL be
// a separate instruction gives us that register.

3
src/cmd/compile/internal/ssa/gen/386Ops.go
View file

@ -362,7 +362,8 @@ func init() {
argLength: 3,
reg: regInfo{
inputs: []regMask{buildReg("DI"), buildReg("AX")},
clobbers: buildReg("DI"),
clobbers: buildReg("DI CX"),
// Note: CX is only clobbered when dynamic linking.
},
},

2
src/cmd/compile/internal/ssa/opGen.go
View file

@ -3511,7 +3511,7 @@ var opcodeTable = [...]opInfo{
{0, 128}, // DI
{1, 1}, // AX
},
clobbers: 128, // DI
clobbers: 130, // CX DI
},
},
{

21
src/cmd/internal/obj/x86/obj6.go
View file

@ -334,6 +334,16 @@ func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) {
lea = ALEAL
mov = AMOVL
reg = REG_CX
if p.To.Type == obj.TYPE_REG && p.To.Reg != p.From.Reg && p.To.Reg != p.From.Index {
switch p.As {
case ALEAL, AMOVL, AMOVWLZX, AMOVBLZX, AMOVWLSX, AMOVBLSX:
// Special case: clobber the destination register with
// the PC so we don't have to clobber CX.
// The SSA backend depends on CX not being clobbered across these instructions.
// See cmd/compile/internal/ssa/gen/386.rules (search for Flag_shared).
reg = p.To.Reg
}
}
}
if p.As == obj.ADUFFCOPY || p.As == obj.ADUFFZERO {
@ -392,7 +402,7 @@ func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) {
dest = p.To
p.As = mov
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_CX
p.To.Reg = reg
p.To.Sym = nil
p.To.Name = obj.NAME_NONE
}
@ -413,7 +423,7 @@ func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) {
q.As = pAs
q.To = dest
q.From.Type = obj.TYPE_REG
q.From.Reg = REG_CX
q.From.Reg = reg
}
}
if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
@ -544,14 +554,11 @@ func rewriteToPcrel(ctxt *obj.Link, p *obj.Prog) {
return
}
var dst int16 = REG_CX
if isName(&p.From) && p.To.Type == obj.TYPE_REG {
if p.To.Type == obj.TYPE_REG && p.To.Reg != p.From.Reg && p.To.Reg != p.From.Index {
switch p.As {
case ALEAL, AMOVL, AMOVWLZX, AMOVBLZX, AMOVWLSX, AMOVBLSX:
dst = p.To.Reg
// Special case: clobber the destination register with
// the PC so we don't have to clobber CX.
// The SSA backend depends on CX not being clobbered across these instructions.
// See cmd/compile/internal/ssa/gen/386.rules (search for Flag_shared).
// Why? See the comment near the top of rewriteToUseGot above.
}
}
q := obj.Appendp(ctxt, p)