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cmd/internal/obj/x86: use ABI scratch registers for WRAPPER prologue

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Currently the prologue generated for WRAPPER assembly functions uses BX
and DI, but these are argument registers in the register-based calling
convention. Thus, these end up being clobbered when we want to have an
ABIInternal assembly function.

Define REGENTRYTMP0 and REGENTRYTMP1, aliases for the dedicated function
entry scratch registers R12 and R13, and use those instead.

For #40724.

Change-Id: Ica78c4ccc67a757359900a66b56ef28c83d88b3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/303314
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Michael Anthony Knyszek 2021-03-19 20:04:38 +00:00 committed by Michael Knyszek
parent 5d6581d747
commit 87c6fa4f47
2 changed files with 42 additions and 34 deletions
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36
src/cmd/internal/obj/x86/a.out.go
View File

@ -258,23 +258,25 @@ const (
REG_DR = REG_DR0
REG_TR = REG_TR0
REGARG = -1
REGRET = REG_AX
FREGRET = REG_X0
REGSP = REG_SP
REGCTXT = REG_DX
REGG = REG_R14 // g register in ABIInternal
REGEXT = REG_R15 // compiler allocates external registers R15 down
FREGMIN = REG_X0 + 5 // first register variable
FREGEXT = REG_X0 + 15 // first external register
T_TYPE = 1 << 0
T_INDEX = 1 << 1
T_OFFSET = 1 << 2
T_FCONST = 1 << 3
T_SYM = 1 << 4
T_SCONST = 1 << 5
T_64 = 1 << 6
T_GOTYPE = 1 << 7
REGARG = -1
REGRET = REG_AX
FREGRET = REG_X0
REGSP = REG_SP
REGCTXT = REG_DX
REGENTRYTMP0 = REG_R12 // scratch register available at function entry in ABIInternal
REGENTRYTMP1 = REG_R13 // scratch register available at function entry in ABIInternal
REGG = REG_R14 // g register in ABIInternal
REGEXT = REG_R15 // compiler allocates external registers R15 down
FREGMIN = REG_X0 + 5 // first register variable
FREGEXT = REG_X0 + 15 // first external register
T_TYPE = 1 << 0
T_INDEX = 1 << 1
T_OFFSET = 1 << 2
T_FCONST = 1 << 3
T_SYM = 1 << 4
T_SCONST = 1 << 5
T_64 = 1 << 6
T_GOTYPE = 1 << 7
)
// https://www.uclibc.org/docs/psABI-x86_64.pdf, figure 3.36

40
src/cmd/internal/obj/x86/obj6.go
View File

@ -658,6 +658,12 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
p = load_g(ctxt, p, newprog, regg) // load g into regg
}
}
var regEntryTmp0, regEntryTmp1 int16
if ctxt.Arch.Family == sys.AMD64 {
regEntryTmp0, regEntryTmp1 = REGENTRYTMP0, REGENTRYTMP1
} else {
regEntryTmp0, regEntryTmp1 = REG_BX, REG_DI
}
if !cursym.Func().Text.From.Sym.NoSplit() {
p = stacksplit(ctxt, cursym, p, newprog, autoffset, int32(textarg), regg) // emit split check
@ -712,17 +718,17 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
// g._panic.argp = bottom-of-frame
// }
//
// MOVQ g_panic(g), BX
// TESTQ BX, BX
// MOVQ g_panic(g), regEntryTmp0
// TESTQ regEntryTmp0, regEntryTmp0
// JNE checkargp
// end:
// NOP
// ... rest of function ...
// checkargp:
// LEAQ (autoffset+8)(SP), DI
// CMPQ panic_argp(BX), DI
// LEAQ (autoffset+8)(SP), regEntryTmp1
// CMPQ panic_argp(regEntryTmp0), regEntryTmp1
// JNE end
// MOVQ SP, panic_argp(BX)
// MOVQ SP, panic_argp(regEntryTmp0)
// JMP end
//
// The NOP is needed to give the jumps somewhere to land.
@ -731,25 +737,25 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
// The layout is chosen to help static branch prediction:
// Both conditional jumps are unlikely, so they are arranged to be forward jumps.
// MOVQ g_panic(CX), BX
// MOVQ g_panic(g), regEntryTmp0
p = obj.Appendp(p, newprog)
p.As = AMOVQ
p.From.Type = obj.TYPE_MEM
p.From.Reg = regg
p.From.Offset = 4 * int64(ctxt.Arch.PtrSize) // g_panic
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_BX
p.To.Reg = regEntryTmp0
if ctxt.Arch.Family == sys.I386 {
p.As = AMOVL
}
// TESTQ BX, BX
// TESTQ regEntryTmp0, regEntryTmp0
p = obj.Appendp(p, newprog)
p.As = ATESTQ
p.From.Type = obj.TYPE_REG
p.From.Reg = REG_BX
p.From.Reg = regEntryTmp0
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_BX
p.To.Reg = regEntryTmp0
if ctxt.Arch.Family == sys.I386 {
p.As = ATESTL
}
@ -769,14 +775,14 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
for last = end; last.Link != nil; last = last.Link {
}
// LEAQ (autoffset+8)(SP), DI
// LEAQ (autoffset+8)(SP), regEntryTmp1
p = obj.Appendp(last, newprog)
p.As = ALEAQ
p.From.Type = obj.TYPE_MEM
p.From.Reg = REG_SP
p.From.Offset = int64(autoffset) + int64(ctxt.Arch.RegSize)
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_DI
p.To.Reg = regEntryTmp1
if ctxt.Arch.Family == sys.I386 {
p.As = ALEAL
}
@ -784,14 +790,14 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
// Set jne branch target.
jne.To.SetTarget(p)
// CMPQ panic_argp(BX), DI
// CMPQ panic_argp(regEntryTmp0), regEntryTmp1
p = obj.Appendp(p, newprog)
p.As = ACMPQ
p.From.Type = obj.TYPE_MEM
p.From.Reg = REG_BX
p.From.Reg = regEntryTmp0
p.From.Offset = 0 // Panic.argp
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_DI
p.To.Reg = regEntryTmp1
if ctxt.Arch.Family == sys.I386 {
p.As = ACMPL
}
@ -802,13 +808,13 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
p.To.Type = obj.TYPE_BRANCH
p.To.SetTarget(end)
// MOVQ SP, panic_argp(BX)
// MOVQ SP, panic_argp(regEntryTmp0)
p = obj.Appendp(p, newprog)
p.As = AMOVQ
p.From.Type = obj.TYPE_REG
p.From.Reg = REG_SP
p.To.Type = obj.TYPE_MEM
p.To.Reg = REG_BX
p.To.Reg = regEntryTmp0
p.To.Offset = 0 // Panic.argp
if ctxt.Arch.Family == sys.I386 {
p.As = AMOVL