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cmd/internal/obj/arm64: simplify huge frame prologue

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CL 307010 for arm64.

Change-Id: I6c6e1bd6065df059e50c3632a9eb669b64fce899
Reviewed-on: https://go-review.googlesource.com/c/go/+/307050
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Austin Clements 2021-04-02 17:20:15 -04:00
parent 24dd8cfe23
commit 4702dd67a7
1 changed files with 18 additions and 38 deletions
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56
src/cmd/internal/obj/arm64/obj7.go
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@ -107,55 +107,35 @@ func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
p.From.Reg = REG_R1
p.Reg = REG_R2
} else {
// Such a large stack we need to protect against wraparound
// if SP is close to zero.
// SP-stackguard+StackGuard < framesize + (StackGuard-StackSmall)
// The +StackGuard on both sides is required to keep the left side positive:
// SP is allowed to be slightly below stackguard. See stack.h.
// CMP $StackPreempt, R1
// BEQ label_of_call_to_morestack
// ADD $StackGuard, SP, R2
// SUB R1, R2
// MOV $(framesize+(StackGuard-StackSmall)), R3
// CMP R3, R2
p = obj.Appendp(p, c.newprog)
// Such a large stack we need to protect against underflow.
// The runtime guarantees SP > objabi.StackBig, but
// framesize is large enough that SP-framesize may
// underflow, causing a direct comparison with the
// stack guard to incorrectly succeed. We explicitly
// guard against underflow.
//
// SUBS $(framesize-StackSmall), SP, R2
// // On underflow, jump to morestack
// BLO label_of_call_to_morestack
// CMP stackguard, R2
p.As = ACMP
p = obj.Appendp(p, c.newprog)
p.As = ASUBS
p.From.Type = obj.TYPE_CONST
p.From.Offset = objabi.StackPreempt
p.Reg = REG_R1
p = obj.Appendp(p, c.newprog)
q = p
p.As = ABEQ
p.To.Type = obj.TYPE_BRANCH
p = obj.Appendp(p, c.newprog)
p.As = AADD
p.From.Type = obj.TYPE_CONST
p.From.Offset = int64(objabi.StackGuard)
p.From.Offset = int64(framesize) - objabi.StackSmall
p.Reg = REGSP
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_R2
p = obj.Appendp(p, c.newprog)
p.As = ASUB
p.From.Type = obj.TYPE_REG
p.From.Reg = REG_R1
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_R2
p = obj.Appendp(p, c.newprog)
p.As = AMOVD
p.From.Type = obj.TYPE_CONST
p.From.Offset = int64(framesize) + (int64(objabi.StackGuard) - objabi.StackSmall)
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_R3
q = p
p.As = ABLO
p.To.Type = obj.TYPE_BRANCH
p = obj.Appendp(p, c.newprog)
p.As = ACMP
p.From.Type = obj.TYPE_REG
p.From.Reg = REG_R3
p.From.Reg = REG_R1
p.Reg = REG_R2
}