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| author | Austin Clements <austin@google.com> | 2021-04-02 17:20:15 -0400 |
|---|---|---|
| committer | Austin Clements <austin@google.com> | 2021-04-05 16:22:13 +0000 |
| commit | 4702dd67a7dcf1eac2309218807287bcd48d4e09 (patch) | |
| tree | 5d8a1acf6502b3a70529ef53285abcd9e3d14614 /src/cmd/internal/obj | |
| parent | 24dd8cfe23b2ffc0641611dd6299c037cb459807 (diff) | |
| download | go-4702dd67a7dcf1eac2309218807287bcd48d4e09.tar.xz | |
cmd/internal/obj/arm64: simplify huge frame prologue
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>
Diffstat (limited to 'src/cmd/internal/obj')
| -rw-r--r-- | src/cmd/internal/obj/arm64/obj7.go | 54 |
1 files changed, 17 insertions, 37 deletions
diff --git a/src/cmd/internal/obj/arm64/obj7.go b/src/cmd/internal/obj/arm64/obj7.go index bed21dbe53..514991e340 100644 --- a/src/cmd/internal/obj/arm64/obj7.go +++ b/src/cmd/internal/obj/arm64/obj7.go @@ -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) - - p.As = ACMP - 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 + // 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 = obj.Appendp(p, c.newprog) - p.As = AADD + p.As = ASUBS 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 } |