From 24e549a717d1e083e7bef9003bce124294e9e975 Mon Sep 17 00:00:00 2001 From: Cherry Zhang Date: Mon, 28 Oct 2019 00:49:13 -0400 Subject: [PATCH] cmd/compile, cmd/internal/obj/ppc64: use LR for indirect calls On PPC64, indirect calls can be made through LR or CTR. Currently both are used. This CL changes it to always use LR. For async preemption, to return from the injected call, we need an indirect jump back to the PC we preeempted. This jump can be made through LR or CTR. So we'll have to clobber either LR or CTR. Currently, LR is used more frequently. In particular, for a leaf function, LR is live throughout the function. We don't want to make leaf functions nonpreemptible. So we choose CTR for the call injection. For code sequences that use CTR, if it is ok to use another register, change it to. Plus, it is a call so it will clobber LR anyway. It doesn't need to also clobber CTR (even without preemption). Change-Id: I07bd0e93b94a1a3aa2be2cd465801136165d8ab8 Reviewed-on: https://go-review.googlesource.com/c/go/+/203822 Run-TryBot: Cherry Zhang Reviewed-by: Keith Randall --- src/cmd/compile/internal/ppc64/ssa.go | 4 ++-- src/cmd/internal/obj/ppc64/obj9.go | 30 +++++++++++---------------- 2 files changed, 14 insertions(+), 20 deletions(-) diff --git a/src/cmd/compile/internal/ppc64/ssa.go b/src/cmd/compile/internal/ppc64/ssa.go index 4af6e9d5ed..73d1d9d3a0 100644 --- a/src/cmd/compile/internal/ppc64/ssa.go +++ b/src/cmd/compile/internal/ppc64/ssa.go @@ -1239,14 +1239,14 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) { p.From.Type = obj.TYPE_REG p.From.Reg = v.Args[0].Reg() p.To.Type = obj.TYPE_REG - p.To.Reg = ppc64.REG_CTR + p.To.Reg = ppc64.REG_LR if v.Args[0].Reg() != ppc64.REG_R12 { v.Fatalf("Function address for %v should be in R12 %d but is in %d", v.LongString(), ppc64.REG_R12, p.From.Reg) } pp := s.Call(v) - pp.To.Reg = ppc64.REG_CTR + pp.To.Reg = ppc64.REG_LR if gc.Ctxt.Flag_shared { // When compiling Go into PIC, the function we just diff --git a/src/cmd/internal/obj/ppc64/obj9.go b/src/cmd/internal/obj/ppc64/obj9.go index 916116d1a3..2a4f005592 100644 --- a/src/cmd/internal/obj/ppc64/obj9.go +++ b/src/cmd/internal/obj/ppc64/obj9.go @@ -130,8 +130,8 @@ func (c *ctxt9) rewriteToUseTOC(p *obj.Prog) { // becomes // MOVD runtime.duffxxx@TOC, R12 // ADD $offset, R12 - // MOVD R12, CTR - // BL (CTR) + // MOVD R12, LR + // BL (LR) var sym *obj.LSym if p.As == obj.ADUFFZERO { sym = c.ctxt.Lookup("runtime.duffzero") @@ -167,13 +167,11 @@ func (c *ctxt9) rewriteToUseTOC(p *obj.Prog) { p2.From.Type = obj.TYPE_REG p2.From.Reg = REG_R12 p2.To.Type = obj.TYPE_REG - p2.To.Reg = REG_CTR + p2.To.Reg = REG_LR p3 := obj.Appendp(p2, c.newprog) p3.As = obj.ACALL - p3.From.Type = obj.TYPE_REG - p3.From.Reg = REG_R12 p3.To.Type = obj.TYPE_REG - p3.To.Reg = REG_CTR + p3.To.Reg = REG_LR } var source *obj.Addr @@ -288,8 +286,8 @@ func (c *ctxt9) rewriteToUseGot(p *obj.Prog) { // becomes // MOVD runtime.duffxxx@GOT, R12 // ADD $offset, R12 - // MOVD R12, CTR - // BL (CTR) + // MOVD R12, LR + // BL (LR) var sym *obj.LSym if p.As == obj.ADUFFZERO { sym = c.ctxt.Lookup("runtime.duffzero") @@ -317,13 +315,11 @@ func (c *ctxt9) rewriteToUseGot(p *obj.Prog) { p2.From.Type = obj.TYPE_REG p2.From.Reg = REG_R12 p2.To.Type = obj.TYPE_REG - p2.To.Reg = REG_CTR + p2.To.Reg = REG_LR p3 := obj.Appendp(p2, c.newprog) p3.As = obj.ACALL - p3.From.Type = obj.TYPE_REG - p3.From.Reg = REG_R12 p3.To.Type = obj.TYPE_REG - p3.To.Reg = REG_CTR + p3.To.Reg = REG_LR } // We only care about global data: NAME_EXTERN means a global @@ -1196,21 +1192,19 @@ func (c *ctxt9) stacksplit(p *obj.Prog, framesize int32) *obj.Prog { p.To.Type = obj.TYPE_REG p.To.Reg = REG_R12 - // MOVD R12, CTR + // MOVD R12, LR p = obj.Appendp(p, c.newprog) p.As = AMOVD p.From.Type = obj.TYPE_REG p.From.Reg = REG_R12 p.To.Type = obj.TYPE_REG - p.To.Reg = REG_CTR + p.To.Reg = REG_LR - // BL CTR + // BL LR p = obj.Appendp(p, c.newprog) p.As = obj.ACALL - p.From.Type = obj.TYPE_REG - p.From.Reg = REG_R12 p.To.Type = obj.TYPE_REG - p.To.Reg = REG_CTR + p.To.Reg = REG_LR } else { // BL runtime.morestack(SB) p = obj.Appendp(p, c.newprog)