cmd/compile/internal/ppc64, cmd/compile/internal/ssa: Remove OldArch checks

Starting in go1.9, the minimum processor requirement for ppc64 is POWER8.
Therefore, the checks for OldArch and the code enabled by it are not necessary
anymore.

Updates #19074

Change-Id: I33d6a78b2462c80d57c5dbcba2e13424630afab4
Reviewed-on: https://go-review.googlesource.com/38404
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/ppc64/ssa.go

@@ -765,27 +765,6 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
 		//   rtmp := 1
 		//   isel rt,0,rtmp,!cond // rt is target in ppc asm
 
-		if v.Block.Func.Config.OldArch {
-			p := s.Prog(ppc64.AMOVD)
-			p.From.Type = obj.TYPE_CONST
-			p.From.Offset = 1
-			p.To.Type = obj.TYPE_REG
-			p.To.Reg = v.Reg()
-
-			pb := s.Prog(condOps[v.Op])
-			pb.To.Type = obj.TYPE_BRANCH
-
-			p = s.Prog(ppc64.AMOVD)
-			p.From.Type = obj.TYPE_CONST
-			p.From.Offset = 0
-			p.To.Type = obj.TYPE_REG
-			p.To.Reg = v.Reg()
-
-			p = s.Prog(obj.ANOP)
-			gc.Patch(pb, p)
-			break
-		}
-		// Modern PPC uses ISEL
 		p := s.Prog(ppc64.AMOVD)
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = 1
@@ -797,30 +776,6 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
 	case ssa.OpPPC64FLessEqual, // These include a second branch for EQ -- dealing with NaN prevents REL= to !REL conversion
 		ssa.OpPPC64FGreaterEqual:
 
-		if v.Block.Func.Config.OldArch {
-			p := s.Prog(ppc64.AMOVW)
-			p.From.Type = obj.TYPE_CONST
-			p.From.Offset = 1
-			p.To.Type = obj.TYPE_REG
-			p.To.Reg = v.Reg()
-
-			pb0 := s.Prog(condOps[v.Op])
-			pb0.To.Type = obj.TYPE_BRANCH
-			pb1 := s.Prog(ppc64.ABEQ)
-			pb1.To.Type = obj.TYPE_BRANCH
-
-			p = s.Prog(ppc64.AMOVW)
-			p.From.Type = obj.TYPE_CONST
-			p.From.Offset = 0
-			p.To.Type = obj.TYPE_REG
-			p.To.Reg = v.Reg()
-
-			p = s.Prog(obj.ANOP)
-			gc.Patch(pb0, p)
-			gc.Patch(pb1, p)
-			break
-		}
-		// Modern PPC uses ISEL
 		p := s.Prog(ppc64.AMOVD)
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = 1

src/cmd/compile/internal/ssa/config.go

@@ -34,7 +34,6 @@ type Config struct {
 	noDuffDevice    bool          // Don't use Duff's device
 	nacl            bool          // GOOS=nacl
 	use387          bool          // GO386=387
-	OldArch         bool          // True for older versions of architecture, e.g. true for PPC64BE, false for PPC64LE
 	NeedsFpScratch  bool          // No direct move between GP and FP register sets
 	BigEndian       bool          //
 	sparsePhiCutoff uint64        // Sparse phi location algorithm used above this #blocks*#variables score
@@ -208,7 +207,6 @@ func NewConfig(arch string, types Types, ctxt *obj.Link, optimize bool) *Config
 		c.hasGReg = true
 		c.noDuffDevice = obj.GOOS == "darwin" // darwin linker cannot handle BR26 reloc with non-zero addend
 	case "ppc64":
-		c.OldArch = true
 		c.BigEndian = true
 		fallthrough
 	case "ppc64le":