[dev.ssa] cmd/compile: initial ARM64 SSA port

Mostly copied from ARM port, with instruction names and Prog fields
adjusted, and 64-bit int ops added. Not complete.

Fib compiles and runs correctly.

Change-Id: Id3ecb0d4b571200a035344b3e8e4408769f76221
Reviewed-on: https://go-review.googlesource.com/25130Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/arm64/galign.go

@@ -6,6 +6,7 @@ package arm64
 
 import (
 	"cmd/compile/internal/gc"
+	"cmd/compile/internal/ssa"
 	"cmd/internal/obj/arm64"
 )
 
@@ -61,6 +62,11 @@ func Main() {
 	gc.Thearch.Doregbits = doregbits
 	gc.Thearch.Regnames = regnames
 
+	gc.Thearch.SSARegToReg = ssaRegToReg
+	gc.Thearch.SSAMarkMoves = func(s *gc.SSAGenState, b *ssa.Block) {}
+	gc.Thearch.SSAGenValue = ssaGenValue
+	gc.Thearch.SSAGenBlock = ssaGenBlock
+
 	gc.Main()
 	gc.Exit(0)
 }

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

@@ -162,6 +162,17 @@ func NewConfig(arch string, fe Frontend, ctxt *obj.Link, optimize bool) *Config
 		c.flagRegMask = flagRegMaskARM
 		c.FPReg = framepointerRegARM
 		c.hasGReg = true
+	case "arm64":
+		c.IntSize = 8
+		c.PtrSize = 8
+		c.lowerBlock = rewriteBlockARM64
+		c.lowerValue = rewriteValueARM64
+		c.registers = registersARM64[:]
+		c.gpRegMask = gpRegMaskARM64
+		c.fpRegMask = fpRegMaskARM64
+		c.flagRegMask = flagRegMaskARM64
+		c.FPReg = framepointerRegARM64
+		c.hasGReg = true
 	case "ppc64le":
 		c.IntSize = 8
 		c.PtrSize = 8