cmd/compile: implement compiler for riscv64

Based on riscv-go port.

Updates #27532

Change-Id: Ia329daa243db63ff334053b8807ea96b97ce3acf
Reviewed-on: https://go-review.googlesource.com/c/go/+/204631
Run-TryBot: Joel Sing <joel@sing.id.au>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

4 files changed, 589 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/riscv64/galign.go b/src/cmd/compile/internal/riscv64/galign.go
new file mode 100644
index 0000000000..4db0fac52e
--- /dev/null
+++ b/src/cmd/compile/internal/riscv64/galign.go
@@ -0,0 +1,25 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package riscv64
+
+import (
+	"cmd/compile/internal/gc"
+	"cmd/internal/obj/riscv"
+)
+
+func Init(arch *gc.Arch) {
+	arch.LinkArch = &riscv.LinkRISCV64
+
+	arch.REGSP = riscv.REG_SP
+	arch.MAXWIDTH = 1 << 50
+
+	arch.Ginsnop = ginsnop
+	arch.Ginsnopdefer = ginsnop
+	arch.ZeroRange = zeroRange
+
+	arch.SSAMarkMoves = ssaMarkMoves
+	arch.SSAGenValue = ssaGenValue
+	arch.SSAGenBlock = ssaGenBlock
+}
diff --git a/src/cmd/compile/internal/riscv64/ggen.go b/src/cmd/compile/internal/riscv64/ggen.go
new file mode 100644
index 0000000000..be31fad441
--- /dev/null
+++ b/src/cmd/compile/internal/riscv64/ggen.go
@@ -0,0 +1,48 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package riscv64
+
+import (
+	"cmd/compile/internal/gc"
+	"cmd/internal/obj"
+	"cmd/internal/obj/riscv"
+)
+
+func zeroRange(pp *gc.Progs, p *obj.Prog, off, cnt int64, _ *uint32) *obj.Prog {
+	if cnt == 0 {
+		return p
+	}
+
+	// Adjust the frame to account for LR.
+	off += gc.Ctxt.FixedFrameSize()
+
+	if cnt < int64(4*gc.Widthptr) {
+		for i := int64(0); i < cnt; i += int64(gc.Widthptr) {
+			p = pp.Appendpp(p, riscv.AMOV, obj.TYPE_REG, riscv.REG_ZERO, 0, obj.TYPE_MEM, riscv.REG_SP, off+i)
+		}
+		return p
+	}
+
+	// TODO(jsing): Add a duff zero implementation for medium sized ranges.
+
+	// Loop, zeroing pointer width bytes at a time.
+	// ADD	$(off), SP, T0
+	// ADD	$(cnt), T0, T1
+	// loop:
+	// 	MOV	ZERO, (T0)
+	// 	ADD	$Widthptr, T0
+	//	BNE	T0, T1, loop
+	p = pp.Appendpp(p, riscv.AADD, obj.TYPE_CONST, 0, off, obj.TYPE_REG, riscv.REG_T0, 0)
+	p.Reg = riscv.REG_SP
+	p = pp.Appendpp(p, riscv.AADD, obj.TYPE_CONST, 0, cnt, obj.TYPE_REG, riscv.REG_T1, 0)
+	p.Reg = riscv.REG_T0
+	p = pp.Appendpp(p, riscv.AMOV, obj.TYPE_REG, riscv.REG_ZERO, 0, obj.TYPE_MEM, riscv.REG_T0, 0)
+	loop := p
+	p = pp.Appendpp(p, riscv.AADD, obj.TYPE_CONST, 0, int64(gc.Widthptr), obj.TYPE_REG, riscv.REG_T0, 0)
+	p = pp.Appendpp(p, riscv.ABNE, obj.TYPE_REG, riscv.REG_T0, 0, obj.TYPE_BRANCH, 0, 0)
+	p.Reg = riscv.REG_T1
+	gc.Patch(p, loop)
+	return p
+}
diff --git a/src/cmd/compile/internal/riscv64/gsubr.go b/src/cmd/compile/internal/riscv64/gsubr.go
new file mode 100644
index 0000000000..d40bdf7a1d
--- /dev/null
+++ b/src/cmd/compile/internal/riscv64/gsubr.go
@@ -0,0 +1,20 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package riscv64
+
+import (
+	"cmd/compile/internal/gc"
+	"cmd/internal/obj"
+	"cmd/internal/obj/riscv"
+)
+
+func ginsnop(pp *gc.Progs) *obj.Prog {
+	// Hardware nop is ADD $0, ZERO
+	p := pp.Prog(riscv.AADD)
+	p.From.Type = obj.TYPE_CONST
+	p.Reg = riscv.REG_ZERO
+	p.To = obj.Addr{Type: obj.TYPE_REG, Reg: riscv.REG_ZERO}
+	return p
+}
diff --git a/src/cmd/compile/internal/riscv64/ssa.go b/src/cmd/compile/internal/riscv64/ssa.go
new file mode 100644
index 0000000000..d33240351f
--- /dev/null
+++ b/src/cmd/compile/internal/riscv64/ssa.go
@@ -0,0 +1,496 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package riscv64
+
+import (
+	"cmd/compile/internal/gc"
+	"cmd/compile/internal/ssa"
+	"cmd/compile/internal/types"
+	"cmd/internal/obj"
+	"cmd/internal/obj/riscv"
+)
+
+// ssaRegToReg maps ssa register numbers to obj register numbers.
+var ssaRegToReg = []int16{
+	riscv.REG_X0,
+	// X1 (LR): unused
+	riscv.REG_X2,
+	riscv.REG_X3,
+	riscv.REG_X4,
+	riscv.REG_X5,
+	riscv.REG_X6,
+	riscv.REG_X7,
+	riscv.REG_X8,
+	riscv.REG_X9,
+	riscv.REG_X10,
+	riscv.REG_X11,
+	riscv.REG_X12,
+	riscv.REG_X13,
+	riscv.REG_X14,
+	riscv.REG_X15,
+	riscv.REG_X16,
+	riscv.REG_X17,
+	riscv.REG_X18,
+	riscv.REG_X19,
+	riscv.REG_X20,
+	riscv.REG_X21,
+	riscv.REG_X22,
+	riscv.REG_X23,
+	riscv.REG_X24,
+	riscv.REG_X25,
+	riscv.REG_X26,
+	riscv.REG_X27,
+	riscv.REG_X28,
+	riscv.REG_X29,
+	riscv.REG_X30,
+	riscv.REG_X31,
+	riscv.REG_F0,
+	riscv.REG_F1,
+	riscv.REG_F2,
+	riscv.REG_F3,
+	riscv.REG_F4,
+	riscv.REG_F5,
+	riscv.REG_F6,
+	riscv.REG_F7,
+	riscv.REG_F8,
+	riscv.REG_F9,
+	riscv.REG_F10,
+	riscv.REG_F11,
+	riscv.REG_F12,
+	riscv.REG_F13,
+	riscv.REG_F14,
+	riscv.REG_F15,
+	riscv.REG_F16,
+	riscv.REG_F17,
+	riscv.REG_F18,
+	riscv.REG_F19,
+	riscv.REG_F20,
+	riscv.REG_F21,
+	riscv.REG_F22,
+	riscv.REG_F23,
+	riscv.REG_F24,
+	riscv.REG_F25,
+	riscv.REG_F26,
+	riscv.REG_F27,
+	riscv.REG_F28,
+	riscv.REG_F29,
+	riscv.REG_F30,
+	riscv.REG_F31,
+	0, // SB isn't a real register.  We fill an Addr.Reg field with 0 in this case.
+}
+
+func loadByType(t *types.Type) obj.As {
+	width := t.Size()
+
+	if t.IsFloat() {
+		switch width {
+		case 4:
+			return riscv.AMOVF
+		case 8:
+			return riscv.AMOVD
+		default:
+			gc.Fatalf("unknown float width for load %d in type %v", width, t)
+			return 0
+		}
+	}
+
+	switch width {
+	case 1:
+		if t.IsSigned() {
+			return riscv.AMOVB
+		} else {
+			return riscv.AMOVBU
+		}
+	case 2:
+		if t.IsSigned() {
+			return riscv.AMOVH
+		} else {
+			return riscv.AMOVHU
+		}
+	case 4:
+		if t.IsSigned() {
+			return riscv.AMOVW
+		} else {
+			return riscv.AMOVWU
+		}
+	case 8:
+		return riscv.AMOV
+	default:
+		gc.Fatalf("unknown width for load %d in type %v", width, t)
+		return 0
+	}
+}
+
+// storeByType returns the store instruction of the given type.
+func storeByType(t *types.Type) obj.As {
+	width := t.Size()
+
+	if t.IsFloat() {
+		switch width {
+		case 4:
+			return riscv.AMOVF
+		case 8:
+			return riscv.AMOVD
+		default:
+			gc.Fatalf("unknown float width for store %d in type %v", width, t)
+			return 0
+		}
+	}
+
+	switch width {
+	case 1:
+		return riscv.AMOVB
+	case 2:
+		return riscv.AMOVH
+	case 4:
+		return riscv.AMOVW
+	case 8:
+		return riscv.AMOV
+	default:
+		gc.Fatalf("unknown width for store %d in type %v", width, t)
+		return 0
+	}
+}
+
+// largestMove returns the largest move instruction possible and its size,
+// given the alignment of the total size of the move.
+//
+// e.g., a 16-byte move may use MOV, but an 11-byte move must use MOVB.
+//
+// Note that the moves may not be on naturally aligned addresses depending on
+// the source and destination.
+//
+// This matches the calculation in ssa.moveSize.
+func largestMove(alignment int64) (obj.As, int64) {
+	switch {
+	case alignment%8 == 0:
+		return riscv.AMOV, 8
+	case alignment%4 == 0:
+		return riscv.AMOVW, 4
+	case alignment%2 == 0:
+		return riscv.AMOVH, 2
+	default:
+		return riscv.AMOVB, 1
+	}
+}
+
+// markMoves marks any MOVXconst ops that need to avoid clobbering flags.
+// RISC-V has no flags, so this is a no-op.
+func ssaMarkMoves(s *gc.SSAGenState, b *ssa.Block) {}
+
+func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
+	s.SetPos(v.Pos)
+
+	switch v.Op {
+	case ssa.OpInitMem:
+		// memory arg needs no code
+	case ssa.OpArg:
+		// input args need no code
+	case ssa.OpPhi:
+		gc.CheckLoweredPhi(v)
+	case ssa.OpCopy, ssa.OpRISCV64MOVconvert:
+		if v.Type.IsMemory() {
+			return
+		}
+		rs := v.Args[0].Reg()
+		rd := v.Reg()
+		if rs == rd {
+			return
+		}
+		as := riscv.AMOV
+		if v.Type.IsFloat() {
+			as = riscv.AMOVD
+		}
+		p := s.Prog(as)
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = rs
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = rd
+	case ssa.OpLoadReg:
+		if v.Type.IsFlags() {
+			v.Fatalf("load flags not implemented: %v", v.LongString())
+			return
+		}
+		p := s.Prog(loadByType(v.Type))
+		gc.AddrAuto(&p.From, v.Args[0])
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = v.Reg()
+	case ssa.OpStoreReg:
+		if v.Type.IsFlags() {
+			v.Fatalf("store flags not implemented: %v", v.LongString())
+			return
+		}
+		p := s.Prog(storeByType(v.Type))
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = v.Args[0].Reg()
+		gc.AddrAuto(&p.To, v)
+	case ssa.OpSP, ssa.OpSB, ssa.OpGetG:
+		// nothing to do
+	case ssa.OpRISCV64ADD, ssa.OpRISCV64SUB, ssa.OpRISCV64XOR, ssa.OpRISCV64OR, ssa.OpRISCV64AND,
+		ssa.OpRISCV64SLL, ssa.OpRISCV64SRA, ssa.OpRISCV64SRL,
+		ssa.OpRISCV64SLT, ssa.OpRISCV64SLTU, ssa.OpRISCV64MUL, ssa.OpRISCV64MULW, ssa.OpRISCV64MULH,
+		ssa.OpRISCV64MULHU, ssa.OpRISCV64DIV, ssa.OpRISCV64DIVU, ssa.OpRISCV64DIVW,
+		ssa.OpRISCV64DIVUW, ssa.OpRISCV64REM, ssa.OpRISCV64REMU, ssa.OpRISCV64REMW,
+		ssa.OpRISCV64REMUW,
+		ssa.OpRISCV64FADDS, ssa.OpRISCV64FSUBS, ssa.OpRISCV64FMULS, ssa.OpRISCV64FDIVS,
+		ssa.OpRISCV64FEQS, ssa.OpRISCV64FNES, ssa.OpRISCV64FLTS, ssa.OpRISCV64FLES,
+		ssa.OpRISCV64FADDD, ssa.OpRISCV64FSUBD, ssa.OpRISCV64FMULD, ssa.OpRISCV64FDIVD,
+		ssa.OpRISCV64FEQD, ssa.OpRISCV64FNED, ssa.OpRISCV64FLTD, ssa.OpRISCV64FLED:
+		r := v.Reg()
+		r1 := v.Args[0].Reg()
+		r2 := v.Args[1].Reg()
+		p := s.Prog(v.Op.Asm())
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = r2
+		p.Reg = r1
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = r
+	case ssa.OpRISCV64FSQRTS, ssa.OpRISCV64FNEGS, ssa.OpRISCV64FSQRTD, ssa.OpRISCV64FNEGD,
+		ssa.OpRISCV64FMVSX, ssa.OpRISCV64FMVDX,
+		ssa.OpRISCV64FCVTSW, ssa.OpRISCV64FCVTSL, ssa.OpRISCV64FCVTWS, ssa.OpRISCV64FCVTLS,
+		ssa.OpRISCV64FCVTDW, ssa.OpRISCV64FCVTDL, ssa.OpRISCV64FCVTWD, ssa.OpRISCV64FCVTLD, ssa.OpRISCV64FCVTDS, ssa.OpRISCV64FCVTSD:
+		p := s.Prog(v.Op.Asm())
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = v.Args[0].Reg()
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = v.Reg()
+	case ssa.OpRISCV64ADDI, ssa.OpRISCV64XORI, ssa.OpRISCV64ORI, ssa.OpRISCV64ANDI,
+		ssa.OpRISCV64SLLI, ssa.OpRISCV64SRAI, ssa.OpRISCV64SRLI, ssa.OpRISCV64SLTI,
+		ssa.OpRISCV64SLTIU:
+		p := s.Prog(v.Op.Asm())
+		p.From.Type = obj.TYPE_CONST
+		p.From.Offset = v.AuxInt
+		p.Reg = v.Args[0].Reg()
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = v.Reg()
+	case ssa.OpRISCV64MOVBconst, ssa.OpRISCV64MOVHconst, ssa.OpRISCV64MOVWconst, ssa.OpRISCV64MOVDconst:
+		p := s.Prog(v.Op.Asm())
+		p.From.Type = obj.TYPE_CONST
+		p.From.Offset = v.AuxInt
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = v.Reg()
+	case ssa.OpRISCV64MOVaddr:
+		p := s.Prog(v.Op.Asm())
+		p.From.Type = obj.TYPE_ADDR
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = v.Reg()
+
+		var wantreg string
+		// MOVW $sym+off(base), R
+		switch v.Aux.(type) {
+		default:
+			v.Fatalf("aux is of unknown type %T", v.Aux)
+		case *obj.LSym:
+			wantreg = "SB"
+			gc.AddAux(&p.From, v)
+		case *gc.Node:
+			wantreg = "SP"
+			gc.AddAux(&p.From, v)
+		case nil:
+			// No sym, just MOVW $off(SP), R
+			wantreg = "SP"
+			p.From.Reg = riscv.REG_SP
+			p.From.Offset = v.AuxInt
+		}
+		if reg := v.Args[0].RegName(); reg != wantreg {
+			v.Fatalf("bad reg %s for symbol type %T, want %s", reg, v.Aux, wantreg)
+		}
+	case ssa.OpRISCV64MOVBload, ssa.OpRISCV64MOVHload, ssa.OpRISCV64MOVWload, ssa.OpRISCV64MOVDload,
+		ssa.OpRISCV64MOVBUload, ssa.OpRISCV64MOVHUload, ssa.OpRISCV64MOVWUload,
+		ssa.OpRISCV64FMOVWload, ssa.OpRISCV64FMOVDload:
+		p := s.Prog(v.Op.Asm())
+		p.From.Type = obj.TYPE_MEM
+		p.From.Reg = v.Args[0].Reg()
+		gc.AddAux(&p.From, v)
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = v.Reg()
+	case ssa.OpRISCV64MOVBstore, ssa.OpRISCV64MOVHstore, ssa.OpRISCV64MOVWstore, ssa.OpRISCV64MOVDstore,
+		ssa.OpRISCV64FMOVWstore, ssa.OpRISCV64FMOVDstore:
+		p := s.Prog(v.Op.Asm())
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = v.Args[1].Reg()
+		p.To.Type = obj.TYPE_MEM
+		p.To.Reg = v.Args[0].Reg()
+		gc.AddAux(&p.To, v)
+	case ssa.OpRISCV64SEQZ, ssa.OpRISCV64SNEZ:
+		p := s.Prog(v.Op.Asm())
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = v.Args[0].Reg()
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = v.Reg()
+	case ssa.OpRISCV64CALLstatic, ssa.OpRISCV64CALLclosure, ssa.OpRISCV64CALLinter:
+		s.Call(v)
+	case ssa.OpRISCV64LoweredWB:
+		p := s.Prog(obj.ACALL)
+		p.To.Type = obj.TYPE_MEM
+		p.To.Name = obj.NAME_EXTERN
+		p.To.Sym = v.Aux.(*obj.LSym)
+	case ssa.OpRISCV64LoweredPanicBoundsA, ssa.OpRISCV64LoweredPanicBoundsB, ssa.OpRISCV64LoweredPanicBoundsC:
+		p := s.Prog(obj.ACALL)
+		p.To.Type = obj.TYPE_MEM
+		p.To.Name = obj.NAME_EXTERN
+		p.To.Sym = gc.BoundsCheckFunc[v.AuxInt]
+		s.UseArgs(16) // space used in callee args area by assembly stubs
+	case ssa.OpRISCV64LoweredZero:
+		mov, sz := largestMove(v.AuxInt)
+
+		//	mov	ZERO, (Rarg0)
+		//	ADD	$sz, Rarg0
+		//	BGEU	Rarg1, Rarg0, -2(PC)
+
+		p := s.Prog(mov)
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = riscv.REG_ZERO
+		p.To.Type = obj.TYPE_MEM
+		p.To.Reg = v.Args[0].Reg()
+
+		p2 := s.Prog(riscv.AADD)
+		p2.From.Type = obj.TYPE_CONST
+		p2.From.Offset = sz
+		p2.To.Type = obj.TYPE_REG
+		p2.To.Reg = v.Args[0].Reg()
+
+		p3 := s.Prog(riscv.ABGEU)
+		p3.To.Type = obj.TYPE_BRANCH
+		p3.Reg = v.Args[0].Reg()
+		p3.From.Type = obj.TYPE_REG
+		p3.From.Reg = v.Args[1].Reg()
+		gc.Patch(p3, p)
+
+	case ssa.OpRISCV64LoweredMove:
+		mov, sz := largestMove(v.AuxInt)
+
+		//	mov	(Rarg1), T2
+		//	mov	T2, (Rarg0)
+		//	ADD	$sz, Rarg0
+		//	ADD	$sz, Rarg1
+		//	BGEU	Rarg2, Rarg0, -4(PC)
+
+		p := s.Prog(mov)
+		p.From.Type = obj.TYPE_MEM
+		p.From.Reg = v.Args[1].Reg()
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = riscv.REG_T2
+
+		p2 := s.Prog(mov)
+		p2.From.Type = obj.TYPE_REG
+		p2.From.Reg = riscv.REG_T2
+		p2.To.Type = obj.TYPE_MEM
+		p2.To.Reg = v.Args[0].Reg()
+
+		p3 := s.Prog(riscv.AADD)
+		p3.From.Type = obj.TYPE_CONST
+		p3.From.Offset = sz
+		p3.To.Type = obj.TYPE_REG
+		p3.To.Reg = v.Args[0].Reg()
+
+		p4 := s.Prog(riscv.AADD)
+		p4.From.Type = obj.TYPE_CONST
+		p4.From.Offset = sz
+		p4.To.Type = obj.TYPE_REG
+		p4.To.Reg = v.Args[1].Reg()
+
+		p5 := s.Prog(riscv.ABGEU)
+		p5.To.Type = obj.TYPE_BRANCH
+		p5.Reg = v.Args[1].Reg()
+		p5.From.Type = obj.TYPE_REG
+		p5.From.Reg = v.Args[2].Reg()
+		gc.Patch(p5, p)
+
+	case ssa.OpRISCV64LoweredNilCheck:
+		// Issue a load which will fault if arg is nil.
+		// TODO: optimizations. See arm and amd64 LoweredNilCheck.
+		p := s.Prog(riscv.AMOVB)
+		p.From.Type = obj.TYPE_MEM
+		p.From.Reg = v.Args[0].Reg()
+		gc.AddAux(&p.From, v)
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = riscv.REG_ZERO
+		if gc.Debug_checknil != 0 && v.Pos.Line() > 1 { // v.Pos == 1 in generated wrappers
+			gc.Warnl(v.Pos, "generated nil check")
+		}
+
+	case ssa.OpRISCV64LoweredGetClosurePtr:
+		// Closure pointer is S4 (riscv.REG_CTXT).
+		gc.CheckLoweredGetClosurePtr(v)
+
+	case ssa.OpRISCV64LoweredGetCallerSP:
+		// caller's SP is FixedFrameSize below the address of the first arg
+		p := s.Prog(riscv.AMOV)
+		p.From.Type = obj.TYPE_ADDR
+		p.From.Offset = -gc.Ctxt.FixedFrameSize()
+		p.From.Name = obj.NAME_PARAM
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = v.Reg()
+
+	case ssa.OpRISCV64LoweredGetCallerPC:
+		p := s.Prog(obj.AGETCALLERPC)
+		p.To.Type = obj.TYPE_REG
+		p.To.Reg = v.Reg()
+
+	default:
+		v.Fatalf("Unhandled op %v", v.Op)
+	}
+}
+
+func ssaGenBlock(s *gc.SSAGenState, b, next *ssa.Block) {
+	s.SetPos(b.Pos)
+
+	switch b.Kind {
+	case ssa.BlockDefer:
+		// defer returns in A0:
+		// 0 if we should continue executing
+		// 1 if we should jump to deferreturn call
+		p := s.Prog(riscv.ABNE)
+		p.To.Type = obj.TYPE_BRANCH
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = riscv.REG_ZERO
+		p.Reg = riscv.REG_A0
+		s.Branches = append(s.Branches, gc.Branch{P: p, B: b.Succs[1].Block()})
+		if b.Succs[0].Block() != next {
+			p := s.Prog(obj.AJMP)
+			p.To.Type = obj.TYPE_BRANCH
+			s.Branches = append(s.Branches, gc.Branch{P: p, B: b.Succs[0].Block()})
+		}
+	case ssa.BlockPlain:
+		if b.Succs[0].Block() != next {
+			p := s.Prog(obj.AJMP)
+			p.To.Type = obj.TYPE_BRANCH
+			s.Branches = append(s.Branches, gc.Branch{P: p, B: b.Succs[0].Block()})
+		}
+	case ssa.BlockExit:
+	case ssa.BlockRet:
+		s.Prog(obj.ARET)
+	case ssa.BlockRetJmp:
+		p := s.Prog(obj.AJMP)
+		p.To.Type = obj.TYPE_MEM
+		p.To.Name = obj.NAME_EXTERN
+		p.To.Sym = b.Aux.(*obj.LSym)
+	case ssa.BlockRISCV64BNE:
+		var p *obj.Prog
+		switch next {
+		case b.Succs[0].Block():
+			p = s.Br(riscv.ABNE, b.Succs[1].Block())
+			p.As = riscv.InvertBranch(p.As)
+		case b.Succs[1].Block():
+			p = s.Br(riscv.ABNE, b.Succs[0].Block())
+		default:
+			if b.Likely != ssa.BranchUnlikely {
+				p = s.Br(riscv.ABNE, b.Succs[0].Block())
+				s.Br(obj.AJMP, b.Succs[1].Block())
+			} else {
+				p = s.Br(riscv.ABNE, b.Succs[1].Block())
+				p.As = riscv.InvertBranch(p.As)
+				s.Br(obj.AJMP, b.Succs[0].Block())
+			}
+		}
+		p.Reg = b.Controls[0].Reg()
+		p.From.Type = obj.TYPE_REG
+		p.From.Reg = riscv.REG_ZERO
+
+	default:
+		b.Fatalf("Unhandled block: %s", b.LongString())
+	}
+}