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cmd/internal/obj/riscv: implement MOV pseudo-instructions

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Add support for rewriting MOV pseudo-instructions into appropriate
RISC-V instructions.

Based on the riscv-go port.

Updates #27532

Change-Id: I22da6f5f12c841d56fb676ab2a37f6d0a686b033
Reviewed-on: https://go-review.googlesource.com/c/go/+/198677
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Joel Sing 2019-10-04 04:02:38 +10:00
parent 1ed932d22b
commit a04aa1f6d1
2 changed files with 368 additions and 0 deletions
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30
src/cmd/asm/internal/asm/testdata/riscvenc.s vendored
View File

@ -237,3 +237,33 @@ start:
// Arbitrary bytes (entered in little-endian mode)
WORD $0x12345678 // WORD $305419896 // 78563412
WORD $0x9abcdef0 // WORD $2596069104 // f0debc9a
// MOV pseudo-instructions
MOV X5, X6 // 13830200
MOV $2047, X5 // 9b02f07f
MOV $-2048, X5 // 9b020080
MOV (X5), X6 // 03b30200
MOV 4(X5), X6 // 03b34200
MOVB (X5), X6 // 03830200
MOVB 4(X5), X6 // 03834200
MOVH (X5), X6 // 03930200
MOVH 4(X5), X6 // 03934200
MOVW (X5), X6 // 03a30200
MOVW 4(X5), X6 // 03a34200
MOV X5, (X6) // 23305300
MOV X5, 4(X6) // 23325300
MOVB X5, (X6) // 23005300
MOVB X5, 4(X6) // 23025300
MOVH X5, (X6) // 23105300
MOVH X5, 4(X6) // 23125300
MOVW X5, (X6) // 23205300
MOVW X5, 4(X6) // 23225300
MOVF 4(X5), F0 // 07a04200
MOVF F0, 4(X5) // 27a20200
MOVF F0, F1 // d3000020
MOVD 4(X5), F0 // 07b04200
MOVD F0, 4(X5) // 27b20200
MOVD F0, F1 // d3000022

338
src/cmd/internal/obj/riscv/obj.go
View File

@ -148,6 +148,248 @@ func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
}
}
// addrToReg extracts the register from an Addr, handling special Addr.Names.
func addrToReg(a obj.Addr) int16 {
switch a.Name {
case obj.NAME_PARAM, obj.NAME_AUTO:
return REG_SP
}
return a.Reg
}
// movToLoad converts a MOV mnemonic into the corresponding load instruction.
func movToLoad(mnemonic obj.As) obj.As {
switch mnemonic {
case AMOV:
return ALD
case AMOVB:
return ALB
case AMOVH:
return ALH
case AMOVW:
return ALW
case AMOVBU:
return ALBU
case AMOVHU:
return ALHU
case AMOVWU:
return ALWU
case AMOVF:
return AFLW
case AMOVD:
return AFLD
default:
panic(fmt.Sprintf("%+v is not a MOV", mnemonic))
}
}
// movToStore converts a MOV mnemonic into the corresponding store instruction.
func movToStore(mnemonic obj.As) obj.As {
switch mnemonic {
case AMOV:
return ASD
case AMOVB:
return ASB
case AMOVH:
return ASH
case AMOVW:
return ASW
case AMOVF:
return AFSW
case AMOVD:
return AFSD
default:
panic(fmt.Sprintf("%+v is not a MOV", mnemonic))
}
}
// rewriteMOV rewrites MOV pseudo-instructions.
func rewriteMOV(ctxt *obj.Link, newprog obj.ProgAlloc, p *obj.Prog) {
switch p.As {
case AMOV, AMOVB, AMOVH, AMOVW, AMOVBU, AMOVHU, AMOVWU, AMOVF, AMOVD:
default:
panic(fmt.Sprintf("%+v is not a MOV pseudo-instruction", p.As))
}
switch p.From.Type {
case obj.TYPE_MEM: // MOV c(Rs), Rd -> L $c, Rs, Rd
switch p.From.Name {
case obj.NAME_AUTO, obj.NAME_PARAM, obj.NAME_NONE:
if p.To.Type != obj.TYPE_REG {
ctxt.Diag("unsupported load at %v", p)
}
p.As = movToLoad(p.As)
p.Reg = addrToReg(p.From)
p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: p.From.Offset}
case obj.NAME_EXTERN, obj.NAME_STATIC:
// AUIPC $off_hi, R
// L $off_lo, R
as := p.As
to := p.To
// The offset is not really encoded with either instruction.
// It will be extracted later for a relocation.
p.As = AAUIPC
p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: p.From.Offset, Sym: p.From.Sym}
p.Reg = 0
p.To = obj.Addr{Type: obj.TYPE_REG, Reg: to.Reg}
p.Mark |= NEED_PCREL_ITYPE_RELOC
p = obj.Appendp(p, newprog)
p.As = movToLoad(as)
p.From = obj.Addr{Type: obj.TYPE_CONST}
p.Reg = to.Reg
p.To = to
default:
ctxt.Diag("unsupported name %d for %v", p.From.Name, p)
}
case obj.TYPE_REG:
switch p.To.Type {
case obj.TYPE_REG:
switch p.As {
case AMOV: // MOV Ra, Rb -> ADDI $0, Ra, Rb
p.As = AADDI
p.Reg = p.From.Reg
p.From = obj.Addr{Type: obj.TYPE_CONST}
case AMOVF: // MOVF Ra, Rb -> FSGNJS Ra, Ra, Rb
p.As = AFSGNJS
p.Reg = p.From.Reg
case AMOVD: // MOVD Ra, Rb -> FSGNJD Ra, Ra, Rb
p.As = AFSGNJD
p.Reg = p.From.Reg
default:
ctxt.Diag("unsupported register-register move at %v", p)
}
case obj.TYPE_MEM: // MOV Rs, c(Rd) -> S $c, Rs, Rd
switch p.As {
case AMOVBU, AMOVHU, AMOVWU:
ctxt.Diag("unsupported unsigned store at %v", p)
}
switch p.To.Name {
case obj.NAME_AUTO, obj.NAME_PARAM, obj.NAME_NONE:
// The destination address goes in p.From and p.To here,
// with the offset in p.From and the register in p.To.
// The source register goes in Reg.
p.As = movToStore(p.As)
p.Reg = p.From.Reg
p.From = p.To
p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: p.From.Offset}
p.To = obj.Addr{Type: obj.TYPE_REG, Reg: addrToReg(p.To)}
case obj.NAME_EXTERN:
// AUIPC $off_hi, TMP
// S $off_lo, TMP, R
as := p.As
from := p.From
// The offset is not really encoded with either instruction.
// It will be extracted later for a relocation.
p.As = AAUIPC
p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: p.To.Offset, Sym: p.To.Sym}
p.Reg = 0
p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
p.Mark |= NEED_PCREL_STYPE_RELOC
p = obj.Appendp(p, newprog)
p.As = movToStore(as)
p.From = obj.Addr{Type: obj.TYPE_CONST}
p.Reg = from.Reg
p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
default:
ctxt.Diag("unsupported name %d for %v", p.From.Name, p)
}
default:
ctxt.Diag("unsupported MOV at %v", p)
}
case obj.TYPE_CONST:
// MOV $c, R
// If c is small enough, convert to:
// ADD $c, ZERO, R
// If not, convert to:
// LUI top20bits(c), R
// ADD bottom12bits(c), R, R
if p.As != AMOV {
ctxt.Diag("unsupported constant load at %v", p)
}
off := p.From.Offset
to := p.To
low, high, err := split32BitImmediate(off)
if err != nil {
ctxt.Diag("%v: constant %d too large: %v", p, off, err)
}
// LUI is only necessary if the offset doesn't fit in 12-bits.
needLUI := high != 0
if needLUI {
p.As = ALUI
p.To = to
// Pass top 20 bits to LUI.
p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: high}
p = obj.Appendp(p, newprog)
}
p.As = AADDIW
p.To = to
p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: low}
p.Reg = REG_ZERO
if needLUI {
p.Reg = to.Reg
}
case obj.TYPE_ADDR: // MOV $sym+off(SP/SB), R
if p.To.Type != obj.TYPE_REG || p.As != AMOV {
ctxt.Diag("unsupported addr MOV at %v", p)
}
switch p.From.Name {
case obj.NAME_EXTERN, obj.NAME_STATIC:
// AUIPC $off_hi, R
// ADDI $off_lo, R
to := p.To
// The offset is not really encoded with either instruction.
// It will be extracted later for a relocation.
p.As = AAUIPC
p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: p.From.Offset, Sym: p.From.Sym}
p.Reg = 0
p.To = to
p.Mark |= NEED_PCREL_ITYPE_RELOC
p = obj.Appendp(p, newprog)
p.As = AADDI
p.From = obj.Addr{Type: obj.TYPE_CONST}
p.Reg = to.Reg
p.To = to
case obj.NAME_PARAM, obj.NAME_AUTO:
p.As = AADDI
p.Reg = REG_SP
p.From.Type = obj.TYPE_CONST
case obj.NAME_NONE:
p.As = AADDI
p.Reg = p.From.Reg
p.From.Type = obj.TYPE_CONST
p.From.Reg = 0
default:
ctxt.Diag("bad addr MOV from name %v at %v", p.From.Name, p)
}
default:
ctxt.Diag("unsupported MOV at %v", p)
}
}
// setPCs sets the Pc field in all instructions reachable from p.
// It uses pc as the initial value.
func setPCs(p *obj.Prog, pc int64) {
@ -157,6 +399,44 @@ func setPCs(p *obj.Prog, pc int64) {
}
}
// stackOffset updates Addr offsets based on the current stack size.
//
// The stack looks like:
// -------------------
// | |
// | PARAMs |
// | |
// | |
// -------------------
// | Parent RA | SP on function entry
// -------------------
// | |
// | |
// | AUTOs |
// | |
// | |
// -------------------
// | RA | SP during function execution
// -------------------
//
// FixedFrameSize makes other packages aware of the space allocated for RA.
//
// A nicer version of this diagram can be found on slide 21 of the presentation
// attached to:
//
// https://golang.org/issue/16922#issuecomment-243748180
//
func stackOffset(a *obj.Addr, stacksize int64) {
switch a.Name {
case obj.NAME_AUTO:
// Adjust to the top of AUTOs.
a.Offset += stacksize
case obj.NAME_PARAM:
// Adjust to the bottom of PARAMs.
a.Offset += stacksize + 8
}
}
func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
if cursym.Func.Text == nil || cursym.Func.Text.Link == nil {
return
@ -188,6 +468,24 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
// TODO(jsing): Implement.
// Update stack-based offsets.
for p := cursym.Func.Text; p != nil; p = p.Link {
stackOffset(&p.From, stacksize)
stackOffset(&p.To, stacksize)
}
// Additional instruction rewriting. Any rewrites that change the number
// of instructions must occur here (before jump target resolution).
for p := cursym.Func.Text; p != nil; p = p.Link {
switch p.As {
case AMOV, AMOVB, AMOVH, AMOVW, AMOVBU, AMOVHU, AMOVWU, AMOVF, AMOVD:
// Rewrite MOV pseudo-instructions. This cannot be done in
// progedit, as SP offsets need to be applied before we split
// up some of the Addrs.
rewriteMOV(ctxt, newprog, p)
}
}
setPCs(cursym.Func.Text, 0)
// Resolve branch and jump targets.
@ -209,6 +507,46 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
}
}
// signExtend sign extends val starting at bit bit.
func signExtend(val int64, bit uint) int64 {
return val << (64 - bit) >> (64 - bit)
}
// split32BitImmediate splits a signed 32-bit immediate into a signed 20-bit
// upper immediate and a signed 12-bit lower immediate to be added to the upper
// result. For example, high may be used in LUI and low in a following ADDI to
// generate a full 32-bit constant.
func split32BitImmediate(imm int64) (low, high int64, err error) {
if !immIFits(imm, 32) {
return 0, 0, fmt.Errorf("immediate does not fit in 32-bits: %d", imm)
}
// Nothing special needs to be done if the immediate fits in 12-bits.
if immIFits(imm, 12) {
return imm, 0, nil
}
high = imm >> 12
// The bottom 12 bits will be treated as signed.
//
// If that will result in a negative 12 bit number, add 1 to
// our upper bits to adjust for the borrow.
//
// It is not possible for this increment to overflow. To
// overflow, the 20 top bits would be 1, and the sign bit for
// the low 12 bits would be set, in which case the entire 32
// bit pattern fits in a 12 bit signed value.
if imm&(1<<11) != 0 {
high++
}
low = signExtend(imm, 12)
high = signExtend(high, 20)
return low, high, nil
}
func regVal(r, min, max int16) uint32 {
if r < min || r > max {
panic(fmt.Sprintf("register out of range, want %d < %d < %d", min, r, max))