cmd/internal/obj/arm64: load large constants into vector registers from rodata

Load large constants into vector registers from rodata, instead of placing them
in the literal pool. This treats VMOVQ/VMOVD/VMOVS the same as FMOVD/FMOVS and
makes use of the existing mechanism for storing values in rodata. Two additional
instructions are required for a load, however these instructions are used
infrequently and already have a high latency.

Updates #59615

Change-Id: I54226730267689963d73321e548733ae2d66740e
Reviewed-on: https://go-review.googlesource.com/c/go/+/515617
Reviewed-by: Eric Fang <eric.fang@arm.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Run-TryBot: Joel Sing <joel@sing.id.au>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/cmd/internal/obj/arm64/asm7.go

@@ -282,7 +282,6 @@ func MOVCONST(d int64, s int, rt int) uint32 {
 const (
 	// Optab.flag
 	LFROM        = 1 << iota // p.From uses constant pool
-	LFROM128                 // p.From3<<64+p.From forms a 128-bit constant in literal pool
 	LTO                      // p.To uses constant pool
 	NOTUSETMP                // p expands to multiple instructions, but does NOT use REGTMP
 	BRANCH14BITS             // branch instruction encodes 14 bits
@@ -423,10 +422,10 @@ var optab = []Optab{
 	/* load long effective stack address (load int32 offset and add) */
 	{AMOVD, C_LACON, C_NONE, C_NONE, C_RSP, C_NONE, 34, 8, REGSP, LFROM, 0},
 
-	// Move a large constant to a vector register.
+	// Load a large constant into a vector register.
-	{AVMOVQ, C_VCON, C_NONE, C_VCON, C_VREG, C_NONE, 101, 4, 0, LFROM128, 0},
+	{AVMOVS, C_ADDR, C_NONE, C_NONE, C_VREG, C_NONE, 65, 12, 0, 0, 0},
-	{AVMOVD, C_VCON, C_NONE, C_NONE, C_VREG, C_NONE, 101, 4, 0, LFROM, 0},
+	{AVMOVD, C_ADDR, C_NONE, C_NONE, C_VREG, C_NONE, 65, 12, 0, 0, 0},
-	{AVMOVS, C_LCON, C_NONE, C_NONE, C_VREG, C_NONE, 101, 4, 0, LFROM, 0},
+	{AVMOVQ, C_ADDR, C_NONE, C_NONE, C_VREG, C_NONE, 65, 12, 0, 0, 0},
 
 	/* jump operations */
 	{AB, C_NONE, C_NONE, C_NONE, C_SBRA, C_NONE, 5, 4, 0, 0, 0},
@@ -1117,9 +1116,6 @@ func span7(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 		if o.flag&LFROM != 0 {
 			c.addpool(p, &p.From)
 		}
-		if o.flag&LFROM128 != 0 {
-			c.addpool128(p, &p.From, p.GetFrom3())
-		}
 		if o.flag&LTO != 0 {
 			c.addpool(p, &p.To)
 		}
@@ -1321,34 +1317,6 @@ func (c *ctxt7) flushpool(p *obj.Prog) {
 	c.pool.start = 0
 }
 
-// addpool128 adds a 128-bit constant to literal pool by two consecutive DWORD
-// instructions, the 128-bit constant is formed by ah.Offset<<64+al.Offset.
-func (c *ctxt7) addpool128(p *obj.Prog, al, ah *obj.Addr) {
-	q := c.newprog()
-	q.As = ADWORD
-	q.To.Type = obj.TYPE_CONST
-	q.To.Offset = al.Offset // q.Pc is lower than t.Pc, so al.Offset is stored in q.
-
-	t := c.newprog()
-	t.As = ADWORD
-	t.To.Type = obj.TYPE_CONST
-	t.To.Offset = ah.Offset
-
-	q.Link = t
-
-	if c.blitrl == nil {
-		c.blitrl = q
-		c.pool.start = uint32(p.Pc)
-	} else {
-		c.elitrl.Link = q
-	}
-
-	c.elitrl = t
-	c.pool.size = roundUp(c.pool.size, 16)
-	c.pool.size += 16
-	p.Pool = q
-}
-
 /*
  * MOVD foo(SB), R is actually
  *   MOVD addr, REGTMP
@@ -1365,8 +1333,8 @@ func (c *ctxt7) addpool(p *obj.Prog, a *obj.Addr) {
 	sz := 4
 
 	if a.Type == obj.TYPE_CONST {
-		if (lit != int64(int32(lit)) && uint64(lit) != uint64(uint32(lit))) || p.As == AVMOVQ || p.As == AVMOVD {
+		if lit != int64(int32(lit)) && uint64(lit) != uint64(uint32(lit)) {
-			// out of range -0x80000000 ~ 0xffffffff or VMOVQ or VMOVD operand, must store 64-bit.
+			// out of range -0x80000000 ~ 0xffffffff, must store 64-bit.
 			t.As = ADWORD
 			sz = 8
 		} // else store 32-bit
@@ -5660,9 +5628,6 @@ func (c *ctxt7) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		o1 = q<<30 | 0xe<<24 | len<<13 | op<<12
 		o1 |= (uint32(rf&31) << 16) | uint32(offset&31)<<5 | uint32(rt&31)
 
-	case 101: // VMOVQ $vcon1, $vcon2, Vd or VMOVD|VMOVS $vcon, Vd -> FMOVQ/FMOVD/FMOVS pool(PC), Vd: load from constant pool.
-		o1 = c.omovlit(p.As, p, &p.From, int(p.To.Reg))
-
 	case 102: /* vushll, vushll2, vuxtl, vuxtl2 */
 		o1 = c.opirr(p, p.As)
 		rf := p.Reg
@@ -7187,13 +7152,13 @@ func (c *ctxt7) opldr(p *obj.Prog, a obj.As) uint32 {
 	case AMOVBU:
 		return LDSTR(0, 0, 1)
 
-	case AFMOVS:
+	case AFMOVS, AVMOVS:
 		return LDSTR(2, 1, 1)
 
-	case AFMOVD:
+	case AFMOVD, AVMOVD:
 		return LDSTR(3, 1, 1)
 
-	case AFMOVQ:
+	case AFMOVQ, AVMOVQ:
 		return LDSTR(0, 1, 3)
 	}
 

src/cmd/internal/obj/arm64/obj7.go

@@ -329,8 +329,33 @@ func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 		break
 	}
 
-	// Rewrite float constants to values stored in memory.
+	// Rewrite float and vector constants to values stored in memory.
 	switch p.As {
+	case AVMOVS:
+		if p.From.Type == obj.TYPE_CONST {
+			p.From.Type = obj.TYPE_MEM
+			p.From.Sym = c.ctxt.Int32Sym(p.From.Offset)
+			p.From.Name = obj.NAME_EXTERN
+			p.From.Offset = 0
+		}
+
+	case AVMOVD:
+		if p.From.Type == obj.TYPE_CONST {
+			p.From.Type = obj.TYPE_MEM
+			p.From.Sym = c.ctxt.Int64Sym(p.From.Offset)
+			p.From.Name = obj.NAME_EXTERN
+			p.From.Offset = 0
+		}
+
+	case AVMOVQ:
+		if p.From.Type == obj.TYPE_CONST {
+			p.From.Type = obj.TYPE_MEM
+			p.From.Sym = c.ctxt.Int128Sym(p.GetFrom3().Offset, p.From.Offset)
+			p.From.Name = obj.NAME_EXTERN
+			p.From.Offset = 0
+			p.RestArgs = nil
+		}
+
 	case AFMOVS:
 		if p.From.Type == obj.TYPE_FCONST {
 			f64 := p.From.Val.(float64)
@@ -365,8 +390,6 @@ func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 			p.From.Name = obj.NAME_EXTERN
 			p.From.Offset = 0
 		}
-
-		break
 	}
 
 	if c.ctxt.Flag_dynlink {

src/cmd/internal/obj/sym.go

@@ -36,6 +36,7 @@ import (
 	"cmd/internal/notsha256"
 	"cmd/internal/objabi"
 	"encoding/base64"
+	"encoding/binary"
 	"fmt"
 	"internal/buildcfg"
 	"log"
@@ -162,6 +163,18 @@ func (ctxt *Link) Float64Sym(f float64) *LSym {
 	})
 }
 
+func (ctxt *Link) Int32Sym(i int64) *LSym {
+	name := fmt.Sprintf("$i32.%08x", uint64(i))
+	return ctxt.LookupInit(name, func(s *LSym) {
+		s.Size = 4
+		s.WriteInt(ctxt, 0, 4, i)
+		s.Type = objabi.SRODATA
+		s.Set(AttrLocal, true)
+		s.Set(AttrContentAddressable, true)
+		ctxt.constSyms = append(ctxt.constSyms, s)
+	})
+}
+
 func (ctxt *Link) Int64Sym(i int64) *LSym {
 	name := fmt.Sprintf("$i64.%016x", uint64(i))
 	return ctxt.LookupInit(name, func(s *LSym) {
@@ -174,6 +187,24 @@ func (ctxt *Link) Int64Sym(i int64) *LSym {
 	})
 }
 
+func (ctxt *Link) Int128Sym(hi, lo int64) *LSym {
+	name := fmt.Sprintf("$i128.%016x%016x", uint64(hi), uint64(lo))
+	return ctxt.LookupInit(name, func(s *LSym) {
+		s.Size = 16
+		if ctxt.Arch.ByteOrder == binary.LittleEndian {
+			s.WriteInt(ctxt, 0, 8, lo)
+			s.WriteInt(ctxt, 8, 8, hi)
+		} else {
+			s.WriteInt(ctxt, 0, 8, hi)
+			s.WriteInt(ctxt, 8, 8, lo)
+		}
+		s.Type = objabi.SRODATA
+		s.Set(AttrLocal, true)
+		s.Set(AttrContentAddressable, true)
+		ctxt.constSyms = append(ctxt.constSyms, s)
+	})
+}
+
 // GCLocalsSym generates a content-addressable sym containing data.
 func (ctxt *Link) GCLocalsSym(data []byte) *LSym {
 	sum := notsha256.Sum256(data)