cmd/internal/obj/arm64, cmd/link: use two instructions rather than three for loads from memory

Reduces size of godoc .text section by about 75k (or 1.4%).

Change-Id: I65850aa569aefbddd6cb07c6ae1addcc39cab6a5
Reviewed-on: https://go-review.googlesource.com/13993Reviewed-by: Russ Cox <rsc@golang.org>

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

@@ -260,16 +260,16 @@ var optab = []Optab{
 	{AMOVW, C_VCONADDR, C_NONE, C_REG, 68, 8, 0, 0, 0},
 	{AMOVD, C_VCON, C_NONE, C_REG, 12, 4, 0, LFROM, 0},
 	{AMOVD, C_VCONADDR, C_NONE, C_REG, 68, 8, 0, 0, 0},
-	{AMOVB, C_REG, C_NONE, C_ADDR, 64, 12, 0, 0, 0},
-	{AMOVBU, C_REG, C_NONE, C_ADDR, 64, 12, 0, 0, 0},
-	{AMOVH, C_REG, C_NONE, C_ADDR, 64, 12, 0, 0, 0},
-	{AMOVW, C_REG, C_NONE, C_ADDR, 64, 12, 0, 0, 0},
-	{AMOVD, C_REG, C_NONE, C_ADDR, 64, 12, 0, 0, 0},
-	{AMOVB, C_ADDR, C_NONE, C_REG, 65, 12, 0, 0, 0},
-	{AMOVBU, C_ADDR, C_NONE, C_REG, 65, 12, 0, 0, 0},
-	{AMOVH, C_ADDR, C_NONE, C_REG, 65, 12, 0, 0, 0},
-	{AMOVW, C_ADDR, C_NONE, C_REG, 65, 12, 0, 0, 0},
-	{AMOVD, C_ADDR, C_NONE, C_REG, 65, 12, 0, 0, 0},
+	{AMOVB, C_REG, C_NONE, C_ADDR, 64, 8, 0, 0, 0},
+	{AMOVBU, C_REG, C_NONE, C_ADDR, 64, 8, 0, 0, 0},
+	{AMOVH, C_REG, C_NONE, C_ADDR, 64, 8, 0, 0, 0},
+	{AMOVW, C_REG, C_NONE, C_ADDR, 64, 8, 0, 0, 0},
+	{AMOVD, C_REG, C_NONE, C_ADDR, 64, 8, 0, 0, 0},
+	{AMOVB, C_ADDR, C_NONE, C_REG, 65, 8, 0, 0, 0},
+	{AMOVBU, C_ADDR, C_NONE, C_REG, 65, 8, 0, 0, 0},
+	{AMOVH, C_ADDR, C_NONE, C_REG, 65, 8, 0, 0, 0},
+	{AMOVW, C_ADDR, C_NONE, C_REG, 65, 8, 0, 0, 0},
+	{AMOVD, C_ADDR, C_NONE, C_REG, 65, 8, 0, 0, 0},
 	{AMOVD, C_TLS_LE, C_NONE, C_REG, 69, 4, 0, 0, 0},
 	{AMOVD, C_TLS_IE, C_NONE, C_REG, 70, 8, 0, 0, 0},
 	{AMUL, C_REG, C_REG, C_REG, 15, 4, 0, 0, 0},
@@ -450,10 +450,10 @@ var optab = []Optab{
 	{AFMOVS, C_LOREG, C_NONE, C_FREG, 31, 8, 0, LFROM, 0},
 	{AFMOVD, C_LAUTO, C_NONE, C_FREG, 31, 8, REGSP, LFROM, 0},
 	{AFMOVD, C_LOREG, C_NONE, C_FREG, 31, 8, 0, LFROM, 0},
-	{AFMOVS, C_FREG, C_NONE, C_ADDR, 64, 12, 0, 0, 0},
-	{AFMOVS, C_ADDR, C_NONE, C_FREG, 65, 12, 0, 0, 0},
-	{AFMOVD, C_FREG, C_NONE, C_ADDR, 64, 12, 0, 0, 0},
-	{AFMOVD, C_ADDR, C_NONE, C_FREG, 65, 12, 0, 0, 0},
+	{AFMOVS, C_FREG, C_NONE, C_ADDR, 64, 8, 0, 0, 0},
+	{AFMOVS, C_ADDR, C_NONE, C_FREG, 65, 8, 0, 0, 0},
+	{AFMOVD, C_FREG, C_NONE, C_ADDR, 64, 8, 0, 0, 0},
+	{AFMOVD, C_ADDR, C_NONE, C_FREG, 65, 8, 0, 0, 0},
 	{AFADDS, C_FREG, C_NONE, C_FREG, 54, 4, 0, 0, 0},
 	{AFADDS, C_FREG, C_FREG, C_FREG, 54, 4, 0, 0, 0},
 	{AFADDS, C_FCON, C_NONE, C_FREG, 54, 4, 0, 0, 0},
@@ -2701,28 +2701,26 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 
 		o1 = ADR(0, uint32(d), uint32(p.To.Reg))
 
-		/* reloc ops */
+	/* reloc ops */
 	case 64: /* movT R,addr -> adrp + add + movT R, (REGTMP) */
 		o1 = ADR(1, 0, REGTMP)
-		o2 = opirr(ctxt, AADD) | REGTMP&31<<5 | REGTMP&31
+		o2 = olsr12u(ctxt, int32(opstr12(ctxt, int(p.As))), 0, REGTMP, int(p.From.Reg))
 		rel := obj.Addrel(ctxt.Cursym)
 		rel.Off = int32(ctxt.Pc)
 		rel.Siz = 8
 		rel.Sym = p.To.Sym
 		rel.Add = p.To.Offset
-		rel.Type = obj.R_ADDRARM64
-		o3 = olsr12u(ctxt, int32(opstr12(ctxt, int(p.As))), 0, REGTMP, int(p.From.Reg))
+		rel.Type = movereloc(p.As)
 
-	case 65: /* movT addr,R -> adrp + add + movT (REGTMP), R */
+	case 65: /* movT addr,R -> adrp REGTMP, 0; ldr R, [REGTMP, #0] + relocs */
 		o1 = ADR(1, 0, REGTMP)
-		o2 = opirr(ctxt, AADD) | REGTMP&31<<5 | REGTMP&31
+		o2 = olsr12u(ctxt, int32(opldr12(ctxt, int(p.As))), 0, REGTMP, int(p.To.Reg))
 		rel := obj.Addrel(ctxt.Cursym)
 		rel.Off = int32(ctxt.Pc)
-		rel.Siz = 8
 		rel.Sym = p.From.Sym
 		rel.Add = p.From.Offset
-		rel.Type = obj.R_ADDRARM64
-		o3 = olsr12u(ctxt, int32(opldr12(ctxt, int(p.As))), 0, REGTMP, int(p.To.Reg))
+		rel.Siz = 8
+		rel.Type = movereloc(p.As)
 
 	case 66: /* ldp O(R)!, (r1, r2); ldp (R)O!, (r1, r2) */
 		v := int32(p.From.Offset)
@@ -4161,3 +4159,19 @@ func movesize(a int) int {
 		return -1
 	}
 }
+
+func movereloc(a int16) int32 {
+	switch movesize(int(a)) {
+	case 0:
+		return obj.R_ARM64_LOAD8
+	case 1:
+		return obj.R_ARM64_LOAD16
+	case 2:
+		return obj.R_ARM64_LOAD32
+	case 3:
+		return obj.R_ARM64_LOAD64
+	case -1:
+		panic("xxx")
+	}
+	return -1
+}

src/cmd/internal/obj/link.go

@@ -457,6 +457,11 @@ const (
 	// referenced (thread local) symbol from the GOT.
 	R_ARM64_TLS_IE
 
+	R_ARM64_LOAD8
+	R_ARM64_LOAD16
+	R_ARM64_LOAD32
+	R_ARM64_LOAD64
+
 	// PPC64.
 
 	// R_POWER_TLS_LE is used to implement the "local exec" model for tls

src/cmd/link/internal/arm64/asm.go

@@ -82,6 +82,30 @@ func elfreloc1(r *ld.Reloc, sectoff int64) int {
 		ld.Thearch.Vput(uint64(sectoff + 4))
 		ld.Thearch.Vput(ld.R_AARCH64_TLSIE_LD64_GOTTPREL_LO12_NC | uint64(elfsym)<<32)
 
+	case obj.R_ARM64_LOAD8:
+		ld.Thearch.Vput(ld.R_AARCH64_ADR_PREL_PG_HI21 | uint64(elfsym)<<32)
+		ld.Thearch.Vput(uint64(r.Xadd))
+		ld.Thearch.Vput(uint64(sectoff + 4))
+		ld.Thearch.Vput(ld.R_AARCH64_LDST8_ABS_LO12_NC | uint64(elfsym)<<32)
+
+	case obj.R_ARM64_LOAD16:
+		ld.Thearch.Vput(ld.R_AARCH64_ADR_PREL_PG_HI21 | uint64(elfsym)<<32)
+		ld.Thearch.Vput(uint64(r.Xadd))
+		ld.Thearch.Vput(uint64(sectoff + 4))
+		ld.Thearch.Vput(ld.R_AARCH64_LDST16_ABS_LO12_NC | uint64(elfsym)<<32)
+
+	case obj.R_ARM64_LOAD32:
+		ld.Thearch.Vput(ld.R_AARCH64_ADR_PREL_PG_HI21 | uint64(elfsym)<<32)
+		ld.Thearch.Vput(uint64(r.Xadd))
+		ld.Thearch.Vput(uint64(sectoff + 4))
+		ld.Thearch.Vput(ld.R_AARCH64_LDST32_ABS_LO12_NC | uint64(elfsym)<<32)
+
+	case obj.R_ARM64_LOAD64:
+		ld.Thearch.Vput(ld.R_AARCH64_ADR_PREL_PG_HI21 | uint64(elfsym)<<32)
+		ld.Thearch.Vput(uint64(r.Xadd))
+		ld.Thearch.Vput(uint64(sectoff + 4))
+		ld.Thearch.Vput(ld.R_AARCH64_LDST64_ABS_LO12_NC | uint64(elfsym)<<32)
+
 	case obj.R_CALLARM64:
 		if r.Siz != 4 {
 			return -1
@@ -178,13 +202,72 @@ func machoreloc1(r *ld.Reloc, sectoff int64) int {
 	return 0
 }
 
+func archrelocaddr(r *ld.Reloc, s *ld.LSym, val *int64) int {
+	var o1, o2 uint32
+	if ld.Ctxt.Arch.ByteOrder == binary.BigEndian {
+		o1 = uint32(*val >> 32)
+		o2 = uint32(*val)
+	} else {
+		o1 = uint32(*val)
+		o2 = uint32(*val >> 32)
+	}
+
+	// We are inserting an address into two instructions: adrp and
+	// then either addi or a load.
+	address := ld.Symaddr(r.Sym) + r.Add
+	pgaddress := (address &^ 0xfff) - ((s.Value + int64(r.Off)) &^ 0xfff)
+	if pgaddress < -1<<31 || pgaddress >= 1<<31 {
+		ld.Ctxt.Diag("relocation for %s is too big (>=2G): %d", s.Name, pgaddress)
+	}
+	pgoff := uint32(address & 0xfff)
+	o1 |= uint32((((pgaddress >> 12) & 3) << 29) | (((pgaddress >> 12 >> 2) & 0x7ffff) << 5))
+
+	switch r.Type {
+	case obj.R_ADDRARM64, obj.R_ARM64_LOAD8:
+		o2 |= pgoff << 10
+
+	case obj.R_ARM64_LOAD16:
+		if pgoff&0x1 != 0 {
+			ld.Diag("offset for 16-byte load/store has unaligned value %d", pgoff)
+		}
+		o2 |= pgoff << 9
+
+	case obj.R_ARM64_LOAD32:
+		if pgoff&0x3 != 0 {
+			ld.Diag("offset for 32-byte load/store has unaligned value %d", pgoff)
+		}
+		o2 |= pgoff << 8
+
+	case obj.R_ARM64_LOAD64:
+		if pgoff&0x7 != 0 {
+			ld.Diag("offset for 64-byte load/store has unaligned value %d", pgoff)
+		}
+		o2 |= pgoff << 7
+
+	default:
+		return -1
+	}
+
+	if ld.Ctxt.Arch.ByteOrder == binary.BigEndian {
+		*val = int64(o1)<<32 | int64(o2)
+	} else {
+		*val = int64(o2)<<32 | int64(o1)
+	}
+	return 0
+}
+
 func archreloc(r *ld.Reloc, s *ld.LSym, val *int64) int {
 	if ld.Linkmode == ld.LinkExternal {
 		switch r.Type {
 		default:
 			return -1
 
-		case obj.R_ADDRARM64:
+		case obj.R_ADDRARM64,
+			obj.R_ARM64_LOAD8,
+			obj.R_ARM64_LOAD16,
+			obj.R_ARM64_LOAD32,
+			obj.R_ARM64_LOAD64:
+
 			r.Done = 0
 
 			// set up addend for eventual relocation via outer symbol.
@@ -253,32 +336,8 @@ func archreloc(r *ld.Reloc, s *ld.LSym, val *int64) int {
 		*val = ld.Symaddr(r.Sym) + r.Add - ld.Symaddr(ld.Linklookup(ld.Ctxt, ".got", 0))
 		return 0
 
-	case obj.R_ADDRARM64:
-		t := ld.Symaddr(r.Sym) + r.Add - ((s.Value + int64(r.Off)) &^ 0xfff)
-		if t >= 1<<32 || t < -1<<32 {
-			ld.Diag("program too large, address relocation distance = %d", t)
-		}
-
-		var o0, o1 uint32
-
-		if ld.Ctxt.Arch.ByteOrder == binary.BigEndian {
-			o0 = uint32(*val >> 32)
-			o1 = uint32(*val)
-		} else {
-			o0 = uint32(*val)
-			o1 = uint32(*val >> 32)
-		}
-
-		o0 |= (uint32((t>>12)&3) << 29) | (uint32((t>>12>>2)&0x7ffff) << 5)
-		o1 |= uint32(t&0xfff) << 10
-
-		// when laid out, the instruction order must always be o1, o2.
-		if ld.Ctxt.Arch.ByteOrder == binary.BigEndian {
-			*val = int64(o0)<<32 | int64(o1)
-		} else {
-			*val = int64(o1)<<32 | int64(o0)
-		}
-		return 0
+	case obj.R_ADDRARM64, obj.R_ARM64_LOAD8, obj.R_ARM64_LOAD16, obj.R_ARM64_LOAD32, obj.R_ARM64_LOAD64:
+		return archrelocaddr(r, s, val)
 
 	case obj.R_ARM64_TLS_LE:
 		r.Done = 0

src/cmd/link/internal/ld/elf.go

@@ -372,6 +372,10 @@ const (
 	R_AARCH64_CALL26                      = 283
 	R_AARCH64_ADR_PREL_PG_HI21            = 275
 	R_AARCH64_ADD_ABS_LO12_NC             = 277
+	R_AARCH64_LDST8_ABS_LO12_NC           = 278
+	R_AARCH64_LDST16_ABS_LO12_NC          = 284
+	R_AARCH64_LDST32_ABS_LO12_NC          = 285
+	R_AARCH64_LDST64_ABS_LO12_NC          = 286
 	R_AARCH64_TLSIE_ADR_GOTTPREL_PAGE21   = 541
 	R_AARCH64_TLSIE_LD64_GOTTPREL_LO12_NC = 542
 	R_AARCH64_TLSLE_MOVW_TPREL_G0         = 547