cmd/internal/obj/arm64: fix the encoding error when operating with ZR

Some arm64 instructions accept ZR as its destination register, such as MOVD,
AND, ADD etc. although it doesn't seem to make much sense, but we should
make sure the encoding is correct. However there exists some encoding mistakes
in the current assembler, they are:
1, 'MOVD $1, ZR' is incorrectly encoded as 'MOVD $1, ZR' + '0x00000000'.
2, 'AND $1, R2, ZR' is incorrectly encoded as 'MOVD $1, R27' + 'AND R27, R2, ZR' +
   '0x00000000'.
3, 'AND $1, ZR' is incorrectly encoded as 'AND $1, ZR, RSP'.

Obviously the first two encoding errors can cause SIGILL, and the third one will
rewrite RSP.

At the same time, I found some weird encodings but they don't cause errors.
4, 'MOVD $0x0001000100010001, ZR' is encoded as 'MOVW $1, ZR' + 'MOVKW $(1<<16), ZR'.
5, 'AND $0x0001000100010001, R2, ZR' is encoded as 'MOVD $1, R27' + 'MOVK $(1<<16), R27' +
   'MOVK $(1<<32), R27'.

Some of these issues also apply to 32-bit versions of these instructions.

These problems are not very complicated, and are basically caused by the improper
adaptation of the class of the constant to the entry in the optab. But the relationship
between these constant classes is a bit complicated, so I don't know how to deal with
issue 4 and 5, because they won't cause errors, so this CL didn't deal with them.

This CL fixed the first three issues.
Issue 1:
  before: 'MOVD $1, ZR' => 'MOVD $1, ZR' + '0x00000000'.
  after:  'MOVD $1, ZR' => 'MOVD $1, ZR'.
Issue 2:
  before: 'AND $1, R2, ZR' => 'MOVD $1, R27' + 'AND R27, R2, ZR' + '0x00000000'.
  after:  'AND $1, R2, ZR' => 'ORR $1, ZR, R27' + 'AND R27, R2, ZR'.
Issue 3:
  before: 'AND $1, ZR' => 'AND $1, ZR, RSP'.
  after:  'AND $1, ZR' => 'ORR $1, ZR, R27' + 'AND R27, ZR, ZR'.

Change-Id: I3c889079229f847b863ad56c88966be12d947202
Reviewed-on: https://go-review.googlesource.com/c/go/+/329750
Reviewed-by: eric fang <eric.fang@arm.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Trust: eric fang <eric.fang@arm.com>
Run-TryBot: eric fang <eric.fang@arm.com>
TryBot-Result: Go Bot <gobot@golang.org>

2 files changed, 19 insertions, 6 deletions

diff --git a/src/cmd/internal/obj/arm64/asm7.go b/src/cmd/internal/obj/arm64/asm7.go
index d99afa3d27..02687ab162 100644
--- a/src/cmd/internal/obj/arm64/asm7.go
+++ b/src/cmd/internal/obj/arm64/asm7.go
@@ -361,12 +361,12 @@ var optab = []Optab{
 	{AANDS, C_REG, C_NONE, C_NONE, C_REG, 1, 4, 0, 0, 0},
 	{ATST, C_REG, C_REG, C_NONE, C_NONE, 1, 4, 0, 0, 0},
 	{AAND, C_MBCON, C_REG, C_NONE, C_RSP, 53, 4, 0, 0, 0},
-	{AAND, C_MBCON, C_NONE, C_NONE, C_REG, 53, 4, 0, 0, 0},
+	{AAND, C_MBCON, C_NONE, C_NONE, C_RSP, 53, 4, 0, 0, 0},
 	{AANDS, C_MBCON, C_REG, C_NONE, C_REG, 53, 4, 0, 0, 0},
 	{AANDS, C_MBCON, C_NONE, C_NONE, C_REG, 53, 4, 0, 0, 0},
 	{ATST, C_MBCON, C_REG, C_NONE, C_NONE, 53, 4, 0, 0, 0},
 	{AAND, C_BITCON, C_REG, C_NONE, C_RSP, 53, 4, 0, 0, 0},
-	{AAND, C_BITCON, C_NONE, C_NONE, C_REG, 53, 4, 0, 0, 0},
+	{AAND, C_BITCON, C_NONE, C_NONE, C_RSP, 53, 4, 0, 0, 0},
 	{AANDS, C_BITCON, C_REG, C_NONE, C_REG, 53, 4, 0, 0, 0},
 	{AANDS, C_BITCON, C_NONE, C_NONE, C_REG, 53, 4, 0, 0, 0},
 	{ATST, C_BITCON, C_REG, C_NONE, C_NONE, 53, 4, 0, 0, 0},
@@ -404,6 +404,8 @@ var optab = []Optab{
 	/* TODO: MVN C_SHIFT */
 
 	/* MOVs that become MOVK/MOVN/MOVZ/ADD/SUB/OR */
+	{AMOVW, C_MBCON, C_NONE, C_NONE, C_REG, 32, 4, 0, 0, 0},
+	{AMOVD, C_MBCON, C_NONE, C_NONE, C_REG, 32, 4, 0, 0, 0},
 	{AMOVW, C_MOVCON, C_NONE, C_NONE, C_REG, 32, 4, 0, 0, 0},
 	{AMOVD, C_MOVCON, C_NONE, C_NONE, C_REG, 32, 4, 0, 0, 0},
 	{AMOVW, C_BITCON, C_NONE, C_NONE, C_RSP, 32, 4, 0, 0, 0},
@@ -2089,13 +2091,18 @@ func cmp(a int, b int) bool {
 			return true
 		}
 
+	case C_MBCON:
+		if b == C_ABCON0 {
+			return true
+		}
+
 	case C_BITCON:
 		if b == C_ABCON0 || b == C_ABCON || b == C_MBCON {
 			return true
 		}
 
 	case C_MOVCON:
-		if b == C_MBCON || b == C_ZCON || b == C_ADDCON0 || b == C_AMCON {
+		if b == C_MBCON || b == C_ZCON || b == C_ADDCON0 || b == C_ABCON0 || b == C_AMCON {
 			return true
 		}
 
@@ -4198,6 +4205,10 @@ func (c *ctxt7) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		if r == 0 {
 			r = rt
 		}
+		if r == REG_RSP {
+			c.ctxt.Diag("illegal source register: %v", p)
+			break
+		}
 		mode := 64
 		v := uint64(p.From.Offset)
 		switch p.As {
@@ -7039,8 +7050,8 @@ func (c *ctxt7) omovlit(as obj.As, p *obj.Prog, a *obj.Addr, dr int) uint32 {
 
 // load a constant (MOVCON or BITCON) in a into rt
 func (c *ctxt7) omovconst(as obj.As, p *obj.Prog, a *obj.Addr, rt int) (o1 uint32) {
-	if cls := oclass(a); cls == C_BITCON || cls == C_ABCON || cls == C_ABCON0 {
-		// or $bitcon, REGZERO, rt
+	if cls := oclass(a); (cls == C_BITCON || cls == C_ABCON || cls == C_ABCON0) && rt != REGZERO {
+		// or $bitcon, REGZERO, rt. rt can't be ZR.
 		mode := 64
 		var as1 obj.As
 		switch as {
diff --git a/src/cmd/internal/obj/arm64/obj7.go b/src/cmd/internal/obj/arm64/obj7.go
index 31b7c43245..a043d0972c 100644
--- a/src/cmd/internal/obj/arm64/obj7.go
+++ b/src/cmd/internal/obj/arm64/obj7.go
@@ -305,7 +305,9 @@ func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 	// for both 32-bit and 64-bit. 32-bit ops will
 	// zero the high 32-bit of the destination register
 	// anyway.
-	if (isANDWop(p.As) || isADDWop(p.As) || p.As == AMOVW) && p.From.Type == obj.TYPE_CONST {
+	// For MOVW, the destination register can't be ZR,
+	// so don't bother rewriting it in this situation.
+	if (isANDWop(p.As) || isADDWop(p.As) || p.As == AMOVW && p.To.Reg != REGZERO) && p.From.Type == obj.TYPE_CONST {
 		v := p.From.Offset & 0xffffffff
 		p.From.Offset = v | v<<32
 	}