cmd/compile/obj/arm64: fix encoding error of FMOVD/FMOVS $0|ZR

Previously the first operand of FMOVD and FMOVS could be $0, which
would be converted to the ZR register. This is prohibited by CL 404316,
also it broken the encoding of "FMOVD/FMOVS ZR, Rn", this CL restores
this instruction format and fixes the encoding issue.

Fixes #54655.
Fixes #54729.

Change-Id: I9c42cd41296bed7ffd601609bd8ecaa27d11e659
Reviewed-on: https://go-review.googlesource.com/c/go/+/425188
Run-TryBot: Eric Fang <eric.fang@arm.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

Author: eric fang

Diff for: src/cmd/asm/internal/asm/testdata/arm64.s

@@ -234,6 +234,10 @@ TEXT	foo(SB), DUPOK|NOSPLIT, $-8
 	FMOVD	$(0.1796875), F2                // 02f0681e
 	FMOVS	$(0.96875), F3                  // 03f02d1e
 	FMOVD	$(28.0), F4                     // 0490671e
+	FMOVD	$0, F0                          // e003679e
+	FMOVS	$0, F0                          // e003271e
+	FMOVD	ZR, F0                          // e003679e
+	FMOVS	ZR, F0                          // e003271e
 	VUADDW	V9.B8, V12.H8, V14.H8           // 8e11292e
 	VUADDW	V13.H4, V10.S4, V11.S4          // 4b116d2e
 	VUADDW	V21.S2, V24.D2, V29.D2          // 1d13b52e

Diff for: src/cmd/internal/obj/arm64/asm7.go

@@ -3884,13 +3884,13 @@ func (c *ctxt7) asmout(p *obj.Prog, o *Optab, out []uint32) {
 	case 29: /* op Rn, Rd */
 		fc := c.aclass(&p.From)
 		tc := c.aclass(&p.To)
-		if (p.As == AFMOVD || p.As == AFMOVS) && (fc == C_REG || tc == C_REG) {
+		if (p.As == AFMOVD || p.As == AFMOVS) && (fc == C_REG || fc == C_ZREG || tc == C_REG) {
 			// FMOV Rx, Fy or FMOV Fy, Rx
 			o1 = FPCVTI(0, 0, 0, 0, 6)
 			if p.As == AFMOVD {
 				o1 |= 1<<31 | 1<<22 // 64-bit
 			}
-			if fc == C_REG {
+			if fc == C_REG || fc == C_ZREG {
 				o1 |= 1 << 16 // FMOV Rx, Fy
 			}
 		} else {

Diff for: src/cmd/internal/obj/arm64/obj7.go

@@ -69,6 +69,8 @@ var zrReplace = map[obj.As]bool{
 	AADCW:  true,
 	AADCS:  true,
 	AADCSW: true,
+	AFMOVD: true,
+	AFMOVS: true,
 }
 
 func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {