cmd/internal/obj/loong64: change the plan9 format of the prefetch instruction PRELDX

before:
    MOVV    $n + $offset, Roff
    PRELDX  (Rbase)(Roff), $hint
after:
    PRELDX  offset(Rbase), $n, $hint

This instruction is supported in CL 671875, but is not actually used

Change-Id: I943d488ea6dc77781cd796ef480a89fede666bab
Reviewed-on: https://go-review.googlesource.com/c/go/+/673155
Reviewed-by: Meidan Li <limeidan@loongson.cn>
Reviewed-by: sophie zhao <zhaoxiaolin@loongson.cn>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

2 files changed, 83 insertions, 16 deletions

diff --git a/src/cmd/internal/obj/loong64/asm.go b/src/cmd/internal/obj/loong64/asm.go
index c92c6b01b2..6e09930183 100644
--- a/src/cmd/internal/obj/loong64/asm.go
+++ b/src/cmd/internal/obj/loong64/asm.go
@@ -416,8 +416,8 @@ var optab = []Optab{
 
 	{AVMOVQ, C_ELEM, C_NONE, C_NONE, C_ARNG, C_NONE, 45, 4, 0, 0},
 
-	{APRELD, C_SOREG, C_NONE, C_U5CON, C_NONE, C_NONE, 46, 4, 0, 0},
-	{APRELDX, C_ROFF, C_NONE, C_U5CON, C_NONE, C_NONE, 47, 4, 0, 0},
+	{APRELD, C_SOREG, C_U5CON, C_NONE, C_NONE, C_NONE, 46, 4, 0, 0},
+	{APRELDX, C_SOREG, C_DCON, C_U5CON, C_NONE, C_NONE, 47, 20, 0, 0},
 
 	{obj.APCALIGN, C_U12CON, C_NONE, C_NONE, C_NONE, C_NONE, 0, 0, 0, 0},
 	{obj.APCDATA, C_32CON, C_NONE, C_NONE, C_32CON, C_NONE, 0, 0, 0, 0},
@@ -1105,6 +1105,22 @@ func (c *ctxt0) oplook(p *obj.Prog) *Optab {
 		c.ctxt.Diag("loong64 ops not initialized, call loong64.buildop first")
 	}
 
+	restArgsIndex := 0
+	restArgsLen := len(p.RestArgs)
+	if restArgsLen > 2 {
+		c.ctxt.Diag("too many RestArgs: got %v, maximum is 2\n", restArgsLen)
+		return nil
+	}
+
+	restArgsv := [2]int{C_NONE + 1, C_NONE + 1}
+	for i, ap := range p.RestArgs {
+		restArgsv[i] = int(ap.Addr.Class)
+		if restArgsv[i] == 0 {
+			restArgsv[i] = c.aclass(&ap.Addr) + 1
+			ap.Addr.Class = int8(restArgsv[i])
+		}
+	}
+
 	a1 := int(p.Optab)
 	if a1 != 0 {
 		return &optab[a1-1]
@@ -1130,6 +1146,9 @@ func (c *ctxt0) oplook(p *obj.Prog) *Optab {
 	a2 := C_NONE
 	if p.Reg != 0 {
 		a2 = c.rclass(p.Reg)
+	} else if restArgsLen > 0 {
+		a2 = restArgsv[restArgsIndex] - 1
+		restArgsIndex++
 	}
 
 	// 2nd destination operand
@@ -1140,22 +1159,20 @@ func (c *ctxt0) oplook(p *obj.Prog) *Optab {
 
 	// 3rd source operand
 	a3 := C_NONE
-	if len(p.RestArgs) > 0 {
-		a3 = int(p.RestArgs[0].Class)
-		if a3 == 0 {
-			a3 = c.aclass(&p.RestArgs[0].Addr) + 1
-			p.RestArgs[0].Class = int8(a3)
-		}
-		a3--
+	if restArgsLen > 0 && restArgsIndex < restArgsLen {
+		a3 = restArgsv[restArgsIndex] - 1
+		restArgsIndex++
 	}
 
 	ops := oprange[p.As&obj.AMask]
 	c1 := &xcmp[a1]
+	c2 := &xcmp[a2]
 	c3 := &xcmp[a3]
 	c4 := &xcmp[a4]
+	c5 := &xcmp[a5]
 	for i := range ops {
 		op := &ops[i]
-		if (int(op.reg) == a2) && c3[op.from3] && c1[op.from1] && c4[op.to1] && (int(op.to2) == a5) {
+		if c1[op.from1] && c2[op.reg] && c3[op.from3] && c4[op.to1] && c5[op.to2] {
 			p.Optab = uint16(cap(optab) - cap(ops) + i + 1)
 			return op
 		}
@@ -2457,16 +2474,40 @@ func (c *ctxt0) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		c.checkindex(p, index, m)
 		o1 = v | (index << 10) | (vj << 5) | vd
 
-	case 46:
-		// preld  offset(Rbase), hint
+	case 46: // preld  offset(Rbase), $hint
 		offs := c.regoff(&p.From)
 		hint := p.GetFrom3().Offset
 		o1 = OP_12IR_5I(c.opiir(p.As), uint32(offs), uint32(p.From.Reg), uint32(hint))
 
-	case 47:
-		// preldx (Rbase)(Roff), hint
-		hint := p.GetFrom3().Offset
-		o1 = OP_5IRR(c.opirr(p.As), uint32(p.From.Index), uint32(p.From.Reg), uint32(hint))
+	case 47: // preldx offset(Rbase), $n, $hint
+		offs := c.regoff(&p.From)
+		hint := p.RestArgs[1].Offset
+		n := uint64(p.GetFrom3().Offset)
+
+		addrSeq := (n >> 0) & 0x1
+		blkSize := (n >> 1) & 0x7ff
+		blkNums := (n >> 12) & 0x1ff
+		stride := (n >> 21) & 0xffff
+
+		if blkSize > 1024 {
+			c.ctxt.Diag("%v: block_size amount out of range[16, 1024]: %v\n", p, blkSize)
+		}
+
+		if blkNums > 256 {
+			c.ctxt.Diag("%v: block_nums amount out of range[1, 256]: %v\n", p, blkSize)
+		}
+
+		v := (uint64(offs) & 0xffff)
+		v += addrSeq << 16
+		v += ((blkSize / 16) - 1) << 20
+		v += (blkNums - 1) << 32
+		v += stride << 44
+
+		o1 = OP_IR(c.opir(ALU12IW), uint32(v>>12), uint32(REGTMP))
+		o2 = OP_12IRR(c.opirr(AOR), uint32(v), uint32(REGTMP), uint32(REGTMP))
+		o3 = OP_IR(c.opir(ALU32ID), uint32(v>>32), uint32(REGTMP))
+		o4 = OP_12IRR(c.opirr(ALU52ID), uint32(v>>52), uint32(REGTMP), uint32(REGTMP))
+		o5 = OP_5IRR(c.opirr(p.As), uint32(REGTMP), uint32(p.From.Reg), uint32(hint))
 
 	case 49:
 		if p.As == ANOOP {
diff --git a/src/cmd/internal/obj/loong64/doc.go b/src/cmd/internal/obj/loong64/doc.go
index 0896168fa1..0818389c8d 100644
--- a/src/cmd/internal/obj/loong64/doc.go
+++ b/src/cmd/internal/obj/loong64/doc.go
@@ -226,5 +226,31 @@ Note: In the following sections 3.1 to 3.6, "ui4" (4-bit unsigned int immediate)
   - When using the AM*_.W[U]/D[U] instruction, registers rd and rj cannot be the same,
     otherwise an exception is triggered, and rd and rk cannot be the same, otherwise
     the execution result is uncertain.
+
+3. Prefetch instructions
+    Instruction format:
+      PRELD	offset(Rbase), $hint
+      PRELDX	offset(Rbase), $n, $hint
+
+    Mapping between Go and platform assembly:
+               Go assembly            |    platform assembly
+      PRELD  offset(Rbase), $hint     | preld hint, Rbase, offset
+      PRELDX offset(Rbase), $n, $hint | move rk, $x; preldx hint, Rbase, rk
+
+      note: $x is the value after $n and offset are reassembled
+
+    Definition of hint value:
+      0: load to L1
+      2: load to L3
+      8: store to L1
+
+      The meaning of the rest of values is not defined yet, and the processor executes it as NOP
+
+    Definition of $n in the PRELDX instruction:
+      bit[0]: address sequence, 0 indicating ascending and 1 indicating descending
+      bits[11:1]:  block size, the value range is [16, 1024], and it must be an integer multiple of 16
+      bits[20:12]: block num, the value range is [1, 256]
+      bits[36:21]: stride, the value range is [0, 0xffff]
 */
+
 package loong64