cmd/compile: simplify zerorange on mips64

Change-Id: I488b55a21eaaf74373c2789a34bf9b3945ced072
Reviewed-on: https://go-review.googlesource.com/c/go/+/700936
Reviewed-by: Michael Pratt <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Keith Randall <[email protected]>

Author: HeliC829

src/cmd/compile/internal/mips64/ggen.go

@@ -5,45 +5,21 @@
 package mips64
 
 import (
-	"cmd/compile/internal/ir"
 	"cmd/compile/internal/objw"
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
 	"cmd/internal/obj/mips"
 )
 
 func zerorange(pp *objw.Progs, p *obj.Prog, off, cnt int64, _ *uint32) *obj.Prog {
-	if cnt == 0 {
-		return p
+	if cnt%int64(types.PtrSize) != 0 {
+		panic("zeroed region not aligned")
 	}
-	if cnt < int64(4*types.PtrSize) {
-		for i := int64(0); i < cnt; i += int64(types.PtrSize) {
-			p = pp.Append(p, mips.AMOVV, obj.TYPE_REG, mips.REGZERO, 0, obj.TYPE_MEM, mips.REGSP, 8+off+i)
-		}
-	} else if cnt <= int64(128*types.PtrSize) {
-		p = pp.Append(p, mips.AADDV, obj.TYPE_CONST, 0, 8+off-8, obj.TYPE_REG, mips.REGRT1, 0)
-		p.Reg = mips.REGSP
-		p = pp.Append(p, obj.ADUFFZERO, obj.TYPE_NONE, 0, 0, obj.TYPE_MEM, 0, 0)
-		p.To.Name = obj.NAME_EXTERN
-		p.To.Sym = ir.Syms.Duffzero
-		p.To.Offset = 8 * (128 - cnt/int64(types.PtrSize))
-	} else {
-		//	ADDV	$(8+frame+lo-8), SP, r1
-		//	ADDV	$cnt, r1, r2
-		// loop:
-		//	MOVV	R0, (Widthptr)r1
-		//	ADDV	$Widthptr, r1
-		//	BNE		r1, r2, loop
-		p = pp.Append(p, mips.AADDV, obj.TYPE_CONST, 0, 8+off-8, obj.TYPE_REG, mips.REGRT1, 0)
-		p.Reg = mips.REGSP
-		p = pp.Append(p, mips.AADDV, obj.TYPE_CONST, 0, cnt, obj.TYPE_REG, mips.REGRT2, 0)
-		p.Reg = mips.REGRT1
-		p = pp.Append(p, mips.AMOVV, obj.TYPE_REG, mips.REGZERO, 0, obj.TYPE_MEM, mips.REGRT1, int64(types.PtrSize))
-		p1 := p
-		p = pp.Append(p, mips.AADDV, obj.TYPE_CONST, 0, int64(types.PtrSize), obj.TYPE_REG, mips.REGRT1, 0)
-		p = pp.Append(p, mips.ABNE, obj.TYPE_REG, mips.REGRT1, 0, obj.TYPE_BRANCH, 0, 0)
-		p.Reg = mips.REGRT2
-		p.To.SetTarget(p1)
+
+	for cnt != 0 {
+		p = pp.Append(p, mips.AMOVV, obj.TYPE_REG, mips.REGZERO, 0, obj.TYPE_MEM, mips.REGSP, off)
+		cnt -= int64(types.PtrSize)
+		off += int64(types.PtrSize)
 	}
 
 	return p