cmd/compile: simplify zerorange on riscv64

Drop large zeroing cases, part of removing duff support.

Change-Id: Ia2936f649901886f3eb1d7ba1f90e3bf40ea2dee
Reviewed-on: https://go-review.googlesource.com/c/go/+/697615
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Julian Zhu <jz531210@gmail.com>
Reviewed-by: Mark Ryan <markdryan@rivosinc.com>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Mark Freeman <markfreeman@google.com>
Reviewed-by: Joel Sing <joel@sing.id.au>

diff --git a/src/cmd/compile/internal/riscv64/ggen.go b/src/cmd/compile/internal/riscv64/ggen.go
index 44488e43276bc24a5dece2337f8f93ecdfc9ae25..d8afb01f3b81b5dcc570217251caacea724d9291 100644 (file)
--- a/src/cmd/compile/internal/riscv64/ggen.go
+++ b/src/cmd/compile/internal/riscv64/ggen.go
@@ -6,7 +6,6 @@ package riscv64
 
 import (
        "cmd/compile/internal/base"
-       "cmd/compile/internal/ir"
        "cmd/compile/internal/objw"
        "cmd/compile/internal/types"
        "cmd/internal/obj"
@@ -14,46 +13,19 @@ import (
 )
 
 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")
        }
 
        // Adjust the frame to account for LR.
        off += base.Ctxt.Arch.FixedFrameSize
 
-       if cnt < int64(4*types.PtrSize) {
-               for i := int64(0); i < cnt; i += int64(types.PtrSize) {
-                       p = pp.Append(p, riscv.AMOV, obj.TYPE_REG, riscv.REG_ZERO, 0, obj.TYPE_MEM, riscv.REG_SP, off+i)
-               }
-               return p
-       }
-
-       if cnt <= int64(128*types.PtrSize) {
-               p = pp.Append(p, riscv.AADDI, obj.TYPE_CONST, 0, off, obj.TYPE_REG, riscv.REG_X25, 0)
-               p.Reg = riscv.REG_SP
-               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))
-               return p
+       for cnt != 0 {
+               p = pp.Append(p, riscv.AMOV, obj.TYPE_REG, riscv.REG_ZERO, 0, obj.TYPE_MEM, riscv.REG_SP, off)
+               cnt -= int64(types.PtrSize)
+               off += int64(types.PtrSize)
        }
 
-       // Loop, zeroing pointer width bytes at a time.
-       // ADD  $(off), SP, T0
-       // ADD  $(cnt), T0, T1
-       // loop:
-       //      MOV     ZERO, (T0)
-       //      ADD     $Widthptr, T0
-       //      BNE     T0, T1, loop
-       p = pp.Append(p, riscv.AADD, obj.TYPE_CONST, 0, off, obj.TYPE_REG, riscv.REG_T0, 0)
-       p.Reg = riscv.REG_SP
-       p = pp.Append(p, riscv.AADD, obj.TYPE_CONST, 0, cnt, obj.TYPE_REG, riscv.REG_T1, 0)
-       p.Reg = riscv.REG_T0
-       p = pp.Append(p, riscv.AMOV, obj.TYPE_REG, riscv.REG_ZERO, 0, obj.TYPE_MEM, riscv.REG_T0, 0)
-       loop := p
-       p = pp.Append(p, riscv.AADD, obj.TYPE_CONST, 0, int64(types.PtrSize), obj.TYPE_REG, riscv.REG_T0, 0)
-       p = pp.Append(p, riscv.ABNE, obj.TYPE_REG, riscv.REG_T0, 0, obj.TYPE_BRANCH, 0, 0)
-       p.Reg = riscv.REG_T1
-       p.To.SetTarget(loop)
        return p
 }