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crypto/internal/fips140/subtle: re-add assembly implementation of xorBytes for mipsx
This CL reapplies CL 666275 , and fixes the previous implementation's unaligned access and panic on mipsx. Updates #74998 Change-Id: I26cd3fdeb54419407bdc0a2f9616924e2e825bc3 Reviewed-on: https://go-review.googlesource.com/c/go/+/696076 Reviewed-by: Keith Randall <khr@google.com> LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Keith Randall <khr@golang.org> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
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Lines changed: 250 additions & 1 deletion

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‎src/crypto/internal/fips140/subtle/xor_generic.go‎

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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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5-
//go:build (!amd64 && !arm64 && !loong64 && !ppc64 && !ppc64le && !riscv64) || purego
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//go:build (!amd64 && !arm64 && !loong64 && !mips && !mipsle && !ppc64 && !ppc64le && !riscv64) || purego
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package subtle
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‎src/crypto/internal/fips140/subtle/xor_mipsx.go‎

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// Copyright 2025 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build (mips || mipsle) && !purego
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package subtle
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import (
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"unsafe"
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)
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const wordSize = unsafe.Sizeof(uintptr(0))
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// dst,a,b,n, all be wordSize aligned, and n must be > 0 and a multiple of wordSize
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//
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//go:noescape
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func xorBytesAligned(dst, a, b *byte, n int)
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func xorBytes(dstb, xb, yb *byte, n int) {
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xp := uintptr(unsafe.Pointer(xb)) % wordSize
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yp := uintptr(unsafe.Pointer(yb)) % wordSize
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dp := uintptr(unsafe.Pointer(dstb)) % wordSize
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if xp != yp || xp != dp {
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dst := unsafe.Slice(dstb, n)
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x := unsafe.Slice(xb, n)
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y := unsafe.Slice(yb, n)
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xorLoop(dst, x, y)
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return
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}
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for (uintptr(unsafe.Pointer(dstb))%wordSize) != 0 && n > 0 {
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*dstb = *xb ^ *yb
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dstb = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(dstb)) + 1))
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xb = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(xb)) + 1))
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yb = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(yb)) + 1))
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n--
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}
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alignedN := n & -int(wordSize)
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if alignedN > 0 {
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xorBytesAligned(dstb, xb, yb, alignedN)
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dstb = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(dstb)) + uintptr(alignedN)))
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xb = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(xb)) + uintptr(alignedN)))
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yb = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(yb)) + uintptr(alignedN)))
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n -= alignedN
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}
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for n > 0 {
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*dstb = *xb ^ *yb
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dstb = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(dstb)) + 1))
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xb = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(xb)) + 1))
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yb = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(yb)) + 1))
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n--
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}
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}
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func xorLoop[T byte | uintptr](dst, x, y []T) {
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x = x[:len(dst)] // remove bounds check in loop
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y = y[:len(dst)] // remove bounds check in loop
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for i := range dst {
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dst[i] = x[i] ^ y[i]
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}
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}

‎src/crypto/internal/fips140/subtle/xor_mipsx.s‎

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// Copyright 2025 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build (mips || mipsle) && !purego
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#include "textflag.h"
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// func xorBytesAligned(dst, a, b *byte, n int)
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TEXT ·xorBytesAligned(SB), NOSPLIT|NOFRAME, $0
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MOVW dst+0(FP), R1
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MOVW a+4(FP), R2
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MOVW b+8(FP), R3
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MOVW n+12(FP), R4
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SGTU $64, R4, R5 // R5 = 1 if (64 > R4)
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BNE R5, xor_32_check
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xor_64:
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MOVW (R2), R6
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MOVW 4(R2), R7
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MOVW 8(R2), R8
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MOVW 12(R2), R9
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MOVW (R3), R10
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MOVW 4(R3), R11
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MOVW 8(R3), R12
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MOVW 12(R3), R13
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XOR R6, R10
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XOR R7, R11
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XOR R8, R12
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XOR R9, R13
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MOVW R10, (R1)
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MOVW R11, 4(R1)
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MOVW R12, 8(R1)
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MOVW R13, 12(R1)
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MOVW 16(R2), R6
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MOVW 20(R2), R7
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MOVW 24(R2), R8
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MOVW 28(R2), R9
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MOVW 16(R3), R10
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MOVW 20(R3), R11
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MOVW 24(R3), R12
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MOVW 28(R3), R13
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XOR R6, R10
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XOR R7, R11
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XOR R8, R12
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XOR R9, R13
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MOVW R10, 16(R1)
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MOVW R11, 20(R1)
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MOVW R12, 24(R1)
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MOVW R13, 28(R1)
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MOVW 32(R2), R6
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MOVW 36(R2), R7
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MOVW 40(R2), R8
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MOVW 44(R2), R9
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MOVW 32(R3), R10
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MOVW 36(R3), R11
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MOVW 40(R3), R12
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MOVW 44(R3), R13
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XOR R6, R10
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XOR R7, R11
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XOR R8, R12
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XOR R9, R13
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MOVW R10, 32(R1)
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MOVW R11, 36(R1)
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MOVW R12, 40(R1)
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MOVW R13, 44(R1)
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MOVW 48(R2), R6
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MOVW 52(R2), R7
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MOVW 56(R2), R8
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MOVW 60(R2), R9
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MOVW 48(R3), R10
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MOVW 52(R3), R11
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MOVW 56(R3), R12
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MOVW 60(R3), R13
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XOR R6, R10
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XOR R7, R11
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XOR R8, R12
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XOR R9, R13
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MOVW R10, 48(R1)
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MOVW R11, 52(R1)
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MOVW R12, 56(R1)
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MOVW R13, 60(R1)
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ADD $64, R2
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ADD $64, R3
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ADD $64, R1
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SUB $64, R4
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SGTU $64, R4, R5
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BEQ R5, xor_64
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BEQ R4, end
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xor_32_check:
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SGTU $32, R4, R5
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BNE R5, xor_16_check
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xor_32:
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MOVW (R2), R6
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MOVW 4(R2), R7
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MOVW 8(R2), R8
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MOVW 12(R2), R9
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MOVW (R3), R10
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MOVW 4(R3), R11
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MOVW 8(R3), R12
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MOVW 12(R3), R13
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XOR R6, R10
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XOR R7, R11
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XOR R8, R12
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XOR R9, R13
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MOVW R10, (R1)
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MOVW R11, 4(R1)
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MOVW R12, 8(R1)
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MOVW R13, 12(R1)
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MOVW 16(R2), R6
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MOVW 20(R2), R7
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MOVW 24(R2), R8
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MOVW 28(R2), R9
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MOVW 16(R3), R10
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MOVW 20(R3), R11
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MOVW 24(R3), R12
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MOVW 28(R3), R13
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XOR R6, R10
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XOR R7, R11
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XOR R8, R12
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XOR R9, R13
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MOVW R10, 16(R1)
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MOVW R11, 20(R1)
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MOVW R12, 24(R1)
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MOVW R13, 28(R1)
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ADD $32, R2
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ADD $32, R3
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ADD $32, R1
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SUB $32, R4
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BEQ R4, end
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xor_16_check:
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SGTU $16, R4, R5
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BNE R5, xor_8_check
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xor_16:
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MOVW (R2), R6
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MOVW 4(R2), R7
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MOVW 8(R2), R8
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MOVW 12(R2), R9
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MOVW (R3), R10
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MOVW 4(R3), R11
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MOVW 8(R3), R12
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MOVW 12(R3), R13
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XOR R6, R10
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XOR R7, R11
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XOR R8, R12
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XOR R9, R13
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MOVW R10, (R1)
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MOVW R11, 4(R1)
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MOVW R12, 8(R1)
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MOVW R13, 12(R1)
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ADD $16, R2
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ADD $16, R3
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ADD $16, R1
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SUB $16, R4
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BEQ R4, end
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xor_8_check:
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SGTU $8, R4, R5
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BNE R5, xor_4
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xor_8:
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MOVW (R2), R6
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MOVW 4(R2), R7
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MOVW (R3), R8
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MOVW 4(R3), R9
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XOR R6, R8
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XOR R7, R9
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MOVW R8, (R1)
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MOVW R9, 4(R1)
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ADD $8, R1
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ADD $8, R2
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ADD $8, R3
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SUB $8, R4
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BEQ R4, end
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xor_4:
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MOVW (R2), R6
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MOVW (R3), R7
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XOR R6, R7
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MOVW R7, (R1)
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ADD $4, R2
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ADD $4, R3
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ADD $4, R1
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SUB $4, R4
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end:
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RET

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