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55 lines
1.2 KiB
ArmAsm
55 lines
1.2 KiB
ArmAsm
/*
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Copyright 2003 Richard Curnow, SuperH (UK) Ltd.
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This file is subject to the terms and conditions of the GNU General Public
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License. See the file "COPYING" in the main directory of this archive
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for more details.
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Tight version of memset for the case of just clearing a page. It turns out
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that having the alloco's spaced out slightly due to the increment/branch
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pair causes them to contend less for access to the cache. Similarly,
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keeping the stores apart from the allocos causes less contention. => Do two
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separate loops. Do multiple stores per loop to amortise the
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increment/branch cost a little.
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Parameters:
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r2 : source effective address (start of page)
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Always clears 4096 bytes.
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Note : alloco guarded by synco to avoid TAKum03020 erratum
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*/
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.section .text..SHmedia32,"ax"
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.little
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.balign 8
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.global clear_page
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clear_page:
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pta/l 1f, tr1
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pta/l 2f, tr2
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ptabs/l r18, tr0
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movi 4096, r7
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add r2, r7, r7
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add r2, r63, r6
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1:
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alloco r6, 0
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synco ! TAKum03020
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addi r6, 32, r6
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bgt/l r7, r6, tr1
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add r2, r63, r6
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2:
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st.q r6, 0, r63
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st.q r6, 8, r63
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st.q r6, 16, r63
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st.q r6, 24, r63
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addi r6, 32, r6
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bgt/l r7, r6, tr2
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blink tr0, r63
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