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89 lines
2.8 KiB
89 lines
2.8 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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/* |
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* arch/alpha/lib/strrchr.S |
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* Contributed by Richard Henderson (rth@tamu.edu) |
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* |
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* Return the address of the last occurrence of a given character |
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* within a null-terminated string, or null if it is not found. |
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*/ |
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#include <asm/export.h> |
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#include <asm/regdef.h> |
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.set noreorder |
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.set noat |
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.align 3 |
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.ent strrchr |
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.globl strrchr |
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strrchr: |
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.frame sp, 0, ra |
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.prologue 0 |
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zapnot a1, 1, a1 # e0 : zero extend our test character |
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mov zero, t6 # .. e1 : t6 is last match aligned addr |
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sll a1, 8, t5 # e0 : replicate our test character |
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mov zero, t8 # .. e1 : t8 is last match byte compare mask |
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or t5, a1, a1 # e0 : |
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ldq_u t0, 0(a0) # .. e1 : load first quadword |
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sll a1, 16, t5 # e0 : |
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andnot a0, 7, v0 # .. e1 : align source addr |
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or t5, a1, a1 # e0 : |
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lda t4, -1 # .. e1 : build garbage mask |
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sll a1, 32, t5 # e0 : |
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cmpbge zero, t0, t1 # .. e1 : bits set iff byte == zero |
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mskqh t4, a0, t4 # e0 : |
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or t5, a1, a1 # .. e1 : character replication complete |
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xor t0, a1, t2 # e0 : make bytes == c zero |
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cmpbge zero, t4, t4 # .. e1 : bits set iff byte is garbage |
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cmpbge zero, t2, t3 # e0 : bits set iff byte == c |
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andnot t1, t4, t1 # .. e1 : clear garbage from null test |
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andnot t3, t4, t3 # e0 : clear garbage from char test |
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bne t1, $eos # .. e1 : did we already hit the terminator? |
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/* Character search main loop */ |
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$loop: |
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ldq t0, 8(v0) # e0 : load next quadword |
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cmovne t3, v0, t6 # .. e1 : save previous comparisons match |
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cmovne t3, t3, t8 # e0 : |
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addq v0, 8, v0 # .. e1 : |
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xor t0, a1, t2 # e0 : |
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cmpbge zero, t0, t1 # .. e1 : bits set iff byte == zero |
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cmpbge zero, t2, t3 # e0 : bits set iff byte == c |
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beq t1, $loop # .. e1 : if we havnt seen a null, loop |
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/* Mask out character matches after terminator */ |
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$eos: |
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negq t1, t4 # e0 : isolate first null byte match |
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and t1, t4, t4 # e1 : |
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subq t4, 1, t5 # e0 : build a mask of the bytes up to... |
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or t4, t5, t4 # e1 : ... and including the null |
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and t3, t4, t3 # e0 : mask out char matches after null |
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cmovne t3, t3, t8 # .. e1 : save it, if match found |
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cmovne t3, v0, t6 # e0 : |
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/* Locate the address of the last matched character */ |
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/* Retain the early exit for the ev4 -- the ev5 mispredict penalty |
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is 5 cycles -- the same as just falling through. */ |
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beq t8, $retnull # .. e1 : |
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and t8, 0xf0, t2 # e0 : binary search for the high bit set |
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cmovne t2, t2, t8 # .. e1 (zdb) |
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cmovne t2, 4, t2 # e0 : |
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and t8, 0xcc, t1 # .. e1 : |
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cmovne t1, t1, t8 # e0 : |
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cmovne t1, 2, t1 # .. e1 : |
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and t8, 0xaa, t0 # e0 : |
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cmovne t0, 1, t0 # .. e1 (zdb) |
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addq t2, t1, t1 # e0 : |
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addq t6, t0, v0 # .. e1 : add our aligned base ptr to the mix |
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addq v0, t1, v0 # e0 : |
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ret # .. e1 : |
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$retnull: |
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mov zero, v0 # e0 : |
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ret # .. e1 : |
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.end strrchr |
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EXPORT_SYMBOL(strrchr)
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