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