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strrchr.S


products/Sources/formale Sprachen/C/Linux/arch/alpha/lib/strrchr.S

/* 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 #include .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)

                                                                                                                                                                                                                                                                                                                                                                                                     

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