/* Copyright (c) 2024, Synopsys, Inc. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1) Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2) Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3) Neither the name of the Synopsys, Inc., nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include #include ; r0 char* dest ; r1 const char* src ; dest and src MUST NOT intercept ; Brief: ; Perform the same operation as strlen for finding the end of r0 string ; If r0 and r1 have ; If 4 byte aligned ; Do 4 byte search until there are no more 4 byte chunks ; Then, do 1 byte search ; Otherwise, 1 byte search until alignment ; Then, do 4 byte search as previously specified ; ;; More in depth description at the end ; ; R0 char* dest (destination string) ; R1 const char* src (source string) ; ret (R0): ; - char* (destiantion string) ; #if defined (__ARC64_ARCH32__) ENTRY (strcat) ; Find end of r0 string ; ========================== STRLEN CODE START ========================== ; Preserve r0 for size calculation when returning mov r13, r0 xor r6, r6, r6 ; Setup byte detector (more information below) [1] mov r8, NULL_32DT_1 asl r9, r8, 7 .L_4_4B_search: #if defined (__ARC64_LL64__) ldd.ab r2r3, [r13, +8] ldd.ab r4r5, [r13, +8] #else ld.ab r2, [r13, +4] ld.ab r3, [r13, +4] ld.ab r4, [r13, +4] ld.ab r5, [r13, +4] #endif ; NULL byte position is detected and encoded in r6 [0] [9] sub r10, r2, r8 sub r11, r3, r8 sub r12, r4, r8 sub r7, r5, r8 bic r10, r10, r2 bic r11, r11, r3 bic r12, r12, r4 bic r7, r7, r5 tst r10, r9 bset.ne r6, r6, 4 tst r11, r9 bset.ne r6, r6, 3 tst r12, r9 bset.ne r6, r6, 2 tst r7, r9 bset.ne r6, r6, 1 breq.d r6, 0, @.L_4_4B_search fls r5, r6 ; [2] ; Point r13 to first NULL byte containing double word [3] sub2 r13, r13, r5 ; Select appropriate register to analyze [4] mov r2, r7 asr.f r6, r6, 3 mov.c r2, r12 asr.f r6, r6, 1 mov.c r2, r11 asr.f r6, r6, 1 mov.c r2, r10 ; Point r13 to first NULL byte in selected double word and r2, r2, r9 ; [5] ffs r2, r2 ; [6] xbfu r2, r2, 0b0111000011 ; [7] add r13, r13, r2 ; [8] ; ========================== STRLEN CODE END >|< ========================== xor r6, r6, r6 .L_4_4B_search_src: #if defined (__ARC64_LL64__) ldd.ab r2r3, [r1, +8] ldd.ab r4r5, [r1, +8] #else ld.ab r2, [r1, +4] ld.ab r3, [r1, +4] ld.ab r4, [r1, +4] ld.ab r5, [r1, +4] #endif ; NULL byte position is detected and encoded in r6 [0] [9] sub r10, r2, r8 sub r11, r3, r8 sub r12, r4, r8 sub r7, r5, r8 bic r10, r10, r2 bic r11, r11, r3 bic r12, r12, r4 bic r7, r7, r5 tst r10, r9 bset.ne r6, r6, 4 tst r11, r9 bset.ne r6, r6, 3 tst r12, r9 bset.ne r6, r6, 2 tst r7, r9 bset.ne r6, r6, 1 brne r6, 0, @.L_found_in_32B #if defined (__ARC64_LL64__) std.ab r2r3, [r13, +8] std.ab r4r5, [r13, +8] #else st.ab r2, [r13, +4] st.ab r3, [r13, +4] st.ab r4, [r13, +4] st.ab r5, [r13, +4] #endif b @.L_4_4B_search_src .L_found_in_32B: fls r6, r6 ; [2] ; Point r1 to first NULL byte containing double word [3] sub2 r1, r1, r6 ;; Store the already loaded data ; 4 -> 1 to 3 -> 0 ;subl r6, r6, 1 ; Invert so the biggest branch is at the end, and we dont need to increase ; block size ; 3 -> 0 to 0 -> 3 ;subl r6, 3, r6 ; Condense the two subs here rsub r6, r6, 4 asl r6, r6, 2 ; Store double words bi [r6] b.d @.L_store_lastL32bits mov r11, r2 nop nop st.ab r2, [r13, +4] b.d @.L_store_lastL32bits mov r11, r3 nop st.ab r2, [r13, +4] st.ab r3, [r13, +4] b.d @.L_store_lastL32bits mov r11, r4 st.ab r2, [r13, +4] st.ab r3, [r13, +4] st.ab r4, [r13, +4] mov r11, r5 ; r11 now contains the data to write .L_store_lastL32bits: sub r10, r11, r8 bic r10, r10, r11 and r10, r10, r9 ; [5] ffs r2, r10 ; [6] add r2, r2, 1 xbfu r2, r2, 0b0111000011 ; [7] mov r3, -1; Bitmask setup ; If the NULL byte is in byte 3 (starting from the right) ; we want to store 8-3 bytes rsub r2, r2, 8 asl r2, r2, 3 ; According to the target byte, setup masks lsr r3, r3, r2 not r4, r3 ; Obtain relevant data from destination ld r10, [r13] ; Get which data from dest is not to be overwritten and OR it ; with the relevant data to write and r3, r3, r11 and r4, r4, r10 or r3, r3, r4 j_s.d [blink] st.ab r3, [r13, +4] ENDFUNC (strcat) #else ENTRY (strcat) ; Find end of r0 string ; ========================== STRLEN CODE START ========================== ; Preserve r0 for size calculation when returning movl r13, r0 xorl r6, r6, r6 ; Setup byte detector (more information below) [1] vpack2wl r8, NULL_32DT_1, NULL_32DT_1 asll r9, r8, 7 .L_4_8B_search: ; Using 128-bit memory operations #if defined (__ARC64_M128__) lddl.ab r2r3, [r13, +16] lddl.ab r4r5, [r13, +16] ; The 64-bit crunching implementation. #elif defined (__ARC64_ARCH64__) ldl.ab r2, [r13, +8] ldl.ab r3, [r13, +8] ldl.ab r4, [r13, +8] ldl.ab r5, [r13, +8] #else # error Unknown configuration #endif ; NULL byte position is detected and encoded in r6 [0] [9] subl r10, r2, r8 subl r11, r3, r8 subl r12, r4, r8 subl r7, r5, r8 bicl r10, r10, r2 bicl r11, r11, r3 bicl r12, r12, r4 bicl r7, r7, r5 tstl r10, r9 bset.ne r6, r6, 4 tstl r11, r9 bset.ne r6, r6, 3 tstl r12, r9 bset.ne r6, r6, 2 tstl r7, r9 bset.ne r6, r6, 1 breq.d r6, 0, @.L_4_8B_search fls r5, r6 ; [2] ; Point r13 to first NULL byte containing double word [3] sub3l r13, r13, r5 ; Select appropriate register to analyze [4] MOVP r2, r7 asr.f r6, r6, 3 MOVP.c r2, r12 asr.f r6, r6, 1 MOVP.c r2, r11 asr.f r6, r6, 1 MOVP.c r2, r10 ; Point r13 to first NULL byte in selected double word andl r2, r2, r9 ; [5] ffsl r2, r2 ; [6] xbful r2, r2, 0b0111000011 ; [7] addl r13, r13, r2 ; [8] ; ========================== STRLEN CODE END >|< ========================== xorl r6, r6, r6 .L_4_8B_search_src: #if defined (__ARC64_M128__) lddl.ab r2r3, [r1, +16] lddl.ab r4r5, [r1, +16] #elif defined (__ARC64_ARCH64__) ldl.ab r2, [r1, +8] ldl.ab r3, [r1, +8] ldl.ab r4, [r1, +8] ldl.ab r5, [r1, +8] #else # error Unknown configuration #endif ; NULL byte position is detected and encoded in r6 [0] [9] subl r10, r2, r8 subl r11, r3, r8 subl r12, r4, r8 subl r7, r5, r8 bicl r10, r10, r2 bicl r11, r11, r3 bicl r12, r12, r4 bicl r7, r7, r5 tstl r10, r9 bset.ne r6, r6, 4 tstl r11, r9 bset.ne r6, r6, 3 tstl r12, r9 bset.ne r6, r6, 2 tstl r7, r9 bset.ne r6, r6, 1 brne r6, 0, @.L_found_in_32B #if defined (__ARC64_M128__) stdl.ab r2r3, [r13, +16] stdl.ab r4r5, [r13, +16] #elif defined (__ARC64_ARCH64__) stl.ab r2, [r13, +8] stl.ab r3, [r13, +8] stl.ab r4, [r13, +8] stl.ab r5, [r13, +8] #else # error Unknown configuration #endif b @.L_4_8B_search_src .L_found_in_32B: fls r6, r6 ; [2] ; Point r1 to first NULL byte containing double word [3] sub3l r1, r1, r6 ;; Store the already loaded data ; 4 -> 1 to 3 -> 0 ;subl r6, r6, 1 ; Invert so the biggest branch is at the end, and we dont need to increase ; block size ; 3 -> 0 to 0 -> 3 ;subl r6, 3, r6 ; Condense the two subs here rsubl r6, r6, 4 asll r6, r6, 2 ; Store double words bi [r6] b.d @.L_store_lastL64bits MOVP r11, r2 nop nop stl.ab r2, [r13, +8] b.d @.L_store_lastL64bits MOVP r11, r3 nop stl.ab r2, [r13, +8] stl.ab r3, [r13, +8] b.d @.L_store_lastL64bits MOVP r11, r4 stl.ab r2, [r13, +8] stl.ab r3, [r13, +8] stl.ab r4, [r13, +8] MOVP r11, r5 ; r11 now contains the data to write .L_store_lastL64bits: subl r10, r11, r8 bicl r10, r10, r11 andl r10, r10, r9 ; [5] ffsl r2, r10 ; [6] addl r2, r2, 1 xbful r2, r2, 0b0111000011 ; [7] movl r3, -1; Bitmask setup ; If the NULL byte is in byte 3 (starting from the right) ; we want to store 8-3 bytes rsubl r2, r2, 8 asl r2, r2, 3 ; According to the target byte, setup masks lsrl r3, r3, r2 notl r4, r3 ; Obtain relevant data from destination ldl r10, [r13] ; Get which data from dest is not to be overwritten and OR it ; with the relevant data to write andl r3, r3, r11 andl r4, r4, r10 orl r3, r3, r4 j_s.d [blink] stl.ab r3, [r13, +8] ENDFUNC (strcat) #endif ;; This code uses a common technique for NULL byte detection inside a word. ;; Details on this technique can be found in: ;; (https://graphics.stanford.edu/~seander/bithacks.html#ZeroInWord) ; ; In sum, this technique allows for detecting a NULL byte inside any given ; amount of bits by performing the following operation ; DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080) [0] ; ; The code above implements this by setting r8 to a 0x01010101... sequence and ; r9 to a 0x80808080... sequence of appropriate length ; As LIMM are 32 bit only, we need to perform MOVHL and ORL [1] operations to ; have the appropriate 64 bit values in place ; ;; Search is done 32 bytes at a time, either with 64 bit loads or 128 bit loads ;; If a NULL byte is detected, the position of the double word is encoded ;; in r6, which is then used to adjust r13 to the exact byte ; ; r6 is set via bset, which means we can simply use a fls to obtain the first ; match (or ffs depending on the values in bset) [2]. ; The reason for starting at 1 and not 0 is so r6 encodes how many double ; words to go back, and it wouldnt make sense to go back 0 (the NULL would be ; in the next loop iteration). ; ; The first step to take is point r13 to the appropriate double word. ; As the chosen encoded information is how many double words to go back, ; we can simply multiply r6 by 8 and reduce r13 by that amount [3] ; ; Then, we need to place the loaded double word containing the first NULL byte ; into a "common" register we can operate on later [4]. ; ; To do this without any jumps, we can shift r6 and perform a conditional mov ; based on the carry flag value. ; The order is very important because the NULL byte can appear in several ; double words, so we want to analyze from last to first. ; ; We can ignore the first asr (which would be asr.f 2, as we started r6 on 1) ; because if r7 isnt the NULL byte, r2 will always be overwritten so we can ; just decide to start at r7, and overwrite it if needed. ; ; Now comes the tricky part. In order to obtain the first NULL byte, we need to ; understand the NULL byte detection operation. It is explained in depth in the ; link above but in short, it works by first setting the highest bit of each ; byte to 1, if the corresponding byte is either 0 or less than 0x80 ; Then, separately, it makes the highest bit of each byte 1, if the byte is ; less than 0x80. The last step is to and these two values (this operation is ; simplified with the subl, bicl and tst instructions). ; ; This means that the evaluated equation result value [5] has zeros for all non ; zero bytes, except for the NULL bytes. Therefore, we can simply find the ; first non zero bit (counting from bit 0) which will be inside the position of ; the first NULL byte. ; ; One thing to note, is that ffs oddly returns 31 if no bit is found, setting ; the zero flag. As r9 is never all 0s at this stage (would mean there is no ; NULL byte and we wouldnt be here) we dont need to worry about that. [6] ; ; We can then convert the bit position into the last byte position by looking ; into bits 3 to 5, and shifting 3 bits to the right. This can be combined into ; a single xbful operation. The bottom 000011 represent shift by 3 and the top ; 0111 represents the mask (3 to 5 shifted by 3 is 0 to 2). We dont need to worry ; about the case where ffs does not find a bit, because we know for sure there is ; at least one NULL byte, and therefore one of the highest bits is set to 1 [7] ; ; Finally, we can add the NULL byte position inside the loaded double word to ; r13 and subtract r0 from r13 to obtain the string size [8] ; ; Some operations are re-ordered such that register dependency is reduced, ; allowing the CPU to run more instructions in parallel [9] ; ; ; Some data was already read, and needs to be stored following the same read ; order. To do this, we need to make the ; ;