X-Git-Url: https://git.saurik.com/apple/libc.git/blobdiff_plain/51631861ddb16afcfcf748cee26c14481549065e..fbd86d4cc20b02a10edcca92fb7ae0a143e63cc4:/ppc/string/memcmp.s?ds=sidebyside diff --git a/ppc/string/memcmp.s b/ppc/string/memcmp.s index d2baaa4..b98cbf2 100644 --- a/ppc/string/memcmp.s +++ b/ppc/string/memcmp.s @@ -24,6 +24,13 @@ #include #undef ASSEMBLER +/* We use mode-independent "g" opcodes such as "srgi". These expand + * into word operations when targeting __ppc__, and into doubleword + * operations when targeting __ppc64__. + */ +#include + + // *************** *********** // * M E M C M P * and * B C M P * // *************** *********** @@ -39,31 +46,33 @@ // finding a difference, we might get a spurious page fault by // reading bytes past the difference. To avoid this, we never do a "lwz" // that crosses a page boundary. +// +// In 64-bit mode, this routine is doubleword parallel. .text .globl EXT(memcmp) .globl EXT(bcmp) .align 5 -LEXT(memcmp) // int memcmp(const char *s1,const char *s2,size_t len); +LEXT(memcmp) // int memcmp(const char *s1,const char *s2,size_t len); LEXT(bcmp) // int bcmp(const char *s1,const char *s2,size_t len); - cmplwi cr1,r5,8 // is buffer too short to bother with word compares? - andi. r0,r3,3 // is LHS word aligned? + cmplgi cr1,r5,2*GPR_BYTES // is buffer too short to bother with parallel compares? + andi. r0,r3,GPR_BYTES-1 // is LHS aligned? blt cr1,Lshort // short buffer, so just compare byte-by-byte beq Laligned // skip if aligned - subfic r0,r0,4 // r0 <- #bytes to word align LHS + subfic r0,r0,GPR_BYTES // r0 <- #bytes to align LHS mtctr r0 // set up for byte loop b Lbyteloop // Handle short buffer or end-of-buffer. // r3 = LHS ptr (unaligned) // r4 = RHS ptr (unaligned) -// r5 = length remaining in buffer (0..7) +// r5 = length remaining in buffer (0..2*GPR_BYTES-1) Lshort: - cmpwi r5,0 // null buffer? + cmpgi r5,0 // null buffer? mtctr r5 // assume not null, and set up for loop - bne Lshortloop // buffer not null + bne Lshortloop // buffer not null li r3,0 // say "equal" blr @@ -79,14 +88,14 @@ Lshortloop: sub r3,r7,r8 // generate return value blr -// We're at a RHS page boundary. Compare 4 bytes in order to cross the -// page but still keep the LHS ptr word-aligned. +// We're at a RHS page boundary. Compare GPR_BYTES bytes in order to cross the +// page but still keep the LHS ptr aligned. Lcrosspage: - cmplwi r5,8 // enough bytes left to use word compares? - li r0,4 // get #bytes to cross RHS page + cmplgi r5,2*GPR_BYTES // enough bytes left to use parallel compares? + li r0,GPR_BYTES // get #bytes to cross RHS page blt Lshort // buffer is about to end - mtctr r0 // set up to compare 4 bytes + mtctr r0 b Lbyteloop // Compare byte-by-byte. @@ -105,14 +114,14 @@ Lbyteloop: cmpw r7,r8 // compare the bytes bdnzt eq,Lbyteloop // loop if more to go and bytes are equal - bne Ldifferent // done if we found differing bytes + bne Ldifferent // done if we found differing bytes -// LHS is now word aligned. Loop over words until end of RHS page or buffer. -// When we get to the end of the page, we compare 4 bytes, so that we keep -// the LHS word aligned. +// LHS is now aligned. Loop over words/doublewords until end of RHS page or buffer. +// When we get to the end of the page, we compare 4/8 bytes, so that we keep +// the LHS aligned. // r3 = LHS ptr (aligned) // r4 = RHS ptr (unaligned) -// r5 = length remaining in buffer (>= 4 bytes) +// r5 = length remaining in buffer (>= GPR_BYTES bytes) Laligned: rlwinm r9,r4,0,0xFFF // get RHS offset in page @@ -121,40 +130,45 @@ Laligned: subfe r8,r5,r5 // * r9 <- min(r0,r5), and r7,r7,r8 // * using algorithm in Compiler Writer's Guide add r9,r0,r7 // *** - srwi. r8,r9,2 // get #words we can compare - rlwinm r9,r9,0,0,29 // get #bytes we will compare word-parallel + srgi. r8,r9,LOG2_GPR_BYTES// get #words/doublewords we can compare + clrrgi r9,r9,LOG2_GPR_BYTES// get #bytes we will compare word-parallel beq-- Lcrosspage // we're at a RHS page boundary mtctr r8 // set up loop count sub r5,r5,r9 // decrement length remaining b Lwordloop -// Compare a word at a time, until one of two conditions: +// Compare a word or doubleword at a time, until one of two conditions: // - a difference is found // - end of count (ie, end of buffer or RHS page, whichever is first) // At this point, registers are as follows: // r3 = LHS ptr (aligned) // r4 = RHS ptr (unaligned) // r5 = length remaining in buffer (may be 0) -// ctr = count of words until end of buffer or RHS page +// ctr = count of word/doublewords until end of buffer or RHS page - .align 5 // align inner loop, which is 8 words long + .align 5 // align inner loop Lwordloop: - lwz r7,0(r3) // r7 <- next 4 LHS bytes - addi r3,r3,4 - lwz r8,0(r4) // r8 <- next 4 RHS bytes - addi r4,r4,4 - xor. r11,r7,r8 // compare the words + lg r7,0(r3) // r7 <- next aligned LHS word or doubleword + addi r3,r3,GPR_BYTES + lg r8,0(r4) // r8 <- next unaligned RHS word or doubleword + addi r4,r4,GPR_BYTES + xor. r11,r7,r8 // compare them bdnzt eq,Lwordloop // loop if ctr!=0 and cr0_eq - beq-- Lcrosspage // skip if buffer or page end reached + beq Lcrosspage // skip if buffer or page end reached wo difference // Found differing bytes. - cntlzw r0,r11 // find 1st difference (r0 = 0..31) - rlwinm r9,r0,0,0x18 // byte align bit offset (r9 = 0,8,16, or 24) - addi r0,r9,8 // now, r0 = 8, 16, 24, or 32 + cntlzg r0,r11 // find 1st difference (r0 = 0..31 or 63) + rlwinm r9,r0,0,0x38 // byte align bit offset (r9 = 0,8,16, or 24 etc) + addi r0,r9,8 // now, r0 = 8, 16, 24, or 32 etc +#if defined(__ppc__) rlwnm r7,r7,r0,24,31 // right justify differing bytes and mask off rest rlwnm r8,r8,r0,24,31 +#else + rldcl r7,r7,r0,56 // right justify differing bytes and mask off rest + rldcl r8,r8,r0,56 +#endif Ldifferent: // bytes in r7 and r8 differ sub r3,r7,r8 // compute return value