mirror of
https://github.com/classilla/tenfourfox.git
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82 lines
3.1 KiB
C
82 lines
3.1 KiB
C
#include <stdio.h>
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#include "plvmx.h"
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/* VMX/AltiVec specific libc functions for TenFourFox. */
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void *vmx_memchr(const void *b, int c, size_t length) {
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/* From:
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https://github.com/ridiculousfish/HexFiend/blob/4d5bcee5715f5f288649f7471d1da5bd06376f46/framework/sources/HFFastMemchr.m
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with some optimizations and fixes. */
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const unsigned char *haystack = (const unsigned char *)b;
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unsigned char needle = (unsigned char)c;
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unsigned prefixLength = (unsigned)((16 - ((unsigned long)haystack) % 16) % 16);
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unsigned suffixLength = (unsigned)(((unsigned long)(haystack + length)) % 16);
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// It is possible for altivecLength to be < 0 for short strings.
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int altivecLength = length - prefixLength - suffixLength;
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if (altivecLength < 32) { // not worth the setup
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while (length--) {
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if (*haystack == needle) return (void *)haystack;
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haystack++;
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}
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return NULL;
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}
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size_t numVectors = altivecLength >> 4;
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while (prefixLength--) {
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if (*haystack == needle) return (void *)haystack;
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haystack++;
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}
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unsigned int mashedByte = (needle << 24 ) | (needle << 16) | (needle << 8) | needle;
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const vector unsigned char searchVector = (vector unsigned int){mashedByte, mashedByte, mashedByte, mashedByte};
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while (numVectors--) {
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if (vec_any_eq(*(const vector unsigned char*)haystack, searchVector)) goto foundResult;
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haystack += 16;
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}
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while (suffixLength--) {
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if (*haystack == needle) return (void *)haystack;
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haystack++;
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}
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return NULL;
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foundResult:
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;
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unsigned int val;
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// Some byte has the result; look in groups of 4 to find which one.
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// Unroll the loop.
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val = *(unsigned int*)haystack;
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if (((val >> 24) & 0xFF) == needle) return (void *)haystack;
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if (((val >> 16) & 0xFF) == needle) return (void *)(1 + haystack);
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if (((val >> 8) & 0xFF) == needle) return (void *)(2 + haystack);
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if ((val & 0xFF) == needle) return (void *)(3 + haystack);
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haystack += 4;
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val = *(unsigned int*)haystack;
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if (((val >> 24) & 0xFF) == needle) return (void *)haystack;
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if (((val >> 16) & 0xFF) == needle) return (void *)(1 + haystack);
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if (((val >> 8) & 0xFF) == needle) return (void *)(2 + haystack);
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if ((val & 0xFF) == needle) return (void *)(3 + haystack);
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haystack += 4;
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val = *(unsigned int*)haystack;
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if (((val >> 24) & 0xFF) == needle) return (void *)haystack;
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if (((val >> 16) & 0xFF) == needle) return (void *)(1 + haystack);
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if (((val >> 8) & 0xFF) == needle) return (void *)(2 + haystack);
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if ((val & 0xFF) == needle) return (void *)(3 + haystack);
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haystack += 4;
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val = *(unsigned int*)haystack;
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if (((val >> 24) & 0xFF) == needle) return (void *)haystack;
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if (((val >> 16) & 0xFF) == needle) return (void *)(1 + haystack);
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if (((val >> 8) & 0xFF) == needle) return (void *)(2 + haystack);
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if ((val & 0xFF) == needle) return (void *)(3 + haystack);
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// unreachable
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fprintf(stderr, "failed vmx_memchr()\n");
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return NULL;
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}
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