fix zero-ing of last n bytes

kitty/simd-string-impl.h

@@ -57,6 +57,7 @@ _Pragma("clang diagnostic pop")
 #define shift_right_by_bits32 simde_mm_srli_epi32
 #define shuffle_epi8 simde_mm_shuffle_epi8
 #define numbered_bytes() set_epi8(15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0)
+#define reverse_numbered_bytes() simde_mm_setr_epi8(15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0)
 // output[i] = MAX(0, a[i] - b[1i])
 #define subtract_saturate_epu8 simde_mm_subs_epu8
 #define create_zero_integer simde_mm_setzero_si128
@@ -93,6 +94,7 @@ _Pragma("clang diagnostic pop")
 #define shift_left_by_eight_bytes(vec) simde_mm256_alignr_epi8(vec, simde_mm256_permute2x128_si256(vec, vec, _MM_SHUFFLE(2, 0, 0, 1)), 8)
 #define shift_left_by_sixteen_bytes(vec) simde_mm256_permute2x128_si256(vec, vec, _MM_SHUFFLE(2, 0, 0, 1))
 #define numbered_bytes() set_epi8(31,30,29,28,27,26,25,24,23,22,21,20,19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0)
+#define reverse_numbered_bytes() simde_mm256_setr_epi8(31,30,29,28,27,26,25,24,23,22,21,20,19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0)
 
 static inline integer_t shuffle_impl256(const integer_t value, const integer_t shuffle) {
 #define K0 simde_mm256_setr_epi8( \
@@ -114,13 +116,31 @@ static inline integer_t shuffle_impl256(const integer_t value, const integer_t s
 #define shuffle_epi8 shuffle_impl256
 #define sum_bytes(x) (sum_bytes_128(simde_mm256_extracti128_si256(vec, 0)) + sum_bytes_128(simde_mm256_extracti128_si256(vec, 1)))
 #endif
+#if 1
+#define print_register_as_bytes(r) { \
+    printf("%s:\n", #r); \
+    alignas(64) uint8_t data[sizeof(r)]; \
+    store_aligned((integer_t*)data, r); \
+    for (unsigned i = 0; i < sizeof(integer_t); i++) { \
+        uint8_t ch = data[i]; \
+        if (' ' <= ch && ch < 0x7f) printf("_%c ", ch); else printf("%.2x ", ch); \
+    } \
+    printf("\n"); \
+}
+#define debug printf
+#else
+#define print_register_as_bytes(r)
+#define debug(...)
+#endif
+
 // }}}
 
 static inline integer_t
-FUNC(zero_last_n_bytes)(integer_t vec, int n) {
+FUNC(zero_last_n_bytes)(integer_t vec, char n) {
     const integer_t threshold = set1_epi8(n);
-    const integer_t index = numbered_bytes();
+    const integer_t index = reverse_numbered_bytes();
-    return andnot_si(cmpgt_epi8(threshold, index), vec);
+    const integer_t mask = cmpgt_epi8(threshold, index);
+    return andnot_si(mask, vec);
 }
 
 static inline const uint8_t*
@@ -141,23 +161,6 @@ FUNC(find_either_of_two_bytes)(const uint8_t *haystack, const size_t sz, const u
     return NULL;
 }
 
-#if 1
-#define print_register_as_bytes(r) { \
-    printf("%s:\n", #r); \
-    alignas(64) uint8_t data[sizeof(r)]; \
-    store_aligned((integer_t*)data, r); \
-    for (unsigned i = 0; i < sizeof(integer_t); i++) { \
-        uint8_t ch = data[i]; \
-        if (' ' <= ch && ch < 0x7f) printf("_%c ", ch); else printf("%.2x ", ch); \
-    } \
-    printf("\n"); \
-}
-#define debug printf
-#else
-#define print_register_as_bytes(r)
-#define debug(...)
-#endif
-
 static inline void
 FUNC(output_plain_ascii)(UTF8Decoder *d, integer_t vec, size_t src_sz) {
 #if BITS == 128
@@ -293,7 +296,7 @@ FUNC(utf8_decode_to_esc)(UTF8Decoder *d, const uint8_t *src, size_t src_sz) {
         src_sz = num_of_bytes_to_first_esc;
         d->num_consumed = src_sz + 1;  // esc is also consumed
     } else d->num_consumed = src_sz;
-    if (src_sz < sizeof(integer_t)/8) zero_last_n_bytes(vec, sizeof(integer_t)/8 - src_sz);
+    if (src_sz < sizeof(integer_t)) vec = zero_last_n_bytes(vec, sizeof(integer_t) - src_sz);
 
     const integer_t one = set1_epi8(1), two = set1_epi8(2), three = set1_epi8(3);
     // Classify the bytes
@@ -452,6 +455,7 @@ FUNC(utf8_decode_to_esc)(UTF8Decoder *d, const uint8_t *src, size_t src_sz) {
 #undef create_zero_integer
 #undef shuffle_epi8
 #undef numbered_bytes
+#undef reverse_numbered_bytes
 #undef zero_last_n_bytes
 #undef sum_bytes
 #ifndef SIMD_STRING_IMPL_INCLUDED_ONCE

kitty_tests/parser.py

@@ -189,6 +189,7 @@ class TestParser(BaseTest):
             self.ae(expected, actual, msg=f'Failed for {x!r} with {which=}\n{expected!r} !=\n{actual!r}')
         for which in (2, 3):
             x = partial(t, which=which)
+            x('2:α3')
             x('2:α3:≤4:😸|')
             x('abcd1234efgh5678')
             x('abc\x1bd1234efgh5678')