Fix: Type-casting UBs of movemask bitsets

Author: ashvardanian

include/stringzilla/find.h

@@ -905,7 +905,7 @@ SZ_PUBLIC sz_cptr_t sz_find_westmere(sz_cptr_t h, sz_size_t h_length, sz_cptr_t
     sz_locate_needle_anomalies_(n, n_length, &offset_first, &offset_mid, &offset_last);
 
     // Broadcast those characters into XMM registers.
-    int matches;
+    sz_u32_vec_t matches_vec;
     sz_u128_vec_t h_first_vec, h_mid_vec, h_last_vec, n_first_vec, n_mid_vec, n_last_vec;
     n_first_vec.xmm = _mm_set1_epi8(n[offset_first]);
     n_mid_vec.xmm = _mm_set1_epi8(n[offset_mid]);
@@ -916,14 +916,14 @@ SZ_PUBLIC sz_cptr_t sz_find_westmere(sz_cptr_t h, sz_size_t h_length, sz_cptr_t
         h_first_vec.xmm = _mm_lddqu_si128((__m128i const *)(h + offset_first));
         h_mid_vec.xmm = _mm_lddqu_si128((__m128i const *)(h + offset_mid));
         h_last_vec.xmm = _mm_lddqu_si128((__m128i const *)(h + offset_last));
-        matches = //
+        matches_vec.i32 = //
             _mm_movemask_epi8(_mm_cmpeq_epi8(h_first_vec.xmm, n_first_vec.xmm)) &
             _mm_movemask_epi8(_mm_cmpeq_epi8(h_mid_vec.xmm, n_mid_vec.xmm)) &
             _mm_movemask_epi8(_mm_cmpeq_epi8(h_last_vec.xmm, n_last_vec.xmm));
-        while (matches) {
-            int potential_offset = sz_u32_ctz(matches);
+        while (matches_vec.u32) {
+            int potential_offset = sz_u32_ctz(matches_vec.u32);
             if (sz_equal_westmere(h + potential_offset, n, n_length)) return h + potential_offset;
-            matches &= matches - 1;
+            matches_vec.u32 &= matches_vec.u32 - 1;
         }
     }
 
@@ -940,7 +940,7 @@ SZ_PUBLIC sz_cptr_t sz_rfind_westmere(sz_cptr_t h, sz_size_t h_length, sz_cptr_t
     sz_locate_needle_anomalies_(n, n_length, &offset_first, &offset_mid, &offset_last);
 
     // Broadcast those characters into XMM registers.
-    int matches;
+    sz_u32_vec_t matches_vec;
     sz_u128_vec_t h_first_vec, h_mid_vec, h_last_vec, n_first_vec, n_mid_vec, n_last_vec;
     n_first_vec.xmm = _mm_set1_epi8(n[offset_first]);
     n_mid_vec.xmm = _mm_set1_epi8(n[offset_mid]);
@@ -953,15 +953,15 @@ SZ_PUBLIC sz_cptr_t sz_rfind_westmere(sz_cptr_t h, sz_size_t h_length, sz_cptr_t
         h_first_vec.xmm = _mm_lddqu_si128((__m128i const *)(h_reversed + offset_first));
         h_mid_vec.xmm = _mm_lddqu_si128((__m128i const *)(h_reversed + offset_mid));
         h_last_vec.xmm = _mm_lddqu_si128((__m128i const *)(h_reversed + offset_last));
-        matches = //
+        matches_vec.i32 = //
             _mm_movemask_epi8(_mm_cmpeq_epi8(h_first_vec.xmm, n_first_vec.xmm)) &
             _mm_movemask_epi8(_mm_cmpeq_epi8(h_mid_vec.xmm, n_mid_vec.xmm)) &
             _mm_movemask_epi8(_mm_cmpeq_epi8(h_last_vec.xmm, n_last_vec.xmm));
-        while (matches) {
-            int potential_offset = sz_u32_clz(matches) - 16;
+        while (matches_vec.u32) {
+            int potential_offset = sz_u32_clz(matches_vec.u32) - 16;
             if (sz_equal_westmere(h + h_length - n_length - potential_offset, n, n_length))
                 return h + h_length - n_length - potential_offset;
-            matches &= ~(1 << (15 - potential_offset));
+            matches_vec.u32 &= ~(1u << (15 - potential_offset));
         }
     }
 
@@ -1029,7 +1029,7 @@ SZ_PUBLIC sz_cptr_t sz_find_haswell(sz_cptr_t h, sz_size_t h_length, sz_cptr_t n
     sz_locate_needle_anomalies_(n, n_length, &offset_first, &offset_mid, &offset_last);
 
     // Broadcast those characters into YMM registers.
-    int matches;
+    sz_u32_vec_t matches_vec;
     sz_u256_vec_t h_first_vec, h_mid_vec, h_last_vec, n_first_vec, n_mid_vec, n_last_vec;
     n_first_vec.ymm = _mm256_set1_epi8(n[offset_first]);
     n_mid_vec.ymm = _mm256_set1_epi8(n[offset_mid]);
@@ -1040,14 +1040,14 @@ SZ_PUBLIC sz_cptr_t sz_find_haswell(sz_cptr_t h, sz_size_t h_length, sz_cptr_t n
         h_first_vec.ymm = _mm256_lddqu_si256((__m256i const *)(h + offset_first));
         h_mid_vec.ymm = _mm256_lddqu_si256((__m256i const *)(h + offset_mid));
         h_last_vec.ymm = _mm256_lddqu_si256((__m256i const *)(h + offset_last));
-        matches = //
+        matches_vec.i32 = //
             _mm256_movemask_epi8(_mm256_cmpeq_epi8(h_first_vec.ymm, n_first_vec.ymm)) &
             _mm256_movemask_epi8(_mm256_cmpeq_epi8(h_mid_vec.ymm, n_mid_vec.ymm)) &
             _mm256_movemask_epi8(_mm256_cmpeq_epi8(h_last_vec.ymm, n_last_vec.ymm));
-        while (matches) {
-            int potential_offset = sz_u32_ctz(matches);
+        while (matches_vec.u32) {
+            int potential_offset = sz_u32_ctz(matches_vec.u32);
             if (sz_equal_haswell(h + potential_offset, n, n_length)) return h + potential_offset;
-            matches &= matches - 1;
+            matches_vec.u32 &= matches_vec.u32 - 1;
         }
     }
 
@@ -1065,7 +1065,7 @@ SZ_PUBLIC sz_cptr_t sz_rfind_haswell(sz_cptr_t h, sz_size_t h_length, sz_cptr_t
     sz_locate_needle_anomalies_(n, n_length, &offset_first, &offset_mid, &offset_last);
 
     // Broadcast those characters into YMM registers.
-    int matches;
+    sz_u32_vec_t matches_vec;
     sz_u256_vec_t h_first_vec, h_mid_vec, h_last_vec, n_first_vec, n_mid_vec, n_last_vec;
     n_first_vec.ymm = _mm256_set1_epi8(n[offset_first]);
     n_mid_vec.ymm = _mm256_set1_epi8(n[offset_mid]);
@@ -1078,15 +1078,15 @@ SZ_PUBLIC sz_cptr_t sz_rfind_haswell(sz_cptr_t h, sz_size_t h_length, sz_cptr_t
         h_first_vec.ymm = _mm256_lddqu_si256((__m256i const *)(h_reversed + offset_first));
         h_mid_vec.ymm = _mm256_lddqu_si256((__m256i const *)(h_reversed + offset_mid));
         h_last_vec.ymm = _mm256_lddqu_si256((__m256i const *)(h_reversed + offset_last));
-        matches = //
+        matches_vec.i32 = //
             _mm256_movemask_epi8(_mm256_cmpeq_epi8(h_first_vec.ymm, n_first_vec.ymm)) &
             _mm256_movemask_epi8(_mm256_cmpeq_epi8(h_mid_vec.ymm, n_mid_vec.ymm)) &
             _mm256_movemask_epi8(_mm256_cmpeq_epi8(h_last_vec.ymm, n_last_vec.ymm));
-        while (matches) {
-            int potential_offset = sz_u32_clz(matches);
+        while (matches_vec.u32) {
+            int potential_offset = sz_u32_clz(matches_vec.u32);
             if (sz_equal_haswell(h + h_length - n_length - potential_offset, n, n_length))
                 return h + h_length - n_length - potential_offset;
-            matches &= ~(1 << (31 - potential_offset));
+            matches_vec.u32 &= ~(1u << (31 - potential_offset));
         }
     }
 
@@ -1388,9 +1388,8 @@ SZ_PUBLIC sz_cptr_t sz_rfind_skylake(sz_cptr_t h, sz_size_t h_length, sz_cptr_t
             int potential_offset = sz_u64_clz(matches);
             if (n_length <= 3 || sz_equal_skylake(h + h_length - n_length - potential_offset, n, n_length))
                 return h + h_length - n_length - potential_offset;
-            sz_assert_((matches & ((sz_u64_t)1 << (63 - potential_offset))) != 0 &&
-                       "The bit must be set before we squash it");
-            matches &= ~((sz_u64_t)1 << (63 - potential_offset));
+            sz_assert_((matches & (1ull << (63 - potential_offset))) != 0 && "The bit must be set before we squash it");
+            matches &= ~(1ull << (63 - potential_offset));
         }
     }
 
@@ -1409,9 +1408,8 @@ SZ_PUBLIC sz_cptr_t sz_rfind_skylake(sz_cptr_t h, sz_size_t h_length, sz_cptr_t
             int potential_offset = sz_u64_clz(matches);
             if (n_length <= 3 || sz_equal_skylake(h + 64 - potential_offset - 1, n, n_length))
                 return h + 64 - potential_offset - 1;
-            sz_assert_((matches & ((sz_u64_t)1 << (63 - potential_offset))) != 0 &&
-                       "The bit must be set before we squash it");
-            matches &= ~((sz_u64_t)1 << (63 - potential_offset));
+            sz_assert_((matches & (1ull << (63 - potential_offset))) != 0 && "The bit must be set before we squash it");
+            matches &= ~(1ull << (63 - potential_offset));
         }
     }
 

include/stringzilla/intersect.h

@@ -288,7 +288,7 @@ SZ_PUBLIC sz_status_t sz_sequence_intersect_serial(
     // Allocate memory for the hash table and initialize it with 0xFF.
     // The higher is the `hash_table_slots` multiple - the more memory we will use,
     // but the less likely the collisions will be.
-    sz_size_t const hash_table_slots = sz_size_bit_ceil(small_sequence->count) * (1 << SZ_SEQUENCE_INTERSECT_BUDGET);
+    sz_size_t const hash_table_slots = sz_size_bit_ceil(small_sequence->count) * (1u << SZ_SEQUENCE_INTERSECT_BUDGET);
     sz_size_t const bytes_per_entry = sizeof(sz_size_t) + sizeof(sz_u64_t);
     sz_size_t *const table_positions = (sz_size_t *)alloc->allocate(hash_table_slots * bytes_per_entry, alloc);
     if (!table_positions) return sz_bad_alloc_k;
@@ -414,7 +414,7 @@ SZ_PUBLIC sz_status_t sz_sequence_intersect_ice(
     // Allocate memory for the hash table and initialize it with 0xFF.
     // The higher is the `hash_table_slots` multiple - the more memory we will use,
     // but the less likely the collisions will be.
-    sz_size_t const hash_table_slots = sz_size_bit_ceil(small_sequence->count) * (1 << SZ_SEQUENCE_INTERSECT_BUDGET);
+    sz_size_t const hash_table_slots = sz_size_bit_ceil(small_sequence->count) * (1u << SZ_SEQUENCE_INTERSECT_BUDGET);
     sz_size_t const bytes_per_entry = sizeof(sz_size_t) + sizeof(sz_u64_t);
     sz_size_t *table_positions = (sz_size_t *)alloc->allocate(hash_table_slots * bytes_per_entry, alloc);
     if (!table_positions) return sz_bad_alloc_k;

include/stringzilla/types.h

@@ -840,6 +840,7 @@ typedef union sz_u16_vec_t {
  */
 typedef union sz_u32_vec_t {
     sz_u32_t u32;
+    sz_i32_t i32;
     sz_u16_t u16s[2];
     sz_i16_t i16s[2];
     sz_u8_t u8s[4];
@@ -852,6 +853,7 @@ typedef union sz_u32_vec_t {
  */
 typedef union sz_u64_vec_t {
     sz_u64_t u64;
+    sz_i64_t i64;
     sz_u32_t u32s[2];
     sz_i32_t i32s[2];
     sz_u16_t u16s[4];