godoc: Warn users that the dst bitmap must be zeroed before

The AVX2 loop will write the zeroes, but the fallback loop won't. If the
number of rows isn't a multiple of 64, both implementation might be
used in one call.

Author: Jille

typeswitch.go

@@ -1,6 +1,7 @@
 package vectorcmp
 
 // VectorEquals compares each entry in rows to search and enables the corresponding bit in dst if equal.
+// dst must be zeroed before this call.
 // Prefer calling VectorEquals8/16/32/64 directly.
 //
 //	for i, v := range rows {
@@ -24,6 +25,7 @@ func VectorEquals[T uint8 | uint16 | uint32 | uint64](dst []byte, search T, rows
 }
 
 // VectorGreaterThan compares each entry in rows to search and enables the corresponding bit in dst if search > rows[i].
+// dst must be zeroed before this call.
 // Prefer calling VectorGreaterThan8/16/32/64 directly.
 //
 //	for i, v := range rows {
@@ -47,6 +49,7 @@ func VectorGreaterThan[T uint8 | uint16 | uint32 | uint64](dst []byte, search T,
 }
 
 // VectorLessThan compares each entry in rows to search and enables the corresponding bit in dst if search < rows[i].
+// dst must be zeroed before this call.
 // Prefer calling VectorLessThan8/16/32/64 directly.
 //
 //	for i, v := range rows {
@@ -70,6 +73,7 @@ func VectorLessThan[T uint8 | uint16 | uint32 | uint64](dst []byte, search T, ro
 }
 
 // VectorGreaterEquals compares each entry in rows to search and enables the corresponding bit in dst if search >= rows[i].
+// dst must be zeroed before this call.
 // Prefer calling VectorGreaterEquals8/16/32/64 directly.
 //
 //	for i, v := range rows {
@@ -93,6 +97,7 @@ func VectorGreaterEquals[T uint8 | uint16 | uint32 | uint64](dst []byte, search
 }
 
 // VectorLesserEquals compares each entry in rows to search and enables the corresponding bit in dst if search <= rows[i].
+// dst must be zeroed before this call.
 // Prefer calling VectorLesserEquals8/16/32/64 directly.
 //
 //	for i, v := range rows {