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8268276: Base64 Decoding optimization for x86 using AVX-512

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Reviewed-by: erikj, sviswanathan, kvn
This commit is contained in:
Scott Gibbons 2021-06-25 03:19:48 +00:00 • committed by Sandhya Viswanathan
parent 08ee7ae672
commit c37988d079
12 changed files with 749 additions and 18 deletions
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17
src/java.base/share/classes/java/util/Base64.java
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@ -753,16 +753,15 @@ public class Base64 {
* chunks of the src that are of a favorable size for the specific
* processor it's running on.
*
* If the intrinsic function does not process all of the bytes in
* src, it must process a multiple of four of them, making the
* returned destination length a multiple of three.
*
* If any illegal base64 bytes are encountered in src by the
* intrinsic, the intrinsic must return the actual number of valid
* data bytes already written to dst. Note that the '=' pad
* character is treated as an illegal Base64 character by
* decodeBlock, so it will not process a block of 4 bytes
* containing pad characters.
* containing pad characters. However, MIME decoding ignores
* illegal characters, so any intrinsic overriding decodeBlock
* can choose how to handle illegal characters based on the isMIME
* parameter.
*
* Given the parameters, no length check is possible on dst, so dst
* is assumed to be large enough to store the decoded bytes.
@ -779,10 +778,12 @@ public class Base64 {
* the offset into dst array to begin writing
* @param isURL
* boolean, when true decode RFC4648 URL-safe base64 characters
* @param isMIME
* boolean, when true decode according to RFC2045 (ignore illegal chars)
* @return the number of destination data bytes produced
*/
@IntrinsicCandidate
private int decodeBlock(byte[] src, int sp, int sl, byte[] dst, int dp, boolean isURL) {
private int decodeBlock(byte[] src, int sp, int sl, byte[] dst, int dp, boolean isURL, boolean isMIME) {
int[] base64 = isURL ? fromBase64URL : fromBase64;
int sl0 = sp + ((sl - sp) & ~0b11);
int new_dp = dp;
@ -810,12 +811,12 @@ public class Base64 {
while (sp < sl) {
if (shiftto == 18 && sp < sl - 4) { // fast path
int dl = decodeBlock(src, sp, sl, dst, dp, isURL);
int dl = decodeBlock(src, sp, sl, dst, dp, isURL, isMIME);
/*
* Calculate how many characters were processed by how many
* bytes of data were returned.
*/
int chars_decoded = (dl / 3) * 4;
int chars_decoded = ((dl + 2) / 3) * 4;
sp += chars_decoded;
dp += dl;