109335 2013-02-08 17:11:10 -0800 ARM_NEON Inline Assembly for copyLCharsFromUCharSource() inefficient for aligned destinations 2013-02-08 18:00:19 -0800 1 1 1 Unclassified WebKit JavaScriptCore 528+ (Nightly build) Other All RESOLVED FIXED P2 Normal --- 1 msaboff msaboff benjamin cmarcelo ojan.autocc webkit.review.bot oldest_to_newest 828846 0 msaboff 2013-02-08 17:11:10 -0800 The ARM_NEON specific code for copyLCharsFromUCharSource() always tries to align the destination, even when it is aligned. The can be seen for moves > 15 characters in length. The code in question is marked if (length >= (2 * memoryAccessSize) - 1) { // Prefix: align dst on 64 bits. const uintptr_t memoryAccessMask = memoryAccessSize - 1; * do { * *destination++ = static_cast<LChar>(*source++); * } while (!isAlignedTo<memoryAccessMask>(destination)); // Vector interleaved unpack, we only store the lower 8 bits. const uintptr_t lengthLeft = end - destination; const LChar* const simdEnd = end - (lengthLeft % memoryAccessSize); do { asm("vld2.8 { d0-d1 }, [%[SOURCE]] !\n\t" "vst1.8 { d0 }, [%[DESTINATION],:64] !\n\t" : [SOURCE]"+r" (source), [DESTINATION]"+r" (destination) : : "memory", "d0", "d1"); } while (destination != simdEnd); } The do { } while should be changed to a while. 828856 1 187391 msaboff 2013-02-08 17:45:23 -0800 Created attachment 187391 Patch In a synthetic test harness, this is a speed up in the small, but above 15 character case. 828861 2 msaboff 2013-02-08 18:00:19 -0800 Committed r142336: <http://trac.webkit.org/changeset/142336> 187391 2013-02-08 17:45:23 -0800 2013-02-08 17:57:01 -0800 Patch 109335.patch text/plain 1564 msaboff SW5kZXg6IFNvdXJjZS9XVEYvQ2hhbmdlTG9nCj09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT0KLS0tIFNvdXJjZS9XVEYvQ2hh bmdlTG9nCShyZXZpc2lvbiAxNDIzMzQpCisrKyBTb3VyY2UvV1RGL0NoYW5nZUxvZwkod29ya2lu ZyBjb3B5KQpAQCAtMSwzICsxLDE2IEBACisyMDEzLTAyLTA4ICBNaWNoYWVsIFNhYm9mZiAgPG1z YWJvZmZAYXBwbGUuY29tPgorCisgICAgICAgIEFSTV9ORU9OIElubGluZSBBc3NlbWJseSBmb3Ig Y29weUxDaGFyc0Zyb21VQ2hhclNvdXJjZSgpIGluZWZmaWNpZW50IGZvciBhbGlnbmVkIGRlc3Rp bmF0aW9ucworICAgICAgICBodHRwczovL2J1Z3Mud2Via2l0Lm9yZy9zaG93X2J1Zy5jZ2k/aWQ9 MTA5MzM1CisKKyAgICAgICAgUmV2aWV3ZWQgYnkgTk9CT0RZIChPT1BTISkuCisKKyAgICAgICAg Q2hhbmdlIGEgImRvIHdoaWxlIiB0byBhICJ3aGlsZSIgc28gdGhhdCB3ZSBkb24ndCBjb3B5IHNp bmdsZSBjaGFyYWN0ZXJzIHRvIGFsaWduIHRoZSAKKyAgICAgICAgZGVzdGluYXRpb24gd2hlbiBp dCBpcyBhbHJlYWR5IGFsaWduZWQuCisKKyAgICAgICAgKiB3dGYvdGV4dC9BU0NJSUZhc3RQYXRo Lmg6CisgICAgICAgIChXVEY6OmNvcHlMQ2hhcnNGcm9tVUNoYXJTb3VyY2UpOgorCiAyMDEzLTAy LTA4ICBKZXIgTm9ibGUgIDxqZXIubm9ibGVAYXBwbGUuY29tPgogCiAgICAgICAgIEJyaW5nIFdl YktpdCB1cCB0byBzcGVlZCB3aXRoIGxhdGVzdCBFbmNyeXB0ZWQgTWVkaWEgc3BlYy4KSW5kZXg6 IFNvdXJjZS9XVEYvd3RmL3RleHQvQVNDSUlGYXN0UGF0aC5oCj09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT0KLS0tIFNvdXJj ZS9XVEYvd3RmL3RleHQvQVNDSUlGYXN0UGF0aC5oCShyZXZpc2lvbiAxNDIzMzQpCisrKyBTb3Vy Y2UvV1RGL3d0Zi90ZXh0L0FTQ0lJRmFzdFBhdGguaAkod29ya2luZyBjb3B5KQpAQCAtMTM4LDkg KzEzOCw4IEBAIGlubGluZSB2b2lkIGNvcHlMQ2hhcnNGcm9tVUNoYXJTb3VyY2UoTEMKICAgICBp ZiAobGVuZ3RoID49ICgyICogbWVtb3J5QWNjZXNzU2l6ZSkgLSAxKSB7CiAgICAgICAgIC8vIFBy ZWZpeDogYWxpZ24gZHN0IG9uIDY0IGJpdHMuCiAgICAgICAgIGNvbnN0IHVpbnRwdHJfdCBtZW1v cnlBY2Nlc3NNYXNrID0gbWVtb3J5QWNjZXNzU2l6ZSAtIDE7Ci0gICAgICAgIGRvIHsKKyAgICAg ICAgd2hpbGUgKCFpc0FsaWduZWRUbzxtZW1vcnlBY2Nlc3NNYXNrPihkZXN0aW5hdGlvbikpCiAg ICAgICAgICAgICAqZGVzdGluYXRpb24rKyA9IHN0YXRpY19jYXN0PExDaGFyPigqc291cmNlKysp OwotICAgICAgICB9IHdoaWxlICghaXNBbGlnbmVkVG88bWVtb3J5QWNjZXNzTWFzaz4oZGVzdGlu YXRpb24pKTsKIAogICAgICAgICAvLyBWZWN0b3IgaW50ZXJsZWF2ZWQgdW5wYWNrLCB3ZSBvbmx5 IHN0b3JlIHRoZSBsb3dlciA4IGJpdHMuCiAgICAgICAgIGNvbnN0IHVpbnRwdHJfdCBsZW5ndGhM ZWZ0ID0gZW5kIC0gZGVzdGluYXRpb247Cg==