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Message-ID: <bbb0a92c-4237-c651-3b8b-84dfaa2a2096@kernel.org>
Date: Mon, 16 Aug 2021 09:53:53 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: dsterba@...e.cz, Andrew Morton <akpm@...ux-foundation.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
terrelln@...com
Subject: Re: [PATCH] lib/zstd: Fix bitwise vs logical operators
On 8/16/2021 8:14 AM, David Sterba wrote:
> You should CC Nick Terell for ZSTD patches, added.
Thanks for the info and adding him, I did not see an entry for lib/zstd/
in MAINTAINERS and there is no consistent person picking up patches
according to git.
Cheers,
Nathan
> On Sat, Aug 14, 2021 at 05:41:54PM -0700, Nathan Chancellor wrote:
>> clang warns several times along the lines of:
>>
>> lib/zstd/compress.c:1043:7: warning: bitwise and of boolean expressions; did you mean logical and? [-Wbool-operation-and]
>> if ((offset_1 > 0) & (ZSTD_read32(ip + 1 - offset_1) == ZSTD_read32(ip + 1))) {
>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> &&
>>
>> Bitwise ANDs do not short circuit, meaning that the ZSTD_read32 calls
>> will be evaluated even if the first condition is not true. This is not
>> always a problem but it is not a standard way to do conditionals so
>> replace the bitwise ANDs with logical ones to fix the warning and make
>> the code clearer.
>>
>> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
>> ---
>> lib/zstd/compress.c | 16 ++++++++--------
>> 1 file changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/lib/zstd/compress.c b/lib/zstd/compress.c
>> index b080264ed3ad..0e515d1d4237 100644
>> --- a/lib/zstd/compress.c
>> +++ b/lib/zstd/compress.c
>> @@ -1040,7 +1040,7 @@ void ZSTD_compressBlock_fast_generic(ZSTD_CCtx *cctx, const void *src, size_t sr
>> const BYTE *match = base + matchIndex;
>> hashTable[h] = curr; /* update hash table */
>>
>> - if ((offset_1 > 0) & (ZSTD_read32(ip + 1 - offset_1) == ZSTD_read32(ip + 1))) {
>> + if ((offset_1 > 0) && (ZSTD_read32(ip + 1 - offset_1) == ZSTD_read32(ip + 1))) {
>> mLength = ZSTD_count(ip + 1 + 4, ip + 1 + 4 - offset_1, iend) + 4;
>> ip++;
>> ZSTD_storeSeq(seqStorePtr, ip - anchor, anchor, 0, mLength - MINMATCH);
>> @@ -1072,7 +1072,7 @@ void ZSTD_compressBlock_fast_generic(ZSTD_CCtx *cctx, const void *src, size_t sr
>> hashTable[ZSTD_hashPtr(base + curr + 2, hBits, mls)] = curr + 2; /* here because curr+2 could be > iend-8 */
>> hashTable[ZSTD_hashPtr(ip - 2, hBits, mls)] = (U32)(ip - 2 - base);
>> /* check immediate repcode */
>> - while ((ip <= ilimit) && ((offset_2 > 0) & (ZSTD_read32(ip) == ZSTD_read32(ip - offset_2)))) {
>> + while ((ip <= ilimit) && ((offset_2 > 0) && (ZSTD_read32(ip) == ZSTD_read32(ip - offset_2)))) {
>> /* store sequence */
>> size_t const rLength = ZSTD_count(ip + 4, ip + 4 - offset_2, iend) + 4;
>> {
>> @@ -1291,7 +1291,7 @@ void ZSTD_compressBlock_doubleFast_generic(ZSTD_CCtx *cctx, const void *src, siz
>> const BYTE *match = base + matchIndexS;
>> hashLong[h2] = hashSmall[h] = curr; /* update hash tables */
>>
>> - if ((offset_1 > 0) & (ZSTD_read32(ip + 1 - offset_1) == ZSTD_read32(ip + 1))) { /* note : by construction, offset_1 <= curr */
>> + if ((offset_1 > 0) && (ZSTD_read32(ip + 1 - offset_1) == ZSTD_read32(ip + 1))) { /* note : by construction, offset_1 <= curr */
>> mLength = ZSTD_count(ip + 1 + 4, ip + 1 + 4 - offset_1, iend) + 4;
>> ip++;
>> ZSTD_storeSeq(seqStorePtr, ip - anchor, anchor, 0, mLength - MINMATCH);
>> @@ -1350,7 +1350,7 @@ void ZSTD_compressBlock_doubleFast_generic(ZSTD_CCtx *cctx, const void *src, siz
>> hashLong[ZSTD_hashPtr(ip - 2, hBitsL, 8)] = hashSmall[ZSTD_hashPtr(ip - 2, hBitsS, mls)] = (U32)(ip - 2 - base);
>>
>> /* check immediate repcode */
>> - while ((ip <= ilimit) && ((offset_2 > 0) & (ZSTD_read32(ip) == ZSTD_read32(ip - offset_2)))) {
>> + while ((ip <= ilimit) && ((offset_2 > 0) && (ZSTD_read32(ip) == ZSTD_read32(ip - offset_2)))) {
>> /* store sequence */
>> size_t const rLength = ZSTD_count(ip + 4, ip + 4 - offset_2, iend) + 4;
>> {
>> @@ -1929,7 +1929,7 @@ void ZSTD_compressBlock_lazy_generic(ZSTD_CCtx *ctx, const void *src, size_t src
>> const BYTE *start = ip + 1;
>>
>> /* check repCode */
>> - if ((offset_1 > 0) & (ZSTD_read32(ip + 1) == ZSTD_read32(ip + 1 - offset_1))) {
>> + if ((offset_1 > 0) && (ZSTD_read32(ip + 1) == ZSTD_read32(ip + 1 - offset_1))) {
>> /* repcode : we take it */
>> matchLength = ZSTD_count(ip + 1 + EQUAL_READ32, ip + 1 + EQUAL_READ32 - offset_1, iend) + EQUAL_READ32;
>> if (depth == 0)
>> @@ -1953,7 +1953,7 @@ void ZSTD_compressBlock_lazy_generic(ZSTD_CCtx *ctx, const void *src, size_t src
>> if (depth >= 1)
>> while (ip < ilimit) {
>> ip++;
>> - if ((offset) && ((offset_1 > 0) & (ZSTD_read32(ip) == ZSTD_read32(ip - offset_1)))) {
>> + if ((offset) && ((offset_1 > 0) && (ZSTD_read32(ip) == ZSTD_read32(ip - offset_1)))) {
>> size_t const mlRep = ZSTD_count(ip + EQUAL_READ32, ip + EQUAL_READ32 - offset_1, iend) + EQUAL_READ32;
>> int const gain2 = (int)(mlRep * 3);
>> int const gain1 = (int)(matchLength * 3 - ZSTD_highbit32((U32)offset + 1) + 1);
>> @@ -1974,7 +1974,7 @@ void ZSTD_compressBlock_lazy_generic(ZSTD_CCtx *ctx, const void *src, size_t src
>> /* let's find an even better one */
>> if ((depth == 2) && (ip < ilimit)) {
>> ip++;
>> - if ((offset) && ((offset_1 > 0) & (ZSTD_read32(ip) == ZSTD_read32(ip - offset_1)))) {
>> + if ((offset) && ((offset_1 > 0) && (ZSTD_read32(ip) == ZSTD_read32(ip - offset_1)))) {
>> size_t const ml2 = ZSTD_count(ip + EQUAL_READ32, ip + EQUAL_READ32 - offset_1, iend) + EQUAL_READ32;
>> int const gain2 = (int)(ml2 * 4);
>> int const gain1 = (int)(matchLength * 4 - ZSTD_highbit32((U32)offset + 1) + 1);
>> @@ -2021,7 +2021,7 @@ void ZSTD_compressBlock_lazy_generic(ZSTD_CCtx *ctx, const void *src, size_t src
>> }
>>
>> /* check immediate repcode */
>> - while ((ip <= ilimit) && ((offset_2 > 0) & (ZSTD_read32(ip) == ZSTD_read32(ip - offset_2)))) {
>> + while ((ip <= ilimit) && ((offset_2 > 0) && (ZSTD_read32(ip) == ZSTD_read32(ip - offset_2)))) {
>> /* store sequence */
>> matchLength = ZSTD_count(ip + EQUAL_READ32, ip + EQUAL_READ32 - offset_2, iend) + EQUAL_READ32;
>> offset = offset_2;
>>
>> base-commit: ba31f97d43be41ca99ab72a6131d7c226306865f
>> --
>> 2.33.0.rc2
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