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Fix fuzzer.c nits and replace CLZ fallback

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This commit is contained in:
Elliot Gorokhovsky
2022-02-16 11:40:05 -05:00
parent 00f2acba36
commit 856c7dc51d
2 changed files with 28 additions and 12 deletions
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lib/common/bits.h
+10 -6
View File
@@ -51,12 +51,16 @@ MEM_STATIC unsigned ZSTD_countTrailingZeros32(U32 val)
MEM_STATIC unsigned ZSTD_countLeadingZeros32_fallback(U32 val) { MEM_STATIC unsigned ZSTD_countLeadingZeros32_fallback(U32 val) {
assert(val != 0); assert(val != 0);
{ {
unsigned result = 0; static const U32 DeBruijnClz[32] = {0, 9, 1, 10, 13, 21, 2, 29,
while ((val & 0x80000000) == 0) { 11, 14, 16, 18, 22, 25, 3, 30,
result++; 8, 12, 20, 28, 15, 17, 24, 7,
val <<= 1; 19, 27, 23, 6, 26, 5, 4, 31};
} val |= val >> 1;
return result; val |= val >> 2;
val |= val >> 4;
val |= val >> 8;
val |= val >> 16;
return DeBruijnClz[(val * 0x07C4ACDDU) >> 27] ^ 31;
} }
} }
tests/fuzzer.c
+18 -6
View File
@@ -3377,22 +3377,26 @@ static int basicUnitTests(U32 const seed, double compressibility)
DISPLAYLEVEL(3, "test%3i : testing bitwise instrinsics PR#3045: ", testNb++); DISPLAYLEVEL(3, "test%3i : testing bitwise instrinsics PR#3045: ", testNb++);
{ {
U32 seed_32 = seed == 0 ? seed + 1 : seed; // these intrinsics are undefined on 0 U32 seed_copy = seed; // need non-const seed to avoid compiler warning for FUZ_rand(&seed)
U64 seed_64 = (U64)seed * 0x87654321; // decent 64-bit distribution U32 rand32 = FUZ_rand(&seed_copy);
U64 rand64 = ((U64)FUZ_rand(&seed_copy) << 32) | FUZ_rand(&seed_copy);
U32 lowbit_only_32 = 1; U32 lowbit_only_32 = 1;
U64 lowbit_only_64 = 1; U64 lowbit_only_64 = 1;
U32 highbit_only_32 = (U32)1 << 31; U32 highbit_only_32 = (U32)1 << 31;
U64 highbit_only_64 = (U64)1 << 63; U64 highbit_only_64 = (U64)1 << 63;
U32 i;
if (rand32 == 0) rand32 = 1; // CLZ and CTZ are undefined on 0
if (rand64 == 0) rand64 = 1; // CLZ and CTZ are undefined on 0
/* Test ZSTD_countTrailingZeros32 */ /* Test ZSTD_countTrailingZeros32 */
CHECK_EQ(ZSTD_countTrailingZeros32(lowbit_only_32), 0u); CHECK_EQ(ZSTD_countTrailingZeros32(lowbit_only_32), 0u);
CHECK_EQ(ZSTD_countTrailingZeros32(highbit_only_32), 31u); CHECK_EQ(ZSTD_countTrailingZeros32(highbit_only_32), 31u);
CHECK_EQ(ZSTD_countTrailingZeros32(seed_32), ZSTD_countTrailingZeros32_fallback(seed_32)); CHECK_EQ(ZSTD_countTrailingZeros32(rand32), ZSTD_countTrailingZeros32_fallback(rand32));
/* Test ZSTD_countLeadingZeros32 */ /* Test ZSTD_countLeadingZeros32 */
CHECK_EQ(ZSTD_countLeadingZeros32(lowbit_only_32), 31u); CHECK_EQ(ZSTD_countLeadingZeros32(lowbit_only_32), 31u);
CHECK_EQ(ZSTD_countLeadingZeros32(highbit_only_32), 0u); CHECK_EQ(ZSTD_countLeadingZeros32(highbit_only_32), 0u);
CHECK_EQ(ZSTD_countLeadingZeros32(seed_32), ZSTD_countLeadingZeros32_fallback(seed_32)); CHECK_EQ(ZSTD_countLeadingZeros32(rand32), ZSTD_countLeadingZeros32_fallback(rand32));
/* Test ZSTD_countTrailingZeros64 */ /* Test ZSTD_countTrailingZeros64 */
CHECK_EQ(ZSTD_countTrailingZeros64(lowbit_only_64), 0u); CHECK_EQ(ZSTD_countTrailingZeros64(lowbit_only_64), 0u);
@@ -3426,8 +3430,16 @@ static int basicUnitTests(U32 const seed, double compressibility)
} }
/* Test MEM_ intrinsics */ /* Test MEM_ intrinsics */
CHECK_EQ(MEM_swap32(seed_32), MEM_swap32_fallback(seed_32)); CHECK_EQ(MEM_swap32(rand32), MEM_swap32_fallback(rand32));
CHECK_EQ(MEM_swap64(seed_64), MEM_swap64_fallback(seed_64)); CHECK_EQ(MEM_swap64(rand64), MEM_swap64_fallback(rand64));
/* Test fallbacks vs intrinsics on a range of small integers */
for (i=1; i <= 1000; i++) {
CHECK_EQ(MEM_swap32(i), MEM_swap32_fallback(i));
CHECK_EQ(MEM_swap64((U64)i), MEM_swap64_fallback((U64)i));
CHECK_EQ(ZSTD_countTrailingZeros32(i), ZSTD_countTrailingZeros32_fallback(i));
CHECK_EQ(ZSTD_countLeadingZeros32(i), ZSTD_countLeadingZeros32_fallback(i));
}
} }
DISPLAYLEVEL(3, "OK \n"); DISPLAYLEVEL(3, "OK \n");