On Tue, Sep 15, 2026 at 10:03 PM Uros Bizjak <[email protected]> wrote:
> On Tue, Sep 15, 2026 at 3:54 PM Shreesh Adiga > <[email protected]> wrote: > > > > Add const folding for x86 _mm_crc32_u8/u16/u32/u64 intrinsics. > > Added tests to ensure the values are computed as expected. > > > > gcc/ChangeLog: > > > > * config/i386/i386.cc (ix86_fold_builtin): Add constant folding > > for the SSE4.2 crc32 intrinsics (_mm_crc32_u8/u16/u32/u64) by > > invoking calculate_reversed_crc with the CRC32C polynomial. > > * hwint.cc (calculate_reversed_crc): Relax the crc_bits >= > > data_bits assertion; the shift-register loop still resolves the > > low crc_bits correctly before the upper data_bits reach bit 0, > > so this allows folding _mm_crc32_u64 where crc_bits == 32 and > > data_bits == 64. > > > > gcc/testsuite/ChangeLog: > > > > * gcc.target/i386/crc32-const-fold.c: New test. > > Please follow GNU ChangeLog standards, like: > > gcc/ChangeLog: > > * config/i386/i386.cc (ix86_fold_builtin) <IX86_BUILTIN_CRC32QI, > IX86_BUILTIN_CRC32HI, IX86_BUILTIN_CRC32SI, IX86_BUILTIN_CRC32DI>: > Add constant folding for the SSE4.2 crc32 intrinsics. > * hwint.cc (calculate_reversed_crc): Remove the crc_bits >= > data_bits assertion. > > gcc/testsuite/ChangeLog: > > * gcc.target/i386/crc32-const-fold.c: New test. > > ChangeLog entry should say *what* is changed, not *why* it is changed. > The explanation itself should go in the commit message. > > OK for the x86 part, the hwint.cc needs a middle-end maintainer's review. > > Hi Andrea, can you help with this hwint.cc changes review part? Thanks, Shreesh > Thanks, > Uros. > > > Signed-off-by: Shreesh Adiga <[email protected]> > > --- > > gcc/config/i386/i386.cc | 18 ++ > > gcc/hwint.cc | 2 +- > > .../gcc.target/i386/crc32-const-fold.c | 154 ++++++++++++++++++ > > 3 files changed, 173 insertions(+), 1 deletion(-) > > create mode 100644 gcc/testsuite/gcc.target/i386/crc32-const-fold.c > > > > diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc > > index bbb60163a75..79970003cf1 100644 > > --- a/gcc/config/i386/i386.cc > > +++ b/gcc/config/i386/i386.cc > > @@ -19246,6 +19246,24 @@ ix86_fold_builtin (tree fndecl, int n_args, > > } > > break; > > > > + case IX86_BUILTIN_CRC32QI: > > + case IX86_BUILTIN_CRC32HI: > > + case IX86_BUILTIN_CRC32SI: > > + case IX86_BUILTIN_CRC32DI: > > + gcc_assert (n_args == 2); > > + if (tree_fits_uhwi_p (args[0]) && tree_fits_uhwi_p (args[1])) > > + { > > + unsigned HOST_WIDE_INT crc = tree_to_uhwi (args[0]); > > + crc &= 0xffffffff; > > + unsigned HOST_WIDE_INT data = tree_to_uhwi (args[1]); > > + unsigned short data_bits = TYPE_PRECISION (TREE_TYPE > (args[1])); > > + unsigned HOST_WIDE_INT res = calculate_reversed_crc (crc, > data, > > + > 0x1EDC6F41, > > + 32, > data_bits); > > + return build_int_cstu (TREE_TYPE (TREE_TYPE (fndecl)), res); > > + } > > + break; > > + > > case IX86_BUILTIN_BEXTR32: > > case IX86_BUILTIN_BEXTR64: > > case IX86_BUILTIN_BEXTRI32: > > diff --git a/gcc/hwint.cc b/gcc/hwint.cc > > index 065911d0a77..d89be33f636 100644 > > --- a/gcc/hwint.cc > > +++ b/gcc/hwint.cc > > @@ -265,7 +265,7 @@ calculate_reversed_crc (unsigned HOST_WIDE_INT crc, > > > > gcc_checking_assert (crc_bits <= 64); > > gcc_checking_assert (data_bits <= 64); > > - gcc_checking_assert (crc_bits >= data_bits); > > + /* allow data_bits > crc_bits for folding _mm_crc32_u64. */ > > > > unsigned HOST_WIDE_INT rev_polynom = reflect_hwi (polynomial, > crc_bits); > > crc ^= data; > > diff --git a/gcc/testsuite/gcc.target/i386/crc32-const-fold.c > b/gcc/testsuite/gcc.target/i386/crc32-const-fold.c > > new file mode 100644 > > index 00000000000..92825c4fc1d > > --- /dev/null > > +++ b/gcc/testsuite/gcc.target/i386/crc32-const-fold.c > > @@ -0,0 +1,154 @@ > > +/* { dg-do compile } */ > > +/* { dg-options "-O2 -mcrc32" } */ > > + > > +#include <immintrin.h> > > + > > +unsigned int > > +test_u8_1 () > > +{ > > + return _mm_crc32_u8 (0x02a24bf8, 0xba); > > +} > > + > > +unsigned int > > +test_u8_2 () > > +{ > > + return _mm_crc32_u8 (0x0cd5e10f, 0xe7); > > +} > > + > > +unsigned int > > +test_u8_3 () > > +{ > > + return _mm_crc32_u8 (0x50e739b8, 0x2e); > > +} > > + > > +unsigned int > > +test_u8_4 () > > +{ > > + return _mm_crc32_u8 (0x3c2db116, 0x3d); > > +} > > + > > +unsigned int > > +test_u8_5 () > > +{ > > + return _mm_crc32_u8 (-1, -1); > > +} > > + > > +unsigned int > > +test_u16_1 () > > +{ > > + return _mm_crc32_u16 (0x02a24bf8, 0xd4ba); > > +} > > + > > +unsigned int > > +test_u16_2 () > > +{ > > + return _mm_crc32_u16 (0x0cd5e10f, 0x42e7); > > +} > > + > > +unsigned int > > +test_u16_3 () > > +{ > > + return _mm_crc32_u16 (0x50e739b8, 0x382e); > > +} > > + > > +unsigned int > > +test_u16_4 () > > +{ > > + return _mm_crc32_u16 (0x3c2db116, 0x7f3d); > > +} > > + > > +unsigned int > > +test_u16_5 () > > +{ > > + return _mm_crc32_u16 (-1, -1); > > +} > > + > > +unsigned int > > +test_u32_1 () > > +{ > > + return _mm_crc32_u32 (0x02a24bf8, 0xf37dd4ba); > > +} > > + > > +unsigned int > > +test_u32_2 () > > +{ > > + return _mm_crc32_u32 (0x0cd5e10f, 0x832b42e7); > > +} > > + > > +unsigned int > > +test_u32_3 () > > +{ > > + return _mm_crc32_u32 (0x50e739b8, 0xcefb382e); > > +} > > + > > +unsigned int > > +test_u32_4 () > > +{ > > + return _mm_crc32_u32 (0x3c2db116, 0xd3947f3d); > > +} > > + > > +unsigned int > > +test_u32_5 () > > +{ > > + return _mm_crc32_u32 (-1, -1); > > +} > > + > > +#ifdef __x86_64__ > > +unsigned long long > > +test_u64_1 () > > +{ > > + return _mm_crc32_u64 (0x9f65239602a24bf8, 0x894a58bff37dd4ba); > > +} > > + > > +unsigned long long > > +test_u64_2 () > > +{ > > + return _mm_crc32_u64 (0x06ef97970cd5e10f, 0x24334e2e832b42e7); > > +} > > + > > +unsigned long long > > +test_u64_3 () > > +{ > > + return _mm_crc32_u64 (0x5024a45450e739b8, 0x289ee1b7cefb382e); > > +} > > + > > +unsigned long long > > +test_u64_4 () > > +{ > > + return _mm_crc32_u64 (0xcbc89e1c3c2db116, 0xa89143dad3947f3d); > > +} > > + > > +unsigned long long > > +test_u64_5 () > > +{ > > + return _mm_crc32_u64 (-1, -1); > > +} > > +#endif > > + > > +/* Test that there is no crc32 instruction emitted. */ > > +/* { dg-final { scan-assembler-not "crc32\[bwlq\]" } } */ > > + > > +/* Test the expected values. */ > > +/* { dg-final { scan-assembler-times "-1606234368," 1 } } */ > > +/* { dg-final { scan-assembler-times "1776624948," 1 } } */ > > +/* { dg-final { scan-assembler-times "-1269171002," 1 } } */ > > +/* { dg-final { scan-assembler-times "-1190655916," 1 } } */ > > +/* { dg-final { scan-assembler-times "16777215," 1 } } */ > > + > > +/* { dg-final { scan-assembler-times "350827643," 1 } } */ > > +/* { dg-final { scan-assembler-times "1464882880," 1 } } */ > > +/* { dg-final { scan-assembler-times "1604487598," 1 } } */ > > +/* { dg-final { scan-assembler-times "-1181930003," 1 } } */ > > +/* { dg-final { scan-assembler-times "65535," 1 } } */ > > + > > +/* { dg-final { scan-assembler-times "2122844148 <(212)%20284-4148>," > 1 } } */ > > +/* { dg-final { scan-assembler-times "881727033," 1 } } */ > > +/* { dg-final { scan-assembler-times "139192539," 1 } } */ > > +/* { dg-final { scan-assembler-times "1861871255," 1 } } */ > > +/* { dg-final { scan-assembler-times "xorl\[\\t \]+%eax, %eax" 1 } } */ > > + > > +/* { dg-final { scan-assembler-times "3230864714" 1 { target { ! ia32 } > } } } */ > > +/* { dg-final { scan-assembler-times "337502055" 1 { target { ! ia32 } > } } } */ > > +/* { dg-final { scan-assembler-times "712052683" 1 { target { ! ia32 } > } } } */ > > +/* { dg-final { scan-assembler-times "1390230251" 1 { target { ! ia32 } > } } } */ > > +/* { dg-final { scan-assembler-times "3080238136" 1 { target { ! ia32 } > } } } */ > > -- > > 2.55.0 > > >
