On 7/26/24 12:05 PM, Mariam Arutunian wrote:
Add two new internal functions (IFN_CRC, IFN_CRC_REV), to provide
faster CRC generation.
One performs bit-forward and the other bit-reversed CRC computation.
If CRC optabs are supported, they are used for the CRC computation.
Otherwise, table-based CRC is generated.
The supported data and CRC sizes are 8, 16, 32, and 64 bits.
The polynomial is without the leading 1.
A table with 256 elements is used to store precomputed CRCs.
For the reflection of inputs and the output, a simple algorithm
involving
SHIFT, AND, and OR operations is used.
Co-authored-by: Joern Rennecke <joern.renne...@embecosm.com
<mailto:joern.renne...@embecosm.com>>
gcc/
* doc/md.texi (crc@var{m}@var{n}4,
crc_rev@var{m}@var{n}4): Document.
* expr.cc (calculate_crc): New function.
(assemble_crc_table): Likewise.
(generate_crc_table): Likewise.
(calculate_table_based_CRC): Likewise.
(emit_crc): Likewise.
(expand_crc_table_based): Likewise.
(gen_common_operation_to_reflect): Likewise.
(reflect_64_bit_value): Likewise.
(reflect_32_bit_value): Likewise.
(reflect_16_bit_value): Likewise.
(reflect_8_bit_value): Likewise.
(generate_reflecting_code_standard): Likewise.
(expand_reversed_crc_table_based): Likewise.
* expr.h (generate_reflecting_code_standard): New function
declaration.
(expand_crc_table_based): Likewise.
(expand_reversed_crc_table_based): Likewise.
* internal-fn.cc: (crc_direct): Define.
(direct_crc_optab_supported_p): Likewise.
(expand_crc_optab_fn): New function
* internal-fn.def (CRC, CRC_REV): New internal functions.
* optabs.def (crc_optab, crc_rev_optab): New optabs.
Signed-off-by: Mariam Arutunian <mariamarutun...@gmail.com
<mailto:mariamarutun...@gmail.com>>
0001-Implement-internal-functions-for-efficient-CRC-compu.patch
diff --git a/gcc/expr.cc b/gcc/expr.cc
index 1baa39b98eb..c9a049aeecc 100644
--- a/gcc/expr.cc
+++ b/gcc/expr.cc
+
+/* Converts and moves a CRC value to a target register.
+
+ CRC_MODE is the mode (data type) of the CRC value.
+ CRC is the initial CRC value.
+ OP0 is the target register. */
+
+void
+emit_crc (machine_mode crc_mode, rtx* crc, rtx* op0)
+{
+ if (GET_MODE_BITSIZE (crc_mode).to_constant () == 32
+ && GET_MODE_BITSIZE (word_mode) == 64)
+ {
+ rtx a_low = gen_lowpart_SUBREG (crc_mode, *crc);
I may have asked this before, but is there a reason we're not just using
gen_lowpart?
Otherwise this looks pretty reasonable.
Just a note. IIRC, you were having some problems with formatting
issues. Rather than forcing you to fight with those, I'm comfortable if
you send me the final patchkit and I'll do a once-over for formatting
and commit the final result.
Jeff
