Re: [PATCH v2] RISC-V: Use vclmul for CRC expansion if available

[Jeff Law]

On 5/9/25 4:09 AM, Anton Blanchard wrote:
If the vector version of clmul (vclmul) is available and the scalar
one is not, use it for CRC expansion.

gcc/Changelog:

        * config/riscv/bitmanip.md (crc_rev<ANYI1:mode><ANYI:mode>4): Check
        TARGET_ZVBC.
        (crc<SUBX1:mode><SUBX:mode>4): Likewise.
        * config/riscv/riscv.cc (expand_crc_using_clmul): Emit code using
        vclmul if TARGET_ZVBC.
        (expand_reversed_crc_using_clmul): Likewise.

gcc/testsuite/ChangeLog:

        * gcc.target/riscv/rvv/base/crc-builtin-zvbc.c: New test.
THanks.  I pushed this after fixing one formatting nit.


+
+      rtx shift_amount = gen_int_mode (GET_MODE_BITSIZE (word_mode) -
+                                      data_size, Pmode);
When we wrap we bring the operator down to the next line.  We usually 
also put expressions like this in an additional level of parenthesis.

But there's an easier way :-)  GET_MODE_BITSIZE (word_mode) is always 
going to be BITS_PER_WORD.  So I used that instead which avoids 
wrapping.  There was another instance a elsewhere I adjusted to be 
consistent.

Thanks!

jeff