https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120858
Bug ID: 120858
Summary: __builtin_rev_crc64_data64 poorly optimised when
computing crc32
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: sh1.gccbug at tikouka dot nz
Target Milestone: ---
There appears to be no __builtin_rev_crc32_data64(). Fine. I know how to fake
that:
return __builtin_rev_crc64_data64(crc32, x, 0x04C11DB700000000);
That calculates the same result, but when the CRC instruction with a 64-bit
operand is available it should be used. Instead we get table-based generation.
https://godbolt.org/z/WWjn55TG1
Tested on armv8-a, but it appears to also happen on x86_64 (you'll need to
include the recent fix for bug 120719 to test that).
