Re: [PATCH] Add loongarch native checksum implementation.

configure.ac:

+AC_SUBST(CFLAGS_CRC)

This seems to be an unnecessary copy-paste. I think we only need one, after all checks have run.

meson.build

+  if cc.links(prog, name: '__builtin_loongarch_crcc_w_b_w, __builtin_loongarch_crcc_w_h_w, __builtin_loongarch_crcc_w_w_w, and __builtin_loongarch_crcc_w_d_w without -march=loongarch64',
+      args: test_c_args)
+    # Use LoongArch CRC instruction unconditionally
+    cdata.set('USE_LOONGARCH_CRC32C', 1)
+    have_optimized_crc = true
+  elif cc.links(prog, name: '__builtin_loongarch_crcc_w_b_w, __builtin_loongarch_crcc_w_h_w, __builtin_loongarch_crcc_w_w_w, and __builtin_loongarch_crcc_w_d_w with -march=loongarch64',
+      args: test_c_args + ['-march=loongarch64'])
+    # Use LoongArch CRC instruction unconditionally

For x86 and Arm, if it fails to link without an -march flag, we allow for a runtime check. The flags "-march=armv8-a+crc" and "-msse4.2" are for instructions not found on all platforms. The patch also checks both ways, and each one results in "Use LoongArch CRC instruction unconditionally". The -march flag here is general, not specific. In other words, if this only runs inside "+elif host_cpu == 'loongarch64'", why do we need both with -march and without?

Also, I don't have a Loongarch machine for testing. Could you show that the instructions are found in the binary, maybe using objdump and grep? Or a performance test?

In the future, you may also consider running the buildfarm client on a machine dedicated for testing. That will give us quick feedback if some future new code doesn't work on this platform. More information here:

--
John Naylor
EDB: http://www.enterprisedb.com