From: Tom Lane <tgl@sss.pgh.pa.us>
To: John Naylor <johncnaylorls@gmail.com>
cc: Eduard Stefes <Eduard.Stefes@ibm.com>,
        "pgsql-hackers@lists.postgresql.org"
 <pgsql-hackers@lists.postgresql.org>,
        "iii@linux.ibm.com" <iii@linux.ibm.com>,
        "rueckner@linux.ibm.com" <rueckner@linux.ibm.com>
Subject: Re: Review/Pull Request: Adding new CRC32C implementation for IBM
 S390X
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Comments: In-reply-to John Naylor <johncnaylorls@gmail.com>
	message dated "Thu, 08 May 2025 05:23:52 +0700"
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Date: Wed, 07 May 2025 18:35:44 -0400
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John Naylor <johncnaylorls@gmail.com> writes:
> We prefer that 'a' and 'b' are declared as global variables, just to
> make it as realistic as possible, although it doesn't seem to make
> much difference when I tried it on Compiler Explorer. (Same for
> autoconf)

Yeah, see commit fdb5dd6331e305f797bb589747f056062c305f0b for
some recent precedent, and for explanation of why we think it's
worth worrying about.  It's not so much that "global" matters,
it's that we don't want the compiler to have the option to
fold the whole test to a constant, which it would be within
its rights to do as you have this.

			regards, tom lane