From 9dc523aa0e20271cfe1474bef9fafbe62b7ff603 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=C3=86var=20Arnfj=C3=B6r=C3=B0=20Bjarmason?= Date: Wed, 31 Aug 2022 11:18:43 +0200 Subject: Makefile + hash.h: remove PPC_SHA1 implementation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Remove the PPC_SHA1 implementation added in a6ef3518f9a ([PATCH] PPC assembly implementation of SHA1, 2005-04-22). When this was added Apple consumer hardware used the PPC architecture, and the implementation was intended to improve SHA-1 speed there. Since it was added we've moved to using sha1collisiondetection by default, and anyone wanting hard-rolled non-DC SHA-1 implementation can use OpenSSL's via the OPENSSL_SHA1 knob. The PPC_SHA1 originally originally targeted 32 bit PPC, and later the 64 bit PPC 970 (a.k.a. Apple PowerPC G5). See 926172c5e48 (block-sha1: improve code on large-register-set machines, 2009-08-10) for a reference about the performance on G5 (a comment in block-sha1/sha1.c being removed here). I can't get it to do anything but segfault on both the BE and LE POWER machines in the GCC compile farm[1]. Anyone who's concerned about performance on PPC these days is likely to be using the IBM POWER processors. There have been proposals to entirely remove non-sha1collisiondetection implementations from the tree[2]. I think per [3] that would be a bit overzealous. I.e. there are various set-ups git's speed is going to be more important than the relatively implausible SHA-1 collision attack, or where such attacks are entirely mitigated by other means (e.g. by incoming objects being checked with DC_SHA1). But that really doesn't apply to PPC_SHA1 in particular, which seems to have outlived its usefulness. As this gets rid of the only in-tree *.S assembly file we can remove the small bits of logic from the Makefile needed to build objects from *.S (as opposed to *.c) The code being removed here was also throwing warnings with the "-pedantic" flag, it could have been fixed as 544d93bc3b4 (block-sha1: remove use of obsolete x86 assembly, 2022-03-10) did for block-sha1/*, but as noted above let's remove it instead. 1. https://cfarm.tetaneutral.net/machines/list/ Tested on gcc{110,112,135,203}, a mixture of POWER [789] ppc64 and ppc64le. All segfault in anything needing object hashing (e.g. t/t1007-hash-object.sh) when compiled with PPC_SHA1=Y. 2. https://lore.kernel.org/git/20200223223758.120941-1-mh@glandium.org/ 3. https://lore.kernel.org/git/20200224044732.GK1018190@coredump.intra.peff.net/ Acked-by: brian m. carlson" Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano --- configure.ac | 3 --- 1 file changed, 3 deletions(-) (limited to 'configure.ac') diff --git a/configure.ac b/configure.ac index 7dcd048204..38ff86678a 100644 --- a/configure.ac +++ b/configure.ac @@ -237,9 +237,6 @@ AC_MSG_NOTICE([CHECKS for site configuration]) # tests. These tests take up a significant amount of the total test time # but are not needed unless you plan to talk to SVN repos. # -# Define PPC_SHA1 environment variable when running make to make use of -# a bundled SHA1 routine optimized for PowerPC. -# # Define NO_OPENSSL environment variable if you do not have OpenSSL. # # Define OPENSSLDIR=/foo/bar if your openssl header and library files are in -- cgit v1.2.1