app-arch/xz-utils: improve USE=pgo for 9999

Takes a lot of inspiration from https://packages.altlinux.org/en/sisyphus/srpms/xz/specfiles/#line-80.

IIRC at least one other distro does this for xz or gzip (was it Clear Linux?)

The testsuite could do with better coverage so supplement it by creating
a tar archive of a bunch of files made during the build, then repeatedly
compress/decompress it to gather profiling data.

That said, I don't get any binary differences at all for liblzma and xz
for my usual flags (-O3 -march=znver2 ...). I do get some small differences
for just -O2. Both tests were done with GCC 14.0.1 20240415.

It would be nice if we could drop -fprofile-partial-training and that's
perhaps the thing to try next. I see this commit as mostly a step towards
being able to do that which should let PGO give smaller binaries with -O2
at least.

Signed-off-by: Sam James <sam@gentoo.org>

1 files changed, 38 insertions, 0 deletions

diff --git a/app-arch/xz-utils/xz-utils-9999.ebuild b/app-arch/xz-utils/xz-utils-9999.ebuild
index ec5227371390..d2e98e50e15a 100644
--- a/app-arch/xz-utils/xz-utils-9999.ebuild
+++ b/app-arch/xz-utils/xz-utils-9999.ebuild
@@ -106,6 +106,7 @@ multilib_src_configure() {
 
 multilib_src_compile() {
 	# -fprofile-partial-training because upstream note the test suite isn't super comprehensive
+	# TODO: revisit that now we have the tar/xz loop below?
 	# See https://documentation.suse.com/sbp/all/html/SBP-GCC-10/index.html#sec-gcc10-pgo
 	local pgo_generate_flags=$(usev pgo "-fprofile-update=atomic -fprofile-dir=${T}/${ABI}-pgo -fprofile-generate=${T}/${ABI}-pgo $(test-flags-CC -fprofile-partial-training)")
 	local pgo_use_flags=$(usev pgo "-fprofile-use=${T}/${ABI}-pgo -fprofile-dir=${T}/${ABI}-pgo $(test-flags-CC -fprofile-partial-training)")
@@ -115,6 +116,43 @@ multilib_src_compile() {
 	if use pgo ; then
 		emake CFLAGS="${CFLAGS} ${pgo_generate_flags}" -k check
 
+		if multilib_is_native_abi ; then
+			(
+				shopt -s globstar
+
+				tar \
+					--sort=name --mtime=@2718281828 \
+					-cf xz-pgo-test-01.tar \
+					{"${S}","${BUILD_DIR}"}/**/*.[cho] \
+					{"${S}","${BUILD_DIR}"}/**/*.so* \
+					{"${S}","${BUILD_DIR}"}/**/**.txt \
+					{"${S}","${BUILD_DIR}"}/tests/files \
+
+				stat --printf="xz-pgo-test-01.tar.tar size: %s\n" xz-pgo-test-01.tar
+				md5sum xz-pgo-test-01.tar
+			)
+
+			local test_variants=(
+				# Borrowed from ALT Linux
+				# https://packages.altlinux.org/en/sisyphus/srpms/xz/specfiles/#line-80
+				'-0 -C none'
+				'-2 -C crc32'
+				'-6 --arm --lzma2 -C crc64'
+				'-6 --x86 --lzma2=lc=4 -C sha256'
+				'-7e --format=lzma'
+
+				# Our own variants
+				''
+				'-9e'
+				'--x86 --lzma2=preset=9e'
+			)
+			local test_variant
+			for test_variant in "${test_variants[@]}" ; do
+				"${BUILD_DIR}"/src/xz/xz -c ${test_variant} xz-pgo-test-01.tar | "${BUILD_DIR}"/src/xz/xz -c -d - > /dev/null
+				assert "Testing '${test_variant}' variant failed"
+			done
+		fi
+
 		if tc-is-clang; then
 			llvm-profdata merge "${T}"/${ABI}-pgo --output="${T}"/${ABI}-pgo/default.profdata || die
 		fi