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glibc: Fix SVE detection on aarch64

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glibc-2.28 complains:

  configure: error: use a compatible toolchain or configure with --disable-mathvec (this results in incomplete ABI).

Apparently this is a problem in the way GCC passes the -mcpu and -march
values to the assembler. As a workaround have the configure check pass
-mcpu as well to override anything we're passing in the environment.

Patch and explanation taken from the Yocto project with thanks.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
This commit is contained in:
Chris Packham 2023-08-31 17:10:15 +12:00
parent b46a0dbd1b
commit cf25b4edb0
1 changed files with 56 additions and 0 deletions
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packages/glibc/2.38/0001-aarch64-configure-Pass-mcpu-along-with-march-to-dete.patch vendored Normal file
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@ -0,0 +1,56 @@
From d836f008a96aa9b2e88c7b394bfc110542e57176 Mon Sep 17 00:00:00 2001
From: Khem Raj <raj.khem@gmail.com>
Date: Fri, 4 Aug 2023 09:34:50 -0700
Subject: [PATCH] aarch64/configure: Pass -mcpu along with -march to detect sve
support
SVE support logic in configure is rightly passing -march=<arch>+sve to
compiler to override whatever user might have passed via environment,
however GCC does not do as intended when -mcpu is part of environment
compiler flags, then it overrides the -march computed from -mcpu and
igonores other -march values so this test fails for lot of aarch64
machines which pass -mcpu that does not support sve. This is seemingly a
bug in GCC [1], until that is fixed we preempt -mcpu along with -march
in the configure test itself. It does not change functionality and yet
lets us through the GCC inconsistency.
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110901
Upstream-Status: Inappropriate [Workaround for a GCC issue]
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
---
sysdeps/aarch64/configure | 2 +-
sysdeps/aarch64/configure.ac | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/sysdeps/aarch64/configure b/sysdeps/aarch64/configure
index 5e91fab023..39dddc66d4 100644
--- a/sysdeps/aarch64/configure
+++ b/sysdeps/aarch64/configure
@@ -327,7 +327,7 @@ else $as_nop
cat > conftest.s <<\EOF
ptrue p0.b
EOF
-if { ac_try='${CC-cc} -c -march=armv8.2-a+sve conftest.s 1>&5'
+if { ac_try='${CC-cc} -c -mcpu=generic+sve -march=armv8.2-a+sve conftest.s 1>&5'
{ { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
(eval $ac_try) 2>&5
ac_status=$?
diff --git a/sysdeps/aarch64/configure.ac b/sysdeps/aarch64/configure.ac
index 8a708f2ef4..b6a146d2be 100644
--- a/sysdeps/aarch64/configure.ac
+++ b/sysdeps/aarch64/configure.ac
@@ -92,7 +92,7 @@ AC_CACHE_CHECK([for SVE support in assembler], [libc_cv_aarch64_sve_asm], [dnl
cat > conftest.s <<\EOF
ptrue p0.b
EOF
-if AC_TRY_COMMAND(${CC-cc} -c -march=armv8.2-a+sve conftest.s 1>&AS_MESSAGE_LOG_FD); then
+if AC_TRY_COMMAND(${CC-cc} -c -mcpu=generic+sve -march=armv8.2-a+sve conftest.s 1>&AS_MESSAGE_LOG_FD); then
libc_cv_aarch64_sve_asm=yes
else
libc_cv_aarch64_sve_asm=no
--
2.41.0