arch/sparc: better default CPU when targetting Linux

By default, sparc64-*-linux is configured with -mcpu=v9. However,
according to https://sourceware.org/ml/libc-alpha/2005-12/msg00027.html:
    "There is no Linux sparc64 port that runs on non-UltraSPARC-I+ ISA
     CPUs."

v9 is such a "non-UltraSPARC-I+ ISA CPU", so it makes no sense to
default to v9 when targetting Linux.

Change the default to ultrasparc, even though it can suboptimally
schedule instructions for newer SPARC CPUs. See the pending patch:
    https://patchwork.ozlabs.org/patch/409424/

Signed-off-by: Alexey Neyman <stilor@att.net>

1 files changed, 13 insertions, 0 deletions

diff --git a/scripts/build/arch/sparc.sh b/scripts/build/arch/sparc.sh
index e3e7491..1cf2acf 100644
--- a/scripts/build/arch/sparc.sh
+++ b/scripts/build/arch/sparc.sh
@@ -2,4 +2,17 @@
 CT_DoArchTupleValues() {
     # That's the only thing to override
     CT_TARGET_ARCH="sparc${target_bits_64}${CT_ARCH_SUFFIX}"
+
+    # By default, sparc64-*-linux is configured with -mcpu=v9. However,
+    # according to https://sourceware.org/ml/libc-alpha/2005-12/msg00027.html,
+    # "There is no Linux sparc64 port that runs on non-UltraSPARC-I+ ISA CPUs."
+    # There is a patch that would change the default to -mcpu=ultrasparc for
+    # sparc64-*-linux configuration: https://patchwork.ozlabs.org/patch/409424/
+    # but that patch has not been integrated (yet). One concern raised about
+    # this patch was that -mcpu=ultrasparc can suboptimally schedule instructions
+    # for newer SPARC CPUs. So, override to -mcpu=ultrasparc and warn the user.
+    if [ "${CT_KERNEL}" = "linux" -a "${CT_ARCH_64}" = "y" -a -z "${CT_ARCH_CPU}" ]; then
+        CT_DoLog WARN "Setting CPU to UltraSPARC-I for sparc64-linux. Set CT_ARCH_CPU if a different CPU is desired."
+        CT_ARCH_WITH_CPU="--with-cpu=ultrasparc"
+    fi
 }