From 940b8114172f458290c08e245e0424e6cfcded96 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Wed, 6 Jul 2022 17:55:49 +0800 Subject: [PATCH] powerpc/Makefile: Don't pass -mcpu=powerpc64 when building 32-bit stable inclusion from stable-v5.10.110 commit 3e7e73ae2bbd197e4212de41b7e9379ca3b5a6af bugzilla: https://gitee.com/openeuler/kernel/issues/I574AL Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3e7e73ae2bbd197e4212de41b7e9379ca3b5a6af -------------------------------- [ Upstream commit 2863dd2db23e0407f6c50b8ba5c0e55abef894f1 ] When CONFIG_GENERIC_CPU=y (true for all our defconfigs) we pass -mcpu=powerpc64 to the compiler, even when we're building a 32-bit kernel. This happens because we have an ifdef CONFIG_PPC_BOOK3S_64/else block in the Makefile that was written before 32-bit supported GENERIC_CPU. Prior to that the else block only applied to 64-bit Book3E. The GCC man page says -mcpu=powerpc64 "[specifies] a pure ... 64-bit big endian PowerPC ... architecture machine [type], with an appropriate, generic processor model assumed for scheduling purposes." It's unclear how that interacts with -m32, which we are also passing, although obviously -m32 is taking precedence in some sense, as the 32-bit kernel only contains 32-bit instructions. This was noticed by inspection, not via any bug reports, but it does affect code generation. Comparing before/after code generation, there are some changes to instruction scheduling, and the after case (with -mcpu=powerpc64 removed) the compiler seems more keen to use r8. Fix it by making the else case only apply to Book3E 64, which excludes 32-bit. Fixes: 0e00a8c9fd92 ("powerpc: Allow CPU selection also on PPC32") Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220215112858.304779-1-mpe@ellerman.id.au Signed-off-by: Sasha Levin Signed-off-by: Yu Liao Reviewed-by: Wei Li Signed-off-by: Zheng Zengkai --- arch/powerpc/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile index 35bf7634e095..a7c353ea0166 100644 --- a/arch/powerpc/Makefile +++ b/arch/powerpc/Makefile @@ -172,7 +172,7 @@ else CFLAGS-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mtune=power7,$(call cc-option,-mtune=power5)) CFLAGS-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mcpu=power5,-mcpu=power4) endif -else +else ifdef CONFIG_PPC_BOOK3E_64 CFLAGS-$(CONFIG_GENERIC_CPU) += -mcpu=powerpc64 endif -- GitLab