linux-kernel - [PATCH 2/2] x86, powerpc: remove -funit-at-a-time compiler option entirely

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Date:   Mon, 12 Nov 2018 11:35:20 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org
Cc:     Richard Weinberger <richard@...ma-star.at>,
        linuxppc-dev@...ts.ozlabs.org,
        Michael Ellerman <mpe@...erman.id.au>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>
Subject: [PATCH 2/2] x86, powerpc: remove -funit-at-a-time compiler option entirely

GCC 4.6 manual says:

-funit-at-a-time
  This option is left for compatibility reasons. -funit-at-a-time has
  no effect, while -fno-unit-at-a-time implies -fno-toplevel-reorder
  and -fno-section-anchors.
  Enabled by default.

Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
---

 arch/powerpc/Makefile | 4 ----
 arch/x86/Makefile     | 4 ----
 arch/x86/Makefile.um  | 5 -----
 3 files changed, 13 deletions(-)

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 8a2ce14..854199c 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -228,10 +228,6 @@ KBUILD_CFLAGS += $(call cc-option,-mno-vsx)
 KBUILD_CFLAGS += $(call cc-option,-mno-spe)
 KBUILD_CFLAGS += $(call cc-option,-mspe=no)
 
-# Enable unit-at-a-time mode when possible. It shrinks the
-# kernel considerably.
-KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
-
 # FIXME: the module load should be taught about the additional relocs
 # generated by this.
 # revert to pre-gcc-4.4 behaviour of .eh_frame
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 88398fd..3508049 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -130,10 +130,6 @@ else
 
         KBUILD_CFLAGS += -mno-red-zone
         KBUILD_CFLAGS += -mcmodel=kernel
-
-        # -funit-at-a-time shrinks the kernel .text considerably
-        # unfortunately it makes reading oopses harder.
-        KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
 endif
 
 ifdef CONFIG_X86_X32
diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
index 577976b..1db7913 100644
--- a/arch/x86/Makefile.um
+++ b/arch/x86/Makefile.um
@@ -26,9 +26,6 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
 # an unresolved reference.
 cflags-y += -ffreestanding
 
-# gcc 4.3.0 needs -funit-at-a-time for extern inline functions.
-KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
-
 KBUILD_CFLAGS += $(cflags-y)
 
 else
@@ -50,6 +47,4 @@ ELF_FORMAT := elf64-x86-64
 LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib64
 LINK-y += -m64
 
-# Do unit-at-a-time unconditionally on x86_64, following the host
-KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
 endif
-- 
2.7.4