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MIPS: Remove compact branch policy Kconfig entries 

Commit c1a0e9bc88 ("MIPS: Allow compact branch policy to be changed")
added Kconfig entries allowing for the compact branch policy used by the
compiler for MIPSr6 kernels to be specified. This can be useful for
debugging, particularly in systems where compact branches have recently
been introduced.

Unfortunately mainline gcc 5.x supports MIPSr6 but not the
-mcompact-branches compiler flag, leading to MIPSr6 kernels failing to
build with gcc 5.x with errors such as:

  mipsel-linux-gnu-gcc: error: unrecognized command line option '-mcompact-branches=optimal'
  make[2]: *** [kernel/bounds.s] Error 1

Fixing this by hiding the Kconfig entry behind another seems to be more
hassle than it's worth, as MIPSr6 & compact branches have been around
for a while now and if policy does need to be set for debug it can be
done easily enough with KCFLAGS. Therefore remove the compact branch
policy Kconfig entries & their handling in the Makefile.

This reverts commit c1a0e9bc88 ("MIPS: Allow compact branch policy to
be changed").

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Fixes: c1a0e9bc88 ("MIPS: Allow compact branch policy to be changed")
Cc: stable <stable@vger.kernel.org> # v4.4+
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14241/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Paul Burton 2016-09-12 10:58:06 +01:00 committed by Ralf Baechle
parent ac7e385f2b
commit b03c1e3b8e
2 changed files with 0 additions and 40 deletions
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36
arch/mips/Kconfig.debug
View File

@ -113,42 +113,6 @@ config SPINLOCK_TEST
help
Add several files to the debugfs to test spinlock speed.
if CPU_MIPSR6
choice
prompt "Compact branch policy"
default MIPS_COMPACT_BRANCHES_OPTIMAL
config MIPS_COMPACT_BRANCHES_NEVER
bool "Never (force delay slot branches)"
help
Pass the -mcompact-branches=never flag to the compiler in order to
force it to always emit branches with delay slots, and make no use
of the compact branch instructions introduced by MIPSr6. This is
useful if you suspect there may be an issue with compact branches in
either the compiler or the CPU.
config MIPS_COMPACT_BRANCHES_OPTIMAL
bool "Optimal (use where beneficial)"
help
Pass the -mcompact-branches=optimal flag to the compiler in order for
it to make use of compact branch instructions where it deems them
beneficial, and use branches with delay slots elsewhere. This is the
default compiler behaviour, and should be used unless you have a
reason to choose otherwise.
config MIPS_COMPACT_BRANCHES_ALWAYS
bool "Always (force compact branches)"
help
Pass the -mcompact-branches=always flag to the compiler in order to
force it to always emit compact branches, making no use of branch
instructions with delay slots. This can result in more compact code
which may be beneficial in some scenarios.
endchoice
endif # CPU_MIPSR6
config SCACHE_DEBUGFS
bool "L2 cache debugfs entries"
depends on DEBUG_FS

4
arch/mips/Makefile
View File

@ -203,10 +203,6 @@ endif
toolchain-virt := $(call cc-option-yn,$(mips-cflags) -mvirt)
cflags-$(toolchain-virt) += -DTOOLCHAIN_SUPPORTS_VIRT
cflags-$(CONFIG_MIPS_COMPACT_BRANCHES_NEVER) += -mcompact-branches=never
cflags-$(CONFIG_MIPS_COMPACT_BRANCHES_OPTIMAL) += -mcompact-branches=optimal
cflags-$(CONFIG_MIPS_COMPACT_BRANCHES_ALWAYS) += -mcompact-branches=always
#
# Firmware support
#