Commit b03c1e3b authored by Paul Burton's avatar Paul Burton Committed by Ralf Baechle
Browse files

MIPS: Remove compact branch policy Kconfig entries 



Commit c1a0e9bc ("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 c1a0e9bc ("MIPS: Allow compact branch policy to
be changed").

Signed-off-by: default avatarPaul Burton <paul.burton@imgtec.com>
Reported-by: default avatarkbuild test robot <fengguang.wu@intel.com>
Fixes: c1a0e9bc ("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: default avatarRalf Baechle <ralf@linux-mips.org>
parent ac7e385f

arch/mips/Kconfig.debug

+0 −36
Original line number Diff line number Diff line
@@ -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

arch/mips/Makefile

+0 −4
Original line number Diff line number Diff line
@@ -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



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