[PATCH 4.4 64/73] MIPS: Remove compact branch policy Kconfig entries

From: Greg Kroah-Hartman
Date: Wed Sep 28 2016 - 05:27:50 EST

4.4-stable review patch. If anyone has any objections, please let me know.


From: Paul Burton <paul.burton@xxxxxxxxxx>

commit b03c1e3b8eed9026733c473071d1f528358a0e50 upstream.

Commit c1a0e9bc885d ("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 c1a0e9bc885d ("MIPS: Allow compact branch policy to
be changed").

Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx>
Reported-by: kbuild test robot <fengguang.wu@xxxxxxxxx>
Fixes: c1a0e9bc885d ("MIPS: Allow compact branch policy to be changed")
Cc: linux-mips@xxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/14241/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/mips/Kconfig.debug | 36 ------------------------------------
arch/mips/Makefile | 4 ----
2 files changed, 40 deletions(-)

--- a/arch/mips/Kconfig.debug
+++ b/arch/mips/Kconfig.debug
@@ -113,42 +113,6 @@ config SPINLOCK_TEST
Add several files to the debugfs to test spinlock speed.

- prompt "Compact branch policy"
- 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.
- 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.
- 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.
-endif # CPU_MIPSR6
bool "L2 cache debugfs entries"
depends on DEBUG_FS
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -204,10 +204,6 @@ toolchain-msa := $(call cc-option-yn,
cflags-$(toolchain-msa) += -DTOOLCHAIN_SUPPORTS_MSA

-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