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MIPS: jump_label: Use compact branches for >= r6

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MIPSr6 introduced compact branches which have no delay slots. Make use
of them for jump labels in order to avoid the need for a nop to fill the
branch or jump delay slot, saving 4 bytes of code for each static branch.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
This commit is contained in:
Paul Burton
2019-04-05 22:50:36 +00:00
parent c838b580ca
commit 9b6584e35f
2 changed files with 34 additions and 8 deletions
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12
arch/mips/include/asm/jump_label.h
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@@ -11,6 +11,7 @@
#ifndef __ASSEMBLY__
#include <linux/types.h>
#include <asm/isa-rev.h>
#define JUMP_LABEL_NOP_SIZE 4
@@ -21,9 +22,14 @@
#endif
#ifdef CONFIG_CPU_MICROMIPS
#define B_INSN "b32"
# define B_INSN "b32"
# define J_INSN "j32"
#elif MIPS_ISA_REV >= 6
# define B_INSN "bc"
# define J_INSN "bc"
#else
#define B_INSN "b"
# define B_INSN "b"
# define J_INSN "j"
#endif
static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
@@ -42,7 +48,7 @@ l_yes:
static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch)
{
asm_volatile_goto("1:\tj %l[l_yes]\n\t"
asm_volatile_goto("1:\t" J_INSN " %l[l_yes]\n\t"
".pushsection __jump_table, \"aw\"\n\t"
WORD_INSN " 1b, %l[l_yes], %0\n\t"
".popsection\n\t"