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MIPS: jump_label: Remove redundant nops 

Both arch_static_branch() & arch_static_branch_jump() emit a control
transfer instruction (ie. branch or jump) without disabling assembler
re-ordering. As such the assembler will automatically fill their delay
slots.

Both functions follow their branch or jump with an explicit nop that at
first appears to be there to fill the delay slot, but given that the
assembler will do that the explicit nops serve no purpose & we end up
with our branch or jump followed by 2 nops. Remove the redundant nops.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
hifive-unleashed-5.2
Paul Burton 2019-04-05 22:50:35 +00:00
parent ec86e545c1
commit c838b580ca
No known key found for this signature in database
GPG Key ID: 3EA79FACB57500DD
1 changed files with 1 additions and 2 deletions
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3
arch/mips/include/asm/jump_label.h
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@ -29,7 +29,7 @@
static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
{
asm_volatile_goto("1:\t" B_INSN " 2f\n\t"
"2:\tnop\n\t"
"2:\t.insn\n\t"
".pushsection __jump_table, \"aw\"\n\t"
WORD_INSN " 1b, %l[l_yes], %0\n\t"
".popsection\n\t"
@ -43,7 +43,6 @@ 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"
"nop\n\t"
".pushsection __jump_table, \"aw\"\n\t"
WORD_INSN " 1b, %l[l_yes], %0\n\t"
".popsection\n\t"