diff options
| author | Maciej W. Rozycki <macro@imgtec.com> | 2017-09-29 16:26:31 +0100 |
|---|---|---|
| committer | James Hogan <jhogan@kernel.org> | 2017-11-08 21:50:52 +0000 |
| commit | d3a0b968186a7e197b7551e4d6080676372152ce (patch) | |
| tree | 5b80d9ec87799dde7054bd6daa00ee3c9611ee4c /arch/mips | |
| parent | b2ec33d438cca839fbb5764bcf5e29cffb3b9721 (diff) | |
MIPS: Use SLL by 0 for 32-bit truncation in `__read_64bit_c0_split'
Optimize `__read_64bit_c0_split' and reduce the instruction count by 1,
observing that a DSLL/DSRA pair by 32, is equivalent to SLL by 0, which
architecturally truncates the value requested to 32 bits on 64-bit MIPS
hardware regardless of whether the input operand is or is not a properly
sign-extended 32-bit value.
Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Reviewed-by: James Hogan <jhogan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/17399/
Signed-off-by: James Hogan <jhogan@kernel.org>
Diffstat (limited to 'arch/mips')
| -rw-r--r-- | arch/mips/include/asm/mipsregs.h | 14 |
1 files changed, 6 insertions, 8 deletions
diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h index a6810923b3f0..6b1f1ad0542c 100644 --- a/arch/mips/include/asm/mipsregs.h +++ b/arch/mips/include/asm/mipsregs.h @@ -1355,19 +1355,17 @@ do { \ if (sel == 0) \ __asm__ __volatile__( \ ".set\tmips64\n\t" \ - "dmfc0\t%M0, " #source "\n\t" \ - "dsll\t%L0, %M0, 32\n\t" \ - "dsra\t%M0, %M0, 32\n\t" \ - "dsra\t%L0, %L0, 32\n\t" \ + "dmfc0\t%L0, " #source "\n\t" \ + "dsra\t%M0, %L0, 32\n\t" \ + "sll\t%L0, %L0, 0\n\t" \ ".set\tmips0" \ : "=r" (__val)); \ else \ __asm__ __volatile__( \ ".set\tmips64\n\t" \ - "dmfc0\t%M0, " #source ", " #sel "\n\t" \ - "dsll\t%L0, %M0, 32\n\t" \ - "dsra\t%M0, %M0, 32\n\t" \ - "dsra\t%L0, %L0, 32\n\t" \ + "dmfc0\t%L0, " #source ", " #sel "\n\t" \ + "dsra\t%M0, %L0, 32\n\t" \ + "sll\t%L0, %L0, 0\n\t" \ ".set\tmips0" \ : "=r" (__val)); \ local_irq_restore(__flags); \ |