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authorMaciej W. Rozycki <macro@imgtec.com>2017-09-29 17:26:31 +0200
committerJames Hogan <jhogan@kernel.org>2017-11-08 22:50:52 +0100
commitd3a0b968186a7e197b7551e4d6080676372152ce (patch)
tree5b80d9ec87799dde7054bd6daa00ee3c9611ee4c
parentMIPS: ralink: Drop obsolete USB_ARCH_HAS_HCD select (diff)
downloadlinux-d3a0b968186a7e197b7551e4d6080676372152ce.tar.xz
linux-d3a0b968186a7e197b7551e4d6080676372152ce.zip
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>
-rw-r--r--arch/mips/include/asm/mipsregs.h14
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); \