On 32-bit targets, gcc is able to do the right thing with a constant
divisor that happens to be a power of two i.e. it turns the division
into a right shift inline.
Signed-off-by: Nicolas Pitre <nico@xxxxxxxxxx>
---
include/asm-generic/div64.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/include/asm-generic/div64.h b/include/asm-generic/div64.h
index 8f4e319334..47aa1e2134 100644
--- a/include/asm-generic/div64.h
+++ b/include/asm-generic/div64.h
@@ -41,7 +41,12 @@ extern uint32_t __div64_32(uint64_t *dividend, uint32_t divisor);
uint32_t __base = (base); \
uint32_t __rem; \
(void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
- if (likely(((n) >> 32) == 0)) { \
+ if (__builtin_constant_p(__base) && \
+ (__base & (__base - 1)) == 0) { \
+ /* constant power of 2: gcc is fine */ \
+ __rem = (n) & (__base - 1); \
+ (n) /= __base; \
+ } else if (likely(((n) >> 32) == 0)) { \
__rem = (uint32_t)(n) % __base; \
(n) = (uint32_t)(n) / __base; \
} else \
--
2.4.3
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