give up on gcc ilog2() constant optimizations

[mirror_ubuntu-zesty-kernel.git] / include / linux / log2.h

diff --git a/include/linux/log2.h b/include/linux/log2.h
index ef3d4f67118ce0f60789e6e749a4773754e01e87..c373295f359fa582859962bbf3295dbd936111ad 100644 (file)
--- a/include/linux/log2.h
+++ b/include/linux/log2.h
@@ -15,12 +15,6 @@
 #include <linux/types.h>
 #include <linux/bitops.h>
 
-/*
- * deal with unrepresentable constant logarithms
- */
-extern __attribute__((const, noreturn))
-int ____ilog2_NaN(void);
-
 /*
  * non-constant log of base 2 calculators
  * - the arch may override these in asm/bitops.h if they can be implemented
@@ -85,7 +79,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
 #define ilog2(n)                               \
 (                                              \
        __builtin_constant_p(n) ? (             \
-               (n) < 1 ? ____ilog2_NaN() :     \
+               (n) < 2 ? 0 :                   \
                (n) & (1ULL << 63) ? 63 :       \
                (n) & (1ULL << 62) ? 62 :       \
                (n) & (1ULL << 61) ? 61 :       \
@@ -148,10 +142,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
                (n) & (1ULL <<  4) ?  4 :       \
                (n) & (1ULL <<  3) ?  3 :       \
                (n) & (1ULL <<  2) ?  2 :       \
-               (n) & (1ULL <<  1) ?  1 :       \
-               (n) & (1ULL <<  0) ?  0 :       \
-               ____ilog2_NaN()                 \
-                                  ) :          \
+               1 ) :                           \
        (sizeof(n) <= 4) ?                      \
        __ilog2_u32(n) :                        \
        __ilog2_u64(n)                          \