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Re: Patch committed: Make exact_log2 and floor_log2 static inline
- From: Ian Lance Taylor <iant at google dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Tue, 16 Jun 2009 10:53:04 -0700
- Subject: Re: Patch committed: Make exact_log2 and floor_log2 static inline
- References: <20090616165802.4350.qmail@pepe.airs.com>
Ian Lance Taylor <iant@google.com> writes:
> The functions exact_log2 and floor_log2 are defined in toplev.h and
> toplev.c as GNU89 extern inline functions. This does not work right
> with C++ or with C99. For C99 we could use the gnu_inline attribute,
> but there is really no advantage to doing so. This patch changes
> floor_log2 and exact_log2 to be static inline. The definitions in
> toplev.c are only provided if the static inline functions are not
> defined, which is to say when compiling with a non-gcc compiler or
> with gcc pre 3.4. This simplifies the code overall.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu. Committed.
>
> Ian
>
>
> 2009-06-16 Ian Lance Taylor <iant@google.com>
>
> * toplev.h (floor_log2): If GCC_VERSION >= 3004, declare as static
> inline, not extern inline.
> (exact_log2): Likewise.
> * toplev.c (floor_log2): Only define if GCC_VERSION < 3004. Don't
> test CLZ_HWI.
> (exact_log2): Likewise, but don't test CTZ_HWI.
Really attaching the patch.
Ian
Index: toplev.c
===================================================================
--- toplev.c (revision 148539)
+++ toplev.c (revision 148540)
@@ -532,11 +532,11 @@ read_integral_parameter (const char *p,
return atoi (p);
}
-/* When compiling with a recent enough GCC, we use the GNU C "extern inline"
- for floor_log2 and exact_log2; see toplev.h. That construct, however,
- conflicts with the ISO C++ One Definition Rule. */
+#if GCC_VERSION < 3004
-#if GCC_VERSION < 3004 || !defined (__cplusplus)
+/* The functions floor_log2 and exact_log2 are defined as inline
+ functions in toplev.h if GCC_VERSION >= 3004. The definitions here
+ are used for older versions of gcc. */
/* Given X, an unsigned number, return the largest int Y such that 2**Y <= X.
If X is 0, return -1. */
@@ -549,9 +549,6 @@ floor_log2 (unsigned HOST_WIDE_INT x)
if (x == 0)
return -1;
-#ifdef CLZ_HWI
- t = HOST_BITS_PER_WIDE_INT - 1 - (int) CLZ_HWI (x);
-#else
if (HOST_BITS_PER_WIDE_INT > 64)
if (x >= (unsigned HOST_WIDE_INT) 1 << (t + 64))
t += 64;
@@ -568,7 +565,6 @@ floor_log2 (unsigned HOST_WIDE_INT x)
t += 2;
if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 1))
t += 1;
-#endif
return t;
}
@@ -581,14 +577,10 @@ exact_log2 (unsigned HOST_WIDE_INT x)
{
if (x != (x & -x))
return -1;
-#ifdef CTZ_HWI
- return x ? CTZ_HWI (x) : -1;
-#else
return floor_log2 (x);
-#endif
}
-#endif /* GCC_VERSION < 3004 || !defined (__cplusplus) */
+#endif /* GCC_VERSION < 3004 */
/* Handler for fatal signals, such as SIGSEGV. These are transformed
into ICE messages, which is much more user friendly. In case the
Index: toplev.h
===================================================================
--- toplev.h (revision 148539)
+++ toplev.h (revision 148540)
@@ -169,14 +169,17 @@ extern void decode_d_option (const char
extern bool fast_math_flags_set_p (void);
extern bool fast_math_flags_struct_set_p (struct cl_optimization *);
+/* Inline versions of the above for speed. */
+#if GCC_VERSION < 3004
+
/* Return log2, or -1 if not exact. */
extern int exact_log2 (unsigned HOST_WIDE_INT);
/* Return floor of log2, with -1 for zero. */
extern int floor_log2 (unsigned HOST_WIDE_INT);
-/* Inline versions of the above for speed. */
-#if GCC_VERSION >= 3004
+#else /* GCC_VERSION >= 3004 */
+
# if HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_LONG
# define CLZ_HWI __builtin_clzl
# define CTZ_HWI __builtin_ctzl
@@ -188,17 +191,18 @@ extern int floor_log2 (
# define CTZ_HWI __builtin_ctz
# endif
-extern inline int
+static inline int
floor_log2 (unsigned HOST_WIDE_INT x)
{
return x ? HOST_BITS_PER_WIDE_INT - 1 - (int) CLZ_HWI (x) : -1;
}
-extern inline int
+static inline int
exact_log2 (unsigned HOST_WIDE_INT x)
{
return x == (x & -x) && x ? (int) CTZ_HWI (x) : -1;
}
+
#endif /* GCC_VERSION >= 3004 */
/* Functions used to get and set GCC's notion of in what directory