On Tue, Feb 06, 2007 at 06:20:39PM +0000, Maciej W. Rozycki wrote:
> > > arch/mips/lib/uncached.c: In function 'run_uncached':
> > > arch/mips/lib/uncached.c:47: warning: comparison is always true due to limited range of data type
> > > arch/mips/lib/uncached.c:48: warning: comparison is always false due to limited range of data type
> > > arch/mips/lib/uncached.c:57: warning: comparison is always true due to limited range of data type
> > > arch/mips/lib/uncached.c:58: warning: comparison is always false due to limited range of data type
> >
> > Thanks, applied.
>
> "Fixing" bugs in the compiler, huh? ;-) I suppose there should be a note
> somewhere nearby then, so there is a remote chance to remove the clutter
> in the future.
Well, some of the warnings are also simply due to broken code. This is
the result of preprocessing the code without Yoichi's patch applied:
[...]
if (sp >= (long)0x80000000 && sp < (long)0xc0000000)
usp = ((((int)(int)(sp)) & 0x1fffffff) | 0xa0000000);
else if ((long long)sp >= (long long)(0x8000000000000000LL | ((0LL)<<59) | (0)) &&
(long long)sp < (long long)(0x8000000000000000LL | ((8LL)<<59) | (0)))
usp = (0x8000000000000000LL | (((long long)2)<<59) | ((((long long)sp) & -1)));
else {
do { __asm__ __volatile__("break %0" : : "i" (512)); } while (0);
usp = sp;
}
[...]
So (0x8000000000000000LL | ((0LL)<<59) | (0)) is 0x8000000000000000LL which
then is casted to _signed_ long long, so becomes -9223372036854775808, the
most negative representable number so the two "comparison is always true
due to limited range of data type" warnings are perfectly correct.
Treating addresses as signed is a dangerous thing and we reallly only
should do it where extending 32-bit addresses to 64-bit because that's
what the architecture does. So I would suggest as part of cleaning u the
mess something like below totally untested patch.
Comments?
Ralf
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
diff --git a/include/asm-mips/addrspace.h b/include/asm-mips/addrspace.h
index c627508..ff2dd38 100644
--- a/include/asm-mips/addrspace.h
+++ b/include/asm-mips/addrspace.h
@@ -10,6 +10,7 @@
#ifndef _ASM_ADDRSPACE_H
#define _ASM_ADDRSPACE_H
+#include <linux/types.h>
#include <spaces.h>
/*
@@ -22,12 +23,12 @@
#define _CONST64_(x) x
#else
#define _ATYPE_ __PTRDIFF_TYPE__
-#define _ATYPE32_ int
-#define _ATYPE64_ __s64
+#define _ATYPE32_ unsigned int
+#define _ATYPE64_ __u64
#ifdef CONFIG_64BIT
-#define _CONST64_(x) x ## L
+#define _CONST64_(x) x ## UL
#else
-#define _CONST64_(x) x ## LL
+#define _CONST64_(x) x ## ULL
#endif
#endif
