On Tue, Jul 15, 2025 at 08:36:46AM -0700, Andrew Pinski wrote:
> On Tue, Jul 15, 2025 at 6:06 AM Jakub Jelinek <ja...@redhat.com> wrote:
> >
> > On Tue, Jul 15, 2025 at 08:21:50AM -0400, Jason Merrill wrote:
> > > Given the above that seems rather unlikely, but I suppose it's fine if you
> > > want to do it that way. The patch is OK either way.
> >
> > Committed just the v2 patch. I can test your patch next with other patches,
> > or do you want to test/commit it yourself?
>
> Just an FYI, this broke aarch64 build since libgcc has -Werror on
> there and we get warnings now in libbid code:
> ```
> ../../../gcc/libgcc/config/libbid/bid_binarydecimal.c: In function
> ‘__binary32_to_bid128’:
> ../../../gcc/libgcc/config/libbid/bid_binarydecimal.c:130:31: error:
> variable ‘c3’ set but not used [-Werror=unused-but-set-variable=]
> 130 | { unsigned long long c0,c1,c2,c3; \
> | ^~
> ../../../gcc/libgcc/config/libbid/bid_binarydecimal.c:146842:5: note:
> in expansion of macro ‘__mul_10x256_to_256’
> 146842 | __mul_10x256_to_256 (z.w[5], z.w[4], z.w[3], z.w[2],
> z.w[5], z.w[4],
> | ^~~~~~~~~~~~~~~~~~~
> ```
> https://builder.sourceware.org/buildbot/#/builders/311/builds/1483
>
> I will see if there is anything simple to be done in the next few hours.
#define __mul_10x64(sum,carryout,input,carryin) \
{ unsigned long long s3 = (input) + ((input) >> 2); \
(carryout) = ((s3 < (unsigned long long)(input))<<3) + (s3>>61); \
s3 = (s3<<3) + ((input&3)<<1); \
(sum) = s3 + (carryin); \
if ((unsigned long long)(sum) < s3) ++(carryout); \
}
// Multiply a 256-bit number by 10, assuming no overflow
#define __mul_10x256_to_256(p3,p2,p1,p0,a3,a2,a1,a0) \
{ unsigned long long c0,c1,c2,c3; \
__mul_10x64(p0,c0,a0,0ull); \
__mul_10x64(p1,c1,a1,c0); \
__mul_10x64(p2,c2,a2,c1); \
__mul_10x64(p3,c3,a3,c2); \
}
So yeah, it is clear why -Wunused-but-set-variable=1 doesn't
warn about it, there is a useless assignment to c3 and then conditional
++c3. And it is clear why it does warn now.
Not having c3 would mean having special macro for the final step,
so I think it is better to just
2025-07-15 Jakub Jelinek <ja...@redhat.com>
* bid_binarydecimal.c (__mul_10x256_to_256): Quiet
-Wunused-but-set-variable=3 warning.
--- libgcc/config/libbid/bid_binarydecimal.c.jj 2025-04-08 14:09:53.599413906
+0200
+++ libgcc/config/libbid/bid_binarydecimal.c 2025-07-15 18:02:15.494219552
+0200
@@ -132,6 +132,7 @@ UINT64 CY;
__mul_10x64(p1,c1,a1,c0); \
__mul_10x64(p2,c2,a2,c1); \
__mul_10x64(p3,c3,a3,c2); \
+ (void)c3; \
}
// Set up indices for low and high parts, depending on the endian-ness.
Untested...
Jakub
