Hi,
Consider code:
char A;
char B;
char sum_A_B ( void )
{
char sum = A + B;
return sum;
}
Compile it on any backend (for example x86):
gcc (SUSE Linux) 4.5.0 20100604 [gcc-4_5-branch revision 160292]
gcc -m32 -O2 -S repro.c -fdump-tree-all-lineno-details
Now look at repro.c.004t.gimple
Konstantin Vladimirov writes:
> It looks really weird. Why gcc promotes char to unsigned char internally?
Hmm, maybe not useful, but if you used "unsigned char" as the variable
types or the -funsigned-char command-line option, it won't ('cause the
variables will already be unsigned)...
-miles
-
On Thu, Jan 26, 2012 at 02:27:45PM +0400, Konstantin Vladimirov wrote:
> Consider code:
>
> char A;
> char B;
>
> char sum_A_B ( void )
> {
> char sum = A + B;
>
> return sum;
> }
> [repro.c : 6:8] A.0 = A;
> [repro.c : 6:8] A.1 = (unsigned char) A.0;
> [repro.c : 6:8] B.2 = B;
> [re
Hi,
If I know what I am doing, and my code itself guarantees, that there
will be no overflows and UB here, can I switch off this signed char to
unsigned char expansion in favor of signed char to signed int
expansion?
---
With best regards, Konstantin
On Thu, Jan 26, 2012 at 3:04 PM, Jakub Jeline
On Thu, Jan 26, 2012 at 12:53 PM, Konstantin Vladimirov
wrote:
> Hi,
>
> If I know what I am doing, and my code itself guarantees, that there
> will be no overflows and UB here, can I switch off this signed char to
> unsigned char expansion in favor of signed char to signed int
> expansion?
No, y
On Thu, Jan 26, 2012 at 03:53:59PM +0400, Konstantin Vladimirov wrote:
> If I know what I am doing, and my code itself guarantees, that there
> will be no overflows and UB here, can I switch off this signed char to
> unsigned char expansion in favor of signed char to signed int
> expansion?
Obviou
I think gcc is missing an option since -mavx controls two different
things. First, the generation of VEX-encoded instructions. Second,
the use of ymm registers. The latter is not always available when the
former is and using VEX-encoded instructions by themselves can have an
advantage. Currentl
On Wed, Jan 25, 2012 at 8:20 PM, Richard Sandiford
wrote:
> Richard Guenther writes:
>> I'd say open a missed optimization bug with the testcase and go ahead
>> with both patches.
>
> OK, I committed the patches yesterday and I've just opened PR 52000
> for the missed optimisation.
Btw, looking
On 26/01/2012 12:53, Konstantin Vladimirov wrote:
Hi,
If I know what I am doing, and my code itself guarantees, that there
will be no overflows and UB here, can I switch off this signed char to
unsigned char expansion in favor of signed char to signed int
expansion?
The big question here is w
On Thursday 26 of January 2012 09:52:22 Ulrich Drepper wrote:
> I think gcc is missing an option since -mavx controls two different
> things. First, the generation of VEX-encoded instructions. Second,
> the use of ymm registers. The latter is not always available when the
> former is and using V
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