if the fix need to be in multiple places, perhaps make a template out of that?
Sun
On Thu, Aug 12, 2010 at 9:27 AM, Ye, Mei <mei...@amd.com> wrote:
> Hello Kalin,
>
>
>
> Looks like you missed another place in Simd_Finalize_Loops that may require
> a similar fix.
>
>
>
> -Mei
>
>
>
> ________________________________
>
> From: Ju, Roy
> Sent: Wednesday, August 11, 2010 3:11 PM
> To: Ye, Mei
> Subject: FW: [Open64-devel] Simd_Finalize_Loops bug in handling unsigned
> comparison loop end
>
>
>
> Mei,
>
> See if you can review this changelist. Thanks.
>
>
>
> Roy
>
>
>
> From: Hui Shi [mailto:]
> Sent: Sunday, August 08, 2010 7:46 PM
> To:
> Subject: [Open64-devel] Simd_Finalize_Loops bug in handling unsigned
> comparison loop end
>
>
>
> Hi, All
>
>
>
> Can LNO gatekeeper help review this fix?
>
>
>
> This bug happens in -m32 on x8664 linux.
>
> Attached is the test case and patch.
>
> command line is
>
> opencc -O3 unsigned_loop_end.c -INLINE:ne=foo:ne=init:ne=check
> -OPT:unroll_times_max=1 -m32
>
>
>
> The bug happens when vectorization is happend on following loop.
>
> int a[100]
>
> int start;
> unsigned i, end;
> for( i = start; i < end; i++) {
> a[i] = a[i+1];
> }
>
> with -m64 unsigned comparison is transformed to signed comparison in
> STD_Canonicalize_Upper_Bound.
>
> with -m32 unsigned comparison is kept in LNO.
>
>
>
> will update loop_end align to vecotrize factor (vect)
>
> i <= start + (((end - start + 1) / vect) * vect) -1
> suppose start is 0, end is 2, vect is 4, original serial loop is
> for( i = 0; i < 2; i++)
> after Simd_Finalize_Loops transformation, simd loop becomes
> for(i = 0, i <= -1; i++),
>
> This loop will itreate 0xffffffff times.
>
>
>
> The fix is change loop end to following form when compraion is unsigned.
> i < start + (((end - start + 1) / vect) * vect)
>
>
>
>
>
> As discussed with Shuxin, we also doubt why SIMD loop's upper need aligned
> with vecotrized factor. Can SIMD only update loop's step?
>
> like for(i = start, i <= end-1; i+= vector_factor)?
>
>
>
>
>
> Best Regards
>
> Shi, Hui
>
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