This patch looks fine to me.
Could you please file a bug to bugs.open64.net to track this issue? Also, I
find the branch is not eliminated at '-m32 -O1'. Could you check that? Thank
you very much.
2010/11/16 Hui Shi <kalin....@gmail.com>
> Can gatekeeper help review this patch?
> This is a bug in cflow optimization exposed when a cmpi32 is changed to
> cmpi8
>
> int main()
> {
> long long ll = 0x7EF0LL;
> unsigned char c = (char) ll;
> if (c != 0xf0)
> return 1;
> return 0;
> }
>
> opencc -O0, run result's value is 0.
> opencc -O1, run result's value is 1.
> This is a problem in O2 or higher is because wopt handle remove this
> branch.
>
> without mov-ext in EBO, cflow can't optimize convert the if branch into
> goto
> opencc -O1 -CG:movext_icmp=off
> [ 2, 0] GTN4(%rsp) :- spadjust GTN4(%rsp)<defopnd> (0x0) ;
> [ 3, 0] TN149 :- ldc64 (0x7ef0) ;
> [ 3, 0] :- store64 TN149 GTN4(%rsp) (sym:ll+0) ;
> [ 4, 0] :- store8 TN149 GTN4(%rsp) (sym:c+0) ;
> [ 0, 0] TN152 :- movzbl TN149 ;
> [ 5, 0] TN33(%rflags) :- cmpi32 TN152 (0xf0) ;
> [ 5, 0] :- je TN33(%rflags) (lab:.L_0_770) ;
>
> when turn on movext_icmp
> [ 3, 0] TN149 :- ldc64 (0x7ef0) ;
> [ 3, 0] :- store64 TN149 GTN4(%rsp) (sym:ll+0) ;
> [ 4, 0] :- store8 TN149 GTN4(%rsp) (sym:c+0) ;
> [ 5, 0] TN33(%rflags) :- cmpi8 TN149 (0xf0) ;
> [ 5, 0] :- je TN33(%rflags) (lab:.L_0_770) ;
>
> it get TN149's value is 0x7ef0, then directly compare with 0xf0 without
> truncate.
>
> There is original a function Extend_Short_Cmp_Src, truncate and sign extend
> short sign value for compare constant.
> The fix is truncate the constant to one bytes or two bytes if compare is
> short unsigned compare.
>
>
>
>
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--
Regards,
Lai Jian-Xin
------------------------------------------------------------------------------
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Spend less time writing and rewriting code and more time creating great
experiences on the web. Be a part of the beta today
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