looks good to me
Sun
On Fri, Jul 22, 2011 at 2:30 PM, 朱庆 <zqing1...@gmail.com> wrote:
> Hi all,
>
> Can gatekeeper help review this fix?
>
> The problem is, when compiling a function like:
>
> long fooBig(long x) {
> return (x * (((long)1) << 63));
> }
>
> EBO will try to optimize this mul operation, in the function
> Convert_Imm_Mul. At the beginning of this function, the statement
>
> INT64 val = imm_val < 0 ? -imm_val : imm_val;
>
> is trying to get the absolute value of imm_val, but in this case,
> imm_val is ((long)1) << 63, which makes .imm_val is the same as
> imm_val. Then, in the loop
>
> int power = 0;
> while( val != 1 ){
> power++;
> val >>= 1;
> }
>
> val will keep being -1, which make this loop endless.
>
> The solution is straightforward, just to change the type of imm_val
> from INT64 to UINT64.
>
> case:
> long fooBig(long x) {
> return (x * (((long)1) << 63));
> }
>
> Patch:
> Index: osprey/be/cg/x8664/ebo_special.cxx
> ===================================================================
> --- osprey/be/cg/x8664/ebo_special.cxx (revision 3690)
> +++ osprey/be/cg/x8664/ebo_special.cxx (working copy)
> @@ -1814,7 +1814,7 @@
> OP *new_op = NULL;
> const BOOL is_64bit = (TN_size(tnr) == 8);
> const TYPE_ID mtype = is_64bit ? MTYPE_I8 : MTYPE_I4;
> - INT64 val = imm_val < 0 ? -imm_val : imm_val;
> + UINT64 val = imm_val < 0 ? -imm_val : imm_val;
> OPS ops = OPS_EMPTY;
>
> if( imm_val == 0 ){
> @@ -1840,6 +1840,8 @@
>
> bool need_an_add = false;
>
> + /* Check for an unsigned power of two + 1. */
> +
> if( val >= 2 &&
> ( (val-1) & (val-2) ) == 0 ){
> val--;
> @@ -1847,7 +1849,7 @@
> }
>
> /* Check whether it can carry an imm opnd. */
> -
> + /* Check for unsigned power of two. */
> if( ( val & ( val - 1 ) ) != 0 ){
> const TOP new_top = TOP_with_Imm_Opnd( op, 1, imm_val );
>
> @@ -1871,6 +1873,8 @@
> tn = tmp;
> }
>
> + /* determine the power of val. */
> +
> int power = 0;
> while( val != 1 ){
> power++;
> @@ -1883,7 +1887,7 @@
> Expand_Add( tnr, tnr, tn, mtype, &ops );
> }
>
> - if( imm_val < 0 )
> + if( imm_val < 0 && imm_val != INT64_MIN )
> Expand_Neg( tnr, tnr, mtype, &ops );
>
> BB_Insert_Ops_After( OP_bb(op), op, &ops );
>
> Thanks
> zhuqing
>
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