One more thing:
the code
if(k & 0xffff!=0) statement;
id equivalent to
if(k & 1) statement;
cause in comparison operation '!=' will be performed first, then '&'.
Therefore, the compiler checks only most bottom nibble of 'k'.
~d
On Mon, 5 Aug 2002 11:34:55 +0300
"Oleg Skidan" <[email protected]> wrote:
> Hello, All !
> During use of mspgcc (build 2002-07-25) I noticed a very
> strange things:
>
> Consider the following fragment of code:
>
> int b(long long k)
> {
> if(k & 0xffff!=0)return 1;
> }
>
> The compiler emits:
>
> .global b
> .type b,@function
> /***********************
> * Function `b'
> ***********************/
> b:
> /* prologue: frame size = 0; addenum 0; alloca:0, varargs:0 , fpr:0*/
> .L__FrameSize_b=0x0
> .L__FrameOffset_b=0x0
> /* prologue end (size=0) */
> and #llo(2), r12 ;<<<<<<<<????????????
> and #llo(0), r13
> and #llo(52), r14 ;<<<<<<<<????????????
> and #llo(0), r15
> tst r12
> jeq .L2
> mov #llo(1), r15
> ret
> .L2:
> mov #llo(0), r15
> .L1:
> /* epilogue: frame size=0 */
> ret
> /* epilogue end (size=1) */
> /* function b size 20 (19) */
> .Lfe1:
> .size b,.Lfe1-b
> /********* End of function ******/
>
> Now lets make a minor changes:
>
> int b(long long k)
> {
> if(k & 0xffff)return 1;
> return 0;
> }
>
> The compiler emits:
>
> .global b
> .type b,@function
> /***********************
> * Function `b'
> ***********************/
> b:
> /* prologue: frame size = 0; addenum 0; alloca:0, varargs:0 , fpr:0*/
> .L__FrameSize_b=0x0
> .L__FrameOffset_b=0x2
> push r11
> /* prologue end (size=1) */
> and #llo(19744), r12 ;<<<<<????
> and #llo(137), r13
> and #llo(46), r14
> and #llo(8192), r15
> mov r12, r11
> bis r13, r11
> bis r14, r11
> bis r15, r11
> tst r11
> jeq .L2
> mov #llo(1), r15
> jmp .L1
> .L2:
> mov #llo(0), r15
> .L1:
> /* epilogue: frame size=0 */
> pop r11
> ret
> /* epilogue end (size=2) */
>
> I think we have a BUG :-(.
> The code is good and correct if argument type is long instead of long long.
>
> All the best, Oleg.
>
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