Jump to content

Boostc: Error In Multiply Code Generation

Recommended Posts

Bug description:

multiply by 256 generates wrong results


Steps to reproduce:

compile the following with BoostC

#include <system.h>

char h, l;
unsigned int gamma;

void main()
 l = 0xE8;       // low byte of gamma
 h = 0x03;       // hi byte of gamma

 gamma = h*256 + l;             // *** wrong, due to shift optimization ?;-)
 gamma = ((int) h) << 8 | l;    // *** correct     gamma = 1000


produces the following code

 gamma = h*256 + l;             // *** wrong, due to shift optimization ?;-)
1FE5          ; {
1FE5   A501            CLRF CompTempVar7
1FE6   A401            CLRF CompTempVar6
1FE7   2108            MOVF gbl_l, W
1FE8   2407            ADDWF CompTempVar6, W
1FE9   A600            MOVWF CompTempVar8
1FEA   2508            MOVF CompTempVar7, W
1FEB   A700            MOVWF CompTempVar9
1FEC   0318            BTFSC STATUS,C
1FED   A70A            INCF CompTempVar9
1FEE   2608            MOVF CompTempVar8, W
1FEF   A200            MOVWF gbl_gamma
1FF0   2708            MOVF CompTempVar9, W
1FF1   A300            MOVWF gbl_gamma+D'1'
1FF2          ; }

 gamma = ((int) h) << 8 | l;                              
1FF2          ; {
1FF2   A401            CLRF CompTempVar10
1FF3   2008            MOVF gbl_h, W
1FF4   A500            MOVWF CompTempVar11
1FF5   2108            MOVF gbl_l, W
1FF6   2404            IORWF CompTempVar10, W
1FF7   A600            MOVWF CompTempVar12
1FF8   2508            MOVF CompTempVar11, W
1FF9   A700            MOVWF CompTempVar13
1FFA   2608            MOVF CompTempVar12, W
1FFB   A200            MOVWF gbl_gamma
1FFC   2708            MOVF CompTempVar13, W
1FFD   A300            MOVWF gbl_gamma+D'1'
1FFE          ; }


Expected behaviour:

the compiler should generate correct code so that gamma evaluates to 1000


Is the problem 100% reproduceable: yes


IDE version: SourceBoost IDE 5.6.1

Compiler: BoostC

Compiler version: Alpha 1.3


OS: Win2000



Link to post
Share on other sites

Join the conversation

You are posting as a guest. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...