On Nov. 11, 2001, I sent in a C51 V6.20 bug report via e-mail to support.us@keil.com. I never received a response, so assumed Keil's policy was to silently introduce the bug fix in a subsequent update. After downloading V6.21, I see that the bug is still present. Now I'm wondering whether my e-mailed bug report was ever acted upon, so I'm going to try the forum as the means to report the bug. I have a section of code with pointer incrementation that compiles and executes correctly when the pointer is defined as a generic pointer or as an xdata pointer, or when the optimization setting is reduced from the default OT(8,SPEED) to OT(7,SPEED). However, when the pointer is defined as a data or idata pointer, the compiler does not emit code to increment the pointer with default optimization. I have provided example code demonstrating the problem. The specific statement is line 50 below.
unsigned char idata u64[8] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }; unsigned char idata s[21]; void U64ToStr( char idata *s, unsigned char idata *binP, unsigned char n ) { unsigned char bcd; unsigned char idata *bcdP; unsigned char bitMsk = 0x80; unsigned char carry; unsigned char i; /* Zero the target buffer (NUL-terminating the string). */ for (bcdP = s, i = n + 1; i != 0; *bcdP++ = 0, i--) ; /* Convert 64 bits of binary to unpacked BCD. For each bit, starting * with the MSBit, BCD = (BCD * 2) + bit. */ for (i = 64; i != 0; i--) { carry = (*binP & bitMsk) ? 1 : 0; for (bcdP = s + n; bcdP != s; /* Iter in body */) { bcd = *--bcdP * 2; bcd += carry; if (bcd < 10) carry = 0; else { carry = 1; bcd -= 10; } *bcdP = bcd; } if ((bitMsk >>= 1) == 0) { bitMsk = 0x80; binP++; } } /* ASCII'fy BCD. */ for (i = n; i != 0; i--) *bcdP++ += '0'; /* <-- C51 BUG: bcdP doesn't increment for (i)data */ } void main( void ) { for (;;) U64ToStr( s, u64, 6 ); }
/* ASCII'fy BCD. */ for (i = n; i != 0; i--) *bcdP++ += '0'; /* <-- C51 BUG: bcdP doesn't increment for (i)data */
/* ASCII'fy BCD. */ for (i = n; i != 0; i--) { *bcdP += '0'; ++bcdP; }
for (i = n; i != 0; i--) { bcdP[i] += '0'; }
Thanks for your thoughts Andrew. Regarding "I have had problems before with packing too much stuff into a single line - particularly the pre/post increment/decrement operators.", the compiler handles the statement fine if I change "binP" to "s":
for (i = n; i != 0; i--) *s++ += '0'; /* Using 's' does work. */ ;---- Variable 's' assigned to Register 'R7' ---- ;---- Variable 'i' assigned to Register 'R4' ---- 0061 AC00 R MOV R4,n 0063 ?C0014: 0063 EC MOV A,R4 0064 600C JZ ?C0017 0066 AE07 MOV R6,AR7 0068 0F INC R7 ; <-- *** 0069 A806 MOV R0,AR6 006B 7430 MOV A,#030H 006D 26 ADD A,@R0 006E F6 MOV @R0,A 006F 1C DEC R4 0070 80F1 SJMP ?C0014
for (i = n; i != 0; i--) { *bcdP += '0'; ++bcdP; } ;---- Variable 'n' assigned to Register 'R1' ---- ;---- Variable 'bcdP' assigned to Register 'R5' ---- ;---- Variable 'i' assigned to Register 'R4' ---- 0063 AC01 MOV R4,AR1 0065 ?C0014: 0065 EC MOV A,R4 0066 6009 JZ ?C0017 0068 A805 MOV R0,AR5 006A 7430 MOV A,#030H 006C 26 ADD A,@R0 006D F6 MOV @R0,A 006E 1C DEC R4 006F 80F4 SJMP ?C0014 0071 ?C0017:
;---- Variable 'n' assigned to Register 'R1' ---- ;---- Variable 'bcdP' assigned to Register 'R5' ---- ;---- Variable 'i' assigned to Register 'R4' ---- 0064 AC01 MOV R4,AR1 0066 ?C0014: 0066 EC MOV A,R4 0067 600A JZ ?C0017 0069 A805 MOV R0,AR5 006B 7430 MOV A,#030H 006D 26 ADD A,@R0 006E F6 MOV @R0,A 006F 0D INC R5 ; <-- *** 0070 1C DEC R4 0071 80F3 SJMP ?C0014 0073 ?C0017: