Hi
This been fixed a while ago.
Grab cvs version of gcc and recompile.
cheers,
~d
On Tuesday 06 January 2004 16:46, Ralf Hildebrandt wrote:
> Hello!
>
> First of all - I am only a C-newbie. Please keep your answers easy.
>
> Ich found a bug in the compiler MSP430-GCC: The software multiplication
> (16bits * 16 bits = 32 bits) produces wrong results. The point, where the
> error occurs is located and a hint for the solution will be presented.
>
> The used operating system is Solaris 5.7, the version of msp430-gcc is
> 3.2.2. The target is any MSP430 without hardware multiplier - e.g.
> MSP430x311-series.
>
> A minimal example:
>
> ////////////////////////////////////////
> #include <msp430x31x.h>
>
> int main(void)
> {
> long int multi(int a, int b);
>
> int a = 0x1234;
> int b = 0xabcd;
> long int res;
>
> /*hide the multiplication in a function
> otherwise the compiler optimizes it away*/
> res = multi(a,b);
>
> /*dummy-operations - otherwise the result would have been never used and
> would be optimized away*/ *((unsigned int*)0x200) = res;
> *((unsigned int*)0x202) = res >> 16;
>
> return 0;
> }
>
> long int multi(int a, int b)
> {
> return (long int)a * b;
> }
> ////////////////////////////////////////
>
> The used Makefile:
> ////////////////////////////////////////
> NAME=mspgcc_mulbug
>
> CPU = msp430x311 #no hardware multiplier
> ASMOPT = -mmcu=${CPU}
> COPT = -mmcu=${CPU} -O2 -Wall -g
> CC = msp430-gcc
>
> ${NAME}.elf: ${NAME}.o
> $(CC) -mmcu=${CPU} -g -o $@ $^
> msp430-objcopy -O ihex $@ ${NAME}.a43
> msp430-objdump -DS ${NAME}.elf >${NAME}.lst
>
> ${NAME}.o: ${NAME}.c
> msp430-gcc ${COPT} -c $<
>
> clean:
> rm -f ${NAME}.elf ${NAME}.a43 ${NAME}.lst ${NAME}.ini *.o
> ////////////////////////////////////////
>
> The point, where the bug occurs is marked in the source code. During "make"
> a list file is created. An extract of the buggy code follows:
> ////////////////////////////////////////
> return (long int)a * b;
> f862: 0a 4f mov r15, r10 ;
> f864: 0c 4e mov r14, r12 ;
> f866: 0b 43 clr r11 ;
> f868: 0a 93 cmp #0, r10 ;subst r3 with
> As==00
> f86a: 01 34 jge $+4 ;abs dst addr
> 0xf86e
> f86c: 3b 43 mov #-1, r11 ;subst r3 with
> As==11
> f86e: 0c 43 clr r12 ;
> f870: 0c 93 cmp #0, r12 ;subst r3 with
> As==00
> f872: 01 34 jge $+4 ;abs dst addr
> 0xf876
> f874: 3d 43 mov #-1, r13 ;subst r3 with
> As==11
> f876: b0 12 84 f8 call #-1916 ;#0xf884
> ////////////////////////////////////////
>
> The final "call" on address 0xF876 is the jump to the software
> multiplication routine. The listed code shows both conversions of "a"
> (register R10) and "b" (register R12) from type "int" to "long int". ("b"
> is converted automatically.)
>
> From address 0xF862 to 0xf86C everthing works fine. (Conversion of "a" from
> "int" to "long int" with correct sign extension.)
>
> The bug is located at address 0xF86E. R12 holds the data of variable "b".
> R13 should be the upper half of "(long int)b" after automatically
> sign-extending R12. But R12 is destroyed instead of R13.
> The correct code would be:
> ////////////////////////////////////////
> f86e: 0d 43 clr r13 ;
> ////////////////////////////////////////
>
>
>
>
> Additional informations:
>
> The bug was observed only when a multiplication should be computed. If one
> replaces the multiplication with an addition, like
> ////////////////////////////////////////
> return (long int)a + b;
> ////////////////////////////////////////
> a different sign-extension algorithm is used and no error can be found.
>
> Unsigned multiplication and any kind of hardware multiplication did not
> show any bugs.
>
>
>
> Ralf Hildebrandt
>
>
>
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