Date:	Sat, 3 Jan 1998 11:39:32 -0800 (PST)
Message-Id:	<199801031939.LAA26799@adit.ap.net>
Mime-Version:	1.0
To:	GAMMELJL AT SLU DOT EDU, djgpp AT delorie DOT com
From:	Nate Eldredge <eldredge AT ap DOT net>
Subject:	Re: code which won't compile with -O2 switch on

At 11:42  1/1/1998 -0600, GAMMELJL AT SLU DOT EDU wrote:
>//The following code compiles and runs correctly. However, if one tries
>//to compile it with the -O2 optimization switch, an error message
>//"cannot reload integer constant operand in 'asm' " appears.  Why?
>//(Note: I don't want a work-around.)  
>
>#include <iostream.h>
>
>unsigned int zmax=10;
>
>#define mode4()                                                 \
>__asm__ (                                                           \
>    "movl $0x1,%%ecx;"                                              \
>    "movl %1(,%%ecx,4),%%eax;"                                      \
>    "addl %2(,%%ecx,4),%%eax;"                                      \
>    "movl %%eax,%0(,%%ecx,4);"                                      \
>    "movl $0x0,%%edx;"                                              \
>    "adcl $0x0,%%edx;"                                              \
>    "L2: incl %%ecx;"                                               \
>    "movl %1(,%%ecx,4),%%eax;"                                      \
>    "addl %%edx,%%eax;"                                             \
>    "movl $0x0,%%edx;"                                              \
>    "adcl $0x0,%%edx;"                                              \
>    "addl %2(,%%ecx,4),%%eax;"                                      \
>    "movl %%eax,%0(,%%ecx,4);"                                      \
>    "adcl $0x0,%%edx;"                                             \
>    "cmp _zmax,%%ecx;"                                         \
>    "jne L2"                                                      \
>    : "=m" (z)                                                    \
>    : "g" (x), "g" (y)                                                  \
>    : "eax", "ecx", "edx", "memory", "cc");
I'm not sure whether this is related to your problem, but you have several
operands like "%1(,%%ecx,4)" in your code. But the %1 operand is declared
with the "g" constraint. This means that GCC would be well within its rights
to generate something like "(%ebx)(,%ecx,4)", which is clearly bogus. I
think you will need to use a constraint like "ri" instead.

Another problem that could be related is that you declare `z' as an output
operand. Since `z' is declared as `int []', it is a constant value, and it
may well be that trying to change it confuses the compiler. You don't want
to change `z's value, so try making it an input instead of an output operand.
Hope this helps.

Nate Eldredge
eldredge AT ap DOT net

- Raw text -