Experimental Physics and
Industrial Control System

Hi- does anyone know why our power-pc compiler likes to turn short & int pointer
dereferences into byte moves, and how to get it to not to?  Some hardware may not
like this, as suggested by bus analyzer.

For instance, this code:

	static void copy4 (int *p, int *q, int n) {
	  while (n-- > 0) *q++ = *p++;
	}

generates this:

        .align 2
        .type    copy4,@function
copy4:
        mr 0,5
        cmpwi 1,0,0
        mr 7,3
        mr 6,4
        addi 5,5,-1
        bclr 4,5
        addi 4,4,3
        addi 3,3,3
.L16:
        lbz 9,-2(3)	<---
        lbz 11,-1(3)	<---
        lbz 10,0(3)	<---
        lbz 0,0(7)	<---
        addi 3,3,4
        addi 7,7,4
        mr 8,5
        addi 5,5,-1
        cmpwi 1,8,0
        slwi 0,0,24
        slwi 9,9,16
        or 9,9,0
        slwi 11,11,8
        or 11,11,9
        or 10,10,11
        srwi 0,10,24
        stb 0,0(6)	<---
        srwi 0,10,16
        stb 0,-2(4)	<---
        srwi 0,10,8
        stb 0,-1(4)	<---
        stb 10,0(4)	<---
        addi 4,4,4
        addi 6,6,4
        bc 12,5,.L16
        blr
.Lfe4:
        .size    copy4,.Lfe4-copy4

Switches which may be relevant:
    .../vxworks/devel/tor-2.0.2/cd/host/sun4-solaris2/bin/ccppc
        -B.../vxworks/devel/tor-2.0.2/cd/host/sun4-solaris2/lib/gcc-lib/
        -nostdinc
        -ansi
        -pedantic
        -DCPU=PPC604
        -D_GNU_TOOL
        -DTRUE=1
        -DNIVXI
        -O2
        -fstrength
        -reduce
        -Wall
        -DVXI
        -mcpu=604
        --no-builtin
        -mstrict-align
        -mlongcall
        -D_REENTRANT
        -DvxWorks
        -DV5_vxWorks
        -fno-builtin

"ccppc --version" yields:
	cygnus-2.7.2-960126 egcs-971225 tornado 2.0

I thought maybe #pragma pack() in the source had something to do with it, but that
made no difference.

I took a look in the tech-talk archives, but couldn't find anything related.  Could
be just poor search skills....

Thanks for any help!

Mike

--
Dr. Dirk Zimoch
Swiss Light Source
Paul Scherrer Institut
Computing and Controls
phone +41 56 310 5182
fax   +41 56 310 4413

References:

PPC compiler splits up ints & shorts? Laznovsky, Michael

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