Apologies if this was the wrong list to ask this on. I will repost (with
a simpler and complete example) to the gcc list. Thanks, Mark
> Hi,
>
> I am trying to migrate my C/C++ cross-compiling (cygwin->powerpc) from
> 2.9.5 to 4.4.2. Specifically I have been successfully using 2.9.5 for
> years and have just built 4.4.2 (no libraries) as I want to compile
for
> newer cores with isel, sse etc. I appear to have a fully working
> compiler (produces a few hundred lines of code that runs correctly in
my
> target hardware) but the code produced is oddly inefficient despite
-O3.
> Under 2.9.5 this:
>
> typedef union
> {
> U32 R;
> struct
> {
> U32 WP:2;
> U32 WRC:2;
> U32 WIE:1;
> U32 DIE:1;
> U32 FP:2;
> U32 FIE:1;
> U32 ARE:1;
> U32 :1;
> U32 WPEXT:4;
> U32 FPEXT:4;
> U32 :13;
> } B;
> } SPR_TCRVAL_t;
>
> ..
>
> {
> SPR_TCRVAL_t tcr;
> tcr.R=0;
> tcr.B.WRC=2;
> tcr.B.WPEXT=10;
> tcr.B.ARE=1;
> <asm macro to assign tcr to SPR 340>
> }
>
> produces a nice simple:
>
> lis 0,0x2054
> mtspr 340,0
>
> Yet under 4.4.2 with all optimisations apparently enabled (constant
> optimisation, function inlining etc all visible in the assembly
output)
> I get:
>
> li 9,2
> li 0,0
> rlwimi 0,9,28,2,3
> li 9,10
> rlwimi 0,9,17,11,14
> li 9,1
> rlwimi 0,9,22,9,9
> mtspr 340,0
>
> !!
>
> Has anyone seen this sort of thing before? Is there anything obviously
> dumb in what I am trying to do? Any pointers gratefully received!
>
> Thanks,
>
> Mark
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