dse2 remove wrong insn

[BELBACHIR Selim]

Everything seems good when I use a union instead of "*((int *)(&af))".

But I think that "*((int *)(&af))" is a valid syntax to get the integer representation of my floating point value (in my test case 0x3F800000 for 1.0f in IEEE-754). It may be target dependant but I think it should work on target having 32 bits float and integer (and IEEE754 compliance).

I have gone on my debugging and I found what was wrong in my backend. I had STACK_POINTER_REGNUM=$C0, ARG_POINTER_REGNUM=$C1, FRAME_POINTER_REGNUM=$C0, no reg elimination macro, and prolog/epilog in adequacy. When I replaced my FRAME_POINTER_REGNUM by its own $C2 reg (i.e. a different value than STACK_POINTER_REGNUM) and added reg elimination macros the problem in dse2 pass disappeared (without adding unnecessary frame pointer in the asm output).
I have done this because looking as dse2.c I saw that some optimization was dealing with frame pointer and I was unsure of the correctness of the macro defining my ABI.

Are there requirement in dse2 pass according to FRAME_POINTER_REGNUM and STACK_POINTER_REGNUM definition ? Does my initial definition of FRAME_POINTER_REGNUM was totally dumb ? I don't know ...

Selim


-----Message d'origine-----
De : gcc-owner@gcc.gnu.org [mailto:gcc-owner@gcc.gnu.org] De la part de Andrew Haley
Envoyé : vendredi 9 décembre 2011 18:37
À : gcc@gcc.gnu.org
Objet : Re: dse2 remove wrong insn

On 12/09/2011 03:05 PM, BELBACHIR Selim wrote:
> int main() {
>   int x; 
>   float af;
>   ff(&x);
>   af = f2(1.0f);
>   return *((int *)(&af));
> }

Please try this again, but with a union rather than a pointer
cast.  I don't think this code is legal C.

Andrew.