[Bug lto/55118] Missed forward propagation of addresses

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55118

Richard Biener  changed:

   What|Removed |Added

 Status|ASSIGNED|RESOLVED
 Resolution|--- |FIXED

--- Comment #3 from Richard Biener  ---
We lower both cases now in laddress (after object-size folding and after
inlining...).  So "fixed" but not really for inlining.

[Bug lto/55118] Missed forward propagation of addresses

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55118



--- Comment #2 from Richard Biener rguenth at gcc dot gnu.org 2012-10-30 
11:11:35 UTC ---

We can't really do much here without breaking type-based alias analysis and

data dependence analysis (which depends on seeing only array-refs when they

were present in the original source).



Which means that it is eventually worth considering to lower the address

forms some more (even the rare case we combine them with dereferences in

forwprop is suspicious).



Thus, lower



  bb 3:

  # i_66 = PHI i_16(3), 0(2)

  _12 = MEM[(const struct Domain *)_10 +

32B].D.119657.domain_m[i_66].D.114927;

  _13 = MEM[(struct Domain *)this_1(D) + 8B].D.119657.domain_m[i_66].D.114927;

  _14 = MEM[(const Element_t[2] )_12];

  MEM[(Element_t[2] )_13][0] = _14;

  _15 = MEM[(const Element_t[2] )_12 + 4];

  MEM[(Element_t[2] )_13][1] = _15;

  i_16 = i_66 + 1;

  if (i_16 != 3)

goto bb 3;



to sth like



  tem = i_66 * 4;

  tem = tem + 32;

  _12 = _10 + tem;



nothing for 4.8 though.  And it will badly interact with __builtin_object_size

again.

[Bug lto/55118] Missed forward propagation of addresses

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55118



Richard Biener rguenth at gcc dot gnu.org changed:



   What|Removed |Added



 Status|UNCONFIRMED |ASSIGNED

   Last reconfirmed||2012-10-29

 Blocks|54776   |

 AssignedTo|unassigned at gcc dot   |rguenth at gcc dot gnu.org

   |gnu.org |

 Ever Confirmed|0   |1



--- Comment #1 from Richard Biener rguenth at gcc dot gnu.org 2012-10-29 
15:37:53 UTC ---

I will investigate what we can do.  I ripped out the old propagation stuff

because we miscompiled things.



The first case cannot be simplified without lowering expr_1(D)-left_m

to expr_1(D) which will cause issues with __builtin_object_size handling.



The 2nd case is because we cannot express dereferencing _5 with TBAA

type Element_t[2] when trying to inline-expand it's address.  That is,



MEM[(const Element_t[2] ) MEM[(const struct Domain

*)D.660972].D.123571.domain_m[i_4].D.118841 ];



does not simplify because of the variable-offset address.  The only case

we can simplify it is if D.118841 has type Element_t[2] but this is usually

not the case as far as I remember.



I'll still look into the details.