The fix for PR116778:

The fix for PR116778:

Brief:
The bug appears in LRA after rematerialization pass while creating live ranges.
File lra.cc:
*************************************************************
      /* Now we know what pseudos should be spilled.  Try to
	 rematerialize them first.  */
      if (lra_remat ())
	{
	  /* We need full live info -- see the comment above.  */
	  lra_create_live_ranges (lra_reg_spill_p, true);
*************************************************************
Wrong call `lra_create_live_ranges (lra_reg_spill_p, true)'
It have to be `lra_create_live_ranges (true, true)'.

The explanation:
**********************************
int main (void)
{
  if (a.u33 * a.u33 != 0)
------^^^^^^^^^^^^^
    goto abrt;
  if (a.u33 * a.u40 * a.u33 != 0)
**********************************
The bug appears here.

Part of the expression `a.u33 * a.u33'
Before LRA:
*************************************************************
(insn 13 11 15 2 (set (reg:QI 184 [ _1+3 ])
        (mem/c:QI (const:HI (plus:HI (symbol_ref:HI ("a") [flags 0x2]  <var_decl 0x7c866435d000 a>)
                    (const_int 3 [0x3]))) [1 a+3 S1 A8])) "bf.c":11:8 86 {movqi_insn_split}
     (nil))
(insn 15 13 16 2 (set (reg:QI 64 [ a+4 ])
        (mem/c:QI (const:HI (plus:HI (symbol_ref:HI ("a") [flags 0x2]  <var_decl 0x7c866435d000 a>)
                    (const_int 4 [0x4]))) [1 a+4 S1 A8])) "bf.c":11:8 86 {movqi_insn_split}
     (nil))
(insn 16 15 20 2 (set (reg:QI 185 [ _1+4 ])
        (zero_extract:QI (reg:QI 64 [ a+4 ])
            (const_int 1 [0x1])
            (const_int 0 [0]))) "bf.c":11:8 985 {*extzvqi_split}
     (nil))
*************************************************************

After LRA:
*************************************************************
(insn 587 11 13 2 (set (reg:QI 24 r24 [368])
        (mem/c:QI (const:HI (plus:HI (symbol_ref:HI ("a") [flags 0x2]  <var_decl 0x7c866435d000 a>)
                    (const_int 3 [0x3]))) [1 a+3 S1 A8])) "bf.c":11:8 86 {movqi_insn_split}
     (nil))
(insn 13 587 15 2 (set (mem/c:QI (plus:HI (reg/f:HI 28 r28)
                (const_int 1 [0x1])) [4 %sfp+1 S1 A8])
        (reg:QI 24 r24 [368])) "bf.c":11:8 86 {movqi_insn_split}
     (nil))
(insn 15 13 16 2 (set (reg:QI 6 r6 [orig:64 a+4 ] [64])
        (mem/c:QI (const:HI (plus:HI (symbol_ref:HI ("a") [flags 0x2]  <var_decl 0x7c866435d000 a>)
                    (const_int 4 [0x4]))) [1 a+4 S1 A8])) "bf.c":11:8 86 {movqi_insn_split}
     (nil))
(insn 16 15 572 2 (set (reg:QI 24 r24 [orig:185 _1+4 ] [185])
        (zero_extract:QI (reg:QI 6 r6 [orig:64 a+4 ] [64])
            (const_int 1 [0x1])
            (const_int 0 [0]))) "bf.c":11:8 985 {*extzvqi_split}
     (nil))
(insn 572 16 20 2 (set (mem/c:QI (plus:HI (reg/f:HI 28 r28)
                (const_int 1 [0x1])) [4 %sfp+1 S1 A8])
        (reg:QI 24 r24 [orig:185 _1+4 ] [185])) "bf.c":11:8 86 {movqi_insn_split}
     (nil))
*************************************************************
Insn 13 and insn 572 use sfp+1 as a spill slot, but in IRA pass it was a two
different pseudos r184 and r185.
Insns 13 use sfp+1 as a spill slot for r184
Insns 572 use the same slot for r185. It's wrong.

Here we have a rematerialization.

Fragment from bf.c.317r.reload:
**************************************************************************************
******** Rematerialization #1: ********

df_worklist_dataflow_doublequeue: n_basic_blocks 14 n_edges 18 count 14 (    1)
df_worklist_dataflow_doublequeue: n_basic_blocks 14 n_edges 18 count 14 (    1)

Cands:
0 (nop=0, remat_regno=185, reload_regno=359):
(insn 16 15 572 2 (set (reg:QI 359 [orig:185 _1+4 ] [185])
                    (zero_extract:QI (reg:QI 64 [ a+4 ])
                        (const_int 1 [0x1])
                        (const_int 0 [0]))) "bf.c":11:8 985 {*extzvqi_split}
                 (nil))

**************************************************************************************
[...]
**************************************************************************************
Ranges after the compression:
 r185: [0..1]
	   Frame pointer can not be eliminated anymore
	   Spilling non-eliminable hard regs: 28 29
	 Spilling r113(28)
	 Spilling r184(29)
	 Spilling r208(29)
	 Spilling r209(28)
  Slot 0 regnos (width = 0):	 185	 209	 208	 184	 113
**************************************************************************************

The bug is here: `r185: [0..1]' wrong live range after compression.
r185 and r184 can't have the same spill slot !

Rematerialization in bf.c.317r.reload looks like:
*************************************************************
   24: r14:QI=r185:QI
    Inserting rematerialization insn before:
  581: r14:QI=zero_extract(r64:QI,0x1,0)

deleting insn with uid = 24.
         Considering alt=0 of insn 16:   (0) =r  (1) rYil  (2) n
          overall=0,losers=0,rld_nregs=0
   32: r22:QI=r185:QI
    Inserting rematerialization insn before:
  582: r22:QI=zero_extract(r64:QI,0x1,0)

deleting insn with uid = 32.
*************************************************************

It's happened because:

Fragment from lra.c (lra):
*************************************************************************
      if (! live_p)
	{
	  /* We need full live info for spilling pseudos into
	     registers instead of memory.  */
	  lra_create_live_ranges (lra_reg_spill_p, true);
	  live_p = true;
	}
      /* We should check necessity for spilling here as the above live
	 range pass can remove spilled pseudos.  */
      if (! lra_need_for_spills_p ())
	break;
      /* Now we know what pseudos should be spilled.  Try to
	 rematerialize them first.  */
      if (lra_remat ())
	{
	  /* We need full live info -- see the comment above.  */
	  lra_create_live_ranges (lra_reg_spill_p, true);
----------------------------------^^^^^^^^^^^^^^^
	  live_p = true;
*************************************************************************

The bug is here.
Rematerialization sometimes can be like spilling pseudos into registers.
  582: r22:QI=zero_extract(r64:QI,0x1,0)

So, here we need a live ranges for all pseudos.

PS: the patch will not affect any target with usable definition of
    TARGET_SPILL_CLASS hook.

	PR target/116778
gcc/
	* lra-lives.cc (complete_info_p): Clarification of the comment.
	* lra.cc (lra): Create a full live info after rematerialization.