[Bug tree-optimization/70013] [6 Regression] packed structure tree-sra loses initialization

["alalaw01 at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70013

--- Comment #10 from alalaw01 at gcc dot gnu.org ---
Hmmm, so this fixes the ICE, generating:

  SR.5_12 = MEM[(struct S0[2] *)&*.LC0].f0;
  MEM[(struct S0[2] *)&*.LC0].f0 = SR.5_12;
  d = *.LC0;
  d$3$f0_14 = MEM[(struct S0[2] *)&*.LC0 + 3B].f0;
  d$0$f0_7 = SR.5_12;
  e$f0_9 = d$3$f0_14;
  _3 = (int) d$0$f0_7;
  c = _3;
  _5 = (int) e$f0_9;
  __builtin_printf ("%x\n", _5);
  d ={v} {CLOBBER};
  return 0;

which in -fdump-tree-optimized (at -O1) looks like:

  SR.5_12 = MEM[(struct S0[2] *)&*.LC0].f0;
  d$3$f0_14 = MEM[(struct S0[2] *)&*.LC0 + 3B].f0;
  _3 = (int) SR.5_12;
  c = _3;
  _5 = (int) d$3$f0_14;
  __builtin_printf ("%x\n", _5);
  return 0;

which is much saner. But I don't really understand why the PARM_DECL case that
I'm adding to here is that way (since r147980 "New implementation of SRA" in
2009, https://gcc.gnu.org/ml/gcc-patches/2009-04/msg02218.html)...

Bootstrapped+regtest on AArch64 (c,c++) and ARM (c,c++,ada), no regressions.
(Constants don't get pushed into the pool on x86.)
----
diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
index
72157edd02e3235e57b786bbf460c94b0c52b2c5..24eac6ae7c4dcd41358b1a020047076afe1a8106
100644
--- a/gcc/tree-sra.c
+++ b/gcc/tree-sra.c
@@ -2427,7 +2427,8 @@ analyze_access_subtree (struct access *root, struct
access *parent,

   if (!hole || root->grp_total_scalarization)
     root->grp_covered = 1;
-  else if (root->grp_write || TREE_CODE (root->base) == PARM_DECL)
+  else if (root->grp_write || TREE_CODE (root->base) == PARM_DECL
+          || constant_decl_p (root->base))
     root->grp_unscalarized_data = 1; /* not covered and written to */
   return sth_created;
 }