Re: [PR 80622] Treat const pools as initialized in SRA

[Richard Biener <rguenther at suse dot de>]

On May 4, 2017 5:09:15 PM GMT+02:00, Martin Jambor <mjambor@suse.cz> wrote:
>Hi,
>
>PR 80622 happens because when setting grp_write lazily, the code does
>not acknowledge that constant pool bases come initialized and so
>contain data even when not written to.  The patch below fixes that but
>it also puts a test for pre-initialization into a special function,
>uses it at all appropriate places and moves the test in question to an
>earlier time, which is a tiny bit cheaper because it may avoid
>unnecessary re-invocation of propagate_subaccesses_across_link.
>
>Bootstrapped and tested on x86_64-linux, OK for trunk?

OK.

Richard.

>Thanks,
>
>Martin
>
>
>
>2017-05-04  Martin Jambor  <mjambor@suse.cz>
>
>	PR tree-optimization/80622
>	* tree-sra.c (comes_initialized_p): New function.
>	(build_accesses_from_assign): Only set write lazily when
>	comes_initialized_p is false.
>	(analyze_access_subtree): Use comes_initialized_p.
>	(propagate_subaccesses_across_link): Assert !comes_initialized_p
>	instead of testing for PARM_DECL.
>
>testsuite/
>	* gcc.dg/tree-ssa/pr80622.c: New test.
>---
> gcc/testsuite/gcc.dg/tree-ssa/pr80622.c | 19 +++++++++++++++++++
>gcc/tree-sra.c                          | 29
>+++++++++++++++++++++--------
> 2 files changed, 40 insertions(+), 8 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr80622.c
>
>diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr80622.c
>b/gcc/testsuite/gcc.dg/tree-ssa/pr80622.c
>new file mode 100644
>index 00000000000..96dcb8fcdc0
>--- /dev/null
>+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr80622.c
>@@ -0,0 +1,19 @@
>+/* { dg-do run } */
>+/* { dg-options "-O" } */
>+
>+struct S { int d; char e; int f; char g; } a;
>+char c;
>+
>+int
>+main ()
>+{
>+  struct S b[][1] = {3, 0, 3, 4, 3, 0, 3, 4, 3, 0, 3, 4, 3, 0, 3, 4,
>3,
>+                      0, 3, 4, 3, 0, 3, 4, 3, 0, 3, 4, 3, 0, 3, 4, 3,
>0,
>+                      3, 4, 3, 4, 7, 7, 3, 5, 0, 3, 4, 7, 7, 3, 5, 0,
>3,
>+                      4, 3, 4, 7, 7, 3, 5, 0, 3, 4, 7, 7, 3, 5, 0, 3,
>4};
>+  a = b[4][0];
>+  c = b[4][0].e;
>+  if (a.g != 4)
>+    __builtin_abort ();
>+  return 0;
>+}
>diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
>index 1606573aead..8ac9c0783ff 100644
>--- a/gcc/tree-sra.c
>+++ b/gcc/tree-sra.c
>@@ -1305,6 +1305,15 @@ disqualify_if_bad_bb_terminating_stmt (gimple
>*stmt, tree lhs, tree rhs)
>   return false;
> }
> 
>+/* Return true if the nature of BASE is such that it contains data
>even if
>+   there is no write to it in the function.  */
>+
>+static bool
>+comes_initialized_p (tree base)
>+{
>+  return TREE_CODE (base) == PARM_DECL || constant_decl_p (base);
>+}
>+
>/* Scan expressions occurring in STMT, create access structures for all
>accesses
>to candidates for scalarization and remove those candidates which occur
>in
>statements or expressions that prevent them from being split apart. 
>Return
>@@ -1364,8 +1373,10 @@ build_accesses_from_assign (gimple *stmt)
>       link->racc = racc;
>       add_link_to_rhs (racc, link);
>/* Let's delay marking the areas as written until propagation of
>accesses
>-	 across link.  */
>-      lacc->write = false;
>+	 across link, unless the nature of rhs tells us that its data comes
>+	 from elsewhere.  */
>+      if (!comes_initialized_p (racc->base))
>+	lacc->write = false;
>     }
> 
>   return lacc || racc;
>@@ -2472,8 +2483,7 @@ 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
>-	   || constant_decl_p (root->base))
>+  else if (root->grp_write || comes_initialized_p (root->base))
>     root->grp_unscalarized_data = 1; /* not covered and written to */
>   return sth_created;
> }
>@@ -2581,11 +2591,14 @@ propagate_subaccesses_across_link (struct
>access *lacc, struct access *racc)
> 
>/* IF the LHS is still not marked as being written to, we only need to
>do so
>      if the RHS at this level actually was.  */
>-  if (!lacc->grp_write &&
>-      (racc->grp_write || TREE_CODE (racc->base) == PARM_DECL))
>+  if (!lacc->grp_write)
>     {
>-      lacc->grp_write = true;
>-      ret = true;
>+      gcc_checking_assert (!comes_initialized_p (racc->base));
>+      if (racc->grp_write)
>+	{
>+	  lacc->grp_write = true;
>+	  ret = true;
>+	}
>     }
> 
>   if (is_gimple_reg_type (lacc->type)