sra: Do not create zero sized accesses (PR 93776)

SRA can get a bit confused with zero-sized accesses like the one in
the testcase.  Since there is nothing in the access, nothing is
scalarized, but we can get order of the structures wrong, which the
verifier is not happy about.

Fixed by simply ignoring such accesses.

2020-02-19  Martin Jambor  <mjambor@suse.cz>

	PR tree-optimization/93776
	* tree-sra.c (create_access): Do not create zero size accesses.
	(get_access_for_expr): Do not search for zero sized accesses.

	testsuite/
	* gcc.dg/tree-ssa/pr93776.c: New test.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 6b53f9a..7ebeaed 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,11 @@
 2020-02-19  Martin Jambor  <mjambor@suse.cz>
 
+       PR tree-optimization/93776
+       * tree-sra.c (create_access): Do not create zero size accesses.
+       (get_access_for_expr): Do not search for zero sized accesses.
+
+2020-02-19  Martin Jambor  <mjambor@suse.cz>
+
        PR tree-optimization/93667
        * tree-sra.c (scalarizable_type_p): Return false if record fields
        do not follow wach other.

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 8033fa0..df79951 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,10 @@
 2020-02-19  Martin Jambor  <mjambor@suse.cz>
 
+       PR tree-optimization/93776
+       * gcc.dg/tree-ssa/pr93776.c: New test.
+
+2020-02-19  Martin Jambor  <mjambor@suse.cz>
+
        PR tree-optimization/93667
        * g++.dg/tree-ssa/pr93667.C: New test.
 

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr93776.c b/gcc/testsuite/gcc.dg/tree-ssa/pr93776.c
new file mode 100644 (file)
index 0000000..c407a62
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr93776.c
@@ -0,0 +1,27 @@
+/* { dg-do compile } */
+/* { dg-options "-O1" } */
+
+struct empty {};
+struct s { int i; };
+struct z
+{
+  int j;
+  struct empty e;
+  struct s s;
+  int k;
+};
+
+void bar (struct z);
+void baz (int);
+
+void foo (void)
+{
+  struct z z, z2;
+
+  z.k = 8;
+  z2.s.i = 1;
+  z = z2;
+  bar (z);
+  z.e = (struct empty) {};
+  baz (z.k);
+}

diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
index 4c7d651..49f9001 100644 (file)
--- a/gcc/tree-sra.c
+++ b/gcc/tree-sra.c
@@ -926,6 +926,8 @@ create_access (tree expr, gimple *stmt, bool write)
       size = max_size;
       unscalarizable_region = true;
     }
+  if (size == 0)
+    return NULL;
   if (size < 0)
     {
       disqualify_candidate (base, "Encountered an unconstrained access.");
@@ -3643,7 +3645,8 @@ get_access_for_expr (tree expr)
        return NULL;
     }
 
-  if (!bitmap_bit_p (candidate_bitmap, DECL_UID (base)))
+  if (max_size == 0
+      || !bitmap_bit_p (candidate_bitmap, DECL_UID (base)))
     return NULL;
 
   return get_var_base_offset_size_access (base, offset, max_size);