Hi,

after we have accidentally dropped the mailing list from our discussion
(my apologies for not spotting that in time), Richi has approved the
following patch which I have bootstrapped and tested on x86_64-linux
(all languages) and on i686-linux, aarch64-linux and ppc64-linux (C, C++
and Fortran) and so I am about to commit it to trunk.

It XFAILS three guality tests which pass at -O0, which means there are
three additional XPASSes - there already are 5 pre-existing XPASSes in
that testcase and 29 outright failures.  I will come back to this next
in April and see whether I can make the tests pass by decoupling the
roles now played by cannot_scalarize_away_bitmap (or at least massage
the testcase to go make the XPASSes go away).  But I won't have time to
do it next two weeks and this patch is important enough to have it in
trunk now.  I intend to backport it to gcc 8 in April too.

Thanks,

Martin


2019-03-08  Martin Jambor  <mjam...@suse.cz>

        PR tree-optimization/85762
        PR tree-optimization/87008
        PR tree-optimization/85459
        * tree-sra.c (contains_vce_or_bfcref_p): New parameter, set the bool
        it points to if there is a type changing MEM_REF.  Adjust all callers.
        (build_accesses_from_assign): Disable total scalarization if
        contains_vce_or_bfcref_p returns true through the new parameter, for
        both rhs and lhs.

        testsuite/
        * g++.dg/tree-ssa/pr87008.C: New test.
        * gcc.dg/guality/pr54970.c: Xfail tests querying a[0] everywhere.
---
 gcc/testsuite/g++.dg/tree-ssa/pr87008.C | 17 ++++++++++++
 gcc/testsuite/gcc.dg/guality/pr54970.c  |  6 ++---
 gcc/tree-sra.c                          | 36 ++++++++++++++++++-------
 3 files changed, 47 insertions(+), 12 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/tree-ssa/pr87008.C

diff --git a/gcc/testsuite/g++.dg/tree-ssa/pr87008.C 
b/gcc/testsuite/g++.dg/tree-ssa/pr87008.C
new file mode 100644
index 00000000000..eef521f9ad5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/pr87008.C
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+extern void dontcallthis();
+
+struct A { long a, b; };
+struct B : A {};
+template<class T>void cp(T&a,T const&b){a=b;}
+long f(B x){
+  B y; cp<A>(y,x);
+  B z; cp<A>(z,x);
+  if (y.a - z.a)
+    dontcallthis ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-not "dontcallthis" "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/guality/pr54970.c 
b/gcc/testsuite/gcc.dg/guality/pr54970.c
index 5d32af07c32..2e0bc5784a9 100644
--- a/gcc/testsuite/gcc.dg/guality/pr54970.c
+++ b/gcc/testsuite/gcc.dg/guality/pr54970.c
@@ -8,17 +8,17 @@
 int
 main ()
 {
-  int a[] = { 1, 2, 3 };       /* { dg-final { gdb-test .+4 "a\[0\]" "1" } } */
+  int a[] = { 1, 2, 3 };       /* { dg-final { gdb-test .+4 "a\[0\]" "1" { 
xfail { *-*-* } } } } */
   int *p = a + 2;              /* { dg-final { gdb-test .+3 "a\[1\]" "2" } } */
   int *q = a + 1;              /* { dg-final { gdb-test .+2 "a\[2\]" "3" } } */
                                /* { dg-final { gdb-test .+1 "*p" "3" } } */
   asm volatile (NOP);          /* { dg-final { gdb-test . "*q" "2" } } */
-  *p += 10;                    /* { dg-final { gdb-test .+4 "a\[0\]" "1" } } */
+  *p += 10;                    /* { dg-final { gdb-test .+4 "a\[0\]" "1" { 
xfail { *-*-* } } } } */
                                /* { dg-final { gdb-test .+3 "a\[1\]" "2" } } */
                                /* { dg-final { gdb-test .+2 "a\[2\]" "13" } } 
*/
                                /* { dg-final { gdb-test .+1 "*p" "13" } } */
   asm volatile (NOP);          /* { dg-final { gdb-test . "*q" "2" } } */
-  *q += 10;                    /* { dg-final { gdb-test .+4 "a\[0\]" "1" } } */
+  *q += 10;                    /* { dg-final { gdb-test .+4 "a\[0\]" "1" { 
xfail { *-*-* } } } } */
                                /* { dg-final { gdb-test .+3 "a\[1\]" "12" } } 
*/
                                /* { dg-final { gdb-test .+2 "a\[2\]" "13" } } 
*/
                                /* { dg-final { gdb-test .+1 "*p" "13" } } */
diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
index eeef31ba496..ca3858d5fc7 100644
--- a/gcc/tree-sra.c
+++ b/gcc/tree-sra.c
@@ -1150,29 +1150,36 @@ contains_view_convert_expr_p (const_tree ref)
   return false;
 }
 
-/* Return true if REF contains a VIEW_CONVERT_EXPR or a MEM_REF that performs
-   type conversion or a COMPONENT_REF with a bit-field field declaration.  */
+/* Return true if REF contains a VIEW_CONVERT_EXPR or a COMPONENT_REF with a
+   bit-field field declaration.  If TYPE_CHANGING_P is non-NULL, set the bool
+   it points to will be set if REF contains any of the above or a MEM_REF
+   expression that effectively performs type conversion.  */
 
 static bool
-contains_vce_or_bfcref_p (const_tree ref)
+contains_vce_or_bfcref_p (const_tree ref, bool *type_changing_p = NULL)
 {
   while (handled_component_p (ref))
     {
       if (TREE_CODE (ref) == VIEW_CONVERT_EXPR
          || (TREE_CODE (ref) == COMPONENT_REF
              && DECL_BIT_FIELD (TREE_OPERAND (ref, 1))))
-       return true;
+       {
+         if (type_changing_p)
+           *type_changing_p = true;
+         return true;
+       }
       ref = TREE_OPERAND (ref, 0);
     }
 
-  if (TREE_CODE (ref) != MEM_REF
+  if (!type_changing_p
+      || TREE_CODE (ref) != MEM_REF
       || TREE_CODE (TREE_OPERAND (ref, 0)) != ADDR_EXPR)
     return false;
 
   tree mem = TREE_OPERAND (TREE_OPERAND (ref, 0), 0);
   if (TYPE_MAIN_VARIANT (TREE_TYPE (ref))
       != TYPE_MAIN_VARIANT (TREE_TYPE (mem)))
-    return true;
+    *type_changing_p = true;
 
   return false;
 }
@@ -1368,15 +1375,26 @@ build_accesses_from_assign (gimple *stmt)
       lacc->grp_assignment_write = 1;
       if (storage_order_barrier_p (rhs))
        lacc->grp_unscalarizable_region = 1;
+
+      if (should_scalarize_away_bitmap && !is_gimple_reg_type (lacc->type))
+       {
+         bool type_changing_p = false;
+         contains_vce_or_bfcref_p (lhs, &type_changing_p);
+         if (type_changing_p)
+           bitmap_set_bit (cannot_scalarize_away_bitmap,
+                           DECL_UID (lacc->base));
+       }
     }
 
   if (racc)
     {
       racc->grp_assignment_read = 1;
-      if (should_scalarize_away_bitmap && !gimple_has_volatile_ops (stmt)
-         && !is_gimple_reg_type (racc->type))
+      if (should_scalarize_away_bitmap && !is_gimple_reg_type (racc->type))
        {
-         if (contains_vce_or_bfcref_p (rhs))
+         bool type_changing_p = false;
+         contains_vce_or_bfcref_p (rhs, &type_changing_p);
+
+         if (type_changing_p || gimple_has_volatile_ops (stmt))
            bitmap_set_bit (cannot_scalarize_away_bitmap,
                            DECL_UID (racc->base));
          else
-- 
2.21.0

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