On Tue, 14 May 2019, Richard Sandiford wrote:

> Richard Biener <rguent...@suse.de> writes:
> > On Tue, 14 May 2019, Richard Sandiford wrote:
> >
> >> Richard Biener <rguent...@suse.de> writes:
> >> > The following makes SSA rewrite (update-address-taken) recognize
> >> > sets of aligned sub-vectors in aligned position
> >> > (v2qi into v16qi, but esp. v8qi into v16qi).  It uses the
> >> > BIT_INSERT_EXPR support for this, enabling that for vector
> >> > typed values.  This makes us turn for example
> >> >
> >> > typedef unsigned char v16qi __attribute__((vector_size(16)));
> >> > v16qi load (const void *p)
> >> > {
> >> >   v16qi r;
> >> >   __builtin_memcpy (&r, p, 8);
> >> >   return r;
> >> > }
> >> >
> >> > into the following
> >> >
> >> > load (const void * p)
> >> > {
> >> >   v16qi r;
> >> >   long unsigned int _3;
> >> >   v16qi _5;
> >> >   vector(8) unsigned char _7;
> >> >
> >> >   <bb 2> :
> >> >   _3 = MEM[(char * {ref-all})p_2(D)];
> >> >   _7 = VIEW_CONVERT_EXPR<vector(8) unsigned char>(_3);
> >> >   r_9 = BIT_INSERT_EXPR <r_8(D), _7, 0 (64 bits)>;
> >> >   _5 = r_9;
> >> >   return _5;
> >> >
> >> > this isn't yet nicely expanded since the BIT_INSERT_EXPR
> >> > expansion simply goes through store_bit_field and there's
> >> > no vector-mode vec_set.
> >> >
> >> > Similar as to the single-element insert SSA rewrite already
> >> > handles the transform is conditional on the involved
> >> > vector types having non-BLKmode.  This is somewhat bad
> >> > since the transform is supposed to enable SSA optimizations
> >> > by rewriting memory vectors into SSA form.  Since splitting
> >> > of larger generic vectors happens very much later only
> >> > this pessimizes their use.  But the BIT_INSERT_EXPR
> >> > expansion doesn't cope with BLKmode entities (source or
> >> > destination).
> >> >
> >> > Extending BIT_INSERT_EXPR this way seems natural given
> >> > the support of CONSTRUCTORs with smaller vectors.
> >> > BIT_FIELD_REF isn't particularly restricted so can be
> >> > used to extract sub-vectors as well.
> >> >
> >> > Code generation is as bad as before (RTL expansion eventually
> >> > spills) but SSA optimizations are enabled on less trivial
> >> > testcases.
> >> >
> >> > Boostrap / regtest running on x86_64-unknown-linux-gnu.
> >> >
> >> > Comments?
> >> >
> >> > Richard.
> >> >
> >> > 2019-05-14  Richard Biener  <rguent...@suse.de>
> >> >
> >> >  PR tree-optimization/90424
> >> >  * tree-ssa.c (non_rewritable_lvalue_p): Handle inserts from
> >> >  aligned subvectors.
> >> >  (execute_update_addresses_taken): Likewise.
> >> >  * tree-cfg.c (verify_gimple_assign_ternary): Likewise.
> >> >
> >> >  * g++.target/i386/pr90424-1.C: New testcase.
> >> >  * g++.target/i386/pr90424-2.C: Likewise.
> >> >
> >> > Index: gcc/tree-ssa.c
> >> > ===================================================================
> >> > --- gcc/tree-ssa.c       (revision 271155)
> >> > +++ gcc/tree-ssa.c       (working copy)
> >> > @@ -1521,14 +1521,28 @@ non_rewritable_lvalue_p (tree lhs)
> >> >        if (DECL_P (decl)
> >> >            && VECTOR_TYPE_P (TREE_TYPE (decl))
> >> >            && TYPE_MODE (TREE_TYPE (decl)) != BLKmode
> >> > -          && operand_equal_p (TYPE_SIZE_UNIT (TREE_TYPE (lhs)),
> >> > -                              TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE 
> >> > (decl))), 0)
> >> > +          && multiple_of_p (sizetype,
> >> > +                            TYPE_SIZE_UNIT (TREE_TYPE (decl)),
> >> > +                            TYPE_SIZE_UNIT (TREE_TYPE (lhs)))
> >> >            && known_ge (mem_ref_offset (lhs), 0)
> >> >            && known_gt (wi::to_poly_offset (TYPE_SIZE_UNIT (TREE_TYPE 
> >> > (decl))),
> >> >                         mem_ref_offset (lhs))
> >> >            && multiple_of_p (sizetype, TREE_OPERAND (lhs, 1),
> >> >                              TYPE_SIZE_UNIT (TREE_TYPE (lhs))))
> >> > -        return false;
> >> > +        {
> >> > +          if (operand_equal_p (TYPE_SIZE_UNIT (TREE_TYPE (lhs)),
> >> > +                               TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE 
> >> > (decl))),
> >> > +                               0))
> >> > +            return false;
> >> > +          /* For sub-vector inserts the insert vector mode has to be
> >> > +             supported.  */
> >> > +          tree vtype = build_vector_type
> >> > +              (TREE_TYPE (TREE_TYPE (decl)),
> >> > +               tree_to_uhwi (TYPE_SIZE (TREE_TYPE (lhs)))
> >> > +               / tree_to_uhwi (TYPE_SIZE (TREE_TYPE (TREE_TYPE 
> >> > (decl)))));
> >> 
> >> AFAICT nothing guarantees tree_fits_uhwi_p for the lhs, so this isn't
> >> poly-int clean.  Is there a guarantee that lhs is a multiple of the
> >> element size even for integers?  Or are we just relying on a vector
> >> of 0 elements being rejected?
> >
> > That it is a multiple of the element size is tested indirectly by
> >
> >> > +     && multiple_of_p (sizetype, 
> >> > +                       TYPE_SIZE_UNIT (TREE_TYPE (decl)),
> >> > +                       TYPE_SIZE_UNIT (TREE_TYPE (lhs)))
> >
> > given 'decl' has vector type.  That also guarantees non-zero size?
> 
> I was thinking of the case where the element size is still bigger
> than lhs, so the division would end up being 0.  Maybe one of those
> conditions indirectly prevents that though.
> 
> > But yes, I guess TYPE_SIZE_UNIT might be a poly-int.
> >
> >> Maybe something like:
> >> 
> >>      tree elt_type = TREE_TYPE (TREE_TYPE (decl));
> >>      unsigned int elt_bits = tree_to_uhwi (TYPE_SIZE (elt_type));
> >>      poly_uint64 lhs_bits, nelts;
> >>      if (poly_int_tree_p (TYPE_SIZE (TREE_TYPE (lhs)), &lhs_bits)
> >>          && multiple_p (lhs_bits, elt_bits, &nelts))
> >>             {
> >>          tree vtype = build_vector_type (elt_type, nelts);
> >
> > This should work.
> >
> > Of course it even more so makes duplicating all the bits in
> > two places ugly :/
> >
> > I guess I might take it as opportunity to refactor the pass
> 
> Sounds good :-)
> 
> > (as excuse to not work on that SLP thing...).
> 
> except for that bit.

The following seems to work for me then ;)

Bootstrap / regtest running on x86_64-unknown-linux-gnu.

To who is listening: the refactoring would queue up stmts we need
to rewrite as discovered from non_rewritable_lvalue_p or
non_rewritable_mem_ref_base together with a transform kind.
During transform we then simply walk those, not re-analyzing
everything.  Probably easyhack but given the ugliness of the code
it might be easy to introduce mistakes as well ;)

Richard.

2019-05-14  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/90424
        * tree-ssa.c (non_rewritable_lvalue_p): Handle inserts from
        aligned subvectors.
        (execute_update_addresses_taken): Likewise.
        * tree-cfg.c (verify_gimple_assign_ternary): Likewise.

        * g++.target/i386/pr90424-1.C: New testcase.
        * g++.target/i386/pr90424-2.C: Likewise.

Index: gcc/tree-ssa.c
===================================================================
--- gcc/tree-ssa.c      (revision 271203)
+++ gcc/tree-ssa.c      (working copy)
@@ -1521,14 +1521,29 @@ non_rewritable_lvalue_p (tree lhs)
       if (DECL_P (decl)
          && VECTOR_TYPE_P (TREE_TYPE (decl))
          && TYPE_MODE (TREE_TYPE (decl)) != BLKmode
-         && operand_equal_p (TYPE_SIZE_UNIT (TREE_TYPE (lhs)),
-                             TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (decl))), 0)
          && known_ge (mem_ref_offset (lhs), 0)
          && known_gt (wi::to_poly_offset (TYPE_SIZE_UNIT (TREE_TYPE (decl))),
                       mem_ref_offset (lhs))
          && multiple_of_p (sizetype, TREE_OPERAND (lhs, 1),
                            TYPE_SIZE_UNIT (TREE_TYPE (lhs))))
-       return false;
+       {
+         poly_uint64 lhs_bits, nelts;
+         if (poly_int_tree_p (TYPE_SIZE (TREE_TYPE (lhs)), &lhs_bits)
+             && multiple_p (lhs_bits,
+                            tree_to_uhwi
+                              (TYPE_SIZE (TREE_TYPE (TREE_TYPE (decl)))),
+                            &nelts))
+           {
+             if (known_eq (nelts, 1))
+               return false;
+             /* For sub-vector inserts the insert vector mode has to be
+                supported.  */
+             tree vtype = build_vector_type (TREE_TYPE (TREE_TYPE (decl)),
+                                             nelts);
+             if (TYPE_MODE (vtype) != BLKmode)
+               return false;
+           }
+       }
     }
 
   /* A vector-insert using a BIT_FIELD_REF is rewritable using
@@ -1866,20 +1881,30 @@ execute_update_addresses_taken (void)
                    && bitmap_bit_p (suitable_for_renaming, DECL_UID (sym))
                    && VECTOR_TYPE_P (TREE_TYPE (sym))
                    && TYPE_MODE (TREE_TYPE (sym)) != BLKmode
-                   && operand_equal_p (TYPE_SIZE_UNIT (TREE_TYPE (lhs)),
-                                       TYPE_SIZE_UNIT
-                                         (TREE_TYPE (TREE_TYPE (sym))), 0)
-                   && tree_fits_uhwi_p (TREE_OPERAND (lhs, 1))
-                   && tree_int_cst_lt (TREE_OPERAND (lhs, 1),
-                                       TYPE_SIZE_UNIT (TREE_TYPE (sym)))
-                   && (tree_to_uhwi (TREE_OPERAND (lhs, 1))
-                       % tree_to_uhwi (TYPE_SIZE_UNIT (TREE_TYPE (lhs)))) == 0)
+                   && known_ge (mem_ref_offset (lhs), 0)
+                   && known_gt (wi::to_poly_offset
+                                  (TYPE_SIZE_UNIT (TREE_TYPE (sym))),
+                                mem_ref_offset (lhs))
+                   && multiple_of_p (sizetype,
+                                     TREE_OPERAND (lhs, 1),
+                                     TYPE_SIZE_UNIT (TREE_TYPE (lhs))))
                  {
                    tree val = gimple_assign_rhs1 (stmt);
                    if (! types_compatible_p (TREE_TYPE (val),
                                              TREE_TYPE (TREE_TYPE (sym))))
                      {
-                       tree tem = make_ssa_name (TREE_TYPE (TREE_TYPE (sym)));
+                       poly_uint64 lhs_bits, nelts;
+                       tree temtype = TREE_TYPE (TREE_TYPE (sym));
+                       if (poly_int_tree_p (TYPE_SIZE (TREE_TYPE (lhs)),
+                                            &lhs_bits)
+                           && multiple_p (lhs_bits,
+                                          tree_to_uhwi
+                                            (TYPE_SIZE (TREE_TYPE
+                                                          (TREE_TYPE (sym)))),
+                                          &nelts)
+                           && maybe_ne (nelts, 1))
+                         temtype = build_vector_type (temtype, nelts);
+                       tree tem = make_ssa_name (temtype);
                        gimple *pun
                          = gimple_build_assign (tem,
                                                 build1 (VIEW_CONVERT_EXPR,
Index: gcc/tree-cfg.c
===================================================================
--- gcc/tree-cfg.c      (revision 271203)
+++ gcc/tree-cfg.c      (working copy)
@@ -4263,8 +4263,17 @@ verify_gimple_assign_ternary (gassign *s
        }
       if (! ((INTEGRAL_TYPE_P (rhs1_type)
              && INTEGRAL_TYPE_P (rhs2_type))
+            /* Vector element insert.  */
             || (VECTOR_TYPE_P (rhs1_type)
-                && types_compatible_p (TREE_TYPE (rhs1_type), rhs2_type))))
+                && types_compatible_p (TREE_TYPE (rhs1_type), rhs2_type))
+            /* Aligned sub-vector insert.  */
+            || (VECTOR_TYPE_P (rhs1_type)
+                && VECTOR_TYPE_P (rhs2_type)
+                && types_compatible_p (TREE_TYPE (rhs1_type),
+                                       TREE_TYPE (rhs2_type))
+                && multiple_p (TYPE_VECTOR_SUBPARTS (rhs1_type),
+                               TYPE_VECTOR_SUBPARTS (rhs2_type))
+                && multiple_of_p (bitsizetype, rhs3, TYPE_SIZE (rhs2_type)))))
        {
          error ("not allowed type combination in BIT_INSERT_EXPR");
          debug_generic_expr (rhs1_type);
Index: gcc/testsuite/g++.target/i386/pr90424-1.C
===================================================================
--- gcc/testsuite/g++.target/i386/pr90424-1.C   (nonexistent)
+++ gcc/testsuite/g++.target/i386/pr90424-1.C   (working copy)
@@ -0,0 +1,32 @@
+/* { dg-do compile { target c++11 } } */
+/* { dg-options "-O2 -msse2 -fdump-tree-optimized" } */
+
+template <class T>
+using V [[gnu::vector_size(16)]] = T;
+
+template <class T, unsigned M = sizeof(V<T>)>
+V<T> load(const void *p) {
+  using W = V<T>;
+  W r;
+  __builtin_memcpy(&r, p, M);
+  return r;
+}
+
+// movq or movsd
+template V<char> load<char, 8>(const void *);     // bad
+template V<short> load<short, 8>(const void *);   // bad
+template V<int> load<int, 8>(const void *);       // bad
+template V<long> load<long, 8>(const void *);     // good
+// the following is disabled because V2SF isn't a supported mode
+// template V<float> load<float, 8>(const void *);   // bad
+template V<double> load<double, 8>(const void *); // good (movsd?)
+
+// movd or movss
+template V<char> load<char, 4>(const void *);   // bad
+template V<short> load<short, 4>(const void *); // bad
+template V<int> load<int, 4>(const void *);     // good
+template V<float> load<float, 4>(const void *); // good
+
+/* We should end up with one load and one insert for each function.  */
+/* { dg-final { scan-tree-dump-times "BIT_INSERT_EXPR" 9 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "MEM" 9 "optimized" } } */
Index: gcc/testsuite/g++.target/i386/pr90424-2.C
===================================================================
--- gcc/testsuite/g++.target/i386/pr90424-2.C   (nonexistent)
+++ gcc/testsuite/g++.target/i386/pr90424-2.C   (working copy)
@@ -0,0 +1,31 @@
+/* { dg-do compile { target c++11 } } */
+/* { dg-options "-O2 -msse2 -fdump-tree-optimized" } */
+
+template <class T>
+using V [[gnu::vector_size(16)]] = T;
+
+template <class T, unsigned M = sizeof(V<T>)>
+V<T> load(const void *p) {
+  V<T> r = {};
+  __builtin_memcpy(&r, p, M);
+  return r;
+}
+
+// movq or movsd
+template V<char> load<char, 8>(const void *);     // bad
+template V<short> load<short, 8>(const void *);   // bad
+template V<int> load<int, 8>(const void *);       // bad
+template V<long> load<long, 8>(const void *);     // good
+// the following is disabled because V2SF isn't a supported mode
+// template V<float> load<float, 8>(const void *);   // bad
+template V<double> load<double, 8>(const void *); // good (movsd?)
+
+// movd or movss
+template V<char> load<char, 4>(const void *);   // bad
+template V<short> load<short, 4>(const void *); // bad
+template V<int> load<int, 4>(const void *);     // good
+template V<float> load<float, 4>(const void *); // good
+
+/* We should end up with one load and one insert for each function.  */
+/* { dg-final { scan-tree-dump-times "BIT_INSERT_EXPR" 9 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "MEM" 9 "optimized" } } */

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