On Thu, Nov 21, 2013 at 07:43:35AM +1000, Richard Henderson wrote:
> On 11/20/2013 07:44 PM, Jakub Jelinek wrote:
> > On Wed, Nov 20, 2013 at 10:31:38AM +0100, Richard Biener wrote:
> >> Aww ;) Nice improvement. Generally when I see this I always wonder
> >> whether we want to do this kind of stuff pre RTL expansion.
> >> 1st to not rely on being able to TER, 2nd to finally eventually
> >> get rid of TER.
> >>
> >> These patches are unfortunately a step backward for #2.
> >>
> >> As of the patch, do we have a way to query whether the target
> >> can efficiently broadcast? If so this IMHO belongs in generic
> >
> > We don't. Perhaps if we'd add optab for vec_dup<mode> and mentioned
> > clearly in the documentation that it should be used only if it is reasonably
> > efficient. But still, even with optab, it would probably better to do it
> > in the veclower* passes than in the vectorizer itself.
>
> I think we can assume that broadcast is relatively efficient, whether or not
> vec_dup is present. I'd lean to making the transformation generic to start
> with, so that you don't need extra handling in the i386 backend.
Ok, here is a generic veclower implementation without looking at any optabs,
so far only handles PLUS_EXPR, what operation other than MULT_EXPR would
make sense here? Though, handling MULT_EXPR also would complicate the code
slightly (it would need to handle say:
_2 = _1(D) + 1;
_3 = _2 + 2;
_4 = _3 * 2;
_5 = _4 * 3;
_6 = { _3, _4, _5, _4 };
where we could start thinking first the operation is PLUS_EXPR, but it
actually is MULT_EXPR with _3 as base). Also, for MULT_EXPR, supposedly
we could handle some values to be constant 0, like in:
_2 = _1(D) * 5;
_3 = _2 * 2;
_4 = _1(D) * 10;
_5 = { _3, 0, _4, _2, _1(D), 0, _4, _2 };
Bootstrap/regtest pending, ok at least for this for the start and can be
improved later on?
2013-11-21 Jakub Jelinek <[email protected]>
* tree-vect-generic.c (optimize_vector_constructor): New function.
(expand_vector_operations_1): Call it.
* gcc.dg/vect/vect-124.c: New test.
--- gcc/tree-vect-generic.c.jj 2013-11-19 21:56:40.000000000 +0100
+++ gcc/tree-vect-generic.c 2013-11-21 11:17:55.146118161 +0100
@@ -988,6 +988,84 @@ expand_vector_operation (gimple_stmt_ite
gimple_assign_rhs1 (assign),
gimple_assign_rhs2 (assign), code);
}
+
+/* Try to optimize
+ a_5 = { b_7, b_7 + 3, b_7 + 6, b_7 + 9 };
+ style stmts into:
+ _9 = { b_7, b_7, b_7, b_7 };
+ a_5 = _9 + { 0, 3, 6, 9 };
+ because vector splat operation is usually more efficient
+ than piecewise initialization of the vector. */
+
+static void
+optimize_vector_constructor (gimple_stmt_iterator *gsi)
+{
+ gimple stmt = gsi_stmt (*gsi);
+ tree lhs = gimple_assign_lhs (stmt);
+ tree rhs = gimple_assign_rhs1 (stmt);
+ tree type = TREE_TYPE (rhs);
+ unsigned int i, j, nelts = TYPE_VECTOR_SUBPARTS (type);
+ bool all_same = true;
+ constructor_elt *elt;
+ tree *cst;
+ gimple g;
+ tree base = NULL_TREE;
+
+ if (nelts <= 2 || CONSTRUCTOR_NELTS (rhs) != nelts)
+ return;
+ FOR_EACH_VEC_SAFE_ELT (CONSTRUCTOR_ELTS (rhs), i, elt)
+ if (TREE_CODE (elt->value) != SSA_NAME
+ || TREE_CODE (TREE_TYPE (elt->value)) == VECTOR_TYPE)
+ return;
+ else
+ {
+ tree this_base = elt->value;
+ if (this_base != CONSTRUCTOR_ELT (rhs, 0)->value)
+ all_same = false;
+ for (j = 0; j < nelts + 1; j++)
+ {
+ g = SSA_NAME_DEF_STMT (this_base);
+ if (is_gimple_assign (g)
+ && gimple_assign_rhs_code (g) == PLUS_EXPR
+ && TREE_CODE (gimple_assign_rhs2 (g)) == INTEGER_CST
+ && TREE_CODE (gimple_assign_rhs1 (g)) == SSA_NAME
+ && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs1 (g)))
+ this_base = gimple_assign_rhs1 (g);
+ else
+ break;
+ }
+ if (i == 0)
+ base = this_base;
+ else if (this_base != base)
+ return;
+ }
+ if (all_same)
+ return;
+ cst = XALLOCAVEC (tree, nelts);
+ for (i = 0; i < nelts; i++)
+ {
+ tree this_base = CONSTRUCTOR_ELT (rhs, i)->value;;
+ cst[i] = build_zero_cst (TREE_TYPE (base));
+ while (this_base != base)
+ {
+ g = SSA_NAME_DEF_STMT (this_base);
+ cst[i] = fold_binary (PLUS_EXPR, TREE_TYPE (base),
+ cst[i], gimple_assign_rhs2 (g));
+ if (cst[i] == NULL_TREE
+ || TREE_CODE (cst[i]) != INTEGER_CST
+ || TREE_OVERFLOW (cst[i]))
+ return;
+ this_base = gimple_assign_rhs1 (g);
+ }
+ }
+ for (i = 0; i < nelts; i++)
+ CONSTRUCTOR_ELT (rhs, i)->value = base;
+ g = gimple_build_assign (make_ssa_name (type, NULL), rhs);
+ gsi_insert_before (gsi, g, GSI_SAME_STMT);
+ g = gimple_build_assign_with_ops (PLUS_EXPR, lhs, gimple_assign_lhs (g),
+ build_vector (type, cst));
+ gsi_replace (gsi, g, false);
+}
/* Return a type for the widest vector mode whose components are of type
TYPE, or NULL_TREE if none is found. */
@@ -1278,6 +1356,17 @@ expand_vector_operations_1 (gimple_stmt_
expand_vector_condition (gsi);
return;
}
+
+ if (code == CONSTRUCTOR
+ && TREE_CODE (lhs) == SSA_NAME
+ && VECTOR_MODE_P (TYPE_MODE (TREE_TYPE (lhs)))
+ && !gimple_clobber_p (stmt)
+ && optimize)
+ {
+ optimize_vector_constructor (gsi);
+ return;
+ }
+
if (rhs_class != GIMPLE_UNARY_RHS && rhs_class != GIMPLE_BINARY_RHS)
return;
--- gcc/testsuite/gcc.dg/vect/vect-124.c.jj 2013-11-20 09:27:35.760798649
+0100
+++ gcc/testsuite/gcc.dg/vect/vect-124.c 2013-11-20 09:29:32.219199794
+0100
@@ -0,0 +1,28 @@
+#include "tree-vect.h"
+
+#ifndef N
+#define N 64
+#endif
+
+int a[N];
+
+__attribute__((noinline, noclone)) void
+foo (int x)
+{
+ int i;
+ for (i = 0; i < N; i++, x += 3)
+ a[i] = x;
+}
+
+int
+main ()
+{
+ int i;
+
+ check_vect ();
+ foo (6);
+ for (i = 0; i < N; i++)
+ if (a[i] != i * 3 + 6)
+ abort ();
+ return 0;
+}
Jakub
