On Sun, 31 Mar 2013, Andrew Pinski wrote:
On Sun, Mar 31, 2013 at 6:31 AM, Marc Glisse <marc.gli...@inria.fr> wrote:
Hello,
this adds constant folding of VEC_COND_EXPR at the tree level by forwarding
to the VEC_PERM_EXPR code (a merge is a special case of a permutation). The
CONSTRUCTOR case may be unreachable for now (it will probably need an extra
piece of code in tree-ssa-forwprop.c), but it seems better to add it at the
same time.
bootstrap+testsuite on x86_64-linux-gnu.
2013-03-31 Marc Glisse <marc.gli...@inria.fr>
PR tree-optimization/56790
* fold-const.c (fold_ternary_loc) <VEC_COND_EXPR>: Add constant
folding.
testsuite/
* g++.dg/ext/pr56790-1.C: New testcase.
--
Marc Glisse
Index: gcc/testsuite/g++.dg/ext/pr56790-1.C
===================================================================
--- gcc/testsuite/g++.dg/ext/pr56790-1.C (revision 0)
+++ gcc/testsuite/g++.dg/ext/pr56790-1.C (revision 0)
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-ccp1" } */
+
+typedef long vec __attribute__ ((vector_size (2 * sizeof (long))));
+
+vec f (void)
+{
+ vec a = { 5, 7 };
+ vec b = { 11, 13 };
+ vec m = { -1, 0 };
+ return m ? a : b;
+}
+
+/* { dg-final { scan-tree-dump "{ 5, 13 }" "ccp1" } } */
+/* { dg-final { scan-tree-dump-not "VEC_COND_EXPR" "ccp1" } } */
+/* { dg-final { cleanup-tree-dump "ccp1" } } */
Property changes on: gcc/testsuite/g++.dg/ext/pr56790-1.C
___________________________________________________________________
Added: svn:keywords
+ Author Date Id Revision URL
Added: svn:eol-style
+ native
Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c (revision 197284)
+++ gcc/fold-const.c (working copy)
@@ -13917,20 +13917,43 @@ fold_ternary_loc (location_t loc, enum t
|| VOID_TYPE_P (type)))
return pedantic_non_lvalue_loc (loc, tem);
return NULL_TREE;
}
else if (TREE_CODE (arg0) == VECTOR_CST)
{
if (integer_all_onesp (arg0))
return pedantic_omit_one_operand_loc (loc, type, arg1, arg2);
if (integer_zerop (arg0))
return pedantic_omit_one_operand_loc (loc, type, arg2, arg1);
+
+ if ((TREE_CODE (arg1) == VECTOR_CST
+ || TREE_CODE (arg1) == CONSTRUCTOR)
+ && (TREE_CODE (arg2) == VECTOR_CST
+ || TREE_CODE (arg2) == CONSTRUCTOR))
+ {
+ unsigned int nelts = TYPE_VECTOR_SUBPARTS (type), i;
+ unsigned char *sel = XALLOCAVEC (unsigned char, nelts);
+ gcc_assert (nelts == VECTOR_CST_NELTS (arg0));
+ for (i = 0; i < nelts; i++)
+ {
+ tree val = VECTOR_CST_ELT (arg0, i);
+ if (integer_all_onesp (val))
+ sel[i] = i;
+ else if (integer_zerop (val))
+ sel[i] = nelts + i;
+ else
+ gcc_unreachable ();
I think this gcc_unreachable here is incorrect as it could cause an
internal compiler error for "target dependent code"
Try for:
typedef long vec __attribute__ ((vector_size (2 * sizeof (long))));
vec f (void)
{
vec a = { 5, 7 };
vec b = { 11, 13 };
vec m = { 3, 2 };
return m ? a : b;
}
I think for the above case we don't want to do any constant folding.
For vectors, we decided in 4.8 that x ? y : z would mean vec_cond_expr <x
!= 0, y, z>, and that is what the C++ front-end generates, so your
testcase works fine and returns a.
Re-reading doc/generic.texi, I see:
"If an element of the first operand evaluates to a zero value, the
corresponding element of the result is taken from the third operand. If it
evaluates to a minus one value, it is taken from the second operand. It
should never evaluate to any other value currently, but optimizations
should not rely on that property."
Well, at least I am not silently relying on that property, but it looks
like you are right and I am supposed to leave those (impossible) values
alone.
--
Marc Glisse
