Hi!
The following testcase regressed for 8+, because we delayed folding in
SAVE_EXPRs and end up passing a CONSTRUCTOR with V4SFmode and 4x 0.0
constants in it rather than a VECTOR_CST to the middle-end folder, which
uses real_zerop and thus doesn't recognize the CONSTRUCTOR in
VEC_COND_EXPR <x < { 0, 0, 0, 0 } ? -x : x> as zero and doesn't fold
it into ABS_EXPR.
We really should move that folding into match.pd, but that is a GCC 9 task.
Fixed by using fold on vector CONSTRUCTORs, the only thing fold does on
those is exactly the CONSTRUCTOR -> VECTOR_CST folding when possible.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2018-03-27 Jakub Jelinek <ja...@redhat.com>
PR c++/85077
* cp-gimplify.c (cp_fold) <case CONSTRUCTOR>: For ctors with vector
type call fold to generate VECTOR_CSTs when possible.
* g++.dg/ext/vector35.C: New test.
--- gcc/cp/cp-gimplify.c.jj 2018-03-20 22:05:57.023431462 +0100
+++ gcc/cp/cp-gimplify.c 2018-03-26 16:08:47.728347579 +0200
@@ -2504,6 +2504,8 @@ cp_fold (tree x)
CONSTRUCTOR_PLACEHOLDER_BOUNDARY (x)
= CONSTRUCTOR_PLACEHOLDER_BOUNDARY (org_x);
}
+ if (VECTOR_TYPE_P (TREE_TYPE (x)))
+ x = fold (x);
break;
}
case TREE_VEC:
--- gcc/testsuite/g++.dg/ext/vector35.C.jj 2018-03-26 16:19:39.330809031
+0200
+++ gcc/testsuite/g++.dg/ext/vector35.C 2018-03-26 16:33:43.997330748 +0200
@@ -0,0 +1,22 @@
+// PR c++/85077
+// { dg-do compile }
+// { dg-options "-Ofast -fdump-tree-forwprop1" }
+
+typedef float V __attribute__((vector_size (4 * sizeof (float))));
+typedef double W __attribute__((vector_size (2 * sizeof (double))));
+
+void
+foo (V *y)
+{
+ V x = *y;
+ *y = x < 0 ? -x : x;
+}
+
+void
+bar (W *y)
+{
+ W x = *y;
+ *y = x < 0 ? -x : x;
+}
+
+// { dg-final { scan-tree-dump-times "ABS_EXPR <" 2 "forwprop1" } }
Jakub
