veclower: Don't ICE on .VEC_CONVERT calls with no lhs [PR96426]

.VEC_CONVERT is a const internal call, so normally if the lhs is not used,
we'd DCE it far before getting to veclower, but with -O0 (or perhaps
-fno-tree-dce and some other -fno-* options) it can happen.
But as the internal fn needs the lhs to know the type to which the
conversion is done (and I think that is a reasonable representation, having
some magic another argument and having to create constants with that type
looks overkill to me), we just should DCE those calls ourselves.
During veclower, we can't really remove insns, as the callers would be
upset, so this just replaces it with a GIMPLE_NOP.

2020-08-04  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/96426
	* tree-vect-generic.c (expand_vector_conversion): Replace .VEC_CONVERT
	call with GIMPLE_NOP if there is no lhs.

	* gcc.c-torture/compile/pr96426.c: New test.

diff --git a/gcc/testsuite/gcc.c-torture/compile/pr96426.c b/gcc/testsuite/gcc.c-torture/compile/pr96426.c
new file mode 100644 (file)
index 0000000..bd573fe
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr96426.c
@@ -0,0 +1,10 @@
+/* PR middle-end/96426 */
+
+typedef long long V __attribute__((vector_size(16)));
+typedef double W __attribute__((vector_size(16)));
+
+void
+foo (V *v)
+{
+  __builtin_convertvector (*v, W);
+}

diff --git a/gcc/tree-vect-generic.c b/gcc/tree-vect-generic.c
index fe6477c859259125b23b89f1ae3f783a88d3a848..6d5d65195ae6e5b8a5c8343c5f3ab67907b10f8f 100644 (file)
--- a/gcc/tree-vect-generic.c
+++ b/gcc/tree-vect-generic.c
@@ -1775,6 +1775,12 @@ expand_vector_conversion (gimple_stmt_iterator *gsi)
   gimple *stmt = gsi_stmt (*gsi);
   gimple *g;
   tree lhs = gimple_call_lhs (stmt);
+  if (lhs == NULL_TREE)
+    {
+      g = gimple_build_nop ();
+      gsi_replace (gsi, g, false);
+      return;
+    }
   tree arg = gimple_call_arg (stmt, 0);
   tree ret_type = TREE_TYPE (lhs);
   tree arg_type = TREE_TYPE (arg);