rs6000: Fix an assertion in update_target_cost_per_stmt [PR103702]

This patch is to fix one wrong assertion which is too aggressive.
Vectorizer can do vec_construct costing for the vector type which
only has one unit.  For the failed case, the passed in vector type
is "vector(1) int", though it doesn't end up with any construction
eventually, we have to handle this kind of possibility.

gcc/ChangeLog:

	PR target/103702
	* config/rs6000/rs6000.cc
	(rs6000_cost_data::update_target_cost_per_stmt): Fix one wrong
	assertion with early return.

gcc/testsuite/ChangeLog:

	PR target/103702
	* gcc.target/powerpc/pr103702.c: New test.

diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index e5471da..a5fd36b 100644 (file)
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -5439,8 +5439,11 @@ rs6000_cost_data::update_target_cost_per_stmt (vect_cost_for_stmt kind,
        {
          tree vectype = STMT_VINFO_VECTYPE (stmt_info);
          unsigned int nunits = vect_nunits_for_cost (vectype);
-         /* We don't expect strided/elementwise loads for just 1 nunit.  */
-         gcc_assert (nunits > 1);
+         /* As PR103702 shows, it's possible that vectorizer wants to do
+            costings for only one unit here, it's no need to do any
+            penalization for it, so simply early return here.  */
+         if (nunits == 1)
+           return;
          /* i386 port adopts nunits * stmt_cost as the penalized cost
             for this kind of penalization, we used to follow it but
             found it could result in an unreliable body cost especially

diff --git a/gcc/testsuite/gcc.target/powerpc/pr103702.c b/gcc/testsuite/gcc.target/powerpc/pr103702.c
new file mode 100644 (file)
index 0000000..585946f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr103702.c
@@ -0,0 +1,24 @@
+/* We don't have one powerpc.*_ok for Power6, use altivec_ok conservatively.  */
+/* { dg-require-effective-target powerpc_altivec_ok } */
+/* { dg-options "-mdejagnu-cpu=power6 -O2 -ftree-loop-vectorize -fno-tree-scev-cprop" } */
+
+/* Verify there is no ICE.  */
+
+unsigned short a, e;
+int *b, *d;
+int c;
+extern int fn2 ();
+void
+fn1 ()
+{
+  void *f;
+  for (;;)
+    {
+      fn2 ();
+      b = f;
+      e = 0;
+      for (; e < a; ++e)
+       b[e] = d[e * c];
+    }
+}
+