[gcc r13-5739] vect: Check gather/scatter offset types [PR108316]

[gcc r13-5739] vect: Check gather/scatter offset types [PR108316]

[Richard Sandiford]

https://gcc.gnu.org/g:740a3be7df29b280f39a04c441fd4917af4eef5e

commit r13-5739-g740a3be7df29b280f39a04c441fd4917af4eef5e
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Wed Feb 8 13:40:29 2023 +0000

    vect: Check gather/scatter offset types [PR108316]
    
    The gather/scatter support can over-widen an offset if the target
    requires it, but this relies on using a pattern sequence to add
    the widening conversion.  That failed in the testcase because an
    earlier pattern (bool) took priority.
    
    I think we should allow patterns to be applied to other patterns,
    but that's quite an invasive change and isn't suitable for stage 4.
    This patch instead punts if the offset type doesn't match the
    expected one.
    
    If we switched to using the SLP representation for everything,
    we would probably handle both patterns by rewriting the graph,
    which should be much easier.
    
    gcc/
            PR tree-optimization/108316
            * tree-vect-stmts.cc (get_load_store_type): When using
            internal functions for gather/scatter, make sure that the type
            of the offset argument is consistent with the offset vector type.
    
    gcc/testsuite/
            PR tree-optimization/108316
            * gcc.dg/vect/pr108316.c: New test.

Diff:
---
 gcc/testsuite/gcc.dg/vect/pr108316.c | 11 +++++++++++
 gcc/tree-vect-stmts.cc               | 17 +++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/gcc/testsuite/gcc.dg/vect/pr108316.c b/gcc/testsuite/gcc.dg/vect/pr108316.c
new file mode 100644
index 00000000000..540b7f2aed4
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr108316.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O3" } */
+
+extern _Bool a[];
+
+void
+foo (short i, int b[][64][1])
+{
+  for (; i < 64; i += 4)
+    a[i] = b[0][i] != 0;
+}
diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index eb4ca1f184e..c86249adcc3 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -2474,6 +2474,23 @@ get_load_store_type (vec_info  *vinfo, stmt_vec_info stmt_info,
       *memory_access_type = VMAT_GATHER_SCATTER;
       if (!vect_check_gather_scatter (stmt_info, loop_vinfo, gs_info))
 	gcc_unreachable ();
+      /* When using internal functions, we rely on pattern recognition
+	 to convert the type of the offset to the type that the target
+	 requires, with the result being a call to an internal function.
+	 If that failed for some reason (e.g. because another pattern
+	 took priority), just handle cases in which the offset already
+	 has the right type.  */
+      else if (gs_info->ifn != IFN_LAST
+	       && !is_gimple_call (stmt_info->stmt)
+	       && !tree_nop_conversion_p (TREE_TYPE (gs_info->offset),
+					  TREE_TYPE (gs_info->offset_vectype)))
+	{
+	  if (dump_enabled_p ())
+	    dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+			     "%s offset requires a conversion\n",
+			     vls_type == VLS_LOAD ? "gather" : "scatter");
+	  return false;
+	}
       else if (!vect_is_simple_use (gs_info->offset, vinfo,
 				    &gs_info->offset_dt,
 				    &gs_info->offset_vectype))