[PATCH] Small hack for DECL_MODE lack of vector_type_mode-like behavior (PR target/78643, PR target/80583)

[Jakub Jelinek]

Hi!

In TYPE_MODE we have a hack for vector types where we dynamically
adjust it based on whether it is used from a function where the vector mode
is or isn't supported (depending on target attribute, function
multiversioning, etc.), but we don't have anything like that in DECL_MODE.

The following is just a small hack that should be backportable to adjust
similarly DECL_MODE when looking at fields - for static VAR_DECLs we already
have code to cope with that, furthermore we need to cope there with the
case where DECL_RTL is created in one context and used in another one.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2017-12-01  Jakub Jelinek  <ja...@redhat.com>

        PR target/78643
        PR target/80583
        * expr.c (get_inner_reference): If DECL_MODE of a non-bitfield
        is BLKmode for vector field with vector raw mode, use TYPE_MODE
        instead of DECL_MODE.

        * gcc.target/i386/pr80583.c: New test.

--- gcc/expr.c.jj       2017-11-27 09:27:41.000000000 +0100
+++ gcc/expr.c  2017-12-01 11:36:19.011863308 +0100
@@ -7032,7 +7032,16 @@ get_inner_reference (tree exp, HOST_WIDE
             size.  */
        mode = TYPE_MODE (DECL_BIT_FIELD_TYPE (field));
       else if (!DECL_BIT_FIELD (field))
-       mode = DECL_MODE (field);
+       {
+         mode = DECL_MODE (field);
+         /* For vector fields re-check the target flags, as DECL_MODE
+            could have been set with different target flags than
+            the current function has.  */
+         if (mode == BLKmode
+             && VECTOR_TYPE_P (TREE_TYPE (field))
+             && VECTOR_MODE_P (TYPE_MODE_RAW (TREE_TYPE (field))))
+           mode = TYPE_MODE (TREE_TYPE (field));
+       }
       else if (DECL_MODE (field) == BLKmode)
        blkmode_bitfield = true;
 
--- gcc/testsuite/gcc.target/i386/pr80583.c.jj  2017-12-01 11:44:28.106603314 
+0100
+++ gcc/testsuite/gcc.target/i386/pr80583.c     2017-12-01 11:44:12.000000000 
+0100
@@ -0,0 +1,13 @@
+/* PR target/80583 */
+/* { dg-do compile } */
+/* { dg-options "-O0 -mno-avx" } */
+
+typedef int V __attribute__((__vector_size__(32)));
+struct S { V a; };
+
+V __attribute__((target ("avx")))
+foo (struct S *b)
+{
+  V x = b->a;
+  return x;
+}

        Jakub