[PATCH] Fix PR70509 (wrong code with extract from a v64qi)

[Zdenek Sojka]

Hello,

as discussed in the PR, when forwprop propagates VEC_PERM_EXPR through 
BIT_FIELD_REF in simplify_bitfield_ref(), the new BIT_FIELD_REF has the index 
of the same type as the vector base type. This patch changes the index to 
bitsize_int().

Bootstrapped on x86_64-pc-linux-gnu, regression test shows the same result as 
without the patch.

I've test both with/out the second patch mentioned in PR70509#c6 ; it was 
pre-approved by Jakub in the PR. I haven't managed to generate a testcase for 
it though.

I was unable to run the testcase via "make check" since my CPU doesn't support 
the avx512bw instruction set; however I have tested a standalone testcase in an 
emulator, before integrating it to the testsuite.

Please replace the changelog entries with a better ones if needed.

Thanks,
Zdenek

gcc/Changelog:

2016-04-04  Zdenek Sojka  

    PR tree-optimization/70509
    * tree-ssa-forwprop.c (simplify_bitfield_ref): Use bitsize_int () instead 
of the vector base type for index.


gcc/testsuite/Changelog:

2016-04-04  Zdenek Sojka  

    PR tree-optimization/70509
    * gcc.target/i386/avx512bw-pr70509.c: New.
=
Index: gcc/tree-ssa-forwprop.c
===================================================================
--- gcc/tree-ssa-forwprop.c	(revision 234705)
+++ gcc/tree-ssa-forwprop.c	(working copy)
@@ -1773,7 +1773,7 @@
 
   if (code == VEC_PERM_EXPR)
     {
-      tree p, m, index, tem;
+      tree p, m, tem;
       unsigned nelts;
       m = gimple_assign_rhs3 (def_stmt);
       if (TREE_CODE (m) != VECTOR_CST)
@@ -1790,9 +1790,8 @@
 	  p = gimple_assign_rhs2 (def_stmt);
 	  idx -= nelts;
 	}
-      index = build_int_cst (TREE_TYPE (TREE_TYPE (m)), idx * size);
       tem = build3 (BIT_FIELD_REF, TREE_TYPE (op),
-		    unshare_expr (p), op1, index);
+		    unshare_expr (p), op1, bitsize_int (idx * size));
       gimple_assign_set_rhs1 (stmt, tem);
       fold_stmt (gsi);
       update_stmt (gsi_stmt (*gsi));
Index: gcc/testsuite/gcc.target/i386/avx512bw-pr70509.c
===================================================================
--- gcc/testsuite/gcc.target/i386/avx512bw-pr70509.c	(revision 0)
+++ gcc/testsuite/gcc.target/i386/avx512bw-pr70509.c	(working copy)
@@ -0,0 +1,26 @@
+/* PR tree-optimization/70509 */
+/* { dg-do run } */
+/* { dg-options "-O1 -mavx512bw" } */
+/* { dg-require-effective-target avx512bw } */
+
+#define AVX512BW
+#include "avx512f-helper.h"
+
+typedef char V __attribute__ ((vector_size (64)));
+
+int __attribute__ ((noinline, noclone))
+foo (V u, V v)
+{
+  u /= v[0x20];
+  return u[0];
+}
+
+void
+TEST (void)
+{
+  int x = foo ((V) { 9 }, (V) { 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+				2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+				3 });
+  if (x != 3)
+    abort ();
+}