[PATCH] Fix loop pattern distribution ICE (PR tree-optimization/54321)

[Jakub Jelinek]

Hi!

The middle-end argument of memset is signed (int), so simplify_builtin_call
correctly checks host_integerp (val2, 0), but later on used tree_low_cst
(val2, 1), so for negative values it would ICE.  Fixed thusly, the memset
is supposed to cast the int to unsigned char internally anyway.

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

2012-08-20  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/54321
        * tree-ssa-forwprop.c (simplify_builtin_call): Pass 0 instead of 1
        as second argument to tree_low_cst call on val2.

        * gcc.c-torture/compile/pr54321.c: New test.

--- gcc/tree-ssa-forwprop.c.jj  2012-08-14 08:45:00.000000000 +0200
+++ gcc/tree-ssa-forwprop.c     2012-08-20 08:11:06.247936035 +0200
@@ -1554,7 +1554,7 @@ simplify_builtin_call (gimple_stmt_itera
          else
            src_buf[0] = tree_low_cst (src1, 0);
          memset (src_buf + tree_low_cst (diff, 1),
-                 tree_low_cst (val2, 1), tree_low_cst (len2, 1));
+                 tree_low_cst (val2, 0), tree_low_cst (len2, 1));
          src_buf[src_len] = '\0';
          /* Neither builtin_strncpy_read_str nor builtin_memcpy_read_str
             handle embedded '\0's.  */
--- gcc/testsuite/gcc.c-torture/compile/pr54321.c.jj    2012-08-20 
08:12:10.955630873 +0200
+++ gcc/testsuite/gcc.c-torture/compile/pr54321.c       2012-08-20 
08:13:27.963398948 +0200
@@ -0,0 +1,12 @@
+/* PR tree-optimization/54321 */
+struct S { char s[0]; } *a;
+
+void
+foo (void)
+{
+  char *b = a->s;
+  int c = 0;
+  b[0] = 0;
+  while (++c < 9)
+    b[c] = 255;
+}

        Jakub