Another --disable-checking bootstrap failure

[Diego Novillo]

Is anyone seeing this on a --disable-checking bootstrap?

Jan, you have been making changes in this area.  Do you recognize this? 
We seem to be freeing SSA_NAMEs too early.  This doesn't trigger with
--enable-checking nor with -v -save-temps.

Thanks.  Diego.

$ stage1/xgcc -Bstage1/ -Bbld/gcc/native.x86-64/x86_64-unknown-linux-gnu/bin/ -c   -g -O2 -DIN_GCC   -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -pedantic -Wno-long-long -Wno-variadic-macros -Wold-style-definition -Werror -fno-common   -DHAVE_CONFIG_H    -I. -I. -Ibld/gcc/src.x86-64/gcc -Ibld/gcc/src.x86-64/gcc/. -Ibld/gcc/src.x86-64/gcc/../include -Ibld/gcc/src.x86-64/gcc/../libcpp/include -Ibld/x86_64/include  bld/gcc/src.x86-64/gcc/df.c -o df.o
bld/gcc/src.x86-64/gcc/df.c: In function `df_bitmaps_free':
bld/gcc/src.x86-64/gcc/df.c:446: internal compiler error: Segmentation fault
Program received signal SIGSEGV, Segmentation fault.
0x000000000090bba3 in lookup_page_table_entry (p=0xd3a170)
    at bld/gcc/src.x86-64/gcc/ggc-page.c:581
581       while (table->high_bits != high_bits)
(gdb) bt
#0  0x000000000090bba3 in lookup_page_table_entry (p=0xd3a170)
    at bld/gcc/src.x86-64/gcc/ggc-page.c:581
#1  0x0000000000909b3c in ggc_set_mark (p=0xd3a170)
    at bld/gcc/src.x86-64/gcc/ggc-page.c:1254
#2  0x00000000006d7751 in gt_ggc_mx_basic_block_def (x_p=0x2a962032a0)
    at gtype-desc.c:437
#3  0x0000000000428e77 in gt_ggc_mx_lang_tree_node (x_p=0x2a96207c80)
    at gt-c-decl.h:228
#4  0x00000000006d71fa in gt_ggc_mx_dataflow_d (x_p=0x2a9622da00)
    at gtype-desc.c:288
#5  0x00000000006d7512 in gt_ggc_mx_tree_ann_d (x_p=0x2a96202690)
    at gtype-desc.c:365
#6  0x0000000000428d02 in gt_ggc_mx_lang_tree_node (x_p=0x2a962130f0)
    at gt-c-decl.h:201
#7  0x00000000006d7a59 in gt_ggc_mx_varray_head_tag (x_p=0x2a96212000)
    at gtype-desc.c:533
#8  0x00000000006d491e in ggc_mark_roots ()
    at bld/gcc/src.x86-64/gcc/ggc-common.c:118
#9  0x000000000090ad00 in ggc_collect ()
    at bld/gcc/src.x86-64/gcc/ggc-page.c:1968
#10 0x00000000004c29e6 in execute_todo (properties=668, flags=5)
    at bld/gcc/src.x86-64/gcc/tree-optimize.c:438
#11 0x00000000004c2c58 in execute_one_pass (pass=0xc75860)
    at bld/gcc/src.x86-64/gcc/tree-optimize.c:512
[ ... ]
(gdb) p *pass
$1 = {
  name = 0xa327db "optimized",
  gate = 0,
  execute = 0x4f06ae <rewrite_out_of_ssa>,
[ ... ]