Re: RFA: Merge definitions of get_some_local_dynamic_name

[Rainer Orth <ro at CeBiTec dot Uni-Bielefeld dot DE>]

Hi Richard,

> Several targets define a function like i386's get_some_local_dynamic_name.
> The function looks through the current output function and returns the first
> (arbitrary) local-dynamic symbol that it finds.  The result can be used in
> a call to __tls_get_addr, since all local-dynamic symbols have the same base.
>
> This patch replaces the various target functions with a single generic one.
> The only difference between the implementations was that s390 checked
> for constant pool references while the others didn't need to (because
> they don't allow TLS symbols to be forced into the pool).  Checking for
> constant pool references is unnecessary but harmless for the other ports.
> Also, the walk is needed only once per TLS-referencing output function,
> so it's hardly critical in terms of compile time.
>
> All uses of this function are in final.  In general it wouldn't be
> safe to call the function earlier than that, since the symbol reference
> could in principle be deleted by any rtl pass.  I've therefore cached
> it in a variable local to final rather than in cfun (which is where
> the ports used to cache it).
>
> Also, i386 was robust against uses of %& in inline asm.  The patch
> makes sure the other ports are too.  Using %& in inline asm would
> often be a mistake, but it should at least trigger a proper error
> rather than an ICE.
>
> Tested on x86_64-linux-gnu.  Also tested by building cross compilers
> before and after the change on:
>
>   alpha-linux-gnu powerpc64-linux-gnu s390x-linux-gnu sparc64-linux-gnu
>
> OK to install?

this patch broke Solaris/SPARC bootstrap: compiling libgo/runtime/proc.c
with -fPIC SEGVs:

/vol/gcc/src/hg/trunk/local/libgo/runtime/proc.c: In function 'procresize':
/vol/gcc/src/hg/trunk/local/libgo/runtime/proc.c:2727:1: internal compiler error: Segmentation Fault
 }
 ^
0x731c97 crash_signal
        /vol/gcc/src/hg/trunk/local/gcc/toplev.c:339
0x45facc get_some_local_dynamic_name()
        /vol/gcc/src/hg/trunk/local/gcc/final.c:1742
0xa0886f sparc_print_operand
        /vol/gcc/src/hg/trunk/local/gcc/config/sparc/sparc.c:8789
0x4606a3 output_operand(rtx_def*, int)
        /vol/gcc/src/hg/trunk/local/gcc/final.c:3848
0x460fdf output_asm_insn(char const*, rtx_def**)
        /vol/gcc/src/hg/trunk/local/gcc/final.c:3778
0x46254b output_asm_insn(char const*, rtx_def**)
        /vol/gcc/src/hg/trunk/local/gcc/recog.h:169
0x46254b final_scan_insn(rtx_insn*, __FILE*, int, int, int*)
        /vol/gcc/src/hg/trunk/local/gcc/final.c:3027
0x462b53 final(rtx_insn*, __FILE*, int)
        /vol/gcc/src/hg/trunk/local/gcc/final.c:2063
0x46470f rest_of_handle_final
        /vol/gcc/src/hg/trunk/local/gcc/final.c:4470
0x46470f execute
        /vol/gcc/src/hg/trunk/local/gcc/final.c:4545

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 1 (LWP 1)]
get_some_local_dynamic_name () at /vol/gcc/src/hg/trunk/local/gcc/final.c:1742
1742		  if (GET_CODE (x) == SYMBOL_REF)

1: x/i $pc
=> 0x45facc <get_some_local_dynamic_name()+84>:	lduh  [ %o0 ], %g1
(gdb) p $o0
$1 = 0

(gdb) where
#0  get_some_local_dynamic_name () at /vol/gcc/src/hg/trunk/local/gcc/final.c:1742
#1  0x00a08870 in sparc_print_operand (file=0x10ab0f0 <_iob+48>, x=0x0, code=<optimized out>) at /vol/gcc/src/hg/trunk/local/gcc/config/sparc/sparc.c:8789
#2  0x004606a4 in output_operand (x=0x0, code=38) at /vol/gcc/src/hg/trunk/local/gcc/final.c:3848
#3  0x00460fe0 in output_asm_insn (templ=templ@entry=0xf1e5c8 "sethi\t%%tldm_hi22(%&), %0", operands=0x107feb0 <recog_data>) at /vol/gcc/src/hg/trunk/local/gcc/final.c:3778
#4  0x0046254c in output_asm_insn (operands=<optimized out>, templ=0xf1e5c8 "sethi\t%%tldm_hi22(%&), %0") at /vol/gcc/src/hg/trunk/local/gcc/recog.h:169
#5  final_scan_insn (insn=insn@entry=0xfac70de8, file=file@entry=0x10ab0f0 <_iob+48>, optimize_p=optimize_p@entry=2, nopeepholes=nopeepholes@entry=0, seen=seen@entry=0xffbfef0c) at /vol/gcc/src/hg/trunk/local/gcc/final.c:3027
#6  0x00462b54 in final (first=0xfac62020, file=0x10ab0f0 <_iob+48>, optimize_p=2) at /vol/gcc/src/hg/trunk/local/gcc/final.c:2063
#7  0x00464710 in rest_of_handle_final () at /vol/gcc/src/hg/trunk/local/gcc/final.c:4470
#8  (anonymous namespace)::pass_final::execute (this=0x10d9050) at /vol/gcc/src/hg/trunk/local/gcc/final.c:4545
#9  0x00661cf4 in execute_one_pass (pass=pass@entry=0x10d9050) at /vol/gcc/src/hg/trunk/local/gcc/passes.c:2151
#10 0x0066235c in execute_pass_list_1 (pass=0x10d9050) at /vol/gcc/src/hg/trunk/local/gcc/passes.c:2203
#11 0x00662380 in execute_pass_list_1 (pass=0x10d8630) at /vol/gcc/src/hg/trunk/local/gcc/passes.c:2204
#12 0x00662380 in execute_pass_list_1 (pass=0x10d7988, pass@entry=0x10d54a8) at /vol/gcc/src/hg/trunk/local/gcc/passes.c:2204
#13 0x006623c4 in execute_pass_list (fn=0xfb5fc5b0, pass=0x10d54a8) at /vol/gcc/src/hg/trunk/local/gcc/passes.c:2214
#14 0x0037d728 in cgraph_node::expand (this=this@entry=0xfb5f5180) at /vol/gcc/src/hg/trunk/local/gcc/cgraphunit.c:1744
#15 0x0037f078 in expand_all_functions () at /vol/gcc/src/hg/trunk/local/gcc/cgraphunit.c:1880
#16 symbol_table::compile (this=0xfb410000) at /vol/gcc/src/hg/trunk/local/gcc/cgraphunit.c:2209
#17 0x00380ee4 in symbol_table::finalize_compilation_unit (this=0xfb410000) at /vol/gcc/src/hg/trunk/local/gcc/cgraphunit.c:2286
#18 0x0020ee34 in c_write_global_declarations () at /vol/gcc/src/hg/trunk/local/gcc/c/c-decl.c:10431
#19 0x00731d58 in compile_file () at /vol/gcc/src/hg/trunk/local/gcc/toplev.c:564
#20 0x00734604 in do_compile () at /vol/gcc/src/hg/trunk/local/gcc/toplev.c:1945
#21 toplev_main (argc=10, argv=0xffbff424) at /vol/gcc/src/hg/trunk/local/gcc/toplev.c:2021
#22 0x001f1184 in _start ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

It seems the new get_some_local_dynamic_name implementation in
function.c lost the non-NULL check the sparc.c version had.  I'm
currently testing the following patch:

diff --git a/gcc/final.c b/gcc/final.c
--- a/gcc/final.c
+++ b/gcc/final.c
@@ -1739,7 +1739,7 @@ get_some_local_dynamic_name ()
       FOR_EACH_SUBRTX (iter, array, PATTERN (insn), ALL)
 	{
 	  const_rtx x = *iter;
-	  if (GET_CODE (x) == SYMBOL_REF)
+	  if (x && GET_CODE (x) == SYMBOL_REF)
 	    {
 	      if (SYMBOL_REF_TLS_MODEL (x) == TLS_MODEL_LOCAL_DYNAMIC)
 		return some_local_dynamic_name = XSTR (x, 0);

	Rainer

-- 
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University