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[PATCH] __builtin_apply / -fdefer-pop bug (ObjC fix!)
- To: gcc at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org, gcc-bugs at gcc dot gnu dot org
- Subject: [PATCH] __builtin_apply / -fdefer-pop bug (ObjC fix!)
- From: Jason McMullan <jmcmullan at linuxcare dot com>
- Date: Wed, 26 Jul 2000 16:36:07 -0400
(please CC: to me, as I do not follow the *@gcc.gnu.org lists)
As many well know, GCC since 2.8.x has had a lot
of bugs with the __builtin_apply() function, especially
with the ObjC front-end. Come to find out, it doesn't
appear to be a problem with __builtin_apply() at all,
but with an over-optimization of -fdefer-pop.
When compiled with -fdefer-pop (without the following
patch) GCC neglects to set the stack pointer appropriately
after the memcpy() call (to move the stack arguments), and
the called function (that __builtin_apply() was trying to call)
is sent a bogus stack pointer.
With the following patch, a NO_DEFER_POP/OK_DEFER_POP
pair - which temporarily inhibits -fdefer-pop - is placed
around the critical section in:
gcc/expr.c:expand_builtin_apply()
Upon recompile of libobjc (or any other source that uses
__builtin_apply()) correct functionality of __builtin_apply
(and henve forward::/performv:: ) is restored to the ObjectiveC
language runtime.
A closer inspection as to why the -fdefer-pop optimization
fails in this instance should be looked at, but this workaround
appears to mirror similar uses of NO_DEFER_POP/OK_DEFER_POP in
expr.c.
* gcc/expr.c - Fix expand_builin_apply() due to -fdefer-pop breakage
------------------- Cut here ----------------
--- expr.c.old Wed Jun 30 18:59:55 1999
+++ expr.c Wed Jul 26 16:21:37 2000
@@ -9987,6 +9987,8 @@
rtx old_stack_level = 0;
rtx call_fusage = 0;
+ NO_DEFER_POP;
+
/* Create a block where the return registers can be saved. */
result = assign_stack_local (BLKmode, apply_result_size (), -1);
@@ -10145,6 +10147,8 @@
else
#endif
emit_stack_restore (SAVE_BLOCK, old_stack_level, NULL_RTX);
+
+ OK_DEFER_POP;
/* Return the address of the result block. */
return copy_addr_to_reg (XEXP (result, 0));
------------------- Cut here ----------------
--
Jason McMullan, Senior Linux Consultant, Linuxcare, Inc.
412.422.8077 tel, 412.656.3519 cell, 415.701.0792 fax
jmcmullan@linuxcare.com, http://www.linuxcare.com/
Linuxcare. Support for the revolution.