http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49709
--- Comment #1 from pinskia at gmail dot com pinskia at gmail dot com
2011-07-12 00:58:13 UTC ---
Hmmm. There was just a recent patch to the tail call area which was supposed to
fix a testcase like this.
Sent from my Palm Pre on ATamp;T
On Jul 11, 2011 17:51, ian at airs dot com lt;gcc-bugzi...@gcc.gnu.orggt;
wrote:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49709
Summary: Bad code gen with -fipa-sra
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: major
Priority: P3
Component: tree-optimization
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: i...@airs.com
Created attachment 24741
--gt; http://gcc.gnu.org/bugzilla/attachment.cgi?id=24741
Test case
I have attached a C test case. When compiled for x86 with -m32 -O2, the test
case aborts. When compiled with -m32, or with -m32 -O2 -fno-ipa-sra it runs to
completion.
I believe the bug is that ipa-sra leaves a call which refers to function
parameters using MEM_REF expressions which refer to fields of the parameters.
These are translated into MEM expressions which load the address of the
parameter into a register and then use a MEM_REF to load an offset from that
register. This MEM does not refer to the internal_arg_pointer, but to a
register which was set based on the internal_arg_pointer. That means that
mem_overlaps_already_clobbered_arg_p in calls.c does not recognize that the MEM
refers to the argument area. That in turn means that gcc thinks that it can
make a tail call, but when setting up the arguments for the call it clobbers
arguments that it has yet to read.
The fix may be to make mem_overlaps_already_clobbered_arg_p much smarter, or to
disable tail calls when applying SRA to a function and passes parameters to it.
