http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49503
--- Comment #2 from Michael Zolotukhin <michael.v.zolotukhin at gmail dot com> 2011-06-22 17:50:34 UTC --- (In reply to comment #1) > (In reply to comment #0) > > > > As _L_mutex_lock is a function, GCC generates a prologue and epilogue for > > it - > > in prologue stack alignment is performed (according to ABI64, stack should > > be > > aligned to 128-bit). > > I didn't see any prologue and epilogue for _L_mutex_lock. Do you have > a run-time testcase to show the problem? I don't have run-time test for this fail, but here is a way to see the problem: Firstly, you need to compile the test (it is in gcc/testsuite/gcc.target/i386): gcc cleanup-1.c -fexceptions -fnon-call-exceptions -fasynchronous-unwind-tables -O0 -lm -g -fno-inline Then, in debugger one can see that before each callq before foo (here 'before' means 'upper in call stack') RSP contains aligned value, after foo (deeper in call stack) - unaligned. Here is corresponding a assembler dump: -Dump of assembler code for function foo: 0x0000000000400886 <+0>: push %rbp 0x0000000000400887 <+1>: mov %rsp,%rbp 0x000000000040088a <+4>: push %r12 0x000000000040088c <+6>: push %rbx 0x000000000040088d <+7>: sub $0x98,%rsp # It is the prologue, 0x0000000000400894 <+14>: mov %edi,-0x114(%rbp) # that I've spoken 0x000000000040089a <+20>: mov -0x114(%rbp),%ebx # about. 0x00000000004008a0 <+26>: lea -0x110(%rbp),%r12 # 0x00000000004008a7 <+33>: test %ebx,%ebx 0x00000000004008a9 <+35>: jne 0x400941 <_L_mutex_lock_216> 0x00000000004008af <+41>: add $0x98,%rsp 0x00000000004008b6 <+48>: pop %rbx 0x00000000004008b7 <+49>: pop %r12 0x00000000004008b9 <+51>: leaveq 0x00000000004008ba <+52>: retq -End of assembler dump. RTL dumps showed that these instructions appear phase "197r.pro_and_epilogue". I'm not sure, if prologue generation is incorrect - in my opinion the problem is with such untrivial call of _L_mutex_lock.
