| Message ID | 4C5AFE39.8090008@twiddle.net |
|---|---|
| State | New |
| Headers | show |
On Thu, Aug 5, 2010 at 11:08 AM, Richard Henderson <rth@twiddle.net> wrote: > On 08/05/2010 09:18 AM, H.J. Lu wrote: >>> FAIL: g++.dg/torture/stackalign/eh-thiscall-1.C -O2 -fwhopr execution test >>> >>> I saw them on Fedora 13. >>> >> >> Those failing tests are compiled with -fpic. Here is stack trace with >> -O -fpic -static: > > Fixed. > > The problem was improper computation of the mask used for the unwind info. > The test could still pass at runtime depending on the memory layout that > the program receives. > It is interesting. I saw it on 32bit host with 32bit HOST_WIDE_INT. Is it a signed vs. unsigned issue? stack_alignment_needed is unsigned.
On 08/05/2010 11:19 AM, H.J. Lu wrote: > It is interesting. I saw it on 32bit host with 32bit HOST_WIDE_INT. Is it > a signed vs. unsigned issue? stack_alignment_needed is unsigned. Yes, signed is the issue. Previously we'd have -stack_alignment_needed / 8 -256u / 8 0xffffff00u / 8 0x1fffffe0u If you receive a memory layout such that the stack is <= 0x1fffffff, the program will happen to work. With the cast we get -32 and not a large unsigned number, which is what we really wanted. r~
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c index dd81825..204211a 100644 --- a/gcc/config/i386/i386.c +++ b/gcc/config/i386/i386.c @@ -8639,7 +8639,8 @@ ix86_emit_save_reg_using_mov (enum machine_mode mode, unsigned int regno, reference to the locations within the frame. Instead, simply compute the location of the aligned frame from the frame pointer. */ - addr = GEN_INT (-crtl->stack_alignment_needed / BITS_PER_UNIT); + addr = GEN_INT (-(HOST_WIDE_INT)crtl->stack_alignment_needed + / BITS_PER_UNIT); addr = gen_rtx_AND (Pmode, hard_frame_pointer_rtx, addr); addr = plus_constant (addr, -cfa_offset); mem = gen_rtx_MEM (mode, addr);