| Message ID | 20170917125123.GP3528@bubble.grove.modra.org |
|---|---|
| State | New |
| Headers | show |
| Series | [RS6000] PR81996, __builtin_return_address(0) fails | expand |
On Sun, Sep 17, 2017 at 10:21:23PM +0930, Alan Modra wrote: > When -fstack-protector-all or -fsanitize=address, rs6000.h sets > FRAME_GROWS_DOWNWARD. This breaks the assumption in > rs6000_return_addr that the stack link is at frame_pointer+0. Well, builtin_return_address(N) already works correctly for N>0, getting the backlink via the frame pointer; it's fetching the return address via the frame pointer that doesn't work. Okay for trunk (and backports later) with those comments fixed. Thanks! Segher > PR target/81996 > * gcc/config/rs6000/rs6000.c (rs6000_return_addr): Use > stack_pointer_rtx for count 0. Update comments. Break up > large rtl expression. > > diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c > index e611c45..f14392d 100644 > --- a/gcc/config/rs6000/rs6000.c > +++ b/gcc/config/rs6000/rs6000.c > @@ -24988,24 +24988,23 @@ debug_stack_info (rs6000_stack_t *info) > rtx > rs6000_return_addr (int count, rtx frame) > { > - /* Currently we don't optimize very well between prolog and body > - code and for PIC code the code can be actually quite bad, so > - don't try to be too clever here. */ > + /* We can't use get_hard_reg_initial_val for LR when count == 0 if LR > + is trashed by the prologue, as it is for PIC on ABI_V4 and Darwin. */ > if (count != 0 > || ((DEFAULT_ABI == ABI_V4 || DEFAULT_ABI == ABI_DARWIN) && flag_pic)) > { > cfun->machine->ra_needs_full_frame = 1; > > - return > - gen_rtx_MEM > - (Pmode, > - memory_address > - (Pmode, > - plus_constant (Pmode, > - copy_to_reg > - (gen_rtx_MEM (Pmode, > - memory_address (Pmode, frame))), > - RETURN_ADDRESS_OFFSET))); > + if (count == 0) > + /* FRAME is set to frame_pointer_rtx by the generic code, but that > + is good for loading 0(r1) only when !FRAME_GROWS_DOWNWARD. */ > + frame = stack_pointer_rtx; > + rtx prev_frame_addr = memory_address (Pmode, frame); > + rtx prev_frame = copy_to_reg (gen_rtx_MEM (Pmode, prev_frame_addr)); > + rtx lr_save_off = plus_constant (Pmode, > + prev_frame, RETURN_ADDRESS_OFFSET); > + rtx lr_save_addr = memory_address (Pmode, lr_save_off); > + return gen_rtx_MEM (Pmode, lr_save_addr); > } > > cfun->machine->ra_need_lr = 1;
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c index e611c45..f14392d 100644 --- a/gcc/config/rs6000/rs6000.c +++ b/gcc/config/rs6000/rs6000.c @@ -24988,24 +24988,23 @@ debug_stack_info (rs6000_stack_t *info) rtx rs6000_return_addr (int count, rtx frame) { - /* Currently we don't optimize very well between prolog and body - code and for PIC code the code can be actually quite bad, so - don't try to be too clever here. */ + /* We can't use get_hard_reg_initial_val for LR when count == 0 if LR + is trashed by the prologue, as it is for PIC on ABI_V4 and Darwin. */ if (count != 0 || ((DEFAULT_ABI == ABI_V4 || DEFAULT_ABI == ABI_DARWIN) && flag_pic)) { cfun->machine->ra_needs_full_frame = 1; - return - gen_rtx_MEM - (Pmode, - memory_address - (Pmode, - plus_constant (Pmode, - copy_to_reg - (gen_rtx_MEM (Pmode, - memory_address (Pmode, frame))), - RETURN_ADDRESS_OFFSET))); + if (count == 0) + /* FRAME is set to frame_pointer_rtx by the generic code, but that + is good for loading 0(r1) only when !FRAME_GROWS_DOWNWARD. */ + frame = stack_pointer_rtx; + rtx prev_frame_addr = memory_address (Pmode, frame); + rtx prev_frame = copy_to_reg (gen_rtx_MEM (Pmode, prev_frame_addr)); + rtx lr_save_off = plus_constant (Pmode, + prev_frame, RETURN_ADDRESS_OFFSET); + rtx lr_save_addr = memory_address (Pmode, lr_save_off); + return gen_rtx_MEM (Pmode, lr_save_addr); } cfun->machine->ra_need_lr = 1;