Re: [PATCH, DWARF] re-init dw_frame_pointer_regnum between functions
committed, thanks sorry for the delay. Christian On 10/14/2014 08:25 PM, Richard Henderson wrote: On 10/14/2014 06:02 AM, Christian Bruel wrote: 2014-09-23 Christian Bruel christian.br...@st.com * execute_dwarf2_frame (dw_frame_pointer_regnum): Reinitialize for each function. It's tempting to make this a local variable within dwarf2out_frame_debug_expr and not try to cache it at all. But this is ok. r~
[PATCH, DWARF] re-init dw_frame_pointer_regnum between functions
Hello,
ARM and Thumb modes use different hard_frame_pointer_regnum ABIs. The
problem is that dwarf2cfi.c:dw_frame_pointer_regnum cache is initialized
only once per file, when creating the CIE.
While testing the ARM attribute target to switch modes between
functions, I got a few assertion with -g, because this value gets
inconsistent with the respective FDEs that have different
hard_frame_pointer_rtx...
The snippet from dwarf2cfi.c illustrates the potential issue with the
mismatch between hard_frame_pointer_rtx and a badly set CFA register :
if (dest == hard_frame_pointer_rtx)
...
cur_cfa-reg = dw_frame_pointer_regnum;
...
I'm not aware of other targets giving the possibility to change the
frame_pointer_regnum ABI in a file, so the issue will only be show up
with the ARM target attribute. However I'd like very much your feedback
on this change, before I can send the remaining ARM parts.
Tested manually for arm-none-eabi with gdb, unwinding and frame access
seem OK when mixing modes.
x86 bootstrapped and regressions tests are running.
Many thanks,
Christian
2014-09-23 Christian Bruel christian.br...@st.com
* execute_dwarf2_frame (dw_frame_pointer_regnum): Reinitialize for each function.
Index: dwarf2cfi.c
===
--- dwarf2cfi.c (revision 216146)
+++ dwarf2cfi.c (working copy)
@@ -2860,7 +2860,6 @@
dw_trace_info cie_trace;
dw_stack_pointer_regnum = DWARF_FRAME_REGNUM (STACK_POINTER_REGNUM);
- dw_frame_pointer_regnum = DWARF_FRAME_REGNUM (HARD_FRAME_POINTER_REGNUM);
memset (cie_trace, 0, sizeof (cie_trace));
cur_trace = cie_trace;
@@ -2913,6 +2912,9 @@
static unsigned int
execute_dwarf2_frame (void)
{
+ /* Different HARD_FRAME_POINTER_REGNUM might coexist in the same file. */
+ dw_frame_pointer_regnum = DWARF_FRAME_REGNUM (HARD_FRAME_POINTER_REGNUM);
+
/* The first time we're called, compute the incoming frame state. */
if (cie_cfi_vec == NULL)
create_cie_data ();
Re: [PATCH, DWARF] re-init dw_frame_pointer_regnum between functions
On 10/14/2014 06:02 AM, Christian Bruel wrote: 2014-09-23 Christian Bruel christian.br...@st.com * execute_dwarf2_frame (dw_frame_pointer_regnum): Reinitialize for each function. It's tempting to make this a local variable within dwarf2out_frame_debug_expr and not try to cache it at all. But this is ok. r~
Re: [PATCH, DWARF] re-init dw_frame_pointer_regnum between functions
On 10/14/2014 11:25 AM, Richard Henderson wrote:
On 10/14/2014 06:02 AM, Christian Bruel wrote:
2014-09-23 Christian Bruel christian.br...@st.com
* execute_dwarf2_frame (dw_frame_pointer_regnum): Reinitialize for each
function.
It's tempting to make this a local variable within dwarf2out_frame_debug_expr
and not try to cache it at all.
But this is ok.
For the record, this also points out that the arm backend ought to be weaned
away from using dwarf2out_frame_debug_expr and use the REG_CFA_* notes
exclusively. That would also fix an apparent error in arm_expand_prologue:
if (IS_INTERRUPT (func_type))
{
/* Interrupt functions must not corrupt any registers.
Creating a frame pointer however, corrupts the IP
register, so we must push it first. */
emit_multi_reg_push (1 IP_REGNUM, 1 IP_REGNUM);
/* Do not set RTX_FRAME_RELATED_P on this insn.
The dwarf stack unwinding code only wants to see one
stack decrement per function, and this is not it. If
this instruction is labeled as being part of the frame
creation sequence then dwarf2out_frame_debug_expr will
die when it encounters the assignment of IP to FP
later on, since the use of SP here establishes SP as
the CFA register and not IP.
Anyway this instruction is not really part of the stack
frame creation although it is part of the prologue. */
Certainly dwarf2cfi can handle arbitrary REG_CFA_ADJUST_CFA notes;
it's just the frame_debug_expr state machine that gets confused.
r~
