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 ();
