This affects only the RISC-V targets, where the compiler options
-gvariable-location-views and consequently also -ginline-points
are disabled by default, which is unexpected and disables some
useful features of the generated debug info.
Due to a bug in the gas assembler the .loc statement
is not usable to generate location view debug info.
That is detected by configure:
configure:31500: checking assembler for dwarf2 debug_view support
configure:31509: .../riscv-unknown-elf/bin/as -o conftest.o conftest.s >&5
conftest.s: Assembler messages:
conftest.s:5: Error: .uleb128 only supports constant or subtract expressions
conftest.s:6: Error: .uleb128 only supports constant or subtract expressions
configure:31512: $? = 1
configure: failed program was
.file 1 "conftest.s"
.loc 1 3 0 view .LVU1
nop
.data
.uleb128 .LVU1
.uleb128 .LVU1
configure:31523: result: no
This results in dwarf2out_as_locview_support being set to false,
and that creates a sequence of events, with the end result that
most inlined functions either have no DW_AT_entry_pc, or one
with a wrong entry pc value.
But the location views can also be generated without using any
.loc statements, therefore we should enable the option
-gvariable-location-views by default, regardless of the status
of -gas-locview-support.
Note however, that the combination of the following compiler options
-g -O2 -gvariable-location-views -gno-as-loc-support
turned out to create invalid assembler intermediate files,
with lots of assembler errors like:
Error: leb128 operand is an undefined symbol: .LVU3
This affects all targets, except RISC-V of course ;-)
and is fixed by the changes in dwarf2out.c
Finally the .debug_loclists created without assembler locview support
did contain location view pairs like v0000000ffffffff v000000000000000
which is the value from FORCE_RESET_NEXT_VIEW, but that is most likely
not as expected either, so change that as well.
---
gcc/dwarf2out.cc | 16 ++++++++++------
gcc/toplev.cc | 4 +---
2 files changed, 11 insertions(+), 9 deletions(-)
v2: fixed the boot-strap error triggered by v1 on any target, except RISC-V,
the issue was triggered by libstdc++-v3/src/c++11/cxx11-ios_failure-lt.s
which is generated using -gno-as-loc-support, which triggered a latent issue.
diff --git a/gcc/dwarf2out.cc b/gcc/dwarf2out.cc
index 346feeb53c8..79f97b5a55e 100644
--- a/gcc/dwarf2out.cc
+++ b/gcc/dwarf2out.cc
@@ -10374,7 +10374,7 @@ dwarf2out_maybe_output_loclist_view_pair
(dw_loc_list_ref curr)
#ifdef DW_LLE_view_pair
dw2_asm_output_data (1, DW_LLE_view_pair, "DW_LLE_view_pair");
- if (dwarf2out_as_locview_support)
+ if (dwarf2out_as_locview_support && dwarf2out_as_loc_support)
{
if (ZERO_VIEW_P (curr->vbegin))
dw2_asm_output_data_uleb128 (0, "Location view begin");
@@ -10396,8 +10396,10 @@ dwarf2out_maybe_output_loclist_view_pair
(dw_loc_list_ref curr)
}
else
{
- dw2_asm_output_data_uleb128 (curr->vbegin, "Location view begin");
- dw2_asm_output_data_uleb128 (curr->vend, "Location view end");
+ dw2_asm_output_data_uleb128 (ZERO_VIEW_P (curr->vbegin)
+ ? 0 : curr->vbegin, "Location view begin");
+ dw2_asm_output_data_uleb128 (ZERO_VIEW_P (curr->vend)
+ ? 0 : curr->vend, "Location view end");
}
#endif /* DW_LLE_view_pair */
@@ -10430,7 +10432,7 @@ output_loc_list (dw_loc_list_ref list_head)
vcount++;
/* ?? dwarf_split_debug_info? */
- if (dwarf2out_as_locview_support)
+ if (dwarf2out_as_locview_support && dwarf2out_as_loc_support)
{
char label[MAX_ARTIFICIAL_LABEL_BYTES];
@@ -10460,10 +10462,12 @@ output_loc_list (dw_loc_list_ref list_head)
}
else
{
- dw2_asm_output_data_uleb128 (curr->vbegin,
+ dw2_asm_output_data_uleb128 (ZERO_VIEW_P (curr->vbegin)
+ ? 0 : curr->vbegin,
"View list begin (%s)",
list_head->vl_symbol);
- dw2_asm_output_data_uleb128 (curr->vend,
+ dw2_asm_output_data_uleb128 (ZERO_VIEW_P (curr->vend)
+ ? 0 : curr->vend,
"View list end (%s)",
list_head->vl_symbol);
}
diff --git a/gcc/toplev.cc b/gcc/toplev.cc
index eee4805b504..292948122de 100644
--- a/gcc/toplev.cc
+++ b/gcc/toplev.cc
@@ -1475,9 +1475,7 @@ process_options ()
= (flag_var_tracking
&& debug_info_level >= DINFO_LEVEL_NORMAL
&& dwarf_debuginfo_p ()
- && !dwarf_strict
- && dwarf2out_as_loc_support
- && dwarf2out_as_locview_support);
+ && !dwarf_strict);
}
else if (debug_variable_location_views == -1 && dwarf_version != 5)
{
--
2.39.2
