The common igen code was forked from the ppc long ago. The lf module
is still pretty similar in API, so we can unfork them with a little
bit of effort.
Some of the generated ppc code is now slightly different, but that's
because of fixes the common igen code has gained, but not the ppc igen
code (e.g. fixing of #line numbers).
The ppc code retains lf_print__c_code because the common igen code
rewrote the logic to a new table.c API. Let's delay that in the ppc
code to at least unfork all this code.
Add standard multiple inclusion protection, and add a few missing
local includes when one header uses another. This isn't complete,
but fixes some short comings seen when merging the ppc igen.
The common sim-endian is a forked & updated version of the ppc code.
Fortunately, they didn't diverge from the basic APIs, so they are
still compatible, which means we can just delete the ppc version now
that the build env is merged at the top-level.
This is a bit redundant for most ports as they go through sim-basics.h
which always includes sim-types.h before including sim-endian.h, but in
order to unify ppc's sim-endian code, we need this include here. Plus,
it's the directly we generally want to go to get away from one header
that defines all APIs and causes hard to untangle dependencies.
The common/ code has macros with the same name but different behavior:
it's for declaring integer constants as 64-bit, not for casting them.
Rename ppc's local variant since it's only used in this file in order
to avoid conflicts.
The objects are still compiled in the subdir, but the creation of the
archive itself is in the top-level. This is a required step before we
can move compilation itself up, and makes it easier to review.
The downside is that each object compile is a recursive make instead of
a single one. It adds some overhead, so it's not great, but it shouldn't
be a big deal. This will go away once compilation is hoisted up.
Currently GDB when executing in reverse over multiple statements in a single
line of source code, GDB stops in the middle of the line. Thus requiring
multiple commands to reach the previous line. GDB should stop at the first
instruction of the line, not in the middle of the line.
The following description of the incorrect behavior was taken from an
earlier message by Pedro Alves <pedro@palves.net>:
https://sourceware.org/pipermail/gdb-patches/2023-January/196110.html
---------------------------------
The source line looks like:
func1 (); func2 ();
in the test case:
(gdb) list 1
1 void func1 ()
2 {
3 }
4
5 void func2 ()
6 {
7 }
8
9 int main ()
10 {
11 func1 (); func2 ();
12 }
compiled with:
$ gcc reverse.c -o reverse -g3 -O0
$ gcc -v
...
gcc version 11.3.0 (Ubuntu 11.3.0-1ubuntu1~22.04)
Now let's debug it with target record, using current gdb git master
(f3d8ae90b236),
$ gdb ~/reverse
GNU gdb (GDB) 14.0.50.20230124-git
...
Reading symbols from /home/pedro/reverse...
(gdb) start
Temporary breakpoint 1 at 0x1147: file reverse.c, line 11.
Starting program: /home/pedro/reverse
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Temporary breakpoint 1, main () at reverse.c:11
11 func1 (); func2 ();
(gdb) record
(gdb) disassemble /s
Dump of assembler code for function main:
reverse.c:
10 {
0x000055555555513f <+0>: endbr64
0x0000555555555143 <+4>: push %rbp
0x0000555555555144 <+5>: mov %rsp,%rbp
11 func1 (); func2 ();
=> 0x0000555555555147 <+8>: mov $0x0,%eax
0x000055555555514c <+13>: call 0x555555555129 <func1>
0x0000555555555151 <+18>: mov $0x0,%eax
0x0000555555555156 <+23>: call 0x555555555134 <func2>
0x000055555555515b <+28>: mov $0x0,%eax
12 }
0x0000555555555160 <+33>: pop %rbp
0x0000555555555161 <+34>: ret
End of assembler dump.
(gdb) n
12 }
So far so good, a "next" stepped over the whole of line 11 and stopped at
line 12.
Let's confirm where we are now:
(gdb) disassemble /s
Dump of assembler code for function main:
reverse.c:
10 {
0x000055555555513f <+0>: endbr64
0x0000555555555143 <+4>: push %rbp
0x0000555555555144 <+5>: mov %rsp,%rbp
11 func1 (); func2 ();
0x0000555555555147 <+8>: mov $0x0,%eax
0x000055555555514c <+13>: call 0x555555555129 <func1>
0x0000555555555151 <+18>: mov $0x0,%eax
0x0000555555555156 <+23>: call 0x555555555134 <func2>
0x000055555555515b <+28>: mov $0x0,%eax
12 }
=> 0x0000555555555160 <+33>: pop %rbp
0x0000555555555161 <+34>: ret
End of assembler dump.
Good, we're at the first instruction of line 12.
Now let's undo the "next", with "reverse-next":
(gdb) reverse-next
11 func1 (); func2 ();
Seemingly stopped at line 11. Let's see exactly where:
(gdb) disassemble /s
Dump of assembler code for function main:
reverse.c:
10 {
0x000055555555513f <+0>: endbr64
0x0000555555555143 <+4>: push %rbp
0x0000555555555144 <+5>: mov %rsp,%rbp
11 func1 (); func2 ();
0x0000555555555147 <+8>: mov $0x0,%eax
0x000055555555514c <+13>: call 0x555555555129 <func1>
=> 0x0000555555555151 <+18>: mov $0x0,%eax
0x0000555555555156 <+23>: call 0x555555555134 <func2>
0x000055555555515b <+28>: mov $0x0,%eax
12 }
0x0000555555555160 <+33>: pop %rbp
0x0000555555555161 <+34>: ret
End of assembler dump.
(gdb)
And lo, we stopped in the middle of line 11! That is a bug, we should have
stepped back all the way to the beginning of the line. The "reverse-next"
should have fully undone the prior "next" command.
--------------------
This patch fixes the incorrect GDB behavior by ensuring that GDB stops at
the first instruction in the line.
The test case gdb.reverse/func-map-to-same-line.exp is added to testsuite
to verify this fix when the line table information is and is not available.
When running GDB's testsuite on aarch64-linux/Ubuntu 20.04 (also spotted on
the ppc backend), there are failures in gdb.reverse/solib-precsave.exp and
gdb.reverse/solib-reverse.exp.
The failure happens around the following code:
38 b[1] = shr2(17); /* middle part two */
40 b[0] = 6; b[1] = 9; /* generic statement, end part two */
42 shr1 ("message 1\n"); /* shr1 one */
Normal execution:
- step from line 38 will land on line 40.
- step from line 40 will land on line 42.
Reverse execution:
- step from line 42 will land on line 40.
- step from line 40 will land on line 40.
- step from line 40 will land on line 38.
The problem here is that line 40 contains two contiguous but distinct
PC ranges in the line table, like so:
Line 40 - [0x7ec ~ 0x7f4]
Line 40 - [0x7f4 ~ 0x7fc]
The two distinct ranges are generated because GCC started outputting source
column information, which GDB doesn't take into account at the moment.
When stepping forward from line 40, we skip both of these ranges and land on
line 42. When stepping backward from line 42, we stop at the start PC of the
second (or first, going backwards) range of line 40.
Since we've reached ecs->event_thread->control.step_range_start, we stop
stepping backwards.
The above issues were fixed by introducing a new function that looks for
adjacent PC ranges for the same line, until we notice a line change. Then
we take that as the start PC of the range. The new start PC for the range
is used for the control.step_range_start when setting up a step range.
The test case gdb.reverse/map-to-same-line.exp is added to test the fix
for the above reverse step issues.
Patch has been tested on PowerPC, X86 and AArch64 with no regressions.
This patch adds two new options to gdb_compile to specify if the compile
should or should not generate the line table information. The
options are supported on clang and gcc version 7 and newer.
Patch has been tested on PowerPC with both gcc and clang.
This commit adds a mechanism for GDB to detect the linetable opcode
DW_LNS_set_epilogue_begin. This opcode is set by compilers to indicate
that a certain instruction marks the point where the frame is destroyed.
While the standard allows for multiple points marked with epilogue_begin
in the same function, for performance reasons, the function that
searches for the epilogue address will only find the last address that
sets this flag for a given block.
This commit also changes amd64_stack_frame_destroyed_p_1 to attempt to
use the epilogue begin directly, and only if an epilogue can't be found
will it attempt heuristics based on the current instruction.
Finally, this commit also changes the dwarf assembler to be able to emit
epilogue-begin instructions, to make it easier to test this patch
Approved-By: Tom Tromey <tom@tromey.com>
Now that the ppc configure script is just namespaced options, we can
move it to ppc/acinclude.m4 and include it directly in the top-level
configure script and kill off the last subdir configure script.
Switch from ad-hoc $silent checks & echo calls to standard
AC_MSG_CHECKING & AC_MSG_RESULT calls. Also delete pointless
variable setting after calling AC_MSG_ERROR.
Now that the ppc script only checks configure options and sets up
variables in the Makefile from those, delete all the compile related
logic to greatly simplify the configure script.
While the sim code doesn't utilize HAVE_LONG_LONG itself, other code
(like libiberty) seem to, so check for it in the top-level for all
ports to leverage.
Move the stub logic to the device files themselves. This makes the
configure & build logic more static which will make it easier to move
to the top-level build, and matches what we did with the common/ hw
tree already.
This also decouples the logic from the two -- in the past, you needed
both sem & shm in order to enable the device models, but now each one
is tied to its own independent knob. Practically speaking, this will
probably not make a difference, but it simplifies the build a bit.
Instead of executing code to see if SysV semaphores & shared memory
are available, switch to just a compile-time test. The system used
to compile might not match the system used to run the code wrt the
current kernel & OS settings, but the library APIs should. So move
the failures from compile-time to runtime so the program is more
portable, and works correctly even when cross-compiling.
Compile tests can use earlier defines, so hoist the HAVE_UNION_SEMUN
define to before the semaphore check, and use it in the test so that
we can merge the 2 versions into one.
This also defines HAVE_UNION_SEMUN even when ac_cv_sysv_sem is not
set, but that's OK as this define is only about a type existing, not
about whether the overall code is usable.
The first arg is the cache var name, and this one was typoed relative
to what the call actually set. We also don't need the manual call to
AC_MSG_RESULT as the AC_CACHE_CHECK takes care of it for us.
The common igen code provides the same misc APIs as the ppc version,
so delete the ppc code and pull in the common one. There is one
minor difference: the ppc code has a unique dumpf function. The
common code switched to lf_printf for the same functionality, but
since that requires changes throughout the igen codebase, delay that
cleanup for now so we can merge the rest.
We want to avoid conflicts with the common igen enums. This should
get migrated over to the common parsing logic, but for now, switch
the name to avoid redefinition.
Now that both igen implementations are in the top-level, we can unify
the filter_filename implementation between them since they're the same
(literally the same code).
