Summary:
This adds support for LSDA (exception table) generation for wasm EH.
Wasm EH mostly follows the structure of Itanium-style exception tables,
with one exception: a call site table entry in wasm EH corresponds to
not a call site but a landing pad.
In wasm EH, the VM is responsible for stack unwinding. After an
exception occurs and the stack is unwound, the control flow is
transferred to wasm 'catch' instruction by the VM, after which the
personality function is called from the compiler-generated code. (Refer
to WasmEHPrepare pass for more information on this part.)
This patch:
- Changes wasm.landingpad.index intrinsic to take a token argument, to
make this 1:1 match with a catchpad instruction
- Stores landingpad index info and catch type info MachineFunction in
before instruction selection
- Lowers wasm.lsda intrinsic to an MCSymbol pointing to the start of an
exception table
- Adds WasmException class with overridden methods for table generation
- Adds support for LSDA section in Wasm object writer
Reviewers: dschuff, sbc100, rnk
Subscribers: mgorny, jgravelle-google, sunfish, llvm-commits
Differential Revision: https://reviews.llvm.org/D52748
llvm-svn: 344575
The initial patch was not reviewed, and does not have any tests;
it should not have been merged.
This reverts 344395, 344390, 344387, 344385, 344381, 344376,
and 344366.
llvm-svn: 344405
Summary: We can fill in the command line and compiler path later if we want.
Reviewers: zturner
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D53179
llvm-svn: 344393
This a resubmission of a patch which was previously reverted
due to breaking several lld tests. The issues causing those
failures have been fixed, so the patch is now resubmitted.
---Original Commit Message---
While it doesn't make a *ton* of sense for POSIX paths to be
in PDBs, it's possible to occur in real scenarios involving
cross compilation.
The tools need to be able to handle this, because certain types
of debugging scenarios are possible without a running process
and so don't necessarily require you to be on a Windows system.
These include post-mortem debugging and binary forensics (e.g.
using a debugger to disassemble functions and examine symbols
without running the process).
There's changes in clang, LLD, and lldb in this patch. After
this the cross-platform disassembly and source-list tests pass
on Linux.
Furthermore, the behavior of LLD can now be summarized by a much
simpler rule than before: Unless you specify /pdbsourcepath and
/pdbaltpath, the PDB ends up with paths that are valid within
the context of the machine that the link is performed on.
Differential Revision: https://reviews.llvm.org/D53149
llvm-svn: 344377
* Move #include outside of namespaces
* Add missing #include
* Add out-of-line virtual destructor to BTFTypeEntry
designated initializers should also be fixed
llvm-svn: 344376
BTF is the debug format for BPF, a kernel virtual machine
and widely used for tracing, networking and security, etc ([1]).
Currently only instruction streams are passed to kernel,
the kernel verifier verifies them before execution. In order to
provide better visibility of bpf programs to user space
tools, some debug information, e.g., function names and
debug line information are desirable for kernel so tools
can get such information with better annotation
for jited instructions for performance or other reasons.
The dwarf is too complicated in kernel and for BPF.
Hence, BTF is designed to be the debug format for BPF ([2]).
Right now, pahole supports BTF for types, which
are generated based on dwarf sections in the ELF file.
In order to annotate performance metrics for jited bpf insns,
it is necessary to pass debug line info to the kernel.
Furthermore, we want to pass the actual code to the
kernel because of the following reasons:
. bpf program typically is small so storage overhead
should be small.
. in bpf land, it is totally possible that
an application loads the bpf program into the
kernel and then that application quits, so
holding debug info by the user space application
is not practical.
. having source codes directly kept by kernel
would ease deployment since the original source
code does not need ship on every hosts and
kernel-devel package does not need to be
deployed even if kernel headers are used.
The only reliable time to get the source code is
during compilation time. This will result in both more
accurate information and easier deployment as
stated in the above.
Another consideration is for JIT. The project like bcc
use MCJIT to compile a C program into bpf insns and
load them to the kernel ([3]). The generated BTF sections
will be readily available for such cases as well.
This patch implemented generation of BTF info in llvm
compiler. The BTF related sections will be generated
when both -target bpf and -g are specified. Two sections
are generated:
.BTF contains all the type and string information, and
.BTF.ext contains the func_info and line_info.
The separation is related to how two sections are used
differently in bpf loader, e.g., linux libbpf ([4]).
The .BTF section can be loaded into the kernel directly
while .BTF.ext needs loader manipulation before loading
to the kernel. The format of the each section is roughly
defined in llvm:include/llvm/MC/MCBTFContext.h and
from the implementation in llvm:lib/MC/MCBTFContext.cpp.
A later example also shows the contents in each section.
The type and func_info are gathered during CodeGen/AsmPrinter
by traversing dwarf debug_info. The line_info is
gathered in MCObjectStreamer before writing to
the object file. After all the information is gathered,
the two sections are emitted in MCObjectStreamer::finishImpl.
With cmake CMAKE_BUILD_TYPE=Debug, the compiler can
dump out all the tables except insn offset, which
will be resolved later as relocation records.
The debug type "btf" is used for BTFContext dump.
Dwarf tests the debug info generation with
llvm-dwarfdump to decode the binary sections and
check whether the result is expected. Currently
we do not have such a tool yet. We will implement
btf dump functionality in bpftool ([5]) as the bpftool is
considered the recommended tool for bpf introspection.
The implementation for type and func_info is tested
with linux kernel test cases. The line_info is visually
checked with dump from linux kernel libbpf ([4]) and
checked with readelf dumping section raw data.
Note that the .BTF and .BTF.ext information will not
be emitted to assembly code and there is no assembler
support for BTF either.
In the below, with a clang/llvm built with CMAKE_BUILD_TYPE=Debug,
Each table contents are shown for a simple C program.
-bash-4.2$ cat -n test.c
1 struct A {
2 int a;
3 char b;
4 };
5
6 int test(struct A *t) {
7 return t->a;
8 }
-bash-4.2$ clang -O2 -target bpf -g -mllvm -debug-only=btf -c test.c
Type Table:
[1] FUNC name_off=1 info=0x0c000001 size/type=2
param_type=3
[2] INT name_off=12 info=0x01000000 size/type=4
desc=0x01000020
[3] PTR name_off=0 info=0x02000000 size/type=4
[4] STRUCT name_off=16 info=0x04000002 size/type=8
name_off=18 type=2 bit_offset=0
name_off=20 type=5 bit_offset=32
[5] INT name_off=22 info=0x01000000 size/type=1
desc=0x02000008
String Table:
0 :
1 : test
6 : .text
12 : int
16 : A
18 : a
20 : b
22 : char
27 : test.c
34 : int test(struct A *t) {
58 : return t->a;
FuncInfo Table:
sec_name_off=6
insn_offset=<Omitted> type_id=1
LineInfo Table:
sec_name_off=6
insn_offset=<Omitted> file_name_off=27 line_off=34 line_num=6 column_num=0
insn_offset=<Omitted> file_name_off=27 line_off=58 line_num=7 column_num=3
-bash-4.2$ readelf -S test.o
......
[12] .BTF PROGBITS 0000000000000000 0000028d
00000000000000c1 0000000000000000 0 0 1
[13] .BTF.ext PROGBITS 0000000000000000 0000034e
0000000000000050 0000000000000000 0 0 1
[14] .rel.BTF.ext REL 0000000000000000 00000648
0000000000000030 0000000000000010 16 13 8
......
-bash-4.2$
The latest linux kernel ([6]) can already support .BTF with type information.
The [7] has the reference implementation in linux kernel side
to support .BTF.ext func_info. The .BTF.ext line_info support is not
implemented yet. If you have difficulty accessing [6], you can
manually do the following to access the code:
git clone https://github.com/yonghong-song/bpf-next-linux.git
cd bpf-next-linux
git checkout btf
The change will push to linux kernel soon once this patch is landed.
References:
[1]. https://www.kernel.org/doc/Documentation/networking/filter.txt
[2]. https://lwn.net/Articles/750695/
[3]. https://github.com/iovisor/bcc
[4]. https://github.com/torvalds/linux/tree/master/tools/lib/bpf
[5]. https://github.com/torvalds/linux/tree/master/tools/bpf/bpftool
[6]. https://github.com/torvalds/linux
[7]. https://github.com/yonghong-song/bpf-next-linux/tree/btf
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Differential Revision: https://reviews.llvm.org/D52950
llvm-svn: 344366
It originally triggered a stepping problem in the debugger, which could
be fixed by adjusting CodeGen/LexicalScopes.cpp however it seems we prefer
the previous behavior anyway.
See the discussion for details: http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20181008/593833.html
This reverts commit r343880.
This reverts commit r343874.
llvm-svn: 344318
This was originally causing some test failures on non-Windows
platforms, which required fixes in the compiler and linker. After
those fixes, however, other tests started failing. Reverting
temporarily until I can address everything.
llvm-svn: 344279
While it doesn't make a *ton* of sense for POSIX paths to be
in PDBs, it's possible to occur in real scenarios involving
cross compilation.
The tools need to be able to handle this, because certain types
of debugging scenarios are possible without a running process
and so don't necessarily require you to be on a Windows system.
These include post-mortem debugging and binary forensics (e.g.
using a debugger to disassemble functions and examine symbols
without running the process).
There's changes in clang, LLD, and lldb in this patch. After
this the cross-platform disassembly and source-list tests pass
on Linux.
Furthermore, the behavior of LLD can now be summarized by a much
simpler rule than before: Unless you specify /pdbsourcepath and
/pdbaltpath, the PDB ends up with paths that are valid within
the context of the machine that the link is performed on.
Differential Revision: https://reviews.llvm.org/D53149
llvm-svn: 344269
DWARF v5 introduces DW_AT_call_all_calls, a subprogram attribute which
indicates that all calls (both regular and tail) within the subprogram
have call site entries. The information within these call site entries
can be used by a debugger to populate backtraces with synthetic tail
call frames.
Tail calling frames go missing in backtraces because the frame of the
caller is reused by the callee. Call site entries allow a debugger to
reconstruct a sequence of (tail) calls which led from one function to
another. This improves backtrace quality. There are limitations: tail
recursion isn't handled, variables within synthetic frames may not
survive to be inspected, etc. This approach is not novel, see:
https://gcc.gnu.org/wiki/summit2010?action=AttachFile&do=get&target=jelinek.pdf
This patch adds an IR-level flag (DIFlagAllCallsDescribed) which lowers
to DW_AT_call_all_calls. It adds the minimal amount of DWARF generation
support needed to emit standards-compliant call site entries. For easier
deployment, when the debugger tuning is LLDB, the DWARF requirement is
adjusted to v4.
Testing: Apart from check-{llvm, clang}, I built a stage2 RelWithDebInfo
clang binary. Its dSYM passed verification and grew by 1.4% compared to
the baseline. 151,879 call site entries were added.
rdar://42001377
Differential Revision: https://reviews.llvm.org/D49887
llvm-svn: 343883
Context: Compiler generated instructions do not have a debug location
assigned to them. However emitting 0-line records for all of them bloats
the line tables for very little benefit so we usually avoid doing that.
Not emitting anything will lead to the previous debug location getting
applied to the locationless instructions. This is not desirable for
block begin and after labels. Previously we would emit simply emit
line-0 records in this case, this patch changes the behavior to do a
forward search for a debug location in these cases before emitting a
line-0 record to further reduce line table bloat.
Inspired by the discussion in https://reviews.llvm.org/D52862
llvm-svn: 343874
Summary:
Use the newly added DebugInfo (DI) Trivial flag, which indicates if a C++ record is trivial or not, to determine Codeview::FunctionOptions.
Clang and MSVC generate slightly different Codeview for C++ records. For example, here is the C++ code for a class with a defaulted ctor,
class C {
public:
C() = default;
};
Clang will produce a LF for the defaulted ctor while MSVC does not. For more details, refer to FIXMEs in the test cases in "function-options.ll" included with this set of changes.
Reviewers: zturner, rnk, llvm-commits, aleksandr.urakov
Reviewed By: rnk
Subscribers: Hui, JDevlieghere
Differential Revision: https://reviews.llvm.org/D45123
llvm-svn: 343626
Add the .cv_fpo_stackalign directive so that we can define $T0, or the
VFRAME virtual register, with it. This was overlooked in the initial
implementation because unlike MSVC, we push CSRs before allocating stack
space, so this value is only needed to describe local variable
locations. Variables that the compiler now addresses via ESP are instead
described as being stored at offsets from VFRAME, which for us is ESP
after alignment in the prologue.
This adds tests that show that we use the VFRAME register properly in
our S_DEFRANGE records, and that we emit the correct FPO data to define
it.
Fixes PR38857
llvm-svn: 343603
Summary:
Before this change, LLVM would always describe locals on the stack as
being relative to some specific register, RSP, ESP, EBP, ESI, etc.
Variables in stack memory are pretty common, so there is a special
S_DEFRANGE_FRAMEPOINTER_REL symbol for them. This change uses it to
reduce the size of our debug info.
On top of the size savings, there are cases on 32-bit x86 where local
variables are addressed from ESP, but ESP changes across the function.
Unlike in DWARF, there is no FPO data to describe the stack adjustments
made to push arguments onto the stack and pop them off after the call,
which makes it hard for the debugger to find the local variables in
frames further up the stack.
To handle this, CodeView has a special VFRAME register, which
corresponds to the $T0 variable set by our FPO data in 32-bit. Offsets
to local variables are instead relative to this value.
This is part of PR38857.
Reviewers: hans, zturner, javed.absar
Subscribers: aprantl, hiraditya, JDevlieghere, llvm-commits
Differential Revision: https://reviews.llvm.org/D52217
llvm-svn: 343543
There are a few leftovers in rL343163 which span two lines. This commit
changes these llvm::sort(C.begin(), C.end, ...) to llvm::sort(C, ...)
llvm-svn: 343426
- Add fix so that all code paths that create DWARFContext
with an ObjectFile initialise the target architecture in the context
- Add an assert that the Arch is known in the Dwarf CallFrameString method
llvm-svn: 343317
This caused the DebugInfo/Sparc/gnu-window-save.ll test to fail.
> Functions that have signed return addresses need additional dwarf support:
> - After signing the LR, and before authenticating it, the LR register is in a
> state the is unusable by a debugger or unwinder
> - To account for this a new directive, .cfi_negate_ra_state, is added
> - This directive says the signed state of the LR register has now changed,
> i.e. unsigned -> signed or signed -> unsigned
> - This directive has the same CFA code as the SPARC directive GNU_window_save
> (0x2d), adding a macro to account for multiply defined codes
> - This patch matches the gcc implementation of this support:
> https://patchwork.ozlabs.org/patch/800271/
>
> Differential Revision: https://reviews.llvm.org/D50136
llvm-svn: 343103
Functions that have signed return addresses need additional dwarf support:
- After signing the LR, and before authenticating it, the LR register is in a
state the is unusable by a debugger or unwinder
- To account for this a new directive, .cfi_negate_ra_state, is added
- This directive says the signed state of the LR register has now changed,
i.e. unsigned -> signed or signed -> unsigned
- This directive has the same CFA code as the SPARC directive GNU_window_save
(0x2d), adding a macro to account for multiply defined codes
- This patch matches the gcc implementation of this support:
https://patchwork.ozlabs.org/patch/800271/
Differential Revision: https://reviews.llvm.org/D50136
llvm-svn: 343089
In some senario, LLVM will remove llvm.dbg.labels in IR. For example,
when the labels are in unreachable blocks, these labels will not
be generated in LLVM IR. In the case, these debug labels will have
address zero as their address. It is not legal address for debugger to
set breakpoints or query sources. So, the patch inhibits the address info
(DW_AT_low_pc) of removed labels.
Fix build failed in BuildBot, clang-stage1-cmake-RA-incremental, on macOS.
Differential Revision: https://reviews.llvm.org/D51908
llvm-svn: 343062
In some senario, LLVM will remove llvm.dbg.labels in IR. For example,
when the labels are in unreachable blocks, these labels will not
be generated in LLVM IR. In the case, these debug labels will have
address zero as their address. It is not legal address for debugger to
set breakpoints or query sources. So, the patch inhibits the address info
(DW_AT_low_pc) of removed labels.
Differential Revision: https://reviews.llvm.org/D51908
llvm-svn: 342943
Currently, we emit DW_AT_addr_base that points to the beginning of
the .debug_addr section. That is not correct for the DWARF5 case because address
table contains the header and the attribute should point to the first entry
following the header.
This is currently the reason why LLDB does not work with such executables correctly.
Patch fixes the issue.
Differential revision: https://reviews.llvm.org/D52168
llvm-svn: 342635
std::vector::iterator type may be a pointer, then
iterator::value_type fails to compile since iterator is not a class,
namespace, or enumeration.
Patch by orivej (Orivej Desh)
Differential Revision: https://reviews.llvm.org/D52142
llvm-svn: 342354
This patch removes addBlockByrefAddress(), it is dead code as far as
clang is concerned: Every byref block capture is emitted with a
complex expression that is equivalent to what this function does.
rdar://problem/31629055
Differential Revision: https://reviews.llvm.org/D51763
llvm-svn: 341737
In DwarfDebug::collectEntityInfo(), if the label entity is processed in
DbgLabels list, it means the label is not optimized out. There is no
need to generate debug info for it with null position.
llvm-svn: 341513
Normalize common kinds of DWARF sub-expressions to make debug info
encoding a bit more compact:
DW_OP_constu [X < 32] -> DW_OP_litX
DW_OP_constu [all ones] -> DW_OP_lit0, DW_OP_not (64-bit only)
Differential revision: https://reviews.llvm.org/D51640
llvm-svn: 341457
This removes the FrameAccess struct that was added to the interface
in D51537, since the PseudoValue from the MachineMemoryOperand
can be safely casted to a FixedStackPseudoSourceValue.
Reviewers: MatzeB, thegameg, javed.absar
Reviewed By: thegameg
Differential Revision: https://reviews.llvm.org/D51617
llvm-svn: 341454
For instructions that spill/fill to and from multiple frame-indices
in a single instruction, hasStoreToStackSlot and hasLoadFromStackSlot
should return an array of accesses, rather than just the first encounter
of such an access.
This better describes FI accesses for AArch64 (paired) LDP/STP
instructions.
Reviewers: t.p.northover, gberry, thegameg, rengolin, javed.absar, MatzeB
Reviewed By: MatzeB
Differential Revision: https://reviews.llvm.org/D51537
llvm-svn: 341301
Summary:
This is a continuation of https://reviews.llvm.org/D49727
Below the original text, current changes in the comments:
Currently, in line with GCC, when specifying reserved registers like sp or pc on an inline asm() clobber list, we don't always preserve the original value across the statement. And in general, overwriting reserved registers can have surprising results.
For example:
extern int bar(int[]);
int foo(int i) {
int a[i]; // VLA
asm volatile(
"mov r7, #1"
:
:
: "r7"
);
return 1 + bar(a);
}
Compiled for thumb, this gives:
$ clang --target=arm-arm-none-eabi -march=armv7a -c test.c -o - -S -O1 -mthumb
...
foo:
.fnstart
@ %bb.0: @ %entry
.save {r4, r5, r6, r7, lr}
push {r4, r5, r6, r7, lr}
.setfp r7, sp, #12
add r7, sp, #12
.pad #4
sub sp, #4
movs r1, #7
add.w r0, r1, r0, lsl #2
bic r0, r0, #7
sub.w r0, sp, r0
mov sp, r0
@APP
mov.w r7, #1
@NO_APP
bl bar
adds r0, #1
sub.w r4, r7, #12
mov sp, r4
pop {r4, r5, r6, r7, pc}
...
r7 is used as the frame pointer for thumb targets, and this function needs to restore the SP from the FP because of the variable-length stack allocation a. r7 is clobbered by the inline assembly (and r7 is included in the clobber list), but LLVM does not preserve the value of the frame pointer across the assembly block.
This type of behavior is similar to GCC's and has been discussed on the bugtracker: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=11807 . No consensus seemed to have been reached on the way forward. Clang behavior has briefly been discussed on the CFE mailing (starting here: http://lists.llvm.org/pipermail/cfe-dev/2018-July/058392.html). I've opted for following Eli Friedman's advice to print warnings when there are reserved registers on the clobber list so as not to diverge from GCC behavior for now.
The patch uses MachineRegisterInfo's target-specific knowledge of reserved registers, just before we convert the inline asm string in the AsmPrinter.
If we find a reserved register, we print a warning:
repro.c:6:7: warning: inline asm clobber list contains reserved registers: R7 [-Winline-asm]
"mov r7, #1"
^
Reviewers: efriedma, olista01, javed.absar
Reviewed By: efriedma
Subscribers: eraman, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D51165
llvm-svn: 341062
Variables declared with the dllimport attribute are accessed via a
stub variable named __imp_<var>. In MinGW configurations, variables that
aren't declared with a dllimport attribute might still end up imported
from another DLL with runtime pseudo relocs.
For x86_64, this avoids the risk that the target is out of range
for a 32 bit PC relative reference, in case the target DLL is loaded
further than 4 GB from the reference. It also avoids having to make the
text section writable at runtime when doing the runtime fixups, which
makes it worthwhile to do for i386 as well.
Add stub variables for all dso local data references where a definition
of the variable isn't visible within the module, since the DLL data
autoimporting might make them imported even though they are marked as
dso local within LLVM.
Don't do this for variables that actually are defined within the same
module, since we then know for sure that it actually is dso local.
Don't do this for references to functions, since there's no need for
runtime pseudo relocations for autoimporting them; if a function from
a different DLL is called without the appropriate dllimport attribute,
the call just gets routed via a thunk instead.
GCC does something similar since 4.9 (when compiling with -mcmodel=medium
or large; from that version, medium is the default code model for x86_64
mingw), but only for x86_64.
Differential Revision: https://reviews.llvm.org/D51288
llvm-svn: 340942
Firstly, require the symbol to be used within the module. If a
symbol is unused within a module, then by definition it cannot be
address-significant within that module. This condition is useful on all
platforms because it could make symbol tables smaller -- without this
change, emitting an address-significance table could cause otherwise
unused undefined symbols to be added to the object file.
But this change is necessary with COFF specifically in order to
preserve the property that an unreferenced undefined symbol in an IR
module does not result in a link failure. This is already the case for
ELF because ELF linkers only reject links with unresolved symbols if
there is a relocation to that symbol, but COFF linkers require all
undefined symbols to be resolved regardless of relocations. So if
a module contains an unreferenced undefined symbol, we need to make
sure not to add it to the address-significance table (and thus the
symbol table) in case it doesn't end up resolved at link time.
Secondly, do not add dllimport symbols to the table. These symbols
won't be able to be resolved because their definitions live in another
module and are accessed via the IAT, and the address-significance
table has no effect on other modules anyway. It wouldn't make sense
to add the IAT entry symbol to the address-significance table either
because the IAT entry isn't address-significant -- the generated code
never takes its address.
Differential Revision: https://reviews.llvm.org/D51199
llvm-svn: 340648
My previoust test case had skipped CUs from one TU out of a two-TU LTO
scenario, which meant the CU index wasn't needed (as it was unambiguous
which CU a table entry applied to) - expanding the test to use 3 TUs,
skipping one (so long as it's not the last one) shows the indexes are
miscomputed. Fix that with a little indirection for the index.
llvm-svn: 340646
There are two forms for label debug information in DWARF format.
1. Labels in a non-inlined function:
DW_TAG_label
DW_AT_name
DW_AT_decl_file
DW_AT_decl_line
DW_AT_low_pc
2. Labels in an inlined function:
DW_TAG_label
DW_AT_abstract_origin
DW_AT_low_pc
We will collect label information from DBG_LABEL. Before every DBG_LABEL,
we will generate a temporary symbol to denote the location of the label.
The symbol could be used to get DW_AT_low_pc afterwards. So, we create a
mapping between 'inlined label' and DBG_LABEL MachineInstr in DebugHandlerBase.
The DBG_LABEL in the mapping is used to query the symbol before it.
The AbstractLabels in DwarfCompileUnit is used to process labels in inlined
functions.
We also keep a mapping between scope and labels in DwarfFile to help to
generate correct tree structure of DIEs.
It also generates label debug information under global isel.
Differential Revision: https://reviews.llvm.org/D45556
llvm-svn: 340039
Fangrui Song