We use `jitlink-check` lines in LIT tests as the primary tool for
testing JITLink backends. Parsing and evaluation of the expressions is
implemented in `RuntimeDyldChecker`. The `stub_addr(obj, name)`
expression allows to obtain the linker-generated stub for the external
symbol `name` in object file `obj`.
This patch adds support for a filter parameter to select one out of many
stubs. This is necessary for the AArch32 JITLink backend, which must be
able to emit two different kinds of stubs depending on the instruction
set state (Arm/Thumb) of the relocation site. Since the new parameter is
optional, we don't have to update existing tests.
Filters are regular expressions without brackets that match exactly one
existing stub. Given object file `armv7.o` with two stubs for external
function `ext` of kinds `armv7_abs_le` and `thumbv7_abs_le`, we get the
following filter results e.g.:
```
stub_addr(armv7.o, ext, thumb) thumbv7_abs_le
stub_addr(armv7.o, ext, thumbv7) thumbv7_abs_le
stub_addr(armv7.o, ext, armv7_abs_le) armv7_abs_le
stub_addr(armv7.o, ext, v7_.*_le) Error: "ext" has 2 candidate stubs in file "armv7.o". Please refine stub-kind filter "v7_.*_le" for disambiguation (encountered kinds are "thumbv7_abs_le", "armv7_abs_le").
stub_addr(armv7.o, ext, v8) Error: "ext" has 2 stubs in file "armv7.o", but none of them matches the stub-kind filter "v8" (all encountered kinds are "thumbv7_abs_le", "armv7_abs_le").
```
Add methods `registerGOTEntry()` and `registerStubEntry()` in
`Session::FileInfo` to factor out generic code from the individual
object type implementations.
We want to use regular `stub_addr()` expressions in `jitlink-check` lines to test the generation of stubs in AArch32, but we don't want this to require a standardized GOT-based PLT implementation. In terms of performance and binary size it doesn't seem beneficial. And in terms of patching branch targets, we should be able to handle range-extension- and interworking-stubs without a lot of extra logic.
In order to allow such AArch32 stubs we add a separate path for `stub_addr()` expressions in `llvm-jitlink-elf`. The relocations in our stubs are not pointing to the GOT, but to the external symbol directly. Thus, we have to avoid access to the block of the edge target. Instead we only return the symbol name, which is enough to use `stub_addr()` expressions in tests.
The name of the AArch32 stubs section differs from the conventional `$__STUBS` on purpose. It allows to add a regular PLT/GOT implementation as an orthogonal feature in the future. In order to also allow decoding of stub target addresses in the future, we mention the stub flavor in the section name as well.
If GOTSym is not defined, we cannot call `GOTSym.getBlock()`. It failed with:
```
Assertion failed: (Base->isDefined() && "Not a defined symbol"), function getBlock, file JITLink.h, line 554.
```
This re-applies 4b17c81d5a5, "[jitlink/rtdydl][checker] Add TargetFlag
dependent disassembler switching support", which was reverted in
4871a9ca546 due to bot failures.
The patch has been updated to add missing plumbing for Subtarget Features and
a CPU string, which should fix the failing tests.
https://reviews.llvm.org/D158280
Some targets such as AArch32 make use of TargetFlags to indicate ISA mode. Depending
on the TargetFlag, MCDisassembler and similar target specific objects should be
reinitialized with the correct Target Triple. Backends with similar needs can
easily extend this implementation for their usecase.
The drivers llvm-rtdyld and llvm-jitlink have their SymbolInfo's extended to take
TargetFlag into account. RuntimeDyldChecker can now create necessary TargetInfo
to reinitialize MCDisassembler and MCInstPrinter. The required triple is obtained
from the new getTripleFromTargetFlag function by checking the TargetFlag.
In addition, breaking changes for RuntimeDyld COFF Thumb tests are fixed by making
the backend emit a TargetFlag.
Reviewed By: lhames, sgraenitz
Differential Revision: https://reviews.llvm.org/D158280
Adds support for the R_X86_64_GOTPC32 relocation, which is a 32-bit delta to
the global offset table.
Since the delta to the GOT doesn't actually require any GOT entries to exist
this commit adds an extra fallback path to the getOrCreateGOTSymbol function:
If the symbol is in the extenal symbols list but no entry exists then the
symbol is turned into an absolute symbol pointing to an arbitrary address in
the current graph's allocation (accessing this address via the symbol would be
illegal, but any access should have triggered creation of a GOT entry which
would prevent this fallback path from being taken in the first place).
This commit also updates the llvm-jitlink tool to scrape the addresses of the
absolute symbols in the graph so that the testcase can see the now-absolute
_GLOBAL_OFFSET_TABLE_ symbol.
I'm planning to deprecate and eventually remove llvm::empty.
I thought about replacing llvm::empty(x) with std::empty(x), but it
turns out that all uses can be converted to x.empty(). That is, no
use requires the ability of std::empty to accept C arrays and
std::initializer_list.
Differential Revision: https://reviews.llvm.org/D133677
This re-applies 133f86e95492b2a00b944e070878424cfa73f87c, which was reverted in
c5965a411c635106a47738b8d2e24db822b7416f while I investigated bot failures.
The original failure contained an arithmetic conversion think-o (on line 419 of
EHFrameSupport.cpp) that could cause failures on 32-bit platforms. The issue
should be fixed in this patch.
Adds utilities for creating anonymous pointers and jump stubs to x86_64.h. These
are used by the GOT and Stubs builder, but may also be used by pass writers who
want to create pointer stubs for indirection.
This patch also switches the underlying type for LinkGraph content from
StringRef to ArrayRef<char>. This avoids any confusion when working with buffers
that contain null bytes in the middle like, for example, a newly added null
pointer content array. ;)
This patch adds a jitlink pass, 'registerELFGraphInfo', that records section
and symbol information about each LinkGraph in the llvm-jitlink session object.
This allows symbols and sections to be referred to by name in llvm-jitlink
regression tests. This will enable a testcase to be written for
https://reviews.llvm.org/D80613.
