This patch is the Part-1 (FE Clang) implementation of HW Exception handling.
This new feature adds the support of Hardware Exception for Microsoft Windows
SEH (Structured Exception Handling).
This is the first step of this project; only X86_64 target is enabled in this patch.
Compiler options:
For clang-cl.exe, the option is -EHa, the same as MSVC.
For clang.exe, the extra option is -fasync-exceptions,
plus -triple x86_64-windows -fexceptions and -fcxx-exceptions as usual.
NOTE:: Without the -EHa or -fasync-exceptions, this patch is a NO-DIFF change.
The rules for C code:
For C-code, one way (MSVC approach) to achieve SEH -EHa semantic is to follow
three rules:
* First, no exception can move in or out of _try region., i.e., no "potential
faulty instruction can be moved across _try boundary.
* Second, the order of exceptions for instructions 'directly' under a _try
must be preserved (not applied to those in callees).
* Finally, global states (local/global/heap variables) that can be read
outside of _try region must be updated in memory (not just in register)
before the subsequent exception occurs.
The impact to C++ code:
Although SEH is a feature for C code, -EHa does have a profound effect on C++
side. When a C++ function (in the same compilation unit with option -EHa ) is
called by a SEH C function, a hardware exception occurs in C++ code can also
be handled properly by an upstream SEH _try-handler or a C++ catch(...).
As such, when that happens in the middle of an object's life scope, the dtor
must be invoked the same way as C++ Synchronous Exception during unwinding
process.
Design:
A natural way to achieve the rules above in LLVM today is to allow an EH edge
added on memory/computation instruction (previous iload/istore idea) so that
exception path is modeled in Flow graph preciously. However, tracking every
single memory instruction and potential faulty instruction can create many
Invokes, complicate flow graph and possibly result in negative performance
impact for downstream optimization and code generation. Making all
optimizations be aware of the new semantic is also substantial.
This design does not intend to model exception path at instruction level.
Instead, the proposed design tracks and reports EH state at BLOCK-level to
reduce the complexity of flow graph and minimize the performance-impact on CPP
code under -EHa option.
One key element of this design is the ability to compute State number at
block-level. Our algorithm is based on the following rationales:
A _try scope is always a SEME (Single Entry Multiple Exits) region as jumping
into a _try is not allowed. The single entry must start with a seh_try_begin()
invoke with a correct State number that is the initial state of the SEME.
Through control-flow, state number is propagated into all blocks. Side exits
marked by seh_try_end() will unwind to parent state based on existing
SEHUnwindMap[].
Note side exits can ONLY jump into parent scopes (lower state number).
Thus, when a block succeeds various states from its predecessors, the lowest
State triumphs others. If some exits flow to unreachable, propagation on those
paths terminate, not affecting remaining blocks.
For CPP code, object lifetime region is usually a SEME as SEH _try.
However there is one rare exception: jumping into a lifetime that has Dtor but
has no Ctor is warned, but allowed:
Warning: jump bypasses variable with a non-trivial destructor
In that case, the region is actually a MEME (multiple entry multiple exits).
Our solution is to inject a eha_scope_begin() invoke in the side entry block to
ensure a correct State.
Implementation:
Part-1: Clang implementation described below.
Two intrinsic are created to track CPP object scopes; eha_scope_begin() and eha_scope_end().
_scope_begin() is immediately added after ctor() is called and EHStack is pushed.
So it must be an invoke, not a call. With that it's also guaranteed an
EH-cleanup-pad is created regardless whether there exists a call in this scope.
_scope_end is added before dtor(). These two intrinsics make the computation of
Block-State possible in downstream code gen pass, even in the presence of
ctor/dtor inlining.
Two intrinsic, seh_try_begin() and seh_try_end(), are added for C-code to mark
_try boundary and to prevent from exceptions being moved across _try boundary.
All memory instructions inside a _try are considered as 'volatile' to assure
2nd and 3rd rules for C-code above. This is a little sub-optimized. But it's
acceptable as the amount of code directly under _try is very small.
Part-2 (will be in Part-2 patch): LLVM implementation described below.
For both C++ & C-code, the state of each block is computed at the same place in
BE (WinEHPreparing pass) where all other EH tables/maps are calculated.
In addition to _scope_begin & _scope_end, the computation of block state also
rely on the existing State tracking code (UnwindMap and InvokeStateMap).
For both C++ & C-code, the state of each block with potential trap instruction
is marked and reported in DAG Instruction Selection pass, the same place where
the state for -EHsc (synchronous exceptions) is done.
If the first instruction in a reported block scope can trap, a Nop is injected
before this instruction. This nop is needed to accommodate LLVM Windows EH
implementation, in which the address in IPToState table is offset by +1.
(note the purpose of that is to ensure the return address of a call is in the
same scope as the call address.
The handler for catch(...) for -EHa must handle HW exception. So it is
'adjective' flag is reset (it cannot be IsStdDotDot (0x40) that only catches
C++ exceptions).
Suppress push/popTerminate() scope (from noexcept/noTHrow) so that HW
exceptions can be passed through.
Original llvm-dev [RFC] discussions can be found in these two threads below:
https://lists.llvm.org/pipermail/llvm-dev/2020-March/140541.htmlhttps://lists.llvm.org/pipermail/llvm-dev/2020-April/141338.html
Differential Revision: https://reviews.llvm.org/D80344/new/
I wouldn't recommend writing code like the testcase; a function
parameter isn't atomic, so using an atomic type doesn't really make
sense. But it's valid, so clang shouldn't crash on it.
The code was assuming hasAggregateEvaluationKind(Ty) implies Ty is a
RecordType, which isn't true. Just use isRecordType() instead.
Differential Revision: https://reviews.llvm.org/D102015
Adding lowering support for bitreverse.
Previously, lowering bitreverse would expand it into a series of other instructions. This patch makes it so this produces a single rbit instruction instead.
Reviewed By: dmgreen
Differential Revision: https://reviews.llvm.org/D102397
`__block` variables used to be always stored on the head instead of stack.
D51564 allowed `__block` variables to the stored on the stack like normal
variablesif they not captured by any escaping block, but the debug-info
generation code wasn't made aware of it so we still unconditionally emit DWARF
expressions pointing to the heap.
This patch makes CGDebugInfo use the `EscapingByref` introduced in D51564 that
tracks whether the `__block` variable is actually on the heap. If it's stored on
the stack instead we just use the debug info we would generate for normal
variables instead.
Reviewed By: ahatanak, aprantl
Differential Revision: https://reviews.llvm.org/D99946
ScheduleDAGFast.cpp is compiled to object file, but the ScheduleDAGFast
object file isn't linked into clang executable file as no symbol is
referred by outside. Add calling to createXxx of ScheduleDAGFast.cpp,
then the ScheduleDAGFast object file will be linked into clang
executable file. The static RegisterScheduler will register scheduler
fast and linearize at clang boot time.
Reviewed By: pengfei
Differential Revision: https://reviews.llvm.org/D101601
This patch adds support for GCC's -fstack-usage flag. With this flag, a stack
usage file (i.e., .su file) is generated for each input source file. The format
of the stack usage file is also similar to what is used by GCC. For each
function defined in the source file, a line with the following information is
produced in the .su file.
<source_file>:<line_number>:<function_name> <size_in_byte> <static/dynamic>
"Static" means that the function's frame size is static and the size info is an
accurate reflection of the frame size. While "dynamic" means the function's
frame size can only be determined at run-time because the function manipulates
the stack dynamically (e.g., due to variable size objects). The size info only
reflects the size of the fixed size frame objects in this case and therefore is
not a reliable measure of the total frame size.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D100509
Support for Darwin's libsystem_m's vector functions has been added to
LLVM in 93a9a8a8d9.
This patch adds support for -fveclib=Darwin_libsystem_m to Clang.
Reviewed By: arphaman
Differential Revision: https://reviews.llvm.org/D102489
The original change was reverted because it was discovered
that clang mishandles thunks, and they receive wrong
attributes for their this/return types - the ones for the function
they will call, not the ones they have.
While i have tried to fix this in https://reviews.llvm.org/D100388
that patch has been up and stuck for a month now,
with little signs of progress.
So while it will be good to solve this for real,
for now we can simply avoid introducing the bug,
by not annotating this/return for thunks.
This reverts commit 6270b3a1ea,
relanding 0aa0458f14.
This commit removes some redundant {insert,extract}_vector intrinsic
chains by implementing the following patterns as instsimplifies:
(insert_vector _, (extract_vector X, 0), 0) -> X
(extract_vector (insert_vector _, X, 0), 0) -> X
Reviewed By: peterwaller-arm
Differential Revision: https://reviews.llvm.org/D101986
There are two reasons this shouldn't be restricted to Power8 and up:
1. For XL compatibility
2. Because clang will expand comparison operators to these intrinsics*
*Without this patch, the following causes a selection error:
int test(vector signed long a, vector signed long b) {
return a < b;
}
This patch provides the handling for the intrinsics in the back
end and removes the Power8 guards from the predicate functions
(vec_{all|any}_{eq|ne|gt|ge|lt|le}).
Add front end diagnostics to report error for unimplemented TLS models set by
- compiler option `-ftls-model`
- attributes like `__thread int __attribute__((tls_model("local-exec"))) var_name;`
Reviewed by: aaron.ballman, nemanjai, PowerPC
Differential Revision: https://reviews.llvm.org/D102070
This patch adds support for WebAssembly globals in LLVM IR, representing
them as pointers to global values, in a non-default, non-integral
address space. Instruction selection legalizes loads and stores to
these pointers to new WebAssemblyISD nodes GLOBAL_GET and GLOBAL_SET.
Once the lowering creates the new nodes, tablegen pattern matches those
and converts them to Wasm global.get/set of the appropriate type.
Based on work by Paulo Matos in https://reviews.llvm.org/D95425.
Reviewed By: pmatos
Differential Revision: https://reviews.llvm.org/D101608
These are required to be constants, this patch makes sure they
are in the accepted range of values.
These are usually created by wrappers in the riscv_vector.h header
which should always be correct. This patch protects against a user
using the builtin directly.
Reviewed By: khchen
Differential Revision: https://reviews.llvm.org/D102086
Analogously to https://reviews.llvm.org/D98794 this patch uses the
`alignstack` attribute to fix incorrect passing of homogeneous
aggregate (HA) arguments on AArch32. The EABI/AAPCS was recently
updated to clarify how VFP co-processor candidates are aligned:
4488e34998
Differential Revision: https://reviews.llvm.org/D100853
Printing pass manager invocations is fairly verbose and not super
useful.
This allows us to remove DebugLogging from pass managers and PassBuilder
since all logging (aside from analysis managers) goes through
instrumentation now.
This has the downside of never being able to print the top level pass
manager via instrumentation, but that seems like a minor downside.
Reviewed By: ychen
Differential Revision: https://reviews.llvm.org/D101797
Follow up on 431e3138a and complete the other possible combinations.
Besides enforcing the new behavior, it also mitigates TSAN false positives when
combining orders that used to be stronger.
This adds additional support for XL compatibility. There are a number
of functions in altivec.h that produce a single instruction (or a
very short sequence) for Power8 but can be done on Power7 without
scalarization. XL provides these implementations.
This patch adds the following overloads for doubleword vectors:
vec_add
vec_cmpeq
vec_cmpgt
vec_cmpge
vec_cmplt
vec_cmple
vec_sl
vec_sr
vec_sra
Update the SIMD builtin load functions to take pointers to const data and update
the intrinsics themselves to not cast away constness.
Differential Revision: https://reviews.llvm.org/D101884
Make the inputs to all narrowing builtins signed, which is how they are
interpreted by the underlying instructions (only the result changes sign
between instructions).
Differential Revision: https://reviews.llvm.org/D101883
If a return value is explicitly rounded to 64 bits, an additional zext
instruction is emitted, and in some cases it prevents tail call
optimization.
As discussed in D100225, this rounding is not necessary and can be
disabled.
Differential Revision: https://reviews.llvm.org/D100591
In matrix type casts, we were doing bitcast when the matrices had the same size. This was incorrect and this patch fixes that.
Also added some new CodeGen tests for signed <-> usigned conversions
Reviewed By: fhahn
Differential Revision: https://reviews.llvm.org/D101754
This patch makes the builtin operand order match the C operand order
for all intrinsics. With this we can use clang_builtin_alias for
all overloaded intrinsics.
This should further reduce the test time for vector intrinsics.
Differential Revision: https://reviews.llvm.org/D101700
This adds the long overdue implementations of these functions
that have been part of the ABI document and are now part of
the "Power Vector Intrinsic Programming Reference" (PVIPR).
The approach is to add new builtins and to emit code with
the fast flag regardless of whether fastmath was specified
on the command line.
Differential revision: https://reviews.llvm.org/D101209
Currently Clang does not add mustprogress to inifinite loops with a
known constant condition, matching C11 behavior. The forward progress
guarantee in C++11 and later should allow us to add mustprogress to any
loop (http://eel.is/c++draft/intro.progress#1).
This allows us to simplify the code dealing with adding mustprogress a
bit.
Reviewed By: aaron.ballman, lebedev.ri
Differential Revision: https://reviews.llvm.org/D96418
Use of bitcast resulted in lanes being swapped for vcreateq with big
endian. Fix this by using vreinterpret. No code change for little
endian. Adds IR lit test.
Differential Revision: https://reviews.llvm.org/D101606
This patch copies implementation from cpuid.h, which preserve base register %rbx around cpuid. It fixes PR50133.
Reviewed By: rnk
Differential Revision: https://reviews.llvm.org/D101338
Renaming the option is based on discussions in https://reviews.llvm.org/D101122.
It is normally not a good idea to rename driver flags but this flag is
new enough and obscure enough that it is very unlikely to have adopters.
While we're here also drop the `<kind>` metavar. It's not necessary and
is actually inconsistent with the documentation in
`clang/docs/ClangCommandLineReference.rst`.
Differential Revision: https://reviews.llvm.org/D101491
The Neon vadd intrinsics were added to the ARMSIMD intrinsic map,
however due to being defined under an AArch64 guard in arm_neon.td,
were not previously useable on ARM. This change rectifies that.
It is important to note that poly128 is not valid on ARM, thus it was
extracted out of the original arm_neon.td definition and separated
for the sake of AArch64.
Reviewed By: DavidSpickett
Differential Revision: https://reviews.llvm.org/D100772
This patch changes the AArch32 crypto instructions (sha2 and aes) to
require the specific sha2 or aes features. These features have
already been implemented and can be controlled through the command
line, but do not have the expected result (i.e. `+noaes` will not
disable aes instructions). The crypto feature retains its existing
meaning of both sha2 and aes.
Several small changes are included due to the knock-on effect this has:
- The AArch32 driver has been modified to ensure sha2/aes is correctly
set based on arch/cpu/fpu selection and feature ordering.
- Crypto extensions are permitted for AArch32 v8-R profile, but not
enabled by default.
- ACLE feature macros have been updated with the fine grained crypto
algorithms. These are also used by AArch64.
- Various tests updated due to the change in feature lists and macros.
Reviewed By: lenary
Differential Revision: https://reviews.llvm.org/D99079
Commit e3d8ee35e4 ("reland "[DebugInfo] Support to emit debugInfo
for extern variables"") added support to emit debugInfo for
extern variables if requested by the target. Currently, only
BPF target enables this feature by default.
As BPF ecosystem grows, callback function started to get
support, e.g., recently bpf_for_each_map_elem() is introduced
(https://lwn.net/Articles/846504/) with a callback function as an
argument. In the future we may have something like below as
a demonstration of use case :
extern int do_work(int);
long bpf_helper(void *callback_fn, void *callback_ctx, ...);
long prog_main() {
struct { ... } ctx = { ... };
return bpf_helper(&do_work, &ctx, ...);
}
Basically bpf helper may have a callback function and the
callback function is defined in another file or in the kernel.
In this case, we would like to know the debuginfo types for
do_work(), so the verifier can proper verify the safety of
bpf_helper() call.
For the following example,
extern int do_work(int);
long bpf_helper(void *callback_fn);
long prog() {
return bpf_helper(&do_work);
}
Currently, there is no debuginfo generated for extern function do_work().
In the IR, we have,
...
define dso_local i64 @prog() local_unnamed_addr #0 !dbg !7 {
entry:
%call = tail call i64 @bpf_helper(i8* bitcast (i32 (i32)* @do_work to i8*)) #2, !dbg !11
ret i64 %call, !dbg !12
}
...
declare dso_local i32 @do_work(i32) #1
...
This patch added support for the above callback function use case, and
the generated IR looks like below:
...
declare !dbg !17 dso_local i32 @do_work(i32) #1
...
!17 = !DISubprogram(name: "do_work", scope: !1, file: !1, line: 1, type: !18, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !2)
!18 = !DISubroutineType(types: !19)
!19 = !{!20, !20}
!20 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
The TargetInfo.allowDebugInfoForExternalVar is renamed to
TargetInfo.allowDebugInfoForExternalRef as now it guards
both extern variable and extern function debuginfo generation.
Differential Revision: https://reviews.llvm.org/D100567
These are intended to mimic warnings available in gcc.
-Wunused-but-set-variable is triggered in the case of a variable which
appears on the LHS of an assignment but not otherwise used.
For instance:
void f() {
int x;
x = 0;
}
-Wunused-but-set-parameter works similarly, but for function parameters
instead of variables.
In C++, they are triggered only for scalar types; otherwise, they are
triggered for all types. This is gcc's behavior.
-Wunused-but-set-parameter is controlled by -Wextra, while
-Wunused-but-set-variable is controlled by -Wunused. This is slightly
different from gcc's behavior, but seems most consistent with clang's
behavior for -Wunused-parameter and -Wunused-variable.
Reviewed By: aeubanks
Differential Revision: https://reviews.llvm.org/D100581
Melanie Blower