This is an alternative to D66980, which was reverted. Instead of
inserting a pseudo instruction that optionally expands to nothing, add a
pass that inserts int3 when appropriate after basic block layout.
Reviewers: hans
Differential Revision: https://reviews.llvm.org/D67201
llvm-svn: 371466
This reverts r370525 (git commit 0bb1630685)
Also reverts r370543 (git commit 185ddc08ee)
The approach I took only works for functions marked `noreturn`. In
general, a call that is not known to be noreturn may be followed by
unreachable for other reasons. For example, there could be multiple call
sites to a function that throws sometimes, and at some call sites, it is
known to always throw, so it is followed by unreachable. We need to
insert an `int3` in these cases to pacify the Windows unwinder.
I think this probably deserves its own standalone, Win64-only fixup pass
that runs after block placement. Implementing that will take some time,
so let's revert to TrapUnreachable in the mean time.
llvm-svn: 370829
Users have complained llvm.trap produce two ud2 instructions on Win64,
one for the trap, and one for unreachable. This change fixes that.
TrapUnreachable was added and enabled for Win64 in r206684 (April 2014)
to avoid poorly understood issues with the Windows unwinder.
There seem to be two major things in play:
- the unwinder
- C++ EH, _CxxFrameHandler3 & co
The unwinder disassembles forward from the return address to scan for
epilogues. Inserting a ud2 had the effect of stopping the unwinder, and
ensuring that it ran the EH personality function for the current frame.
However, it's not clear what the unwinder does when the return address
happens to be the last address of one function and the first address of
the next function.
The Visual C++ EH personality, _CxxFrameHandler3, needs to figure out
what the current EH state number is. It does this by consulting the
ip2state table, which maps from PC to state number. This seems to go
wrong when the return address is the last PC of the function or catch
funclet.
I'm not sure precisely which system is involved here, but in order to
address these real or hypothetical problems, I believe it is enough to
insert int3 after a call site if it would otherwise be the last
instruction in a function or funclet. I was able to reproduce some
similar problems locally by arranging for a noreturn call to appear at
the end of a catch block immediately before an unrelated function, and I
confirmed that the problems go away when an extra trailing int3
instruction is added.
MSVC inserts int3 after every noreturn function call, but I believe it's
only necessary to do it if the call would be the last instruction. This
change inserts a pseudo instruction that expands to int3 if it is in the
last basic block of a function or funclet. I did what I could to run the
Microsoft compiler EH tests, and the ones I was able to run showed no
behavior difference before or after this change.
Differential Revision: https://reviews.llvm.org/D66980
llvm-svn: 370525
For consistency with normal instructions and clarity when reading IR,
it's best to print the %0, %1, ... names of function arguments in
definitions.
Also modifies the parser to accept IR in that form for obvious reasons.
llvm-svn: 367755
Summary:
I found the following case having tail blocks with no successors merging opportunities after block placement.
Before block placement:
bb0:
...
bne a0, 0, bb2:
bb1:
mv a0, 1
ret
bb2:
...
bb3:
mv a0, 1
ret
bb4:
mv a0, -1
ret
The conditional branch bne in bb0 is opposite to beq.
After block placement:
bb0:
...
beq a0, 0, bb1
bb2:
...
bb4:
mv a0, -1
ret
bb1:
mv a0, 1
ret
bb3:
mv a0, 1
ret
After block placement, that appears new tail merging opportunity, bb1 and bb3 can be merged as one block. So the conditional constraint for merging tail blocks with no successors should be removed. In my experiment for RISC-V, it decreases code size.
Author of original patch: Jim Lin
Reviewers: haicheng, aheejin, craig.topper, rnk, RKSimon, Jim, dmgreen
Reviewed By: Jim, dmgreen
Subscribers: xbolva00, dschuff, javed.absar, sbc100, jgravelle-google, aheejin, kito-cheng, dmgreen, PkmX, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D54411
llvm-svn: 363284
Summary:
Make recoverfp intrinsic target-independent so that it can be implemented for AArch64, etc.
Refer D53541 for the context. Clang counterpart D56748.
Reviewers: rnk, efriedma
Reviewed By: rnk, efriedma
Subscribers: javed.absar, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D56747
llvm-svn: 351281
In order to set breakpoints on labels and list source code around
labels, we need collect debug information for labels, i.e., label
name, the function label belong, line number in the file, and the
address label located. In order to keep these information in LLVM
IR and to allow backend to generate debug information correctly.
We create a new kind of metadata for labels, DILabel. The format
of DILabel is
!DILabel(scope: !1, name: "foo", file: !2, line: 3)
We hope to keep debug information as much as possible even the
code is optimized. So, we create a new kind of intrinsic for label
metadata to avoid the metadata is eliminated with basic block.
The intrinsic will keep existing if we keep it from optimized out.
The format of the intrinsic is
llvm.dbg.label(metadata !1)
It has only one argument, that is the DILabel metadata. The
intrinsic will follow the label immediately. Backend could get the
label metadata through the intrinsic's parameter.
We also create DIBuilder API for labels to be used by Frontend.
Frontend could use createLabel() to allocate DILabel objects, and use
insertLabel() to insert llvm.dbg.label intrinsic in LLVM IR.
Differential Revision: https://reviews.llvm.org/D45024
Patch by Hsiangkai Wang.
llvm-svn: 331841
Summary:
This change comes from using lld for i686-windows-msvc. Before this change, lld
emits an error of:
error: relocation against symbol in discarded section: .xdata
It's possible that this could be addressed in lld, but I think this change is
reasonable on its own.
At a high level, this is being generated:
A (.text comdat) -> B (.text) -> C (.xdata comdat)
Where A is a C++ inline function, which references B, an exception handler
thunk, which references C, the exception handling info.
With this structure, lld will error when applying relocations to B if the C it
references has been discarded (some other C has been selected).
This change checks if A is comdat, and if so places the exception registration
thunk (B) in the comdata group of A (and B).
It appears that MSVC makes the __ehhandler function comdat.
Is it possible that duplicate thunks are being emitted into the final binary
with other linkers, or are they stripping the unused thunks?
Reviewers: rnk, majnemer, compnerd, smeenai
Reviewed By: rnk, compnerd
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D38940
llvm-svn: 316219
Summary:
MSVC provide exception handlers with enhanced information to deal with security buffer feature (/GS).
To be more secure, the security cookies (GS and SEH) are validated when unwinding the stack.
The following code:
```
void f() {}
void foo() {
__try {
f();
} __except(1) {
f();
}
}
```
Reviewers: majnemer, rnk
Subscribers: thakis, llvm-commits, chrisha
Differential Revision: http://reviews.llvm.org/D21101
llvm-svn: 274239
Currently each Function points to a DISubprogram and DISubprogram has a
scope field. For member functions the scope is a DICompositeType. DIScopes
point to the DICompileUnit to facilitate type uniquing.
Distinct DISubprograms (with isDefinition: true) are not part of the type
hierarchy and cannot be uniqued. This change removes the subprograms
list from DICompileUnit and instead adds a pointer to the owning compile
unit to distinct DISubprograms. This would make it easy for ThinLTO to
strip unneeded DISubprograms and their transitively referenced debug info.
Motivation
----------
Materializing DISubprograms is currently the most expensive operation when
doing a ThinLTO build of clang.
We want the DISubprogram to be stored in a separate Bitcode block (or the
same block as the function body) so we can avoid having to expensively
deserialize all DISubprograms together with the global metadata. If a
function has been inlined into another subprogram we need to store a
reference the block containing the inlined subprogram.
Attached to https://llvm.org/bugs/show_bug.cgi?id=27284 is a python script
that updates LLVM IR testcases to the new format.
http://reviews.llvm.org/D19034
<rdar://problem/25256815>
llvm-svn: 266446
32-bit X86 EH on Windows utilizes a stack of registration nodes
allocated and deallocated on entry/exit. A registration node contains a
bunch of EH personality specific information like which try-state we are
currently in.
Because a setjmp target allows control flow from arbitrary program
points, there is no way to ensure that the try-state we are in is
correctly updated once we transfer control.
MSVC compatible compilers, like MSVC and ICC, utilize runtime helpers to
reinitialize the try-state when a longjmp occurs. This is implemented
by adding additional arguments to _setjmp3: the desired try-state and
a helper routine to update the try-state.
Differential Revision: http://reviews.llvm.org/D17721
llvm-svn: 262241
Inline-asm calls aren't annotated with funclet bundle operands because
they don't throw and cannot be inlined through. We shouldn't require
them to bear an funclet bundle operand.
llvm-svn: 261942
32-bit x86 Windows targets use a linked-list of nodes allocated on the
stack, referenced to via thread-local storage. The personality routine
interprets one of the fields in the node as a 'state number' which
indicates where the personality routine should transfer control.
State transitions are possible only before call-sites which may throw
exceptions. Our previous scheme had us update the state number before
all call-sites which may throw.
Instead, we can try to minimize the number of times we need to store by
reasoning about the nearest store which dominates the current call-site.
If the last store agrees with the current call-site, then we know that
the state-update is redundant and can be elided.
This is largely straightforward: an RPO walk of the blocks allows us to
correctly forward propagate the information when the function is a DAG.
Currently, loops are not handled optimally and may trigger superfluous
state stores.
Differential Revision: http://reviews.llvm.org/D16763
llvm-svn: 261122
Those commits created an artificial edge from a cleanup to a synthesized
catchswitch in order to get the MSVC personality routine to execute
cleanups which don't cleanupret and are not wrapped by a catchswitch.
This worked well enough but is not a complete solution in situations
where there the cleanup infinite loops.
However, the real deal breaker behind this approach comes about from a
degenerate case where the cleanup is post-dominated by unreachable *and*
throws an exception. This ends poorly because the catchswitch will
inadvertently catch the exception.
Because of this we should go back to our previous behavior of not
executing certain cleanups (identical behavior with the Itanium ABI
implementation in clang, GCC and ICC).
N.B. I think this could be salvaged by making the catchpad rethrow the
exception and properly transforming throwing calls in the cleanup into
invokes.
llvm-svn: 259338
A cleanup can have paths which unwind or end up in unreachable.
If there is an unreachable path *and* a path which unwinds to caller,
we would mistakenly inject an unwind path to a catchswitch on the
unreachable path. This results in a verifier assertion firing because
the cleanup unwinds to two different places: to the caller and to the
catchswitch.
This occured because we used getCleanupRetUnwindDest to determine if the
cleanuppad had no cleanuprets.
This is incorrect, getCleanupRetUnwindDest returns null for cleanuprets
which unwind to caller.
llvm-svn: 258651
Cleanups in C++ are a little weird. They are only guaranteed to be
reliably executed if, and only if, there is a viable catch handler which
can handle the exception.
This means that reachability of a cleanup is lexically determined by it
being nested with a try-block which unwinds to a catch. It is *cannot*
be reasoned about by examining the control flow edges leaving a cleanup.
Usually this is not a problem. It becomes a problem when there are *no*
edges out of a cleanup because we believed that code post-dominated by
the cleanup is dead. In LLVM's case, this code is what informs the
personality routine about the presence of a suitable catch handler.
However, the lack of edges to that catch handler makes the handler
become unreachable which causes us to remove it. By removing the
handler, the cleanup becomes unreachable.
Instead, inject a catch-all handler with every cleanup that has no
unwind edges. This will allow us to properly unwind the stack.
This fixes PR25997.
llvm-svn: 258580
Summary:
Funclet-based EH personalities/tables likely can't handle these, and they
can't be generated at source, so make them officially illegal in IR as
well.
Reviewers: andrew.w.kaylor, rnk, majnemer
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D15963
llvm-svn: 257274
Summary:
A funclet EH pad may be exited by an unwind edge, which may be a
cleanupret exiting its cleanuppad, an invoke exiting a funclet, or an
unwind out of a nested funclet transitively exiting its parent. Funclet
EH personalities require all such exceptional exits from a given funclet to
have the same unwind destination, and EH preparation / state numbering /
table generation implicitly depends on this. Formalize it as a rule of
the IR in the LangRef and verifier.
Reviewers: rnk, majnemer, andrew.w.kaylor
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D15962
llvm-svn: 257273
Summary:
Add a pass to update catchrets when their successors get cloned; the
existing pass doesn't catch these because it walks the funclet whose
blocks are being cloned but the catchret is in a child funclet.
Also update the test for removing incoming PHI values; when the
predecessor is a catchret, the relevant color is the catchret's parentPad,
not its block's color.
Reviewers: andrew.w.kaylor, rnk, majnemer
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D15840
llvm-svn: 256689
We visited the same catchswitch twice because it was both the child of
another funclet and the predecessor of a cleanuppad.
Instead, change the numbering algorithm to only recurse if the unwind
destination of the inner funclet agrees with the unwind destination of
the catchswitch.
This fixes PR25926.
llvm-svn: 256317
SimplifyCFG allows tail merging with code which terminates in
unreachable which, in turn, makes it possible for an invoke to end up in
a funclet which it was not originally part of.
Using operand bundles on invokes allows us to determine whether or not
an invoke was part of a funclet in the source program.
Furthermore, it allows us to unambiguously answer questions about the
legality of inlining into call sites which the personality may have
trouble with.
Differential Revision: http://reviews.llvm.org/D15517
llvm-svn: 255674
It turns out that terminatepad gives little benefit over a cleanuppad
which calls the termination function. This is not sufficient to
implement fully generic filters but MSVC doesn't support them which
makes terminatepad a little over-designed.
Depends on D15478.
Differential Revision: http://reviews.llvm.org/D15479
llvm-svn: 255522
While we have successfully implemented a funclet-oriented EH scheme on
top of LLVM IR, our scheme has some notable deficiencies:
- catchendpad and cleanupendpad are necessary in the current design
but they are difficult to explain to others, even to seasoned LLVM
experts.
- catchendpad and cleanupendpad are optimization barriers. They cannot
be split and force all potentially throwing call-sites to be invokes.
This has a noticable effect on the quality of our code generation.
- catchpad, while similar in some aspects to invoke, is fairly awkward.
It is unsplittable, starts a funclet, and has control flow to other
funclets.
- The nesting relationship between funclets is currently a property of
control flow edges. Because of this, we are forced to carefully
analyze the flow graph to see if there might potentially exist illegal
nesting among funclets. While we have logic to clone funclets when
they are illegally nested, it would be nicer if we had a
representation which forbade them upfront.
Let's clean this up a bit by doing the following:
- Instead, make catchpad more like cleanuppad and landingpad: no control
flow, just a bunch of simple operands; catchpad would be splittable.
- Introduce catchswitch, a control flow instruction designed to model
the constraints of funclet oriented EH.
- Make funclet scoping explicit by having funclet instructions consume
the token produced by the funclet which contains them.
- Remove catchendpad and cleanupendpad. Their presence can be inferred
implicitly using coloring information.
N.B. The state numbering code for the CLR has been updated but the
veracity of it's output cannot be spoken for. An expert should take a
look to make sure the results are reasonable.
Reviewers: rnk, JosephTremoulet, andrew.w.kaylor
Differential Revision: http://reviews.llvm.org/D15139
llvm-svn: 255422
Now that the register allocator knows about the barriers on funclet
entry and exit, testing has shown that this is unnecessary.
We still demote PHIs on unsplittable blocks due to the differences
between the IR CFG and the Machine CFG.
llvm-svn: 253619
Summary:
The value that the CoreCLR personality passes to a funclet for the
establisher frame may be the root function's frame or may be the parent
funclet's (mostly empty) frame in the case of nested funclets. Each
funclet stores a pointer to the root frame in its own (mostly empty)
frame, as does the root function itself. All frames allocate this slot at
the same offset, measured from the post-prolog stack pointer, so that the
same sequence can accept any ancestor as an establisher frame parameter
value, and so that a single offset can be reported to the GC, which also
looks at this slot.
This change allocate the slot when processing function entry, and records
its frame index on the WinEHFuncInfo object, then inserts the code to
set/copy it during prolog emission.
Reviewers: majnemer, AndyAyers, pgavlin, rnk
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D14614
llvm-svn: 252983
Summary:
The CLR's personality routine passes these in rdx/edx, not rax/eax.
Make getExceptionPointerRegister a virtual method parameterized by
personality function to allow making this distinction.
Similarly make getExceptionSelectorRegister a virtual method parameterized
by personality function, for symmetry.
Reviewers: pgavlin, majnemer, rnk
Subscribers: jyknight, dsanders, llvm-commits
Differential Revision: http://reviews.llvm.org/D14344
llvm-svn: 252383
Windows EH funclets need to always return to a single parent funclet. However, it is possible for earlier optimizations to combine funclets (probably based on one funclet having an unreachable terminator) in such a way that this condition is violated.
These changes add code to the WinEHPrepare pass to detect situations where a funclet has multiple parents and clone such funclets, fixing up the unwind and catch return edges so that each copy of the funclet returns to the correct parent funclet.
Differential Revision: http://reviews.llvm.org/D13274?id=39098
llvm-svn: 252249
Previously, subprograms contained a metadata reference to the function they
described. Because most clients need to get or set a subprogram for a given
function rather than the other way around, this created unneeded inefficiency.
For example, many passes needed to call the function llvm::makeSubprogramMap()
to build a mapping from functions to subprograms, and the IR linker needed to
fix up function references in a way that caused quadratic complexity in the IR
linking phase of LTO.
This change reverses the direction of the edge by storing the subprogram as
function-level metadata and removing DISubprogram's function field.
Since this is an IR change, a bitcode upgrade has been provided.
Fixes PR23367. An upgrade script for textual IR for out-of-tree clients is
attached to the PR.
Differential Revision: http://reviews.llvm.org/D14265
llvm-svn: 252219
Summary:
The CLR's personality routine passes the pointer to the establisher frame
in RCX, not RDX.
Reviewers: pgavlin, majnemer, rnk
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D14343
llvm-svn: 252135
Summary:
Some shared code for handling eh.exceptionpointer and eh.exceptioncode
needs to not share the part that truncates to 32 bits, which is intended
just for exception codes.
Reviewers: rnk
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D13747
llvm-svn: 250588
Summary:
When a cleanup's cleanupendpad or cleanupret targets a catchendpad, stop
trying to propagate the cleanup's parent's color to the catchendpad, since
what's needed is the cleanup's grandparent's color and the catchendpad
will get that color from the catchpad linkage already. We already had
this exclusion for invokes, but were missing it for
cleanupendpad/cleanupret.
Also add a missing line that tags cleanupendpads' states in the
EHPadStateMap, without with lowering invokes that target cleanupendpads
which unwind to other handlers (and so don't have the -1 state) will fail.
This fixes the reduced IR repro in PR25163.
Reviewers: majnemer, andrew.w.kaylor, rnk
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D13797
llvm-svn: 250534
Summary:
Emit the handler and clause locations immediately after the standard
xdata.
Clauses are emitted in the same order and format used to communiate them
to the CLR Execution Engine.
Add a lit test to verify correct table generation on a small but
interesting example function.
Reviewers: majnemer, andrew.w.kaylor, rnk
Subscribers: pgavlin, AndyAyers, llvm-commits
Differential Revision: http://reviews.llvm.org/D13451
llvm-svn: 250219
The new implementation works at least as well as the old implementation
did.
Also delete the associated preparation tests. They don't exercise
interesting corner cases of the new implementation. All the codegen
tests of the EH tables have already been ported.
llvm-svn: 249918
Summary:
- Recurse from cleanupendpads to their cleanuppads, to make sure the
cleanuppad is visited if it has a cleanupendpad but no cleanupret.
- Check for and avoid double-processing cleanuppads, to allow for them to
have multiple cleanuprets (plus cleanupendpads).
- Update Cxx state numbering to visit toplevel cleanupendpads and to
recurse from cleanupendpads to their preds, to ensure we number any
funclets in inlined cleanups. SEH state numbering already did this.
Reviewers: rnk
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D13374
llvm-svn: 249792
We remove unreachable blocks because it is pointless to consider them
for coloring. However, we still had stale pointers to these blocks in
some data structures after we removed them from the function.
Instead, remove the unreachable blocks before attempting to do anything
with the function.
This fixes PR25099.
llvm-svn: 249617
Summary:
This is necessary to keep the cloner from making bogus copies of debug
metadata attached to the IR it is cloning.
Also, avoid running RemapInstruction over all instructions in the common
case that no cloning was performed.
Reviewers: rnk, andrew.w.kaylor, majnemer
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D13514
llvm-svn: 249591
Fangrui Song