Commit Graph

21 Commits

Author SHA1 Message Date
Duncan Sands
57810cdac4 Fix PR1628. When exception handling is turned on,
labels are generated bracketing each call (not just
invokes).  This is used to generate entries in
the exception table required by the C++ personality.
However it gets in the way of tail-merging.  This
patch solves the problem by no longer placing labels
around ordinary calls.  Instead we generate entries
in the exception table that cover every instruction
in the function that wasn't covered by an invoke
range (the range given by the labels around the invoke).
As an optimization, such entries are only generated for
parts of the function that contain a call, since for
the moment those are the only instructions that can
throw an exception [1].  As a happy consequence, we
now get a smaller exception table, since the same
region can cover many calls.  While there, I also
implemented folding of invoke ranges - successive
ranges are merged when safe to do so.  Finally, if
a selector contains only a cleanup, there's a special
shorthand for it - place a 0 in the call-site entry.
I implemented this while there.  As a result, the
exception table output (excluding filters) is now
optimal - it cannot be made smaller [2].  The
problem with throw filters is that folding them
optimally is hard, and the benefit of folding them is
minimal.

[1] I tested that having trapping instructions (eg
divide by zero) in such a region doesn't cause trouble.
[2] It could be made smaller with the help of higher
layers, eg by having branch folding reorder basic blocks
ending in invokes with the same landing pad so they
follow each other.  I don't know if this is worth doing.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41718 91177308-0d34-0410-b5e6-96231b3b80d8
2007-09-05 11:27:52 +00:00
Duncan Sands
6590b0457c There is an impedance matching problem between LLVM and
gcc exception handling: if an exception unwinds through
an invoke, then execution must branch to the invoke's
unwind target.  We previously tried to enforce this by
appending a cleanup action to every selector, however
this does not always work correctly due to an optimization
in the C++ unwinding runtime: if only cleanups would be
run while unwinding an exception, then the program just
terminates without actually executing the cleanups, as
invoke semantics would require.  I was hoping this
wouldn't be a problem, but in fact it turns out to be the
cause of all the remaining failures in the LLVM testsuite
(these also fail with -enable-correct-eh-support, so turning
on -enable-eh didn't make things worse!).  Instead we need
to append a full-blown catch-all to the end of each
selector.  The correct way of doing this depends on the
personality function, i.e. it is language dependent, so
can only be done by gcc.  Thus this patch which generalizes
the eh.selector intrinsic so that it can handle all possible
kinds of action table entries (before it didn't accomodate
cleanups): now 0 indicates a cleanup, and filters have to be
specified using the number of type infos plus one rather than
the number of type infos.  Related gcc patches will cause
Ada to pass a cleanup (0) to force the selector to always
fire, while C++ will use a C++ catch-all (null).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41484 91177308-0d34-0410-b5e6-96231b3b80d8
2007-08-27 15:47:50 +00:00
Anton Korobeynikov
2365f51ed0 Long live the exception handling!
This patch fills the last necessary bits to enable exceptions
handling in LLVM. Currently only on x86-32/linux.

In fact, this patch adds necessary intrinsics (and their lowering) which
represent really weird target-specific gcc builtins used inside unwinder.

After corresponding llvm-gcc patch will land (easy) exceptions should be
more or less workable. However, exceptions handling support should not be 
thought as 'finished': I expect many small and not so small glitches
everywhere.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@39855 91177308-0d34-0410-b5e6-96231b3b80d8
2007-07-14 14:06:15 +00:00
Duncan Sands
14da32a486 Make sure only one copy of a filter is placed in the
exception handling table if we encounter it multiple
times.  Filters could be folded harder than this, but
that would mean a lot more work for not much gain.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37908 91177308-0d34-0410-b5e6-96231b3b80d8
2007-07-05 15:15:01 +00:00
Duncan Sands
09085fe63d The semantics of invoke require that we always jump to the unwind block
(landing pad) when an exception unwinds through the call.  This doesn't
quite match the way the dwarf unwinder works: by default it only jumps to
the landing pad if the catch or filter specification matches, and otherwise
it keeps on unwinding.  There are two ways of specifying to the unwinder
that it should "always" (more on why there are quotes here later) jump to
the landing pad: follow the specification by a 0 typeid, or follow it by
the typeid for the NULL typeinfo.  GCC does the first, and this patch makes
LLVM do the same as gcc.  However there is a problem: the unwinder performs
optimizations based on C++ semantics (it only expects destructors to be
run if the 0 typeid fires - known as "cleanups"), meaning it assumes that no
exceptions will be raised and that the raised exception will be reraised
at the end of the cleanup code.  So if someone writes their own LLVM code
using the exception intrinsics they will get a nasty surprise if they don't
follow these rules.  The other possibility of using the typeid corresponding
to NULL (catch-all) causes the unwinder to make no assumptions, so this is
probably what we should use in the long-run.  However since we are still
having trouble getting exception handling working properly, for the moment
it seems best to closely imitate GCC.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37399 91177308-0d34-0410-b5e6-96231b3b80d8
2007-06-02 17:16:06 +00:00
Duncan Sands
73ef58ab92 Integrate exception filter support and exception catch support. This
simplifies the code in DwarfWriter, allows for multiple filters and
makes it trivial to specify filters accompanied by cleanups or catch-all
specifications (see next patch).  What a deal!  Patch blessed by Anton.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37398 91177308-0d34-0410-b5e6-96231b3b80d8
2007-06-02 16:53:42 +00:00
Anton Korobeynikov
070280e97f Mark all calls as "could throw", when exceptions are enabled. Emit necessary LP info too. This fixes PR1439
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37311 91177308-0d34-0410-b5e6-96231b3b80d8
2007-05-23 11:08:31 +00:00
Anton Korobeynikov
8c7c17354c Emit multiple common EH frames for multiple (including blank) personality
functions. This partly fixes PR1414: now we're restricted only to one
personality function per eh frame, not per module. Further work on
"multiple personalities" topic needs representative example.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37018 91177308-0d34-0410-b5e6-96231b3b80d8
2007-05-13 15:42:26 +00:00
Anton Korobeynikov
0ff3ca4f92 More DWARF-related things cleanup:
1. Fix PR1380
2. Apply Duncan's patch from PR1410
3. Insert workaround for "one personality function per module" as noted in PR1414
4. Emit correct debug frames for x86/linux. This partly fixes DebugInfo/2006-11-06-StackTrace.cpp: stack trace is
shown correctly, but arguments for function on top of stack are displayed incorrectly.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37015 91177308-0d34-0410-b5e6-96231b3b80d8
2007-05-12 22:36:25 +00:00
Devang Patel
1e4c23a2d1 Fix http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070507/049516.html
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36998 91177308-0d34-0410-b5e6-96231b3b80d8
2007-05-11 23:14:43 +00:00
Anton Korobeynikov
432a7faf03 Ooops. Some debugging stuff :)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36978 91177308-0d34-0410-b5e6-96231b3b80d8
2007-05-10 22:38:46 +00:00
Anton Korobeynikov
eeb37e0b80 Allow multiple invokes per landing pad. This (probably) fixes PR1410.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36977 91177308-0d34-0410-b5e6-96231b3b80d8
2007-05-10 22:34:59 +00:00
Devang Patel
1997473cf7 Drop 'const'
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36662 91177308-0d34-0410-b5e6-96231b3b80d8
2007-05-03 01:11:54 +00:00
Devang Patel
3e15bf33e0 Use 'static const char' instead of 'static const int'.
Due to darwin gcc bug, one version of darwin linker coalesces
static const int, which defauts PassID based pass identification.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36652 91177308-0d34-0410-b5e6-96231b3b80d8
2007-05-02 21:39:20 +00:00
Lauro Ramos Venancio
c718288f49 Fix build error.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36648 91177308-0d34-0410-b5e6-96231b3b80d8
2007-05-02 20:37:47 +00:00
Devang Patel
794fd75c67 Do not use typeinfo to identify pass in pass manager.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36632 91177308-0d34-0410-b5e6-96231b3b80d8
2007-05-01 21:15:47 +00:00
Jim Laskey
59e8434a85 Collect eh filter info.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34804 91177308-0d34-0410-b5e6-96231b3b80d8
2007-03-01 20:25:32 +00:00
Jim Laskey
59667fe203 Add structures used for collecting eh information.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34473 91177308-0d34-0410-b5e6-96231b3b80d8
2007-02-21 22:38:31 +00:00
Jim Laskey
b82313fdc2 Support for non-landing pad exception handling.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33755 91177308-0d34-0410-b5e6-96231b3b80d8
2007-02-01 16:31:34 +00:00
Jim Laskey
c1c47c3fa4 Out of line function.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33641 91177308-0d34-0410-b5e6-96231b3b80d8
2007-01-29 23:40:33 +00:00
Jim Laskey
6da186480b rename files
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33552 91177308-0d34-0410-b5e6-96231b3b80d8
2007-01-26 21:38:26 +00:00