This classof() is effectively saying that a MachineCodeEmitter "is-a"
JITEmitter, but JITEmitter is in fact a descendant of
MachineCodeEmitter, so this is not semantically correct. Consequently,
none of the assertions that rely on these classof() actualy check
anything.
Remove the RTTI (which didn't actually check anything) and use
static_cast<> instead.
Post-Mortem Bug Analysis
========================
Cause of the bug
----------------
r55022 appears to be the source of the classof() and assertions removed
by this commit. It aimed at removing some dynamic_cast<> that were
solely in the assertions. A typical diff hunk from that commit looked
like:
- assert(dynamic_cast<JITEmitter*>(MCE) && "Unexpected MCE?");
- JITEmitter *JE = static_cast<JITEmitter*>(getCodeEmitter());
+ assert(isa<JITEmitter>(MCE) && "Unexpected MCE?");
+ JITEmitter *JE = cast<JITEmitter>(getCodeEmitter());
Hence, the source of the bug then seems to be an attempt to replace
dynamic_cast<> with LLVM-style RTTI without properly setting up the
class hierarchy for LLVM-style RTTI. The bug therefore appears to be
simply a "thinko".
What initially indicated the presence of the bug
------------------------------------------------
After implementing automatic upcasting for isa<>, classof() functions of
the form
static bool classof(const Foo *) { return true; }
were removed, since they only serve the purpose of optimizing
statically-OK upcasts. A subsequent recompilation triggered a build
failure on the isa<> tests within the removed asserts, since the
automatic upcasting (correctly) failed to substitute this classof().
Key to pinning down the root cause of the bug
---------------------------------------------
After being alerted to the presence of the bug, some thought about the
semantics which were being asserted by the buggy classof() revealed that
it was incorrect.
How the bug could have been prevented
-------------------------------------
This bug could have been prevented by better documentation for how to
set up LLVM-style RTTI. This should be solved by the recently added
documentation HowToSetUpLLVMStyleRTTI. However, this bug suggests that
the documentation should clearly explain the contract that classof()
must fulfill. The HowToSetUpLLVMStyleRTTI already explains this
contract, but it is a little tucked away. A future patch will expand
that explanation and make it more prominent.
There does not appear to be a simple way to have the compiler prevent
this bug, since fundamentally it boiled down to a spurious classof()
where the programmer made an erroneous statement about the conversion.
This suggests that perhaps the interface to LLVM-style RTTI of classof()
is not the best. There is already some evidence for this, since in a
number of places Clang has classof() forward to classofKind(Kind K)
which evaluates the cast in terms of just the Kind. This could probably
be generalized to simply a `static const Kind MyKind;` field in leaf
classes and `static const Kind firstMyKind, lastMyKind;` for non-leaf
classes, and have the rest of the work be done inside Casting.h,
assuming that the Kind enum is laid out in a preorder traversal of the
inheritance tree.
llvm-svn: 165764
This adds 'elf' as a recognized target triple environment value and overrides the default generated object format on Windows platforms if that value is present. This patch also enables MCJIT tests on Windows using the new environment value.
llvm-svn: 165030
The assumption that the target address for the relocation will always be
sizeof(intptr_t) and will always contain an addend for the relocation
value is very wrong. Default to no addend for now.
rdar://12157052
llvm-svn: 163765
When comparing to the macho relocation type enum value, make sure we're only
comparing against the bits in the RelType that correspond.
llvm-svn: 163764
No new tests are added.
All tests in ExecutionEngine/MCJIT that have been failing pass after this patch
is applied (when "make check" is done on a mips board).
Patch by Petar Jovanovic.
llvm-svn: 162135
allocations of executable memory would not be padded
to account for the size of the allocation header.
This resulted in undersized allocations, meaning that
when the allocation was written to later the next
allocation's header would be corrupted.
llvm-svn: 161984
include/llvm/Analysis/DebugInfo.h to include/llvm/DebugInfo.h.
The reasoning is because the DebugInfo module is simply an interface to the
debug info MDNodes and has nothing to do with analysis.
llvm-svn: 159312
LLVM is now -Wunused-private-field clean except for
- lib/MC/MCDisassembler/Disassembler.h. Not sure why it keeps all those unaccessible fields.
- gtest.
llvm-svn: 158096
IntItem cleanup. IntItemBase, IntItemConstantIntImp and IntItem merged into IntItem. All arithmetic operators was propogated from APInt. Also added comparison operators <,>,<=,>=. Currently you will find set of macros that propogates operators from APInt to IntItem in the beginning of IntegerSubset. Note that THESE MACROS WILL REMOVED after all passes will case-ranges compatible. Also note that these macros much smaller pain that something like this:
if (V->getValue().ugt(AnotherV->getValue()) { ... }
These changes made IntItem full featured integer object. It allows to make IntegerSubset class generic (move out all ConstantInt references inside and add unit-tests) in next commits.
llvm-svn: 157810
Implemented IntItem - the wrapper around APInt. Why not to use APInt item directly right now?
1. It will very difficult to implement case ranges as series of small patches. We got several large and heavy patches. Each patch will about 90-120 kb. If you replace ConstantInt with APInt in SwitchInst you will need to changes at the same time all Readers,Writers and absolutely all passes that uses SwitchInst.
2. We can implement APInt pool inside and save memory space. E.g. we use several switches that works with 256 bit items (switch on signatures, or strings). We can avoid value duplicates in this case.
3. IntItem can be easyly easily replaced with APInt.
4. Currenly we can interpret IntItem both as ConstantInt and as APInt. It allows to provide SwitchInst methods that works with ConstantInt for non-updated passes.
Why I need it right now? Currently I need to update SimplifyCFG pass (EqualityComparisons). I need to work with APInts directly a lot, so peaces of code
ConstantInt *V = ...;
if (V->getValue().ugt(AnotherV->getValue()) {
...
}
will look awful. Much more better this way:
IntItem V = ConstantIntVal->getValue();
if (AnotherV < V) {
}
Of course any reviews are welcome.
P.S.: I'm also going to rename ConstantRangesSet to IntegersSubset, and CRSBuilder to IntegersSubsetMapping (allows to map individual subsets of integers to the BasicBlocks).
Since in future these classes will founded on APInt, it will possible to use them in more generic ways.
llvm-svn: 157576
